assignment of vitamins

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10.1 – Introduction to Vitamins

Learning objectives.

• Define the term vitamin.
• Compare and contrast fat-and water-soluble vitamins and identify vitamins that fit in each category.

To combat this issue the Island Food Community of Pohnpei has been instrumental in promoting the citizens of Pohnpei to increase local karat banana consumption. The karat banana is rich in beta-carotene (a source of vitamin A) and increasing consumption among the locals will decrease the prevalence of vitamin A deficiencies in Pohnpei. For further information on this issue visit the Island Food Community of Pohnpei’s website and watch this video .

Vitamins are organic compounds that are traditionally assigned to two groups fat-soluble(hydrophobic) or water-soluble (hydrophilic). This classification determines where they act in the body. Water-soluble vitamins act in the cytosol of cells or in extracellular fluids such as blood; fat-soluble vitamins are largely responsible for protecting cell membranes from free radical damage. The body can synthesize some vitamins, but others must be obtained from the diet.

One major difference between fat-soluble vitamins and water-soluble vitamins is the way they are absorbed in the body. Vitamins are absorbed primarily in the small intestine and their bioavailability is dependent on the quality of the diet. Including a small amount of fat or oils in your meal enhances fat-soluble vitamin absorption.  Once fat-soluble vitamins have been absorbed in the small intestine, they are packaged and incorporated into chylomicrons along with other fatty acids and transported in the lymphatic system to the liver. Water-soluble vitamins, on the other hand, are absorbed in the small intestine but are transported to the liver through blood vessels. (Figure 10.1.3 ).

1 Yamamura CM, Sullivan KM. Risk factors for vitamin A deficiency among preschool-aged children in Pohnpei, Federated States of Micronesia . J Trop Pediatr. 2004; 50(1),16-9. https://www.ncbi.nlm.nih.gov/pubmed/14984164. Accessed May 23, 2019.

key Takeaways

• Vitamins are organic compounds that are traditionally assigned to two groups fat-soluble(hydrophobic) or water-soluble (hydrophilic).
• Water-soluble vitamins act in the cytosol of cells or in extracellular fluids such as blood; fat-soluble vitamins are largely responsible for protecting cell membranes from free radical damage. The body can synthesize some vitamins, but others must be obtained from the diet.
• The fat-soluble vitamins include vitamins A, D, E, K. The water-soluble vitamins include the B vitamins and vitamin C.

Contributors

University of Hawai’i at Mānoa Food Science and Human Nutrition Program: Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

Nutrition 100 Nutritional Applications for a Healthy Lifestyle Copyright © by Lynn Klees is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Vitamins and the chemistry behind them

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From practical experiments to a directed activity related to text (DART), try these activities for 11–16 year olds to investigate the chemistry of vitamins

In this series of activities, students learn about a range of chemical ideas while investigating vitamins and vitamin supplements. Designed for 11–16 year olds, the resources give students the opportunity to conduct practical experiments, evaluate evidence for claims made about vitamins and engage with a variety of scientific and historical contexts. Stimulate your students to explore:

• The link between vitamin C and scurvy
• The structure and properties of vitamin C and how to test for it
• How vitamins were discovered
• Evidence for vitamin C preventing colds
• Whether vitamin supplements are effective

Each activity includes instructions for students, as well as editable worksheets and resources available for download.

1. Vitamin C and scurvy

In this directed activity related to text (DART), students read about the effects of scurvy, its historical prevalence among sailors and the discovery of a link between scurvy and vitamin C. The core of the activity is an extract from James Lind’s ’Of the Prevention of the Scurvy’, in which the Royal Navy surgeon describes an experiment conducted in 1747 to compare treatments for the disease.

After reading both texts, students answer a series of questions to check and consolidate their understanding, before considering how Lind could have improved his experiment and whether his conclusion was correct.

Download the resources

‘vitamin c and scurvy’ worksheet.

PDF | Editable Word document

2. Testing for vitamin C

Students conduct a practical experiment to compare the amounts of vitamin C in different fruit juices using a simple test with iodine solution. They then answer questions to reflect on what they have found out and compare their results with the labels on the fruit juice packaging.

The ‘Testing for vitamin C’ worksheet includes extension questions which relate the experiment to the DART, ’Vitamin C and scurvy’, as well as suggestions for further investigations to find out more about vitamin C.

An additional handout, ‘Did you know about vitamin C?’, provides further information about the chemical structure of vitamin C and how it used by the body.

‘Testing for vitamin C’ worksheet

‘did you know about vitamin c’ handout, plan a lesson around this activity.

Try this activity as part of a complete lesson plan for 14–16 year olds, measuring the amount of vitamin C in different fruit juices using a simple titration.

3. Catching a cold?

In this activity, students investigate the familiar claim that vitamin C helps to prevent or treat colds. They read about the work of Linus Pauling during the 1970s and evaluate the data he used to support this claim, identifying weaknesses in the original study and assessing how these might impact the conclusions we can draw from it.

An additional handout, ‘Did you know about Linus Pauling?’, provides background information about Pauling’s life and work.

‘Catching a cold?’ worksheet

‘did you know about linus pauling’ handout.

Discover a complete lesson plan for 14–16 year olds drawing on this activity to  examine the evidence behind vitamins and vitamin supplements .

4. A cold survey

Students carry out a survey to determine whether vitamin C might help prevent colds. After answering the survey for themselves, students collate responses from the rest of the class, as well as responses collected from family and friends if there is sufficient time. They then work through a series of questions to analyse their results, identifying any patterns and drawing conclusions based on the available evidence.

‘A cold survey’ worksheet

5. are vitamins a waste of money.

Students work in groups to consider a range of views on vitamins pills and supplements. They rank four statements according to how strongly they agree with them, and provide reasons for their rankings, before presenting their decisions to the rest of the class. Together, students agree an answer to the question, ‘Are vitamins a waste of money?’, giving evidence in support.

An additional handout, ‘Did you know about Casimir Funk?’, introduces students to the scientist credited with the discovery of vitamins.

‘The pill thrill: are vitamins a waste of money?’ worksheet

‘did you know about casimir funk’ handout.

Use this activity as part of a complete lesson plan for 14–16 year olds,  exploring whether vitamin pills work .

6. Key words

This handout provides information about terms relating to vitamins and the contexts used for these activities. Key words include ‘clinical trial’, ‘deficiency disease’, ‘double blind’, ‘placebo’, ‘RDI or RDA’ and ‘vitamins’.

‘Key words’ handout

Vitamin c and scurvy worksheet, testing for vitamin c worksheet, did you know about vitamin c handout, catching a cold worksheet, did you know about linus pauling handout, a cold survey worksheet, the pill thrill: are vitamins a waste of money worksheet, did you know about casimir funk handout, key words handout, additional information.

This activity was originally part of the Contemporary Chemistry website, compiled and published in 2004 with V. Kind’s Contemporary chemistry for schools and colleges .

The chemistry behind fireworks

Crystal chemistry

Hydrogen fuel cells: the future of transport?

Investigating catalysts and what sank the Kursk

Shampoo and the chemistry of hair care

Lipid chemistry and dietary fats

Star chemistry and molecules in outer space

Cleaning chemistry: soaps and detergents

Atoms and nanochemistry

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Unit 8 – Vitamins and Minerals Part 1

8.1 Introduction to Vitamins and Minerals

Vitamins and minerals are micronutrients, and by definition, they make up a relatively small part of our diet. However, when it comes to these nutrients, a little bit goes a long way. They have many essential jobs in our bodies.

For example, if you’ve taken a drink of water today, you can thank the minerals that serve as electrolytes, helping to balance fluids in the body.  If you’ve taken a step, you can thank the vitamin D, calcium, and other minerals that make your bones strong. If you’ve taken a breathe, you can thank the many vitamins and minerals that serve as cofactors in making blood, which helps deliver oxygen throughout the body.

There are 13 vitamins and 16 minerals important to human nutrition, and each serves multiple functions in the body. Entire books have been written about each one, and we could easily spend a whole term learning about all of these amazing nutrients. But as this is an introductory course, we’ll use the next two units to introduce you to some of the most interesting vitamins and minerals, with a focus on those that are commonly lacking in the human diet.

We’ll begin this unit with a general introduction to vitamins and minerals, and consider the role of dietary supplements in meeting our vitamin and mineral requirements. Then, we’ll spend the remainder of this unit and the next exploring major functions of vitamins and minerals, food sources of each, and what happens if we consume too little or too much of each.

Unit Learning Objectives

After completing this unit, you should be able to:

• Classify the vitamins as fat-soluble or water-soluble, including differences in absorption, storage, and toxicity.
• Identify the major minerals and trace minerals, including factors that impact absorption and bioavailability.
• Identify common food sources of vitamins and minerals and how processing affects nutrient retention in foods.
• Describe how vitamins can be made in the body through provitamins and intestinal bacteria.
• Define dietary supplements and describe how supplements are regulated and the concerns with their safety and efficacy.
• Identify guidelines and recommendations for choosing nutrition supplements and for their appropriate use.
• Describe the role of electrolytes in fluid balance, as well as the more specific functions, food sources, and effects of deficiency and toxicity for sodium, potassium, and chloride.
• Describe the general function of antioxidants, as well as the more specific functions, food sources, and effects of deficiency and toxicity for vitamin E, vitamin C, and selenium.
• Describe how vitamin A and beta-carotene contribute to normal vision, and know common food sources and effects of deficiency and toxicity of vitamin A.

Attribution:

• Lane Community College’s Nutrition: Science and Everyday Application   CC BY-NC.4

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“assorted-color tomatoes” by Vince Lee on Unsplash ( license information )

Introduction to Nutrition and Wellness Copyright © 2022 by Janet Colson; Sandra Poirier; and Yvonne Dadson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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9.1: Introduction to Vitamins

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• The University of Hawaiʻi
• University of Hawai’i at Mānoa

Learning Objectives

• Describe the functions and sources of antioxidant micronutrients, phytochemicals, and antioxidant minerals
• Describe the functions of vitamins in catabolic pathways, anabolic pathways, and blog

Malia paha he iki ‘unu, pa‘a ka pōhaku nui ‘a‘ole e ka‘a

Perhaps it is the small stone that can keep the big rock from rolling down

Vitamins are obtained from the different types of foods that we consume. If a diet is lacking a certain type of nutrient, a vitamin deficiency may occur. The traditional diet in Pohnpei (an island in the Federal States of Micronesia) consisted of a diet rich in local tropical produce such as bananas, papaya, mango, pineapple, coconut as well as seafood. However, due to a shift in dietary patterns from fresh foods to processed and refined foods the island is suffering from a magnitude of health concerns. A study conducted by the Department of Health of the Federated States of Micronesia on children aged two to four years old in Pohnpei showed that the prevalence for vitamin A deficiency among children aged 2-5 was 53 percent[1].

To combat this issue the Island Food Community of Pohnpei has been instrumental in promoting the citizens of Pohnpei to increase local karat banana consumption. The karat banana is rich in beta-carotene (a source of vitamin A) and increasing consumption among the locals will decrease the prevalence of vitamin A deficiencies in Pohnpei. For further information on this issue visit the Island Food Community of Pohnpei’s website at http://www.islandfood.org/ and watch the video at https://www.youtube.com/watch?v=DGVxnefqbTQ .

Vitamins are organic compounds that are traditionally assigned to two groups fat-soluble(hydrophobic) or water-soluble (hydrophilic). This classification determines where they act in the body. Water-soluble vitamins act in the cytosol of cells or in extracellular fluids such as blood; fat-soluble vitamins are largely responsible for protecting cell membranes from free radical damage. The body can synthesize some vitamins, but others must be obtained from the diet.

One major difference between fat-soluble vitamins and water-soluble vitamins is the way they are absorbed in the body. Vitamins are absorbed primarily in the small intestine and their bioavailability is dependent on the food composition of the diet. Fat-soluble vitamins are absorbed along with dietary fat. Therefore, if a meal is very low in fat, the absorption of the fat-soluble vitamins will be impaired. Once fat-soluble vitamins have been absorbed in the small intestine, they are packaged and incorporated into chylomicrons along with other fatty acids and transported in the lymphatic system to the liver. Water-soluble vitamins on the other hand are absorbed in the small intestine but are transported to the liver through blood vessels. (Figure \(\PageIndex{3}\)).

• Yamamura CM, Sullivan KM. Risk factors for vitamin A deficiency among preschool aged children in Pohnpei, Federated States of Micronesia. J Trop Pediatr. 2004; 50(1),16-9. https://www.ncbi.nlm.nih.gov/pubmed/14984164 . Accessed October 15, 2017.

Contributors and Attributions

University of Hawai’i at Mānoa Food Science and Human Nutrition Program : Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal

• Biology Article

Vitamins And Minerals

Vitamins and minerals are both essential nutrients which are required in a daily diet. Altogether, there are 13 essential vitamins and many minerals which are required for the body to function properly and to maintain the optimal health. Both vitamins and minerals combine to perform hundreds of roles in the body.

Let us learn in detail about these vitamins and minerals below.

Also Read:  Difference between Vitamins and Minerals

Vitamins are organic compounds, found in natural foods which are required for normal growth and maintenance of the body. Both humans and animals require vitamins for their growth.

The word vitamin is a combination of Latin words “vita” and “amine” which means life and nitrogen respectively. Casimir Funk discovered a substance that helps in the growth and maintenance of the body and named it in 1884.

Vitamins act as a catalyst in the generation of energy by utilizing carbohydrates and fats properly. Humans cannot live without vitamins and the human body cannot produce it on its own (except vitamin D and Vitamin B3). So it should be taken in required quantities through other sources such as the food we take, vitamin capsules etc. Vitamins can be found in major foods like meat, leafy vegetables, fruits etc.

Vitamin deficiency may cause some diseases and overdose also causes diseases.

Types of Vitamins

Vitamins are of two types:

• Fat-soluble – which are dissolved in fat
• Water-soluble – which are dissolved in water

Here is a table that illustrates the type of vitamins, sources, and diseases due to vitamin deficiency.

Minerals are also organic compounds found in nature, which helps in the growth of the human body. Minerals are essential for the human body to work properly. Deficiency of minerals leads to several disorders.

List of Minerals, their sources and functions

For more information about Vitamins, Minerals and sources of nutrition, visit BYJU’S.

• Vitamin B-12 Deficiency
• Vitamin A Deficiency
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• Nutrition In Human Beings

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Vitamins: Introduction, Classification, Benefits, Supplements and Deficiencies Posted on : 25-11-2017 Posted by : Admin

Vitamins-introduction.

The vitamins are a group of complex organic compounds required in small quantities by the body for the maintenance of good health. They are not normally synthesized in the body and hence are to be supplied through the diet.

Casimir Funk, a Warsaw-born biochemist was the first to coin the word "vitamin" in 1911. While working on effect of poor diet on nerve inflammation in chickens. Chickens raised on diet deficient in a particular compound developed nerve imflammation, and when that particular compound was replaced the chickenswere normal. He isolated and named that substance "vitamine" as this substance was vital for life and it was an amine. Later it was discovered that all vitamins are not amines and the letter "e" was removed from the ending and finally the name VITAMIN was given.

All the vitamins are named so in the order of their discovery. The one exception was vitamin K which was assigned its name "K" from the term "Koagulation" by Henrik Dam. There are 13 different vitamins in the human body. Out of these only vitamin K and D are produced by the human body.

Unlike other groups of nutrients the vitamins are not chemically similar to each other. Each vitamin has a specific chemical structure and a specific function in the living system. Most of the vitamins act as coenzymes in the body. Normally a well-balanced diet will supply all the necessary vitamins in sufficient quantity.

Vitamin Classification

Energy is the primary requirement for performing various activities. We get energy from the food we eat. Apart from the normal food we consume, our body requires other compounds like vitamins in small amounts for the proper body functioning and deficiency of these compounds may cause disorders. Vitamins are generally classified into the following two main groups, based on their solubility.

Fat soluble vitamins

These vitamins are not soluble in water but are readily soluble in fat dissolving organic solvents. They need presence of fats for their transport and metabolism. They are found in foodstuffs in association with lipids. The fat soluble vitamins are absorbed along with dietary fats. Adequate bile flow and good micelle formation favor absorption of fat-soluble vitamins. These vitamins are excreted primarily in the faeces via bile. The following are the characteristics of fat soluble vitamins,

• Adsorbed with dietary fat in micelles
• Excreted much more slowly
• Stored in adipose tissue & liver and hence they pose a greater risk of toxicity when consumed in excess
• Chylomicrons containing fat-soluble vitamins are transported via the lymph to the bloodstream and eventually to the liver.

The following is the list of fat soluble vitamins,

• Vitamin A (Retinol)
• Vitamin D (Calciferol)
• Vitamin E (Tocopherol)
• Vitamin K (Phytonadione)

Water soluble vitamins

Water soluble vitamins are are the ones which dissolve in water. These vitamins are sent out of the body through urine. The ups and downs in the fat absorption do not affect the absorption of water soluble vitamins. The following are the main characteristics of water soluble vitamins,

• Dissolve in water
• Readily excreted by kidney
• Function as a coenzyme & in energy metabolism
• Vitamin C, thiamin and riboflavin are especially susceptible to heat and alkalinity
• Hydrophilic compounds and water leach them from vegetables
• Marginal deficiency more common

The following is the list of water soluble vitamins,

1. Vitamin B complex (includes B1, B2, B3, B5, B6, B7, B9, B12)

2. Vitamin C (Ascorbic acid)

Vitamin B complex has a major role to play in all the metabolic processes of the cell. The vitamins in this comples are all water-soluble vitamins. The B vitamins were initially considered to be a single vitamin and was called vitamin B. Further experiments proved that vitamin B is actually a groups of separate chemicals which existed together in same food material. The complete group of all the vitamins B members are referred to as a vitamin B complex. They are eight in number. Individual member of this group is called by its name for example vitamin B1, vitamin B2...

• Energy metabolism
• Immune system health
• Nervous system function
• Hormone balancing
• Health skin, hair and teeth
• Antioxidant effects
• Healthy cholesterol levels
• Vitamin B1 (Chemical name thiamine )
• Vitamin B2 (Chemical name riboflavin )
• Vitamin B3 (Chemical name niacin/niacin amide )
• Vitamin B5 (Chemical name pantothenic acid )
• Vitamin B6 (Chemical name pyridoxine )
• Vitamin B7 (Chemical name biotin )
• Vitamin B9 (Chemical name folic acid )
• Vitamin B12 (Chemical name cyanocobalamin )

Because vitamins in B complex group acts as coenzymes for key metabolic processes, its deficiency may lead to poor intake of all other vitamins, difficulties with vitamin absorption and conditions causing increased metabolism which deplete vitamin levels at a higher rate than normal. Since the vitamin B complex work in harmony, a deficiency in one type may have broad implications. Poor intake of B vitamins is most often a problem in strict vegetarians and the elderly. People who frequently fast or diet may also benefit from B vitamin supplements.

Benefits of vitamins

• Vitamins have the ability to prevent and treat various diseases like heart problem, high cholesterol level, eye disorder and skin disorder.
• Vitamins also facilitate various mechanisms of the body.
• Vitamins have the ability to perform functions which cannot be performed by any other nutrients.

Vitamin supplements

Vitamins can be ingested by humans in a variety of ways. Generally vitamins are acquired through the foods we eat, but due to variation in our location, culture and food habits, some may take more vitamin or some may take less vitamins. When the intake of vitamins is less than the required quantity, then vitamins must  be supplied from outside.  Vitamin supplements boost the vitamin content in our body. To improve the overall health and maintain a good balance of body multivitamins are often prescribed.

Some vitamins become more usable by the body when subjected to steam or cooking. On the other hand water soluble vitamins like vitamin B and vitamin C leak into the water while boilin or cooking.

Vitamin deficiencies

To avoid deficiencies, humans must often consume vitamins. Also the storage capacity of the human body for various vitamins is different. While vitamin A, D and B12 are stored for quite a significant time in the liver, Vitamin B3 is stored only for a couple of weeks.

Vitamin deficiency can be primary or secondary. Primary vitamin deficiency arises when the body does not get enough vitamins through dietary sources. Secondary vitamin deficiency arises when the absorption of the vitamin is limited by the body due to various underlying disorders.

Moreover, overdoses of vitamins may result in vitamin poisoning with side effects like nausea, diarrhea and vomiting.

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Biochemistry, fat soluble vitamins.

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Last Update: September 19, 2022 .

• Introduction

Vitamins are vital micronutrients that cannot be synthesized endogenously or in insufficient amounts, and the principal means by which we get vitamins is through our diet. Vitamins can classify as water-soluble or fat-soluble. The fat-soluble vitamins include vitamins A, D, E, and K. Fat-soluble vitamins play integral roles in a multitude of physiological processes such as vision, bone health, immune function, and coagulation. This review discusses the biochemistry, transport, and roles of these vitamins highlighting deficiency syndromes and potential toxicities.

• Fundamentals

Sources of Vitamin A

In animals, the body stores vitamin A as a molecule called retinol. Egg yolk, milk, liver, cheese, and butter are all rich in vitamin A. We derive vitamin A from plant sources in the form of plant carotenoids, which convert to retinol during digestion. Plants abundant in vitamin A include dark green leafy vegetables (spinach, amaranth, among others), carrots, squash, yellow maize, mangoes, and papayas. [1]

Sources of Vitamin D

Vitamin D is found primarily in two forms, D2 and D3. Vitamin D2 (ergocalciferol) is present in certain foods such as salmon, tuna, and mackerel. Smaller quantities are present in beef liver, cheese, and egg yolks. Many countries fortify natural milk with vitamin D. This is a practice implemented to decrease the prevalence of rickets and osteomalacia. Vitamin D3 (cholecalciferol) is synthesized in the skin after exposure to sunlight, hence its nickname the "sunshine vitamin."

Sources of Vitamin E

The predominant form of vitamin E is a-tocopherol. However, other tocopherols and tocotrienols are also present in circulation, such as the alpha, gamma, beta, and delta forms. Naturally occurring sources of vitamin E include vegetable oils, seeds, nuts, and whole grains. [2]

Sources of Vitamin K

Vitamin K has two primary forms, K1 and K2. Vitamin K1 (phylloquinone) is present in green leafy vegetables, cabbage, and cauliflower. Lesser quantities are in fish, meat, and some fruits. The gut microflora synthesizes vitamin K2 (menaquinone). [3]

• Cellular Level

Despite structural differences between fat-soluble vitamins, they are absorbed and transported similarly due to their low solubility in hydrophilic media. The body absorbs fat-soluble vitamins into newly forming micelles in the small intestine. Micelles are lipid clusters that contain hydrophobic groups internally and hydrophilic groups externally. This process relies on the secretion of bile and pancreatic enzymes. After absorption into enterocytes, fat-soluble vitamins become packaged into chylomicrons, which then get secreted into the lymphatic system before entering the bloodstream. Chylomicrons are metabolized by lipoprotein lipase, which causes the release of fat-soluble vitamins into tissues for use and storage.

Because they are stored in tissue, the fat-soluble vitamins are retained by the body for a longer time than the water-soluble vitamins. Remnants of the chylomicron are then taken back up by the liver and recycled. Alpha-tocopherol is targeted into lipoproteins in the liver by a specific tocopherol transfer protein (TTP), mutations of which can result in vitamin E deficiency. [4]

Vitamin A plays an integral role in the differentiation and proliferation of epithelial cells in the eyes, salivary glands, and genitourinary tract. Vitamin A is a precursor to the nuclear hormone all-trans retinoic acid, which heterodimerizes with retinoic acid receptors (RAR) in the nucleus. RAR-retinoid X receptor heterodimers serve as transcription factors that bind certain elements in promoters of genes. These genes encode important structural proteins, extracellular matrix proteins, and enzymes throughout the body. Retinal, a component of vitamin A, derives its name from its ability to produce rhodopsin in the retina, thereby aiding in vision, especially in low light settings. Additionally, vitamin A stimulates T-lymphocyte differentiation and B-lymphocyte activation in response to immune stimuli. [5]

The primary function of vitamin D is to raise plasma calcium and phosphate concentrations, which promotes the mineralization of osteoid in the bone. The ability to elevate calcium levels is necessary for the proper functioning of the neuromuscular junction, nerve transmission, and secretion and actions of hormones. Vitamin D3 from the skin and vitamin D2 from the diet are prohormones that undergo hydroxylation to 25-hydroxycholecalciferol in the liver via the enzyme 25-hydroxylase. 25-hydroxycholecalciferol becomes further hydroxylated in the kidney to its biologically most active form, 1,25-dihydroxycholecalciferol. Hydroxylation in the kidney into a biologically active form occurs via 1-a-hydroxylase, an enzyme under tight regulation by parathyroid hormone. The active form of vitamin D increases the duodenal absorption of calcium and phosphate and calcium reabsorption from the distal convoluted tubule by upregulating calcium transporters that move calcium across epithelial cells. Importantly, vitamin D activates osteoclasts, our body’s bone-resorbing cells. The human body maintains equilibrium with bone formation and resorption. To effectively mineralize bone, some level of bone resorption is necessary. [6]  

Vitamin E, exclusively acquired from the diet, is best known for its antioxidant activity. Vitamin E inhibits the generation of reactive oxygen species during fat oxidation. It protects polyunsaturated fatty acids in cell membranes from oxidative destruction, thereby maintaining membrane fluidity and stability. While it inhibits lipid peroxidation, including oxidation of LDL, supplementation has not resulted in a reduction in cardiovascular events. [7]

Vitamin K is necessary to activate certain clotting factors in the liver, which are responsible for coagulation. For activation to occur, the clotting proteins must bind calcium. Vitamin K-dependent gamma-carboxylation of certain glutamic acid residues allows the proteins to bind calcium and carry out the coagulation cascade. Specifically, vitamin K serves as a cofactor for gamma-glutamyl carboxylase and catalyzes the post-translational synthesis of gamma-carboxy-glutamyl residues. This process activates prothrombin and factors VII, IX, X, protein C and S. Oxidation of vitamin K hydroquinone supplies energy for these carboxylation reactions. Regeneration of vitamin K hydroquinone relies on vitamin K epoxide reductase and vitamin K quinone reductase.

Vitamin A levels are tested by measuring serum retinol. Testing is indicated in patients who exhibit signs of vitamin-A deficiency such as night blindness, xerophthalmia, and Bitot spots. The World Health Organization (WHO) states that serum retinol accurately estimates hepatic vitamin A stores in states of extreme deficiency and excess. Low serum retinol levels are considered to be less than 0.70 micromole/L and can evaluate the extent of vitamin A deficiency. Plasma retinol levels in vitamin A-toxicity are generally greater than 3.5 micromole/L. [8]  The recommended dietary allowance (RDA) of vitamin A is 900 microgram retinol activity equivalents in men and 700 microgram retinol activity equivalents in women. 

Vitamin D is measurable in the serum in two forms, 25-hydroxyvitamin D and 1,25-dihydroxy vitamin D. 25-hydroxyvitamin D is the principal circulating form (levels in ng/ml). It has a half-life of 2 weeks and is the best measure of vitamin-D status. Testing is indicated in populations at high risk for fractures, including those with osteoporosis, osteopenia, and the elderly. Treatment initiation depends on the extent of the deficiency. The Endocrine Society states that levels of 25-hydroxyvitamin D below 20 ng/ml are considered insufficient. According to The US Institute of Medicine, a 25-hydroxyvitamin D level of 20 ng/mL or greater is optimal for bone strength. Levels exceeding 100 ng/ml are considered toxic and puts the patient at risk for hypercalcemia, calculi, and renal damage. Hence, optimum levels appear to be between 20 to 30 ng/ml, with levels over 50 ng/ml avoided. Testing levels of 1,25-hydroxyvitamin D may also be indicated in patients with kidney failure or suspected hypercalcemia from granulomas in sarcoidosis or suspected hyperparathyroidism. Low levels of the active metabolite are commonly observed in early renal failure, while increased levels may present in sarcoidosis and primary hyperparathyroidism. The RDA for vitamin D is 600 IU per day. In individuals older than 70 years, the RDA is 800 IU per day.

The best indicator of the vitamin E level is serum alpha-tocopherol. The recommended level of vitamin E ranges from 5 to 17 microgram/mL in adults and 3 to 18.4 microgram/mL in children. In patients with hyperlipidemia, it is preferable to report standardized lipid levels. Testing may be necessary for patients suffering from sensorimotor neuropathy or a fat malabsorption disorder such as cystic fibrosis. The RDA for vitamin E is 15 mg per day. 

According to the Food and Nutrition Board, a healthy intake of Vitamin K ranges from 70 to 140 micrograms daily. Vitamin-K deficiency and toxicity are rare in the US population, and thus, dietary vitamin-K testing is not generally indicated. The principal test utilized to evaluate bleeding due to a possible vitamin-K deficiency is prothrombin time (PT). In the case of prolonged PT, vitamin K injections or oral supplements may be necessary. Vitamin-K deficiency can be confirmed as the cause of bleeding if PT/INR normalizes in response to the injection or oral supplementation of vitamin K. The RDA for vitamin K in individuals less than six months is 2 mcg per day. The RDA in adult males and females is 120 mcg per day and 90 mcg per day, respectively.

• Pathophysiology

Although rare in developed nations, vitamin A deficiency is a significant health concern in non-industrialized countries. It is responsible for over 500,000 cases of corneal lesions in children per year. In the United States, vitamin A deficiency most commonly results from fat malabsorption syndromes, alcoholism, and liver disease. Uptake of vitamin A can also become impaired by iron deficiency, pancreatic insufficiency, and inflammatory bowel disease. Severe deficiency can lead to various ocular signs, most notably night blindness (nyctalopia) and xerophthalmia. Keratin accumulation in the conjunctiva causing Bitot’s spots is a pathognomic physical finding. Other ocular manifestations include conjunctival xerosis, corneal drying and ulceration, and follicular hyperkeratosis. [1] [9]  Due to the role of vitamin A in T-lymphocyte proliferation and differentiation, deficiency also increases the risk of infections. Notably, vitamin A is an effective treatment for measles, decreasing mortality in children and hospitalized patients. [10]  Additionally, by inducing differentiation of acute promyelocytic anemia cells, all-trans retinoic acid (ATRA) is considered an effective treatment for acute promyelocytic leukemia. [11] In outpatient settings, isotretinoin is a common prescription for the treatment of severe acne vulgaris.

Vitamin-D deficiency has become a global concern with dire health consequences. Common risk factors include old age, exclusively breastfed infants, immobility, reduced kidney function, dark skin, malabsorption syndromes, decreased sunlight exposure, and obesity. [12]  Manifestations of deficiency include muscle aches and weakness with bone pain in the back, extremities, and pelvis. In children, vitamin-D deficiency leads to impaired mineralization of cartilage at growth plates leading to rickets. Patients with rickets may have a bow-leg deformity, rachitic rosary, stunted growth with short stature, dental deformities, abnormal spinal curvature, craniotabes, and frequent fractures. In adults, low vitamin-D levels lead to impaired mineralization of osteoid, leading to osteomalacia. Osteomalacia characteristically demonstrates diffuse bone and joint pain, myopathy, hypocalcemic tetany, and a waddling gait.

Vitamin-E deficiency is extremely rare and principally occurs in individuals with fat malabsorption and abetalipoproteinemia (defect in microsomal transfer protein) and hypobetalipoproteinemia (mutation in apolipoprotein B) disorders. Symptoms of deficiency include limb and truncal ataxia, hyporeflexia, and upward gaze limitations. Rarer manifestations are muscle weakness and constriction of visual fields.  If left untreated, deficiency can result in blindness, memory impairment, and arrhythmias. [13]  Multiple clinical trials have shown that vitamin-E supplementation decreases histological and biochemical evidence of liver dysfunction in patients with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). The increased inflammation and oxidative stress observed in obesity theoretically heighten vitamin-E requirements in this subset of patients. Additionally, these findings raise the question of whether vitamin-E deficiency could exacerbate liver dysfunction. [4]

Vitamin-K deficiency is clinically significant due to its prevalence in a variety of patient populations. Risk factors include antibiotic use, which interferes with vitamin-K production in the gut, nutritional deficiency, and high ingestion of vitamins A and E. Newborns are also at risk for deficiency due to immature gut flora, poor placental transfer, and low content in breast milk. The risk in newborns becomes further increased with a maternal history of anticonvulsant and anticoagulant use. A common clinical syndrome that results from vitamin-K deficiency is a hemorrhagic disease of the newborn, a life-threatening bleeding condition in neonates. Neonates with this condition present with failure to thrive, low birth weight, and excessive bleeding from the umbilical stump and mucous membranes. They are at higher risk for intracranial hemorrhage. This condition is treated prophylactically through vitamin-K injections at birth. In adults, deficiency can also cause easy bleeding and bruising with an elevated PT.

Vitamin-A toxicity most commonly is the result of over-supplementation, wild game liver consumption, and isotretinoin therapy. Hypervitaminosis A leads to intracranial swelling, which manifests as headaches, papilledema, and seizures. Other findings include arthralgias, alopecia, dry mucous membranes, desquamation of skin, hypercalcemia, and liver damage. Isoretinoic acid, an acne treatment, is contraindicated in women who are pregnant or may become pregnant due to a risk of spontaneous abortion and birth defects in the fetus. [14]

Vitamin-D toxicity, although rare, can occur in individuals taking large doses of vitamin-D supplements with a heavy intake of fortified foods. The majority of symptoms of hypervitaminosis D stem from hypercalcemia caused by excessive calcium absorption in the duodenum and distal convoluted tubule. Clinical manifestations include gastrointestinal issues such as decreased appetite, diarrhea, nausea, vomiting, and constipation. Hypercalcemia can result in polyuria, polydipsia, pruritus, and the development of kidney stones. Bone, muscle, and joint pain are also common manifestations. [12]

Hypervitaminosis E is most commonly a result of over-supplementation and is otherwise very rare. Since high doses of Vitamin E (800 mg per day) inhibit platelet aggregation, it is contraindicated in patients on anticoagulants. [15]

Vitamin-K toxicity is uncommon overall but is more prevalent in formula-fed infants and those who receive menadione injections, a synthetic vitamin-K precursor that is water-soluble. Symptoms on hypervitaminosis K include hemolytic anemia, jaundice in newborns with hyperbilirubinemia, and liver damage.

• Clinical Significance

Prevention of fat-soluble vitamin deficiencies and toxicities relies on a diverse team of healthcare professionals. The interprofessional team involves physicians, medical assistants, dieticians, pharmacists, and patients. For example, a pediatrician must recognize risk factors for vitamin-D deficiency in a neonate, including being exclusively breastfed and having darker skin. Nurses, who often spend the most time with patients, are in a position to recognize abnormal signs and symptoms in high-risk patients and report their findings to the physician. Their watchful eye is vital in catching alarming symptoms early, such as headaches and seizures caused by vitamin-A toxicity. Primary and tertiary prevention of fat-soluble vitamin excess or deficiency is carried out by dieticians and nutritionists, who play an essential role in modulating a patient’s diet and ensuring the meeting of their dietary needs. [16]  

Pharmacists are responsible for ensuring that other members of the interprofessional team are aware of the potential risks of medications that may lead to vitamin excess or deficiency. Finally, the role of the physician is to follow proper screening protocols, recognize signs and symptoms of fat-soluble vitamin abnormalities early, order the correct labs, and work to coordinate the other members of the patient’s team optimally.

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Disclosure: Priya Reddy declares no relevant financial relationships with ineligible companies.

Disclosure: Ishwarlal Jialal declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Reddy P, Jialal I. Biochemistry, Fat Soluble Vitamins. [Updated 2022 Sep 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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Vitamins Alternative Assignment

Select one of the vitamins listed below..

Research the vitamin to discover the following:

• Is the vitamin fat soluble or water soluble.
• How much of the vitamin should most humans consume regularly?
• What does the vitamin do for the human body?
• What happens when a person is deficient in the vitamin?
• What happens if the person has too much of the vitamin in his/her system?
• Name at least three food sources of the vitamin.

Prepare a short presentation for your classmates to teach them about the vitamin you select. Be sure to present about the importance of the vitamin in human nutrition.

Vitamin B1 (Thiamine)

Vitamin B2 (Riboflavin)

Vitamin B3 (Niacin)

Vitamin B5 (Pantothenic Acid)

Vitamin B6 (Pyridoxine)

Vitamin B7 (Biotin)

Vitamin B9 (Folic Acid)

Vitamin B12 (Cobalamin)

Vitamin C (Ascorbic Acid)

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10: Enzymes and Vitamins

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• 10.1: Enzymes An enzyme is a biological catalyst, a substance that increases the rate of a chemical reaction without being changed or consumed in the reaction. A systematic process is used to name and classify enzymes.
• 10.2: Enzyme Action A substrate binds to a specific region on an enzyme known as the active site, where the substrate can be converted to product. The substrate binds to the enzyme primarily through hydrogen bonding and other electrostatic interactions. The induced-fit model says that an enzyme can undergo a conformational change when binding a substrate. Enzymes exhibit varying degrees of substrate specificity.
• 10.3: Enzyme Activity Initially, an increase in substrate concentration increases the rate of an enzyme-catalyzed reaction. As the enzyme molecules become saturated with substrate, this increase in reaction rate levels off. The rate of an enzyme-catalyzed reaction increases with an increase in the concentration of an enzyme. At low temperatures, an increase in temperature increases the rate of an enzyme-catalyzed reaction; at higher temperatures, the protein will denature. Enzymes have optimum pH ranges.
• 10.4: Enzyme Inhibition An irreversible inhibitor inactivates an enzyme by bonding covalently to a particular group at the active site. A reversible inhibitor inactivates an enzyme through noncovalent, reversible interactions. A competitive inhibitor competes with the substrate for binding at the active site of the enzyme. A noncompetitive inhibitor binds at a site distinct from the active site.
• 10.5: Enzyme Cofactors and Vitamins Vitamins are organic compounds that are essential in very small amounts for the maintenance of normal metabolism. Vitamins are divided into two broad categories: fat-soluble vitamins and water-soluble vitamins. Most water-soluble vitamins are needed for the formation of coenzymes, which are organic molecules needed by some enzymes for catalytic activity.

It’s only a semi-myth that eating carrots will help you see in the dark. A carrot’s main nutrient, beta-carotene (responsible for this root vegetable’s characteristic orange color), is a precursor to vitamin A and helps your eyes to adjust in dim conditions. Vitamin A can’t give you superpowers of night vision or cure your dependence on contact lenses, but eating an adequate amount will support eye health.

Vitamin A also stimulates the production and activity of white blood cells, takes part in remodeling bone, helps maintain healthy endothelial cells (those lining the body’s interior surfaces), and regulates cell growth and division such as needed for reproduction.

The two main forms of vitamin A in the human diet are preformed vitamin A (retinol, retinyl esters), and provitamin A carotenoids such as alpha-carotene and beta-carotene that are converted to retinol. Preformed vitamin A comes from animal products, fortified foods, and vitamin supplements. Carotenoids are found naturally in plant foods. There are other types of carotenoids found in food that are not converted to vitamin A but have health-promoting properties; these include lycopene, lutein, and zeaxanthin.

Recommended Amounts

  Vitamin A is currently listed on the Nutrition Facts label measured in international units (IU). However, the Institute of Medicine lists the Recommended Dietary Allowances (RDA) of vitamin A in micrograms (mcg) of retinol activity equivalents (RAE) to account for different absorption rates of preformed vitamin A and provitamin A carotenoids. Under the Food and Drug Administration’s (FDA) new food and dietary supplement labeling regulations, as of July 2018 large companies will no longer list vitamin A as IU but as “mcg RAE.” [1]

•   RDA:  The Recommended Dietary Allowance for adults 19 years and older is 900 mcg RAE for men (equivalent to 3,000 IU) and 700 mcg RAE for women (equivalent to 2,333 IU).
• UL:   The Tolerable Upper Intake Level is the maximum daily intake unlikely to cause harmful effects on health. The UL for vitamin A from retinol is 3,000 micrograms of preformed vitamin A.  

Vitamin A and Health

The evidence suggests that eating a variety of foods rich in vitamin A, especially fruits and vegetables , is protective from certain diseases, though the health benefit of vitamin A supplements is less clear.

Lung Cancer: Observational studies following nonsmokers and current or former smokers have found that higher intakes of carotenoids from fruits and vegetables are associated with a lower risk of lung cancer. However, three large clinical trials did not find that supplements of beta-carotene and vitamin A helped to prevent or reduce lung cancer risk. In fact, two of those three trials actually found a significant increase in lung cancer risk among study participants taking supplements with beta-carotene or retinyl palmitate (a form of vitamin A). [1] Therefore, it is recommended that current or former smokers and workers exposed to asbestos do not use high-dose beta-carotene and retinyl palmitate supplements. Additionally, based on current evidence the U.S. Preventive Services Task Force advises against the use of beta-carotene supplements for the prevention of any cancer, stating that there is potentially greater harm in using these supplements than any suggested benefit. [2]

Prostate Cancer: Lycopene is a carotenoid that gives fruits and vegetables a pink or red hue, as in tomatoes and grapefruit. There has been interest in lycopene’s effects on cancer due to its antioxidant properties. Observational studies have noted a decreased risk of prostate cancer in men who eat high amounts of fruits and vegetables. Unfortunately, studies have not provided a clear answer specific to lycopene. Observational studies and clinical trials have shown either a protective effect of lycopene-rich foods (specifically tomatoes) or supplements, or no effect. [3] A Harvard study of more than 51,000 men from the Health Professionals Follow-up Study found a protective effect from advanced stages of prostate cancer in those with higher intakes of tomato sauce. [4] A 2015 meta-analysis of 26 studies found that higher lycopene intakes appeared protective from prostate cancer incidence. [5] However, an FDA review stated that definite conclusions about lycopene could not be made, one reason being that accurate reporting of lycopene intake is difficult due to variations in lycopene content during cooking and storage. [6] Another was that lycopene-rich foods often contain other cancer-protective compounds, so it would be difficult to isolate any health benefits to lycopene

The randomized controlled Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) trial examines the effects of the MIND diet to prevent cognitive decline. It found that higher blood levels of alpha-carotene (a form of vitamin A that includes lutein and zeaxanthin) were associated with better cognition (e.g., memory, learning, attention) in participants at risk for cognitive decline. [7] Foods contributing to higher alpha-carotene levels included fruits, and green leafy and orange vegetables.

Age-related macular degeneration (AMD) is a common painless eye condition but a leading cause of vision loss among people age 50 and older. It distorts the sharp, central vision needed to see fine details such as for reading and driving. The exact cause is unclear but oxidative stress is believed to play a role. Smokers and those with poor diets lacking fruits and vegetables have a higher risk of developing AMD. Lutein and zeaxanthin are two carotenoids with protective antioxidant effects that are found in the retina, the eye tissue that is damaged by AMD. Studies have looked to see if supplements containing lutein and zeaxanthin, as well as beta-carotene, might be useful for preventing or treating this condition. The NIH-funded Age-Related Eye Disease Studies (AREDS, AREDS2) found that daily intakes of high-dose vitamins including vitamins C and E and lutein and zeaxanthin slowed the progression of intermediate and late-stage AMD, particularly in participants who ate the lowest amounts of carotenoids. [8,9] Beta-carotene was not found to be protective.

Food Sources

Many breakfast cereals, juices, dairy products, and other foods are fortified with retinol (preformed vitamin A). Many fruits and vegetables and some supplements contain beta-carotene, lycopene, lutein, or zeaxanthin.

• Leafy green vegetables ( kale , spinach, broccoli), orange and yellow vegetables (carrots, sweet potatoes , pumpkin and other winter squash , summer squash)
• Red bell pepper
• Cantaloupe, mango
• Fortified foods

Signs of Deficiency and Toxicity

Deficiency Vitamin A deficiency is rare in Western countries but may occur. Conditions that interfere with normal digestion can lead to vitamin A malabsorption such as celiac disease, Crohn’s disease, cirrhosis, alcoholism, and cystic fibrosis. Also at risk are adults and children who eat a very limited diet due to poverty or self-restriction.  Mild vitamin A deficiency may cause fatigue, susceptibility to infections, and infertility. The following are signs of a more serious deficiency.

• Xerophthalmia, a severe dryness of the eye that if untreated can lead to blindness
• Nyctalopia or night blindness
• Irregular patches on the white of the eyes
• Dry skin or hair

Toxicity Vitamin A toxicity may be more common in the U.S. than a deficiency, due to high doses of preformed vitamin A (retinol) found in some supplements. Vitamin A is also fat-soluble, meaning that any amount not immediately needed by the body is absorbed and stored in fat tissue or the liver. If too much is stored, it can become toxic. The tolerable upper intake of 3,000 mcg of preformed vitamin A, more than three times the current recommended daily level, is thought to be safe. However, there is some evidence that this much preformed vitamin A might increase the risk of bone loss, hip fracture [10-12], or some birth defects. [13] Another reason to avoid too much preformed vitamin A is that it may interfere with the beneficial actions of vitamin D . Signs of toxicity include the following.

• Vision changes such as blurry sight
• Nausea and vomiting
• Sensitivity to bright light like sunlight

In contrast to preformed vitamin A, beta-carotene is not toxic even at high levels of intake. The body can form vitamin A from beta-carotene as needed, and there is no need to monitor intake levels as with preformed vitamin A. Therefore, it is preferable to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene; many multivitamin manufacturers have already reduced the amount of preformed vitamin A in their products. However, there is no strong reason for most people to take individual high-dose beta-carotene supplements. Smokers in particular should avoid these, since some randomized trials in smokers have linked high-dose supplements with increased lung cancer risk. [14-16]

Did You Know?  

• Sometimes people take cod liver oil for vitamin D but may not be aware it is also very high in vitamin A, beyond the RDA at 192%, in the same synthetic form as in supplements (retinyl palmitate). So if you use cod liver oil, make sure your other supplements do not contain extra vitamin A. Other forms of fish oil supplements typically do not contain significant amounts of vitamin A, but always check the label.
• Retinoids in skin creams can cause skin to become highly sensitive to bright light, so it is advised to apply vitamin A creams at night and to avoid strong sun after their use.  

Vitamins and Minerals

• National Institutes of Health Office of Dietary Supplements: Vitamin A Fact Sheet for Health Professionals https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/#en24 . Accessed 6/18/2018.
• U.S Preventive Services Task Force, Mangione CM, Barry MJ, Nicholson WK, Cabana M, Chelmow D, Coker TR, Davis EM, Donahue KE, Doubeni CA, Jaén CR, Kubik M, Li L, Ogedegbe G, Pbert L, Ruiz JM, Stevermer J, Wong JB. Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: US Preventive Services Task Force Recommendation Statement. JAMA . 2022 Jun 21;327(23):2326-2333.
• National Cancer Institute. Prostate Cancer, Nutrition, and Dietary Supplements (PDQ®)–Health Professional Version: Lycopene. https://cancer.gov/about-cancer/treatment/cam/hp/prostate-supplements-pdq#section/_16 . Accessed 6/18/2018.
• Giovannucci, E., et al. Risk factors for prostate cancer incidence and progression in the health professionals follow-up study. Int J Cancer , 2007. 121(7): p. 1571-8.
• Chen P, Zhang W, Wang X, Zhao K, Negi DS, Zhuo L, Qi M, Wang X, Zhang X. Lycopene and Risk of Prostate Cancer: A Systematic Review and Meta-Analysis. Medicine . 2015 Aug;94(33):e1260.
• Kavanaugh CJ1, Trumbo PR, Ellwood KC. The U.S. Food and Drug Administration’s evidence-based review for qualified health claims: tomatoes, lycopene, and cancer. J Natl Cancer Inst . 2007 Jul 18;99(14):1074-85. Epub 2007 Jul 10.
• Liu X, Dhana K, Furtado JD, Agarwal P, Aggarwal NT, Tangney C, Laranjo N, Carey V, Barnes LL, Sacks FM. Higher circulating α-carotene was associated with better cognitive function: an evaluation among the MIND trial participants. Journal of Nutritional Science . 2021;10:e64.
• Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8.  Arch Ophthalmol . 2001;119(10):1417-1436.
• Age-Related Eye Disease Study 2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA . 2013 May 15;309(19):2005-15.
• Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. JAMA . 2002; 287:47-54.
• Michaelsson K, Lithell H, Vessby B, Melhus H. Serum retinol levels and the risk of fracture. N Engl J Med. 2003; 348:287-94.
• Penniston KL, Tanumihardjo SA. The acute and chronic toxic effects of vitamin A. Am J Clin Nutr . 2006; 83:191-201.
• Azais-Braesco V, Pascal G. Vitamin A in pregnancy: requirements and safety limits. Am J Clin Nutr . 2000; 71:1325S-33S.
• Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med . 1996; 334:1150-5.
• Albanes D, Heinonen OP, Taylor PR, et al. Alpha-tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. J Natl Cancer Inst . 1996; 88:1560-70.
• Virtamo J, Pietinen P, Huttunen JK, et al. Incidence of cancer and mortality following alpha-tocopherol and beta-carotene supplementation: a postintervention follow-up. JAMA . 2003; 290:476-85.
• Xia Q1, Yin JJ, Wamer WG, Cherng SH, Boudreau MD, Howard PC, Yu H, Fu PP. Photoirradiation of retinyl palmitate in ethanol with ultraviolet light–formation of photodecomposition products, reactive oxygen species, and lipid peroxides. Int J Environ Res Public Health . 2006 Jun;3(2):185-90.
• American Academy of Dermatology press release. Analysis finds sunscreens containing retinyl palmitate do not cause skin cancer. August 10, 2010. https://aad.org/media/news-releases/analysis-finds-sunscreens-containing-retinyl-palmitate-do-not-cause-skin-cancer . Accessed 6/25/2018.

Last reviewed March 2023

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