Wow! What a topic this one turned out to be.... age and gender seem to be the biggest issue. So what I am going to do is lay out specific facts and let you decide what is best for your body!
The common denominator was a multivitamin almost all experts and studies recommended taking a multivitamin. With that said, there are multivitamins for men and women and children too! They are different dosage of various vitamins, there are also multivitamins for over 50. Another interesting fact is men don't need extra calcium, and high intake might increase the risk of prostate cancer. Women receiving vitamin E experienced a statistically significant 24 percent reduction in total cardiovascular disease mortality.
Fish oil was another common vitamin. Some studies have found fish oil, which contains omega 3 fatty acids, can help lower triglyceride levels, lower blood pressure, and help depression, among other uses. Some take a B6 or B12 for weight loss and energy, if you are taking folic acid, which is a B vitamin, you'll do better when you also take the other Bs that make up the B complex. That's how nutrients occur naturally and how the body best utilizes them, so take a B complex (I do everyday) not just one B vitamin.
Postmenopausal women almost never need iron, and taking too much might pose a risk for heart health.
More than 150 million Americans take dietary supplements according to the Council for Responsible Nutrition, a supplement industry trade group. They all take at least two supplements -- some take three or four or more. The Journal of the American Medical Association, also found that vitamin E even appeared to raise the risk of bleeding strokes, which, while rare, are often the most deadly.
The experts also agree that taking vitamins is only part of the larger puzzle. You also need to watch your diet and exercise.