Furthermore, many prescription and over-the-counter medications increase our need for certain vitamins and minerals. For example, birth control pills cause decreases in zinc, folic acid, vitamin B12, vitamin B6 and vitamin C. Aspirin causes increased loss of vitamin C. Pollution, stress, exercise, alcohol and particular family history or risk factors all cause an increased need for vitamin supplements. Complete vitamin-mineral supplementing is the only effective way to ensure that all the essential interactions take place.

To help people maintain good health, health organizations in many countries have established tables of recommended daily allowances (RDA). These tables list the minimum amount of a vitamin or mineral required daily to prevent diseases when one is in otherwise good health. Many people believe that much higher doses of vitamins and minerals are beneficial, especially in the prevention of health problems like heart disease and cancer. These levels are referred to as the optimal daily intake (ODI) and are significantly higher than the RDAs. The ODI is an unofficial range of nutrient values designed to address optimal health and the prevention of disease based on clinical studies. Vitamins and minerals may also be taken in higher dosages for short periods of time for therapeutic effect. For example, vitamin C and zinc may be taken at higher levels during a cold or the flu.

Different people have different needs. Teenagers need different vitamins in different amounts than elderly people do, women usually need more iron and calcium than men and vegetarians most often need a multivitamin supplement to stay in good health. Following the recommended daily allowance is always safe, but you should have your doctor test your blood or urine for deficiencies to to find out if you need more of a certain nutrient. Testing your blood's antioxidant level is also a good way to measure whether your body is producing the correct amount of enzymes.

Generally, most vitamins are best tolerated and absorbed when taken with food. They are also best taken in dosages spaced throughout the day rather than all at once to maintain proper intake levels. If you must take them all at once, be sure to take them with your largest meal of the day.

What forms of minerals are most beneficial?

Not all forms of vitamins and minerals are alike; some are more readily absorbed than others. Capsules are usually the most absorbable compared to tablets. Tablets and timed-released pills may be difficult for some people to break down, particularly if they are experiencing low levels of stomach acid or digestive enzymes.