Vitamins: what they are and what they do

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 and water soluble vitamins

Vitamins are either fat-soluble or water-soluble.

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

Below, we run through the different types of vitamins.

Vitamin A

Carrots are a good source of vitamins A and B3.

  • 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

More information is available in our Vitamin A article.

Vitamin B

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

More information is available in our Vitamin B article.

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

Broccoli belongs to the cruciferous vegetable family and is a good source of vitamins A, B3, and B5.

  • 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

More information is available in our Vitamin B3 article.

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

More information is available in our Vitamin B5 article.

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.

More information is available in our Vitamin B6 article.

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

More information is available in our Vitamin B7 article.

Vitamin 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.

More information is available in our Vitamin B9 article.

Vitamin B12

Eggs are a good source of 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

More information is available in our Vitamin B12 article.

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.

More information is available in our Vitamin C article.

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.

More information is available in our Vitamin D article.

Vitamin E

Almonds are a good source of 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.

More information is available in our Vitamin K article.

The US National Library of Medicine says that the best way to get enough vitamins for good health is to follow a balanced diet with a wide range of foods. Some people may need to take a daily multivitamin.

Vitamin wheel

Use this easy-to-reference diagram to learn about the vitamin groups and common foods containing them.

Video: The ABCs of vitamins

The ABCD’s of Vitamins (Video Medical And Professional 2020).

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