Vitamins are micronutrients essential for daily functioning. Thirteen types of vitamins are required for your body to stay healthy. Organic compounds are considered vitamins if a lack of the compound in your diet causes health problems. Each vitamin has a specific function, and deficiency in any of them can cause health issues, including neurological disorders, bone degeneration and diseases of the central nervous system. The majority of your daily vitamin requirements come food, and you can also add vitamin supplements to your diet.
Fat-Soluble and Water-Soluble Vitamins
Vitamins are soluble in either fat or water. The fat-soluble vitamins are absorbed by your small intestine, then stored in your fatty tissue and slowly excreted for later use. Vitamins A, D, E and K are fat-soluble. Your body does not require daily doses of fat-soluble vitamins, however, many foods contain small amounts of these vitamins. Water-soluble vitamins dissolve in water before your body absorbs them, and these vitamins are metabolized rapidly. You need daily doses of water-soluble vitamins to stay healthy. The B vitamins and vitamin C are water-soluble, and many foods you eat daily have abundant amounts of these vitamins. Water-soluble vitamins not used by your body are eliminated through urine.
Function, Intake and Upper Limits of Fat-Solubles
Vitamin A contributes to a healthy immune system, bone development and vision. The recommended dietary allowance for vitamin A in adults is 700 to 900 mcg per day, with an upper limit not to exceed 3,000 mcg. Vitamin D helps your body absorb calcium for bone health and helps your immune system fight bacteria and viruses. Vitamin D is recommended for adults at 15 mcg per day, with an upper limit of 100 mcg. Vitamin E is an antioxidant that protects your cells from toxins. Vitamin E is also important in the formation of red blood cells and helping your body use vitamin K. Vitamin K promotes blood coagulation and bone metabolism. Dietary allowance for vitamin E in adults is 15 mg daily, with an upper limit of 1,000 mg. The daily allowance for vitamin K is 90 to 120 mcg, with no upper limit precaution.
Function, Intake and Upper Limits of Water-Solubles
There are eight specific types of B vitamins. Thiamine, riboflavin and niacin make up the first set of the B group, followed by pantothenic acid, pyridoxine, biotin, folic acid and cobalamin. As a whole, the B vitamin group maintains central nervous system functioning by supporting metabolism, cell growth and brain health. Similar foods contain several B vitamins. The recommended daily allowances for the group range from 30 mcg to 16 mg, and these amounts can be easily consumed through a healthy diet. B vitamins from food will not result in adverse effects, but it's possible to exceed the upper limit doses by taking too much of a B vitamin supplement. Read supplement labels for the correct dosages.
Vitamin C is an antioxidant that protects your immune system, and aids in healing wounds and in the absorption of iron. Recommended dietary intake is 75 to 90 mg per day, with an upper limit of 2,000 mg.
Vitamins in Food
Food is the best source of daily vitamin needs, as opposed to taking supplements. A diet rich in plant-based foods like vegetables, fruit and grains contains the majority of vitamins. Animal-based foods including eggs, dairy and meats contain all the B vitamins in addition to vitamins A and D. To get your daily requirement of vitamins without taking additional supplements, eat four to six small meals daily, and include each basic food group in most meals. Take multivitamins only as an adjunct to a healthy diet, not as a replacement for food.
References
- National Institute of Medicine: Dietary Reference Intakes
- Office of Dietary Supplements: Supplement Fact Sheet: Vitamins and Minerals
- MayoClinic.com: Dietary Supplements; Nutrition in a Pill?
- Nemours Foundation: Vitamins and Minerals
- FamilyDoctor.org: Dietary Supplements; What You Need to Know
- Linus Pauling Institute: Micronutrient Information Center
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