Eating healthy, well-balanced meals and snacks is the most important thing. In particular, you should be eating five servings of fruits and vegetables a day. If your eating isn't well-rounded, a vitamin supplement isn't going to help much. Foods contain many beneficial substances that you just cannot get in pill form.

That all said, there are certain groups of people who may need supplements:
Women - calcium, iron, folic acid
Adolescents - calcium, iron, multi-vitamin/mineral
Seniors - multi-vitamin/mineral, calicium, vitamin D, vitamin B12
Vegetarians - calcium, vitamin D, iron, vitamin B12
Smokers - vitamin C

Almost anyone could potentially benefit from a vitamin and mineral supplement if their eating is less than optimal all the time. Your best bet is to pick one with no more than 100 to 150 percent of the daily value for the listed vitamins and minerals (there should be at least 20 listed). Make sure it contains 400 mg of folic acid and 400 IU of vitamin D. Men may want a supplement without iron because they need less iron than women. Store-brand supplements are just as good as name-brand supplements, so compare.

Vitamin C and E are two vitamins that are getting closer examination for people with diabetes. Both are antioxidants, i.e. substances that neutralize or inactivate free radicals. Free radicals are trouble-makers. They are unstable oxygen molecules that damage cells, which in turn can lead to diseases like cancer, heart disease and nerve disease. These free radicals are formed by pollution, ultraviolet light, X rays, and even one's own body metabolism. By neutralizing free radicals, it is believed that we can prevent some of the damage caused by these harmful molecules.

People with diabetes tend to have lower levels of vitamin C in their bodies, which may be due to higher blood sugar levels hampering the uptake of Vitamin C by cells. A 1995 study that gave 2,000 mg of vitamin C to people with type 2 diabetes showed an improvement in both blood sugar levels and lipid (cholesterol and triglyceride) levels. More research needs to be done, however. Also, more than 1,000 mg daily may cause kidney stones, diarrhea or other problems.

There is also mounting evidence that vitamin E may prevent heart disease, and may also play a role in preventing kidney and/or eye damage — all of which are problems for people with diabetes. However it's too early to make definite conclusions or to know what the right amount might be to get these beneficial effects. The recommended daily requirement for vitamin E is 30 IU, although the antioxidant properties of vitamin E seem to kick in at doses of at least 100 IU or more. Amounts greater than 800 IU may increase the risk of stroke in people with high blood pressure and may interfere with medication that prevents blood clots.

Chromium, in the form of chromium picolinate, has received a lot of press over the past few years, thanks to claims that it can reduce body fat and build muscle, all without dieting. No good evidence exists that chromium is effective in weight loss; but several studies over the past 30 years have suggested that it may help improve blood glucose and lipid levels. Unfortunately, chromium is a trace vitamin so it's hard to measure how much people take or how much we need. Fortunately, it is relatively safe. In fact, many health care providers routinely recommend chromium supplementation for their patients with diabetes, especially those with type 2. Don't take a chromium supplement without first discussing it with your health care team. Recommended dose is 50-200 mcg, and don't take more than 400 mcg. Kidney damage and chromosome damage may occur in extremely high amounts.