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Vitamins
Definition
Vitamins are a group of substances that are essential for normal cell function, growth, and development.
There are 13 essential vitamins, meaning they are needed for the body to function. They are:
- Vitamin A
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
- Vitamin B1 (thiamine)
- Vitamin B2 (riboflavin)
- Vitamin B3 (niacin)
- Pantothenic acid
- Biotin
- Vitamin B6
- Vitamin B12
- Folate (folic acid)
Vitamins are grouped into two categories:
- Fat-soluble vitamins are stored in the body's fatty tissue. The four fat-soluble vitamins are vitamins A, D, E, and K.
- There are nine water-soluble vitamins. The body must use water-soluble vitamins right away. Any left over water-soluble vitamins leave the body through the urine. Vitamin B12 is the only water-soluble vitamin that can be stored in the liver for many years.
Function
Each of the vitamins listed below has an important job in the body. A vitamin deficiency occurs when you do not get enough of a certain vitamin. Vitamin deficiency can cause health problems.
Not eating enough fruits, vegetables, beans, lentils, whole grains and fortified dairy foods may increase your risk for health problems, including heart disease, cancer, and poor bone health (osteoporosis).
- Vitamin A helps form and maintain healthy teeth, bones, soft tissue, mucus membranes, and skin.
- Vitamin B6 is also called pyridoxine. Vitamin B6 helps form red blood cells and maintain brain function. This vitamin also plays an important role in the proteins that are part of many chemical reactions in the body. Eating larger amounts of protein may reduce vitamin B6 levels in the body.
- Vitamin B12, like the other B vitamins, is important for metabolism. It also helps form red blood cells and maintain the central nervous system.
- Vitamin C, also called ascorbic acid, is an antioxidant that promotes healthy teeth and gums. It helps the body absorb iron and maintain healthy tissue. It also promotes wound healing.
- Vitamin D is also known as the "sunshine vitamin," since it is made by the body after being in the sun. Ten to 15 minutes of sunshine three times a week is enough to produce the body's requirement of vitamin D. People who do not live in sunny places may not make enough vitamin D. It is very difficult to get enough vitamin D from food sources alone. Vitamin D helps the body absorb calcium, which you need for the normal development and maintenance of healthy teeth and bones. It also helps maintain proper blood levels of calcium and phosphorus.
- Vitamin E is an antioxidant also known as tocopherol. It plays a role in the formation of red blood cells and helps the body use vitamin K.
- Vitamin K is not listed among the essential vitamins, but without it blood would not stick together (coagulate). Some studies suggest that it is important for promoting bone health.
- Biotin is essential for the metabolism of proteins and carbohydrates, and in the production of hormones and cholesterol.
- Niacin is a B vitamin that helps maintain healthy skin and nerves. It is also has cholesterol-lowering effects.
- Folate works with vitamin B12 to help form red blood cells. It is needed for the production of DNA, which controls tissue growth and cell function. Any woman who is pregnant should be sure to get enough folate. Low levels of folate are linked to birth defects such as spina bifida. Many foods are now fortified with folic acid.
- Pantothenic acid is essential for the metabolism of food. It is also plays a role in the production of hormones and cholesterol.
- Riboflavin (vitamin B2) works with the other B vitamins. It is important for body growth and the production of red blood cells.
- Thiamine (vitamin B1) helps the body cells change carbohydrates into energy. Getting plenty of carbohydrates is very important during pregnancy and breast-feeding. It is also essential for heart function and healthy nerve cells.
Food Sources
FAT-SOLUBLE VITAMINS
Vitamin A:
- Dark-colored fruit
- Dark leafy vegetables
- Egg yolk
- Fortified milk and dairy products (cheese, yogurt, butter, and cream)
- Liver, beef, and fish
Vitamin D:
- Fish (fatty fish such as salmon, mackerel, herring, and orange roughy)
- Fish liver oils (cod's liver oil)
- Fortified cereals
- Fortified milk and dairy products (cheese, yogurt, butter, and cream)
Vitamin E:
- Avocado
- Dark green vegetables (spinach, broccoli, asparagus, turnip greens)
- Margarine (made from safflower, corn, and sunflower oil)
- Oils (safflower, corn, and sunflower)
- Papaya and mango
- Seeds and nuts
- Wheat germ and wheat germ oil
Vitamin K:
- Cabbage
- Cauliflower
- Cereals
- Dark green vegetables (broccoli, Brussels sprouts, asparagus)
- Dark leafy vegetables (spinach, kale, collards, turnip greens)
- Fish, liver, beef, eggs
WATER-SOLUBLE VITAMINS
Biotin:
- Chocolate
- Cereal
- Egg yolk
- Legumes
- Milk
- Nuts
- Organ meats (liver, kidney)
- Pork
- Yeast
Folate:
- Asparagus and broccoli
- Beets
- Brewer's yeast
- Dried beans (cooked pinto, navy, kidney, and lima)
- Fortified cereals
- Green, leafy vegetables (spinach and romaine lettuce)
- Lentils
- Oranges and orange juice
- Peanut butter
- Wheat germ
Niacin (vitamin B3):
- Avocado
- Eggs
- Enriched breads and fortified cereals
- Fish (tuna and salt-water fish)
- Lean meats
- Legumes
- Nuts
- Potato
- Poultry
Pantothenic acid:
- Avocado
- Broccoli, kale, and other vegetables in the cabbage family
- Eggs
- Legumes and lentils
- Milk
- Mushroom
- Organ meats
- Poultry
- White and sweet potatoes
- Whole-grain cereals
Thiamine (vitamin B1):
- Dried milk
- Egg
- Enriched bread and flour
- Lean meats
- Legumes (dried beans)
- Nuts and seeds
- Organ meats
- Peas
- Whole grains
Pyroxidine (vitamin B6):
- Avocado
- Banana
- Legumes (dried beans)
- Meat
- Nuts
- Poultry
- Whole grains (milling and processing removes a lot of this vitamin)
Vitamin B12:
- Meat
- Eggs
- Fortified foods such as soymilk
- Milk and milk products
- Organ meats (liver and kidney)
- Poultry
- Shellfish
NOTE: Animal sources of vitamin B13 are absorbed much better by the body than plant sources
Vitamin C (ascorbic acid):
- Broccoli
- Brussels sprouts
- Cabbage
- Cauliflower
- Citrus fruits
- Potatoes
- Spinach
- Strawberries
- Tomato juice
- Tomatoes
Side Effects
Many people think that if some is good, a lot is better. This is not always the case. High doses of certain vitamins can be poisonous. Ask your doctor what is best for you.
Recommendations
The Recommended Dietary Allowances (RDAs) for vitamins reflect how much of each vitamin most people should get each day.
- The RDA for vitamins may be used as goals for each person.
- How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and your health, are also important.
The best way to get all the daily vitamins you need is to eat a balanced diet that contains a wide variety of fruits, vegetables, fortified dairy foods, legumes (dried beans), lentils, and whole grains.
Dietary supplements are another way to get the vitamins you need if the food you eat is not supplying enough vitamins. Supplements can be helpful during pregnancy and for special medical problems.
If you take supplements, DO NOT take more than 100% of the RDA. Be very careful about taking large amounts of fat-soluble vitamin supplements -- vitamins A, D, E, and K. Because these vitamins are stored in fat cells, they can build up in your body and may cause harmful effects.
References
Escott-Stump S, ed. Nutrition and Diagnosis-Related Care. 6th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2008.
Sarubin Fragaakis A, Thomson C. The Health Professional's Guide to Popular Dietary Supplements. 3rd ed. Chicago, IL. American Dietetic Association; 2007.
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academy Press, Washington, DC, 2000.
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron Manganese, Molybdenium, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001.
Reviewed By: Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center Diabetes Care Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
