An academic article warns the ineffectiveness of multi vitamins and other supplements.
Anals of Internal Medicine: Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements
In this document with an exaggerated title, Guallar et al. refers three articles which clarified that several supplements had not been beneficial to prevent chronic diseases. The authors conclude that the vast normal people should not take supplement for health.
It should be pointed out that this article is only an editorial. Editorials are not usually evaluated by other researchers before publication. As far as I assess, the level of reliability as a review of this article is low, since the authors have not searched the past studies comprehensively. Reading this article we cannot know whether there are some studies which is opposed to the claim of the authors.
Nonetheless, I agree with this paper in the gist. In general, taking supplements has minimal effect to improve your health.
This article caused a broad discussion not only in the US but also in Japan. There are many opinions about this matter in an internet forum attached with the reference article. I read through it to notice some readers made points.
First of all, basic customs of diet considerably differ in each country. American people tend to take more fat than Japanese. In contrast, Japanese are fond of eating fishes which include protein. Since most of the participants of the past investigation referred were Western, this result is not easy to adapt to Japanese.
Second, as the authors commented, there are a few people with congenital deficiency of metabolism. For those patients, supplementary therapy is indispensable. In addition, perhaps there are persons who can receive the benefit for some other reasons. This kind of results of small specific samples tend not to be clarified in a mega survey.
After all, it is no doubt that supplements cannot completely substitute for usual diet. There is no elixir in the world. I hope the users take supplement in appropriate manner without being deceived.