Vitamins: Their Functions and Sources
Jan 17, · Animal sources of vitamin A include: fish liver oil. beef liver. cheese, milk, and other dairy products. Sources of beta carotene include: sweet potato. kale, spinach, and other green, leafy vegetables. carrots. cantaloupe. black-eyed peas. fortified breakfast cereals. Feb 16, · These include the following: Bone maintenance: Vitamin D regulates the circulating levels of calcium and phosphorus, which are the most important Immune system regulation: It also regulates and strengthens immune system function (23 Trusted Source).
Jump to content. The tables below list the vitaminswhat they do in the body their functionsand their sources in food. Water-soluble vitamins travel freely through the body, and excess amounts usually are excreted by the kidneys.
The body needs water-soluble vitamins in frequent, small doses. These vitamins are not as vitamuns as fat-soluble vitamins to reach toxic levels. But niacin, vitamin B6, folate, choline, and vitamin C have upper consumption limits. Vitamin B6 at high levels over a long period of time has been shown to cause irreversible nerve damage.
A balanced diet usually provides enough of these vitamins. People older than 50 and some vegetarians may need what are the 7 senses use supplements to get enough B Part of an enzyme needed for energy metabolism; important to nerve function.
Found in all nutritious foods in moderate amounts: pork, whole-grain or enriched breads and cereals, legumes, nuts and seeds. Riboflavin vitamin B2. Part of an enzyme needed for energy metabolism; important for vvitamins system, digestive system, and skin health. Meat, poultry, fish, whole-grain or enriched breads and cereals, vegetables especially mushrooms, asparagus, and leafy green vegetablespeanut butter. Part of an enzyme needed for protein metabolism; helps make red blood cells.
Folic acid. Part of an enzyme needed solubke making DNA and new cells, especially red blood cells. Leafy green vegetables and legumes, seeds, orange juice, and liver; now added to most refined grains. Antioxidant ; part of an enzyme needed for what are the functions of fat soluble vitamins metabolism; important for immune system health; aids in iron absorption.
Fag only in fruits and vegetables, especially citrus fruits, vegetables in the cabbage family, cantaloupe, strawberries, peppers, tomatoes, potatoes, lettuce, papayas, mangoes, kiwifruit. Fat-soluble vitamins are stored in the body's cells and are not excreted as easily as water-soluble vitamins.
They do not need to be consumed as often as water-soluble vitamins, although adequate amounts are needed. If you take too much of a fat-soluble vitamin, it could become toxic. Your body is especially sensitive to too much vitamin A from animal sources retinol and too much vitamin D.
A balanced diet usually provides enough fat-soluble vitamins. Needed for vision, healthy skin and mucous membranes, bone and tooth growth, immune system health. Vitamin A from animal sources retinol : fortified milk, cheese, cream, butter, fortified margarine, eggs, liver. Beta-carotene from plant sources : Leafy, dark green vegetables; dark orange fruits apricots, cantaloupe and vegetables carrots, winter squash, sweet potatoes, pumpkin.
Needed for proper absorption of calcium ; stored in bones. Egg yolks, liver, fatty fish, fortified milk, fortified margarine. When exposed to sunlight, the skin can make vitamin D. Polyunsaturated plant oils soybean, corn, cottonseed, safflower ; leafy green vegetables; wheat germ; whole-grain products; liver; egg yolks; nuts and seeds.
Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. Learn more. Top of the page. Vitamins: Their Functions and Sources. Topic Overview The tables below solublw the vitaminswhat they do in the body their functionsand their sources in food. Water-soluble vitamins Ahat vitamins travel freely through the body, and excess amounts usually are excreted by the kidneys. Needed for vision, healthy skin and mucous membranes, bone and tooth growth, immune system health Vitamin A from animal sources retinol : fortified milk, how to find my isp dns, cream, butter, fortified margarine, eggs, liver Beta-carotene from plant sources : Leafy, dark green vegetables; dark orange fruits apricots, cantaloupe and vegetables carrots, winter squash, sweet potatoes, pumpkin Vitamin D Needed for proper absorption of calcium ; stored in bones Egg yolks, liver, fatty fish, fortified milk, fortified margarine.
Vitamin E Antioxidant; protects cell walls Polyunsaturated plant oils soybean, corn, cottonseed, safflower ; leafy green vegetables; wheat germ; whole-grain products; liver; egg yolks; nuts and seeds Vitamin K Needed for proper blood clotting Leafy green vegetables such as kale, collard greens, and spinach; green vegetables such as broccoli, brussels sprouts, and asparagus; also produced in intestinal tract by bacteria.
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Current as of: December 17, Part of an enzyme needed for energy metabolism; important for normal vision and skin health. Milk and milk products; leafy green vegetables; whole-grain, enriched breads and cereals. Part of an enzyme needed for energy metabolism. What happens when you report an assault in foods; also produced in intestinal tract by bacteria.
Part of solubble enzyme needed for making new cells; important to nerve function. Meat, poultry, fish, seafood, eggs, milk and milk products; not found in plant foods. Vitamin A teh animal sources retinol : fortified milk, cheese, cream, butter, fortified margarine, eggs, liver Beta-carotene from plant sources : Leafy, dark green vegetables; dark orange fruits apricots, cantaloupe and vegetables carrots, winter squash, sweet potatoes, pumpkin.
4 rows · Sep 21, · Fat-soluble vitamins - A, D, E, and K - dissolve in fat and can be stored in your liver and. 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 . Dec 01, · Fat-soluble vitamins are vitamins that require fat to “dissolve” and be usable in the body. These are vitamins that require the addition of food – either the meal they “arrived” in, or in addition to their taking – to be turned into something transportable.
Vitamin A is a generic term for a group of similar compounds called retinoids. 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. 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.
A deficiency in vitamin A thus results in less rhodopsin and a decrease in the detection of low-level light, a condition referred to as night-blindness. Insufficient intake of dietary vitamin A over time can also cause complete vision loss.
In fact, vitamin A deficiency is the number one cause of preventable blindness worldwide. Vitamin A not only supports the vision function of eyes but also maintains the coverings and linings of the eyes.
Vitamin A deficiency can lead to the dysfunction of the linings and coverings of the eye eg. The progression of this condition can cause ulceration of the cornea and eventually blindness. 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 s, 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. UNICEF estimates that the distribution of over half a billion vitamin A capsules prevents , childhood deaths annually. 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. 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. 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. 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. 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, international units and beta-carotene had a 28 percent higher incidence of lung cancer midway through the study, which was consequently stopped.
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, micrograms per day 10, 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.
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 is given in mcg of retinol activity requirements RAE to take into account the many different forms it is available in.
The human body converts all dietary sources of vitamin A into retinol. Therefore, 1 mcg of retinol is equivalent to 12 mcg of beta-carotene, and 24 mcg of alpha-carotene or beta-cryptoxanthin. For example, 12 micrograms of fruit- or vegetable-based beta-carotene will yield 1 microgram of retinol. Currently vitamin A listed in food and on supplement labels use international units IUs. The following conversions are listed below  :. 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.
Updated September 5, Accessed October 7, The dietary sources of carotenoids will be given in the following text. In the United States, the most consumed carotenoids are alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin. See Table 9. Accessed October 22, Vitamin D refers to a group of fat-soluble vitamins derived from cholesterol. Vitamins D2 ergocalciferol and D3 calcitriol 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. 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, IU micrograms of vitamin D3.
Activated vitamin D3 calcitriol regulates blood calcium levels in concert with parathyroid hormone. 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. 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. 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 issue of the Journal of the American Medical Association, concluded that oral vitamin D supplements at doses of — 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. Many other health benefits have been linked to higher intakes of vitamin D, from decreased cardiovascular disease to the prevention of infection.
Furthermore, evidence from laboratory studies conducted in cells, tissues, and animals suggest vitamin D prevents the growth of certain cancers, blocks inflammatory pathways, reverses atherosclerosis, increases insulin secretion, and blocks viral and bacterial infection and many other things. Vitamin D deficiency has been linked to an increased risk for autoimmune diseases. Immune diseases, rheumatoid arthritis, multiple sclerosis, and Type 1 diabetes have been observed in populations with inadequate vitamin D levels.
Additionally, vitamin D deficiency is linked to an increased incidence of hypertension. Until the results come out from the VITAL study, the bulk of scientific evidence touting other health benefits of vitamin D is from laboratory and observational studies and requires confirmation in clinical intervention studies. 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. The National Osteoporosis Foundation recommends slightly higher levels and that adults under age fifty get between and international units of vitamin D every day, and adults fifty and older get between and 1, international units of vitamin D every day.
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. Source: Ross, A. J Clin Endocrinol Metab. Accessed October 10, Vitamin E occurs in eight chemical forms, of which alpha-tocopherol appears to be the only form that is recognized to meet human requirements. 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.