Why do I need vitamins in my diet?

Your body needs vitamins -- 13 of them -- in order to carry out many of its day-to-day operations. But it can only make two of them, vitamins D and K, and it doesn't always make enough of those. So in general, you have to consume the vitamins you need.

A balanced diet can usually do the trick, but your doctor may recommend supplements in some situations. For instance, supplements may be a good idea if you have a particular health problem, or if you're a vegetarian or are pregnant or breast-feeding. However, moderation matters. You can get sick from both under-supplies and over-supplies of some vitamins.
Deborah Beauvais
Nutrition & Dietetics
Vitamins have many functions and influence the health of nearly every organ in the body. Their combination with other substances such as minerals, proteins and enzymes brings about certain chemical reactions. Individual vitamins have specific functions which vary widely and can overlap. They are involved in growth, the ability to produce healthy offspring and the maintenance of health. They play a role in metabolism, enabling the body to use other essential nutrients such as carbohydrates, fats, proteins and minerals. Vitamins are important for a normal appetite, in digestion, mental alertness and resistance to bacterial infections.

In addition to satisfying the body’s daily needs and preventing deficiency diseases, vitamins have several therapeutic effects. For example, niacin can be used to lower cholesterol and vitamin A derivatives can be used to treat acne. Large doses of vitamins may slow, or even reverse many diseases previously thought an inevitable part of aging, such as cancer, heart disease, osteoporosis, impaired immunity, nerve degeneration and other chronic health problems.
Vitamins are not substitutes for food. They cannot be assimilated without taking in food. They have no energy value of their own and are not components of body structures.
Kelly Traver
Internal Medicine
Vitamins are required in a variety of chemical reactions critical for sustaining life. Some vitamins are fat-soluble, including vitamins A, D, E, and K. These vitamins are not easily excreted, so they can reach toxic levels if you ingest too much. This usually happens only if you take large quantities of vitamin supplements.

The water-soluble vitamins are the B vitamins and vitamin C. These vitamins are easily excreted. I don't recommend megadoses of any vitamins or supplements, but if you do take megadoses of these vitamins, you will just urinate the excess amount out of your system.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.