The answer for most of us is none.
I say most of us, because pregnant women and vegetarians often require supplements, as do those with specific metabolic disorders. The rest of us are better off saving our money.
Naturopaths and others who make their living out of promoting the sale of vitamin, mineral, and other supplements notwithstanding, very few of us need dietary supplements. In fact, they may do more harm than good. Once you move out of the areas that are CAM financed or influenced, descriptions of the actual risks and benefits are easier to find.
For example, Consumer Reports from 2012 and Forbes from 2011 both recommend not wasting your money or your health because there is little evidence for the widespread use of supplements. In some instances, the evidence points to greater risks over potential or nonexistent benefits.
There are numerous studies that have pointed out that some vitamin and mineral supplements actually increase mortality. So, as more evidence comes in, the case for dietary supplements gets weaker and weaker, even as sales increase.
Much of the drive for supplements comes from advertisements paid for by manufacturers in the multi-billion dollar supplements industry; an industry that has convinced half of the population of North America that our diet is insufficient to maintain health. News outlets, driven by ratings rather than facts, encourage articles and columns by naturopaths and others who push supplements as cure-alls for almost every ailment, supplements they are more than happy to sell to you.
CAM practitioners often claim that physicians are financed and influenced by the pharmaceutical industry, but do not turn that criticism inward, to examine the products they recommend and sell. However, a group that mostly sees patients after they have been treated by others has their own take.
From the website of the American College of Medical Toxicology
In other words, naturopaths may be dangerous to your health.