Vitamins: What They Are and What They Do

Vitamins are organic compounds which are needed in small quantities to sustain life. We need to take vitamins from food because the human body either does not produce enough of them or none at all.

Each organism has different vitamin requirements. For example, vitamin C (ascorbic acid) is necessary for humans but not for dogs, because dogs can produce (synthesize) enough for their own needs, while humans cannot.

This article explains what vitamins are, what they do, and what foods provide each type.

Here are some key points about vitamins. More detail and supporting information is in the main article.

• There are 13 known vitamins
• Vitamins are either water-soluble or fat-soluble
• Fat-soluble vitamins are easier for the body to store than water-soluble
• Vitamins always contain carbon, so they are described as "organic"

What are Vitamins

A vitamin is one of a group of organic substances, present in minute amounts in natural foodstuffs; they are essential to normal metabolism. If we do not take enough of these compounds, certain medical conditions can result.

Put simply, a vitamin is both:

• An organic compound (contains carbon)
• An essential nutrient the body cannot produce enough of and which it needs to get from food

There are currently 13 recognized vitamins.

Fat-soluble vitamins

Fat-soluble vitamins are stored in the fatty tissues of the body and the liver. Fat-soluble vitamins are easier to store than water-soluble ones and can stay in the body as reserves for days, some of them for months.

Fat-soluble vitamins are absorbed through the intestinal tract with the help of fats (lipids).

Vitamins A, D, E, and K are fat-soluble.

Water-soluble vitamins

Water-soluble vitamins do not get stored in the body for long - they soon get excreted in urine. Because of this, water-soluble vitamins need to be replaced more often than fat-soluble ones.

Vitamins C and all the B vitamins are water-soluble.

List of vitamins

Vitamin A 

• Chemical names - retinol, retinal, and four carotenoids (including beta carotene)
• Fat soluble
• Deficiency may cause night-blindness and keratomalacia (an eye disorder that results in a dry cornea)
• Good sources include: liver, cod liver oil, carrots, broccoli, sweet potato, butter, kale, spinach, pumpkin, collard greens, some cheeses, egg, apricot, cantaloupe melon, and milk.

Vitamin B

• Chemical name - thiamine
• Water soluble.
• Deficiency may cause beriberi and Wernicke-Korsakoff syndrome.
• Good sources include: yeast, pork, cereal grains, sunflower seeds, brown rice, whole-grain rye, asparagus, kale, cauliflower, potatoes, oranges, liver, and eggs.

Vitamin B2

• Chemical name - riboflavin.
• Water soluble.
• Deficiency may cause ariboflavinosis.
• Good sources include: asparagus, bananas, persimmons, okra, chard, cottage cheese, milk, yogurt, meat, eggs, fish, and green beans.

Vitamin B3.

• Chemical names - niacin, niacinamide.
• Water soluble.
• Deficiency may cause pellagra (characterized by diarrhea, dermatitis, and mental disturbance).
• Good sources include: liver, heart, kidney, chicken, beef, fish (tuna, salmon), milk, eggs, avocados, dates, tomatoes, leafy vegetables, broccoli, carrots, sweet potatoes, asparagus, nuts, whole-grains, legumes, mushrooms, and brewer's yeast.

Vitamin B5

• Chemical name - pantothenic acid.
• Water soluble.
• Deficiency may cause paresthesia ("pins and needles").
• Good sources include: meats, whole-grains (milling may remove it), broccoli, avocados, royal jelly, and fish ovaries.

Vitamin B6

• Chemical names - pyridoxine, pyridoxamine, pyridoxal.
• Water soluble.
• Deficiency may cause anemia, peripheral neuropathy (damage to parts of the nervous system other than the brain and spinal cord).
• Good sources include: meats, bananas, whole-grains, vegetables, and nuts. When milk is dried, it loses about half of its B6. Freezing and canning can also reduce content.

Vitamin B7

• Chemical name - biotin
• Water soluble
• Deficiency may cause dermatitis or enteritis (inflammation of the intestine)
• Good sources include: egg yolk, liver, some vegetables.

Vitatamin B9

• Chemical names - folic acid, folinic acid.
• Water soluble.
• Deficiency during pregnancy is linked to birth defects. Pregnant women are encouraged to supplement folic acid for the entire year before they get pregnant.

• Good sources include: leafy vegetables, legumes, liver, baker's yeast, some fortified grain products, and sunflower seeds. Several fruits have moderate amounts, as does beer.

Vitamin B12

• Chemical names - cyanocobalamin, hydroxocobalamin, methylcobalamin.
• Water soluble.
• Deficiency may cause megaloblastic anemia (a condition where bone marrow produces unusually large, abnormal, immature red blood cells).
• Good sources include: fish, shellfish, meat, poultry, eggs, milk and dairy products, some fortified cereals and soy products, as well as fortified nutritional yeast.
• Vegans are advised to take B12 supplements.

Vitamin C

 

• Chemical names - ascorbic acid.
• Water soluble.
• Deficiency may cause megaloblastic anemia.
• Good sources include: fruit and vegetables. The Kakadu plum and the camu camu fruit have the highest vitamin C contents of all foods. Liver also has high levels. Cooking destroys vitamin C.

It is an antioxidant which protects the body against oxidative stress. As an antioxidant, vitamin C can inhibit the oxidation of other molecules.

Oxidation reactions produce free radicals which can start chain reactions that damage cells.

Vitamin C is found principally in vegetables and fruit.

We need vitamin C to maintain and form bones, skin and blood vessels..

Vitamin C is an organic compound, so are the other vitamins. This means that it contains the elements carbon and oxygen and is a substance that exists in living things.

Vitamin C is water soluble and our body does not store it. In order to ensure that we have adequate levels of the vitamin in our system, we need to regularly receive the nutrient from the food.1

Chemical breakdown of vitamin C, according to ChemSpider:2

• Average mass: 176.1241 Da
•  Monoisotopic mass: 176.032089 Da
• Systematic name: (5R)-5-[(1S)-1,2-Dihydroxyethyl]-3,4-dihydroxy-2(5H)-furanone
• Molecular Formula: C6H8O6 

Vitamin C plays an important role in the following:

CollagenVitamin C is involved in the production of collagen. Collagen is the main component of connective tissue and the most abundant protein in mammals.
Experts say that 1% to 2% of muscle tissue is collagen.
Collagen is a vital and abundant component of fibrous tissues, such as tendon, ligament, skin, cornea, cartilage, bone, the gut, and blood vessels.
According to Linus Pauling³, "while it has been known for half a century (these words written in 1985) that vitamin C is essential to the manufacture of collagen, the process is only now yielding to inquiry. It appears that vitamin C is involved at every step."

Healing

Vitamin C plays a significant role in the healing of wounds, cuts and grazes.
One study, published in the journal Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology⁴, revealed that "wound healing in subjects judged not deficient in vitamin C can be significantly accelerated with supplements of this nutrient above the recommended daily allowance (RDA)."

Infections

Individuals with adequate levels of vitamin C are thought to be better able to fight off infections compared to people with vitamin C deficiency. There are also possible benefits of vitamin C in "the prevention of acute respiratory infections, especially in populations that are malnourished or physically stressed", according to a study titled "Vitamin C and acute respiratory infections".⁵

Recent developments on vitamin C and infections from MNT news
Vitamin C can kill drug-resistant tuberculosis bacteria. Vitamin C can kill drug-resistant tuberculosis (TB) bacteria in laboratory culture, according to experts at Albert Einstein College of Medicine of Yeshiva University. Adding vitamin C to existing TB drugs could shorten TB therapy. The finding calls attention to a novel area for drug design.⁶

Cancer

Vitamin C slows down the conversion of irritants into cancer-causing substances. Examples of irritants include tobacco smoke, smog, and some substances found in foods.
In addition, research led by Dr. Mark Levine, found that high intravenous doses of vitamin C kills cancer cells.
According to Dr. Ronald Hoffman⁷, "research currently underway has shown that high concentrations of vitamin C can stop the growth, or even kill a wide range of cancer cells. Only intravenous administration of vitamin C can deliver the high doses found to be effective against cancer."

Recent developments on vitamin C and cancer from MNT news
Vitamin C supplements affect cancer drugs. Experiments on lab cultured cells and mice suggested that high amounts of vitamin C derivative at the cellular level, as results from taking supplements, may actually reduce the effect of anti-cancer drugs by helping the cancer cells live longer.⁸

Other benefits

• Cardiovascular - experts believe vitamin C widens the blood vessels, which may help protect us from developing hypertension (high blood pressure) and heart disease.
• Cholesterol - individuals with adequate levels of vitamin C have better cholesterol level control compared to others.
• Scurvy - if you consume plenty of vitamin C you will not get scurvy, a disease that causes swollen joints, bleeding gums, loose teeth, anemia and tiredness. Scurvy used to be a problem among ship crews many years ago because of a lack of fruit and vegetable consumption.
• Eyes - vitamin C is thought to help lower the risk of cataracts.
• Diabetes patients - individuals with diabetes who eat plenty of vitamin C rich fruit and vegetables are less likely to experience deterioration of the kidneys, eyes and nerves.
• Iron - iron absorption is better if you consume plenty of vitamin C.
• Lead - levels may be considerably reduced if we have adequate quantities of vitamin C.
• Histamine - a 1992 study⁹ found that people who took 2 grams of vitamin C per day had considerably lower blood levels of histamine. Histamine is a substance our immune system produces, resulting in inflammation and other problems.

Can vitamin C treat the common cold?

Several studies have failed to produce conclusive and compelling evidence demonstrating vitamin C's use in treating the common cold, except in some rare cases.
Some studies have shown that regular consumption of vitamin C supplements makes no difference to people's risk of catching a cold. Athletes who train for long periods in subarctic conditions may have some protection from catching cold.
A small study found common cold frequency was reduced with vitamin C supplementation, but made no difference to the duration of a cold once somebody got ill - the authors of the study warned that other larger studies did not have similar findings.¹⁰
It is important to stress that those with adequate vitamin C intake are likely to catch fewer colds than individuals with vitamin C deficiency. The lack of evidence is on whether taking extra vitamin C helps cure illnesses once they start.

Recent developments on vitamin C and the common cold from MNT news
Vitamin C helps marathon runners reduce risk of catching a cold. A review of placebo-controlled trials on Vitamin C and the common cold finds the vitamin may help people under heavy physical stress, such as marathon runners and skiers, reduce their risk of catching a cold.¹¹

How much vitamin C do we need?

Men should consume 90 mg of vitamin C per day and females should consume 75 mg per day, according to the U.S. Food and Drug Administration.¹²
Experts continue to disagree what the best daily dose is for optimal health. Most health care professionals, dietitians and nutritionists agree that a well-balanced diet with lots of fruit and vegetables contains enough vitamin C for good health, with no need for supplements. Regular smokers, pregnant others and some people under stress may need more.
If you have too much vitamin C there is a risk of developing diarrhea.
Health authorities around the world have varying recommended daily intake rates:

• Food.gov.uk - 40 milligrams per day for adults, 50 mg for pregnant women, and 70mg/day during lactation¹³
• Dietitians of Canada - 75 mg/day day for females and 90 mg/day for males¹⁴

A 25-year-old man should never have more than 2,000 milligrams (2 grams) per day, according to the Institute of Medicine, USA.

Vitamin C sources

 

• Oranges and orange juice
• Strawberries
• Red and green peppers
• Broccoli
• Blackcurrants
• Potatoes
• Brussels sprouts

Vitamin D

 

• Chemical names - ergocalciferol, cholecalciferol.
• Fat soluble.
• Deficiency may cause rickets and osteomalacia (softening of the bones).
• Good sources: produced in the skin after exposure to UV (ultraviolet) B light from the sun or artificial sources. Also found in fatty fish, eggs, beef liver, and mushrooms.

Vitamin D, also known as the sunshine vitamin, can be produced in the body with mild sun exposure or consumed in food or supplements.
Adequate vitamin D intake is important for the regulation of calcium and phosphorus absorption, maintenance of healthy bones and teeth, and is suggested to supply a protective effect against multiple diseases and conditions such as cancer, type 1 diabetes and multiple sclerosis.
Vitamin D has multiple roles in the body, helping to:

• Maintain the health of bones and teeth
• Support the health of the immune system, brain and nervous system
• Regulate insulin levels and aid diabetes management
• Support lung function and cardiovascular health
• Influence the expression of genes involved in cancer development.

In spite of the name, vitamin D is considered a pro-hormone and not actually a vitamin. This is because the body is capable of producing its own vitamin D through the action of sunlight on the skin, while vitamins are nutrients that cannot be synthesized by the body and must be acquired through the diet or supplements.
It is estimated that sensible sun exposure on bare skin for 5-10 minutes 2-3 times per week allows the body the ability to produce sufficient vitamin D, but vitamin D has a half-life of only two weeks, meaning that stores can run low, especially in winter. Recent studies have suggested that up to 50% of adults and children worldwide are vitamin D deficient. There are several likely factors contributing to vitamin D deficiency, which will be looked at further in this article.
Vitamin D is produced when sunlight converts cholesterol on the skin into calciol (vitamin D3). Vitamin D3 is then converted into calcidiol (25-hydroxyvitamin D3) in the liver. The kidneys then convert calcidiol into the active form of vitamin D, called calcitriol (1,25-hydroxyvitamin D3). As such, statins and other medications or supplements that inhibit cholesterol synthesis, liver function or kidney function can impair the synthesis of vitamin D.

Fast facts on vitamin D
Here are some key points about vitamin D. More detail and supporting information is in the main article.

• Vitamin D's primary role is to support the development and maintenance of bones and teeth.
• A fair-skinned person with full body exposure to the sun can synthesize up to 20,000 IU of vitamin D3 in 20 minutes.
• Vitamin D deficiency is common, especially in the elderly, infants, people with dark skin and people living at higher latitudes or who get little sun exposure.
• Vitamin D deficiency has been seen in up to 80% of hip fracture patients.
• 800IU of vitamin D per day reduces the risk of fracture by 20% in the elderly and decreases the risk of falls.
• The metabolism of vitamin D may be affected by some medications, including barbiturates, phenobarbital, dilantin, isoniazid and statin drugs.

• Vitamin D for healthy bones

Vitamin D plays a substantial role in the regulation of calcium and maintenance of phosphorus levels in the blood, two factors that are extremely important for maintaining healthy bones. We need vitamin D to absorb calcium in the intestines and to reclaim calcium that would otherwise be excreted through the kidneys.

Vitamin D deficiency in children can cause rickets, a disease characterized by a severely bow-legged appearance triggered by impaired mineralization and softening of the bones.
In adults, vitamin D deficiency manifests as osteomalacia or osteoporosis. Osteomalacia results in poor bone density, muscular weakness and often causes small pseudo fractures of the spine, femur and humerus. Osteoporosis is the most common bone disease among post-menopausal women and older men.

• Reduced risk of flu

Children given 1,200 IU of vitamin D per day for 4 months during the winter reduced their risk of influenza A infection by over 40%.²

•  Reduced risk of diabetes

Several observational studies have shown an inverse relationship between blood concentrations of vitamin D in the body and risk of type 2 diabetes. In type 2 diabetics, insufficient vitamin D levels may have an adverse effect on insulin secretion and glucose tolerance.3 In one particular study, infants who received 2,000 IU/day of vitamin D had an 88% lower risk of developing type 1 diabetes by the age of 32.

• Healthy infants

Children with normal blood pressure who were given 2,000 IU/day had significantly lower arterial wall stiffness after 16 weeks compared with children who were given only 400 IU/day.
Low vitamin D status has also been associated with a higher risk and severity of atopic childhood diseases and allergic diseases, including asthma, atopic dermatitis and eczema. Vitamin D may enhance the anti-inflammatory effects of glucocorticoids, making it potentially useful as a supportive therapy for people with steroid-resistant asthma.^5,8

• Healthy pregnancy

Pregnant women who are deficient in vitamin D seem to be at greater risk of developing preeclampsia and needing a cesarean section. Poor vitamin D status is also associated with gestational diabetes mellitus and bacterial vaginosis in pregnant women. It is also important to note that vitamin D levels that were too high during pregnancy were associated with an increase in food allergy of the child during the first two years of life.

• Cancer prevention

Vitamin D is extremely important for regulating cell growth and for cell-to-cell communication. Some studies have suggested that calcitriol (the hormonally active form of vitamin D) can reduce cancer progression by slowing the growth and development of new blood vessels in cancerous tissue, increasing cancer cell death and by reducing cell proliferation and metastases. Vitamin D has an influence on more than 200 human genes, which can be impaired when D status is suboptimal.³
Vitamin D deficiency has also been associated with an increased risk of cardiovascular disease, hypertension, multiple sclerosis, autism, Alzheimer's disease, rheumatoid arthritis, asthma severity and swine flu, however more reliable studies are needed before these associations can be proven.

Vitamin D food sources

 

Sunlight is the most common and efficient source of vitamin D. The richest food sources of vitamin D are fish oil and fatty fish. Here is a list of foods with good levels of vitamin D:

• Cod liver oil, 1 tablespoon: 1,360 IU
• Herring, fresh, raw, 4 ounces: 1,056 IU
• Swordfish, cooked, 4 ounces: 941 IU
• Raw maitake mushrooms, 1 cup: 786 IU
• Salmon, sockeye, cooked, 4 ounces: 596 IU
• Sardines, canned, 4 ounces: 336 IU
• Fortified skim milk, 1 cup: 120 IU
• Tuna, canned in water, drained, 3 ounces: 68 IU
• Egg, chicken, whole large: 44 IU.

 

Vitamin E

 

• Chemical names - tocopherols, tocotrienols.
• Fat soluble.
• Deficiency is uncommon. Deficiency may cause hemolytic anemia in newborns (a condition where blood cells are destroyed and removed from the blood too early).
• Good sources include: kiwi fruit, almonds, avocado, eggs, milk, nuts, leafy green vegetables, unheated vegetable oils, wheat germ, and whole-grains.

Vitamin K

 

• Chemical names - phylloquinone, menaquinones.
• Fat soluble.
• Deficiency may cause bleeding diathesis (an unusual susceptibility to bleeding).
• Good sources include: leafy green vegetables, avocado, kiwi fruit. Parsley contains a lot of vitamin K.

Phylloquinone, also known as vitamin K1, is found in plants and performs the traditional functions of vitamin K. Phylloquinone is an active factor in photosynthesis and is found in high amounts in leafy green vegetables like kale and Swiss chard.
Vitamin K1 can be converted to its storage form, Vitamin K2, by bacteria in the large intestine. Vitamins K3-5 are synthetic and can be purchased as supplements.
Vitamin K plays a major role in blood clotting, bone metabolism and the regulation of blood calcium levels. It is absorbed in the small intestine and stored in fatty tissue and the liver. Vitamin K is utilized by the liver in the production of prothrombin (clotting factor).
However, vitamin K is also a nutrient of concern for many people as it can alter the effects of several common medications such as warfarin.
Vitamin K deficiency is rare and typically only occurs in people with malabsorptive conditions or after long-term treatment with antibiotics. Symptoms of deficiency include prolonged clotting time, hemorrhage and excessive bleeding.

This MNT Knowledge Center feature provides an in-depth look at the recommended intake of vitamin K and a breakdown of its possible health benefits, how to incorporate more vitamin K into your diet and any potential health risks of consuming vitamin K.

 Source :

http://www.medicalnewstoday.com/