The Journal of the American Medical Association is looking at trends in dietary supplement use from 1999 to 2012. Studies over the last two decades have found little evidence of whether or not they benefit you. Despite that the vitamin and supplement industry continues to grow.

It is now a $32,000,000,000 a year business, Pieter Cohen, MD,from the Cambridge Health Alliance says, "Supplements are tremendously popular. In the late 1980s, more than one-third of Americans were using these sort of products. And today a little more than half of all American adults use dietary supplements."

In the current issue of JAMA, Dr. Pieter Cohen discusses the results of a new study examining trends in dietary supplement use. They asked 38,000 people about what vitamins, minerals, and supplements they used. They then compared the results to identify trends and changes. Dr. Cohen says, "There was very high use of supplements going into, at the start of the study in 1999, 52%. What's interesting is that did not budge at all over the next 13 years and it was exactly the same, 52% at the end of the 13 years."

Cohen says he is surprised that supplement usage has stayed the same even though studies have shown that many supplements have little to no benefit adding "how will a consumer know if a supplement has certain side effects or risks? These are things that are not well presented given today's regulatory environment. And I think those are some major questions for the near future."

The supplement with largest increase over the past 13 years is Vitamin D. The number of adults taking this supplement is up nearly 200%. Vitamin D may be beneficial for heart disease and some cancers.