I’ll often see a dietary study referenced as support for a supplement or, more rarely, vice versa. A dietary study looks at the nutrients in certain foods, while a dietary supplement study looks at taking a specific supplement. You can’t apply the conclusions about nutrients in the diet, say omega-3s or vitamin D, to the individual supplements. It’s like comparing apples and tennis balls. For example, based on dietary studies, researchers believed beta-carotene was the active component in many plant foods that was reducing the risk of heart disease and cancer.
But in several supplement studies of beta-carotene, people who took the pill ended up with an increased risk of lung cancer if they were current or possibly even former smokers, and in all the other trials, it showed no health benefit. (And there went hundreds of millions of dollars on clinical trial research!) Similarly, eating foods with selenium might reduce the risk of cancer, but taking selenium to prevent cancer has shown no benefit (and, again, it cost hundreds of millions of taxpayer dollars to show this).
The take-home message here is, if someone is selling you a supplement and referring to dietary studies with that ingredient, it proves nothing and it’s likely a waste of your money. Always look at how the supplement itself has performed in clinical trials. As I was writing this section, I came across an “expert” on the Internet using studies of magnesium rich–food that showed a reduced risk of bone fractures and high blood pressure as a reason to buy a special magnesium supplement. And the beat goes on!
The Supplement Handbook - Mark Moyad
