Chapter 16: Fat-Soluble Vitamins

Vitamin A

Vitamin A is a generic term for a group of similar compounds called retinoids. Retinol is the form of vitamin A found in animal-derived foods, and is converted in the body to the biologically active forms of vitamin A: retinal and retinoic acid. About 10 percent of plant-derived carotenoids, including beta-carotene, can be converted in the body to retinoids and are another source of functional vitamin A. Carotenoids are pigments synthesized by plants that give them their yellow, orange, and red color. Over six hundred carotenoids have been identified and, with just a few exceptions, all are found in the plant kingdom. There are two classes of carotenoids—the xanthophylls, which contain oxygen, and the carotenes, which do not.

In plants, carotenoids absorb light for use in photosynthesis and act as antioxidants. Beta-carotene, alpha-carotene, and beta-cryptoxanthin are converted to some extent to retinol in the body. The other carotenoids, such as lycopene, are not. Many biological actions of carotenoids are attributed to their antioxidant activity, but they likely act by other mechanisms, too.

Vitamin A is fat-soluble and is packaged into chylomicrons in small intestine, and transported to the liver. The liver stores and exports vitamin A as needed; it is released into the blood bound to a retinol-binding protein, which transports it to cells. Carotenoids are not absorbed as well as vitamin A, but similar to vitamin A, they do require fat in the meal for absorption. In intestinal cells, carotenoids are packaged into the lipid-containing chylomicrons inside small intestine mucosal cells and then transported to the liver. In the liver, carotenoids are repackaged into lipoproteins, which transport them to cells.

The retinoids are aptly named as their most notable function is in the retina of the eye where they aid in vision, particularly in seeing under low-light conditions. This is why night blindness is the most definitive sign of vitamin A deficiency. Vitamin A has several important functions in the body, including maintaining vision and a healthy immune system. Many of vitamin A’s functions in the body are similar to the functions of hormones, particularly the hydrophobic steroid hormones. For example, vitamin A can has an intracellular receptor that directly interacts with DNA, changing which genes are transcribed and translated into proteins. Vitamin A assists in maintaining healthy skin and the linings and coverings of tissues; it also regulates growth and development. As an antioxidant, vitamin A protects cellular membranes, helps in maintaining glutathione levels, and influences the amount and activity of enzymes that detoxify free radicals.

Vision

Retinol that is circulating in the blood is taken up by cells in the eye retina, where it is converted to retinal and is used to help the pigment rhodopsin, which is involved in the eye’s ability to see under low light conditions. Vitamin A is also important in maintaining the health of the eye coverings.

Vitamin A deficiency is the major cause of preventable blindness worldwide. An estimated 250,000 to 500,000 children becoming blind annually from this vitamin deficiency . About half the children that lose their sight due to vitamin A deficiency are dead within one year.^[1]

The earliest symptoms of a vitamin A deficiency are due to the loss of vitamin A-containing rhodopsin in the retina leading to an inability to see in low light conditions, or night blindness. As the vitamin deficiency persists, the coverings and linings of the eye are damaged. This leads to xerophthalmia, characterized by eye dryness and buildup of keratin on the eye coverings (called Bitot spots, see Figure 16.1), and ultimately destruction of the cornea and irreversible blindness.

 

Vitamin A deficiency, while rare in developed nations, remains commons in many parts of the world particularly regions of sub-Saharan Africa and parts of South Asia. Pregnant women and young children are most affected. Approaches to combat this include vitamin A supplementation in the form of pills or injections (see this Unicef link for more details) and promoting food fortification. Golden rice, rice that has been genetically modified to have high levels of vitamin A, was to combat this problem but has faced problems in deployment due to oppositions to GMOs.

Immunity

The common occurrence of advanced xerophthalmia in children who died from infectious diseases led scientists to hypothesize that supplementing vitamin A in the diet for children with xerophthalmia might reduce disease-related mortality. In Asia in the late 1980s, targeted populations of children were administered vitamin A supplements, and the death rates from measles and diarrhea declined by up to 50 percent. Vitamin A supplementation in these deficient populations did not reduce the number of children who contracted these diseases, but it did decrease the severity of the diseases so that they were no longer fatal. Soon after the results of these studies were communicated to the rest of the world, the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) commenced worldwide campaigns against vitamin A deficiency. UNICEF estimates that the distribution of over half a billion vitamin A capsules prevents 350,000 childhood deaths annually.^[2]

In the twenty-first century, science has demonstrated that vitamin A greatly affects the immune system. What we are still lacking are clinical trials investigating the proper doses of vitamin A required to help ward off infectious disease and how large of an effect vitamin A supplementation has on populations that are not deficient in this vitamin. This brings up one of our common themes in this text—micronutrient deficiencies may contribute to the development, progression, and severity of a disease, but this does not mean that an increased intake of these micronutrients will solely prevent or cure disease. The effect, as usual, is cumulative and depends on the diet as a whole, among other things.

Growth and Development

Vitamin A acts similarly to some hormones in that it is able to change the amount of proteins in cells by interacting with DNA. This is the primary way that vitamin A affects growth and development. Vitamin A deficiency in children is linked to growth retardation; however, vitamin A deficiency is often accompanied by protein malnutrition and iron deficiency, thereby confounding the investigation of vitamin A’s specific effects on growth and development.

In the fetal stages of life, vitamin A is important for limb, heart, eye, and ear development and in both deficiency and excess, vitamin A causes birth defects. Furthermore, both males and females require vitamin A in the diet to effectively reproduce.

Cancer

Vitamin A’s role in regulating cell growth and death, especially in tissues that line and cover organs, suggests it may be effective in treating certain cancers of the lung, neck, and liver. It has been shown in some observational studies that vitamin A-deficient populations have a higher risk for some cancers. However, vitamin A supplements have actually been found to increase the risk of lung cancer in people who are at high risk for the disease (i.e., smokers, ex-smokers, workers exposed to asbestos). The Beta-Carotene and Retinol Efficacy Trial (CARET) involving over eighteen thousand participants who were at high risk for lung cancer found that people who took supplements containing very high doses of vitamin A (25,000 international units) and beta-carotene had a 28 percent higher incidence of lung cancer midway through the study, which was consequently stopped.^[3]

Vitamin A Toxicity

Vitamin A toxicity, or hypervitaminosis A, is rare. Typically, it requires you to ingest ten times the RDA of preformed vitamin A in the form of supplements (it would be hard to consume such high levels from a regular diet) for a substantial amount of time, although some people may be more susceptible to vitamin A toxicity at lower doses. The signs and symptoms of vitamin A toxicity include dry, itchy skin, loss of appetite, swelling of the brain, and joint pain. In severe cases, vitamin A toxicity may cause liver damage and coma.

Vitamin A is essential during pregnancy, but doses above 3,000 micrograms per day (10,000 international units) have been linked to an increased incidence of birth defects. Pregnant women should check the amount of vitamin A contained in any prenatal or pregnancy multivitamin she is taking to assure the amount is below the UL.

Dietary Reference Intakes for Vitamin A

There is more than one source of vitamin A in the diet. There is preformed vitamin A, which is abundant in many animal-derived foods, and there are carotenoids, which are found in high concentrations in vibrantly colored fruits and vegetables and some oils.

Some carotenoids are converted to retinol in the body by intestinal cells and liver cells. However, only minuscule amounts of certain carotenoids are converted to retinol, meaning fruits and vegetables are not necessarily good sources of vitamin A.

The RDA for vitamin A includes all dietary sources of vitamin A, all of which the human body converts all dietary sources of vitamin A into retinol. The RDA for vitamin A is given in µg of retinol activity equivalents (RAE) to account for the many different forms it is available in. One µm RAE is equivalent to 1 µg of retinol, 12 µg of dietary beta-carotene, and 24 µg of dietary alpha-carotene or beta-cryptoxanthin. Stated another way, 12 micrograms of fruit- or vegetable-based beta-carotene will yield 1 microgram of retinol in the body. While RAE is now the reporting standard, some sources may use international units (IUs) to quantify vitamin A content. The following conversions may be useful:

• 1 IU retinol = 0.3 mcg RAE
• 1 IU beta-carotene from dietary supplements = 0.15 mcg RAE
• 1 IU beta-carotene from food = 0.05 mcg RAE
• 1 IU alpha-carotene or beta-cryptoxanthin = 0.025 mcg RAE

The RDA for vitamin A is considered sufficient to support growth and development, reproduction, vision, and immune system function while maintaining adequate stores (good for four months) in the liver.

Table 16.1 Dietary Reference Intakes for Vitamin A. Source: Vitamin A – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements.  Updated March 10, 2025. Accessed August 22, 2025. Public domain.

Age Group	RDA (or AI*) Males and Females (µg RAE/day)	UL (µg RAE/day)
Infants (0–6 months)	400*	600
Infants (7–12 months)	500*	600
Children (1–3 years)	300	600
Children (4–8 years)	400	900
Children (9–13 years)	600	1,700
Adolescents (14–18 years)	900 (males), 700 (females)	2,800
Adults (> 19 years)	900 (males), 700 (females)	3,000

Dietary Sources of Vitamin A and Beta-Carotene

Preformed vitamin A is found only in foods from animals, with the liver being the richest source because that’s where vitamin A is stored. In the United States, commonly consumed carotenoids are alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin.^[4]

Table 16.2 Vitamin A Content of Various Foods. Source: Vitamin A – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements.  Updated March 10, 2025. Accessed March 3, 2026. Public domain.

Food	Serving	Vitamin A (µg RAE)	Percent Daily Value
Beef liver, cooked	3 oz.	6,582	731
Sweet potato, baked	1 whole	1,403	156
Carrots, raw	½ cup	459	51
Milk, skim, added vitamins D and A	1 c.	149	17
Sweet red pepper, raw	½ c.	117	13
Black-eyed peas, boiled	1 c.	66	7
Broccoli, boiled	½ c.	60	7

Vitamin D

Vitamin D refers to a group of fat-soluble vitamins derived from cholesterol. Vitamins D2 (ergocalciferol) and D3 (cholecalciferol) are the only ones known to have biological actions in the human body. The skin synthesizes vitamin D when exposed to sunlight. In fact, for most people, more than 90 percent of their vitamin D3 comes from the casual exposure to the UVB rays in sunlight. Anything that reduces your exposure to the sun’s UVB rays decreases the amount of vitamin D3 your skin synthesizes. That would include long winters, your home’s altitude, whether you are wearing sunscreen, and the color of your skin (including tanned skin). Do you ever wonder about an increased risk for skin cancer by spending too much time in the sun? Do not fret. Less than thirty minutes of sun exposure to the arms and legs will increase blood levels of vitamin D3 more than orally taking 10,000 IU (250 micrograms) of vitamin D3.

Vitamin D’s Functional Role

Whether consumed in food or synthesized in the skin, vitamin D must be chemically modified by the liver and then then kidneys into its biologically active form, called calcitriol. Calcitriol regulates blood calcium levels in concert with parathyroid hormone. Calcitriol increases blood calcium concentration in three ways:

• Increasing absorption of calcium (and phosphate) from digested food in the small intestine into the blood,
• Reducing urinary excretion of calcium, resulting in more calcium remaining in the blood,
• Increasing the breakdown of bone, which releases calcium and phosphate into the blood.

The third effect listed above, increasing breakdown of bone, might seem counterintuitive but it is seemingly “outweighed” in importance by the other two. In the absence of an adequate intake of vitamin D, less than 15 percent of calcium is absorbed from foods or supplements. The effects of calcitriol on calcium homeostasis are critical for bone health. Without adequate calcium and phosphate, proper bone mineral cannot be made and maintained. Figure 16.3 summaries the metabolism and role of vitamin D in blood calcium regulation.

 

A deficiency of vitamin D in children causes the bone disease nutritional rickets. Rickets is very common among children in developing countries and is characterized by soft, weak, deformed bones that are exceptionally susceptible to fracture. In adults, vitamin D deficiency causes a similar disease called osteomalacia, which is characterized by low BMD. Osteomalacia has the same symptoms and consequences as osteoporosis and often coexists with osteoporosis. Vitamin D deficiency is common, especially in the elderly population, dark-skinned populations, and in the many people who live in the northern latitudes where sunlight exposure is much decreased during the long winter season.

Health Benefits

Observational studies have shown that people with low levels of vitamin D in their blood have lower BMD and an increased incidence of osteoporosis. In contrast, diets with high intakes of salmon, which contains a large amount of vitamin D, are linked with better bone health. A review of twelve clinical trials, published in the May 2005 issue of the Journal of the American Medical Association, concluded that oral vitamin D supplements at doses of 700–800 international units per day, with or without coadministration of calcium supplements, reduced the incidence of hip fracture by 26 percent and other nonvertebral fractures by 23 percent.^[5] A reduction in fracture risk was not observed when people took vitamin D supplements at doses of 400 international units.

Much research has been conducted to investigate potential links between vitamin D and a whole host of health conditions and diseases. The association of vitamin D and bone health seems to be the best characterized. Links between vitamin and some forms of cancer, cardiovascular disease, depression, type 2 diabetes, and others, have been investigated. However, evidence has been inconsistent or not significant, and high-quality clinical trials are generally lacking.^[6] One major trial, the VITAL study, found no significant effects of high dose vitamin D supplementation on the prevention of either cancer or cardiovascular disease.^[7]

Vitamin D Toxicity

Although vitamin D toxicity is rare, too much can cause high levels of calcium concentrations or hypercalcemia. Hypercalcemia can lead to a large amount of calcium to be excreted through the urine which can cause kidney damage.  Calcium deposits may also develop in soft tissues such as the kidneys, blood vessels, or other parts of the cardiovascular system. However, it is important to know that the synthesis of vitamin D from the sun does not cause vitamin D toxicity due to the skin production of vitamin D3 being a tightly regulated process.

Dietary Sources of Vitamin D

Table 16.3 Vitamin D Content of Various Foods. Source: Vitamin D – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated June 27, 2025. Accessed March 3, 2026. Public domain.

Food	Serving	Vitamin D (µg)	Percent Daily Value
Cod liver oil	1 tbsp.	34	170
Salmon, cooked	3 oz.	14.2	71
Mushrooms, white, raw, exposed to UV light	½ c.	9.2	46
Milk, 2%, vitamin D-fortified	1 c.	2.9	15
Sardines, canned in oil, drained	2 fish	1.2	6
Egg, scrambled	1 large	1.1	6
Beef liver, braised	3 oz.	1.0	5
Apple	1 large	0	0

Dietary Reference Intakes for Vitamin D

For adults, the RDA is 15 µg of vitamin D for adults up to 70 years of age, and 20 µg for those 71 years and older. The tolerable upper intake level (UL) for vitamin D is 100 µg per day for adults. Toxicity from excess vitamin D is rare, but certain diseases such as hyperparathyroidism, lymphoma, and tuberculosis make people more sensitive to the increases in calcium caused by high intakes of vitamin D.

Table 16.4 Dietary Reference Intakes for Vitamin D. Source: Vitamin D – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated June 27, 2025. Accessed August 22, 2025. Public domain.

Age Group	RDA (or AI*) (µg/day)	UL (µg/day)
Infant (0–6 months)	10*	25
Infants (6–12 months)	10*	38
Children (1–3 years)	15	63
Children (4–8 years)	15	75
Children (9–13 years)	15	100
Adolescents (14–18 years)	15	100
Adults (19–71 years)	15	100
Adults (> 71 years)	20	100

Vitamin E

Vitamin E occurs in eight chemical forms, of which alpha-tocopherol appears to be the only form that is recognized to meet human requirements. Alpha-tocopherol and vitamin E’s other constituents are fat-soluble and primarily responsible for protecting cell membranes against lipid destruction caused by free radicals, therefore making it an antioxidant. When alpha-tocopherol interacts with a free radical it is no longer capable of acting as an antioxidant unless it is enzymatically regenerated. Vitamin C helps to regenerate some of the alpha-tocopherol, but the remainder is eliminated from the body. Therefore, to maintain vitamin E levels, you ingest it as part of your diet.

Insufficient levels are rare (signs and symptoms of such conditions are not always evident) but are primarily the result of nerve degeneration. People with malabsorption disorders, such as Crohn’s disease or cystic fibrosis, and babies born prematurely, are at higher risk for vitamin E deficiency.

Vitamin E has many other important roles and functions in the body such as boosting the immune system by helping to fight off bacteria and viruses.  It also enhances the dilation of blood vessels and inhibiting the formation of blood clotting.  Despite vitamin E’s numerous beneficial functions when taken in recommended amounts, large studies do not support the idea that taking higher doses of this vitamin will increase its power to prevent or reduce disease risk.^[8,9]

Fat in the diet is required for vitamin E absorption as it is packaged into lipid-rich chylomicrons in intestinal cells and transported to the liver. The liver stores some of the vitamin E or packages it into lipoproteins, which deliver it to cells.

Cardiovascular Disease

Vitamin E reduces the oxidation of LDLs, and it was therefore hypothesized that vitamin E supplements would protect against atherosclerosis. However, large clinical trials have not consistently found evidence to support this hypothesis. In fact, in the “Women’s Angiographic Vitamin and Estrogen Study,” postmenopausal women who took 400 international units (264 milligrams) of vitamin E and 500 milligrams of vitamin C twice per day had higher death rates from all causes.^[10]

Other studies have not confirmed the association between increased vitamin E intake from supplements and increased mortality. There is more consistent evidence from observational studies that a higher intake of vitamin E from foods is linked to a decreased risk of dying from a heart attack.

Cancer

Large clinical trials that evaluated whether there was a link between vitamin E and cardiovascular disease risk also looked at cancer risk. These trials, called the HOPE-TOO Trial and Women’s Health Study, did not find that vitamin E at doses of 400 international units (264 milligrams) per day or 600 international units (396 milligrams) every other day reduced the risk of developing any form of cancer.^[11-12]

Eye Conditions

Oxidative stress plays a role in age-related loss of vision, called macular degeneration. Age-related macular degeneration (AMD) primarily occurs in people over age fifty and is the progressive loss of central vision resulting from damage to the center of the retina, referred to as the macula. There are two forms of AMD, dry and wet, with wet being the more severe form.

In the dry form, deposits form in the macula; the deposits may or may not directly impair vision, at least in the early stages of the disease. In the wet form, abnormal blood vessel growth in the macula causes vision loss. Clinical trials evaluating the effects of vitamin E supplements on AMD and cataracts (clouding of the lens of an eye) did not consistently observe a decreased risk for either. However, scientists do believe vitamin E in combination with other antioxidants such as zinc and copper may slow the progression of macular degeneration in people with early-stage disease.^[13]

Dementia

The brain’s high glucose consumption makes it more vulnerable than other organs to oxidative stress. Oxidative stress has been implicated as a major contributing factor to dementia and Alzheimer’s disease. Some studies suggest vitamin E supplements delay the progression of Alzheimer’s disease and cognitive decline, but again, not all of the studies confirm the relationship. More studies are needed to better assess the dose and dietary requirements of vitamin E and, for that matter, whether other antioxidants lower the risk of dementia, a disease that not only devastates the mind, but also puts a substantial burden on loved ones, caretakers, and society in general.^[13]

Vitamin E Toxicity

Currently, researchers have not found any adverse effects from consuming vitamin E in food. Although that may be the case, supplementation of alpha-tocopherol in animals has shown to cause hemorrhage and disrupt blood coagulation.  Extremely high levels of vitamin E can interact with vitamin K-dependent clotting factors causing an inhibition of blood clotting.^[13]

Dietary Reference Intakes for Vitamin E

Food and supplement labels in the US list vitamin e content in milligrams, though reporting is not required unless vitamin E was added to the food. Past rules allowed reporting in international units (IU). Further confusion can arise because IUs for naturally occurring vitamin E vs. synthetically produced vitamin E are different. The conversion factors below may be useful:

• 1 mg alpha-tocopherol = 1.49 IU natural form = 2.22 IU synthetic form
• 1 IU natural form = 0.67 mg alpha-tocopherol

Table 16.5 Dietary Reference Intakes for Vitamin E. Source:  Vitamin E – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated March 26, 2021. Accessed August 22, 2025. Public domain.

Age Group	RDA (or AI*) Males and Females (mg/day)	UL (mg/day)
Infants (0–6 months)	4*	–
Infants (7–12 months)	5*	–
Children (1–3 years)	6	200
Children (4–8 years)	7	300
Children (9–13 years)	11	600
Adolescents (14–18 years)	15	800
Adults (> 19 years)	15	1,000

Vitamin E supplements often contain more than 400 international units, which is almost twenty times the RDA. The UL for vitamin E is set at 1000 mg for adults. There is some evidence that taking vitamin E supplements at high doses has negative effects on health. As mentioned, vitamin E inhibits blood clotting and a few clinical trials have found that people taking vitamin E supplements have an increased risk of stroke. In contrast to vitamin E from supplements, there is no evidence that consuming foods containing vitamin E compromises health.

Dietary Sources of Vitamin E

Vitamin E is found in many foods, especially those higher in fat, such as nuts and oils. Some spices, such as paprika and red chili pepper, and herbs, such as oregano, basil, cumin, and thyme, also contain vitamin E. Keep in mind that spices and herbs are commonly used in very small amounts in cooking and therefore are a lesser source of dietary vitamin E.

Table 16.6 Vitamin E Content of Various Foods. Source:  Vitamin E – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated March 26, 2021. Accessed March 4, 2026. Public domain.

Food	Serving Size	Vitamin E (mg)	Percent Daily Value
Wheat germ oil	1 tbsp.	20.3	135
Sunflower seeds, dry roasted	1 oz.	7.4	49
Almonds, dry roasted	1 oz.	6.8	45
Sunflower oil	1 Tbsp	5.6	37
Hazelnuts, dry roasted	1 oz.	4.3	29
Peanut butter	2 Tbsp.	2.9	19
Peanuts, dry roasted	1 oz.	2.2	15
Corn oil	1 Tbsp.	1.9	13
Kiwi	1 medium	1.1	7
Tomato, raw	1 medium	0.7	5
Spinach, raw	1 c.	0.6	4

Vitamin K

Blood Clotting

Vitamin K refers to a group of fat-soluble vitamins that are similar in chemical structure. Vitamin K is critical for blood function acting as coenzymes which play an essential role in blood coagulation. Blood-clotting proteins are synthesized in our liver and continuously circulating in the blood. Upon injury to a blood vessel, platelets stick to the wound forming a plug and secrete a factor called tissue factor. Tissue factor begins a cascade, activating coagulation factor VII which activates the next factor and so forth. Eventually thrombin is activated which cleaves fibrogen into fibrin. The fibrin forms a clot. Vitamin K is essential to the function of factors VII, IX, X and thrombin. Without vitamin K, blood would not clot.

 

A deficiency in vitamin K causes bleeding disorders. It is relatively rare, but people who have liver or pancreatic disease, celiac disease, or malabsorption conditions are at higher risk for vitamin K deficiency. Signs and symptoms include nosebleeds, easy bruising, broken blood vessels, bleeding gums, and heavy menstrual bleeding in women. The function of the anticoagulant drug warfarin is impaired by excess vitamin K intake from supplements. Calcium additionally plays a role in activation of blood-clotting proteins.

Bone Health

Vitamin K is also required for maintaining bone health. It modifies the protein osteocalcin, which is involved in the bone remodeling process. All the functions of osteocalcin and the other vitamin K-dependent proteins in bone tissue are not well understood and are under intense study. Some studies do show that people who have diets low in vitamin K also have an increased risk for bone fractures.

Dietary Reference Intakes for Vitamin K

The AI of vitamin K for adult females is 90 micrograms per day, and for males it is 120 micrograms per day. Deficiencies are rare as our body can recycle the vitamin K it uses and our intestinal flora synthesizes significant amounts.

A UL for vitamin K has not been set because it has a low potential for toxicity and no adverse effects on humans from consuming vitamin K from either food or supplements have been reported.

Table 16.7 Dietary Reference Intakes for Vitamin K. Source: Vitamin K – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated March 29, 2021. Accessed August 22, 2025. Public domain.

Age Group	RDA (or AI*) (µg/day)
Infants (0–6 months)	2.0*
Infants (7–12 months)	2.5*
Children (1–3 years)	30
Children (4–8 years)	55
Children (9–13 years)	60
Adolescents (14–18 years)	75
Adult Males (> 19 years)	120 (males), 90 (females)

Dietary Sources of Vitamin K

Vitamin K is present in many foods. It is found in highest concentrations in green vegetables such as broccoli, cabbage, kale, parsley, spinach, and lettuce. Additionally, vitamin K can be synthesized via bacteria in the large intestine. The exact amount of vitamin K synthesized by bacteria that is actually absorbed in the lower intestine is not known, but likely contributes less than 10 percent of the recommended intake. Newborns have low vitamin K stores and it takes time for the sterile newborn gut to acquire the good bacteria it needs to produce vitamin K. So, it has become a routine practice to inject newborns with a single intramuscular dose of vitamin K. This practice has basically eliminated vitamin K-dependent bleeding disorders in babies.

Table 16.8 Dietary Sources of Vitamin K. Source: Vitamin K – Health Professional Fact Sheet. National Institutes of Health, Office of Dietary Supplements. Updated March 29, 2021. Accessed March 4, 2026. Public domain.

Food	Serving	Vitamin K (µg)	Percent Daily Value
Collard greens, boiled	½ c.	530	442
Spinach, raw	1 c.	145	121
Broccoli, boiled	½ c.	110	92
Okra, raw	½ c.	16	13
Blueberries, raw	½ c.	14	12
Chicken breast	3 oz.	13	11
Grapes	½ c.	11	9
Carrots, raw	1 medium	8	7
Ground beef	3 oz.	6	5

Summary of Fat-soluble Vitamins

Table 16.9 Fat-Soluble Vitamins

Vitamin	Sources	Recommended Intake for adults	Major functions	Deficiency diseases and symptoms	Groups at risk of deficiency	Toxicity	UL
Vitamin A (retinol, retinal, retinoic acid,carotene, beta-carotene)	Retinol: beef and chicken liver, skim milk, whole milk, cheddar cheese; Carotenoids: pumpkin, carrots, squash, collards, peas	700-900 µg/day	Antioxidant, vision, cell differentiation, reproduction, immune function	Xerophthalmia, night blindness, eye infections; poor growth, dry skin, impaired immune function	People living in poverty (especially infants and children), premature infants, pregnant and lactating women people who consume low-fat or low-protein diets	Hypervitaminosis A: Dry, itchy skin, hair loss, liver damage, joint pain, fractures, birth defects, swelling of the brain	3000 µg/day
Vitamin D	Swordfish, salmon, tuna, orange juice (fortified), milk (fortified), sardines, egg, synthesis from sunlight	15-20 µg/day	Absorption and regulation of calcium and phosphorus, maintenance of bone	Rickets in children: abnormal growth, misshapen bones, bowed legs, soft bones; osteomalacia in adults	Breastfed infants, older adults people with limited sun exposure, people with dark skin	Calcium deposits in soft tissues, damage to the heart, blood vessels, and kidneys	100 µg/day
Vitamin E	Sunflower seeds, almonds, hazelnuts,peanuts	15 mg/day	Antioxidant, protects cell membranes	Broken red blood cells, nerve damage	People with poor fat absorption, premature infants	Inhibition of vitamin K clotting factors	1000 mcg/day from supplemental sources
Vitamin K	Vegetable oils, leafy greens, synthesis by intestinal bacteria	90-120 µg/day	Synthesis of blood clotting proteins and proteins needed for bone health and cell growth	Hemorrhage	Newborns, people on long term antibiotics	Anemia, brain damage	ND

References

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4. Kim K, et al. Changes in Intake and Major Food Sources of Carotenoids among U.S. Adults between 2009-2018. Metabolites. 2023 Dec 24; 14(1): 13. https://doi.org/10.3390/metabo14010013
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Attributions

Adapted by Pattie S. Green, Ph.D. and Jonathan E. Pottle, Ph.D. at Tacoma Community College from Human Nutrition, “Fat Soluble Vitamins,” by University of Hawai‘i at Mānoa Food Science and Human which is licensed under a Creative Commons Attribution 4.0 International License.