Myth 5: “Studies Have Shown…” Means that Clinical Research Conclusively Showed Whatever Statement Follows
The Truth: Most studies that “show” a vitamin/mineral supplement provides a health benefit are observational ones, which survey people about various behaviors (e.g., diet, exercise, supplement use), then use statistical analyses to identify links with disease. When an observational research finds, “People who took a multivitamin, daily, for ‘X’ number of years have an ‘X’ percent lower chance of developing colon cancer than those who didn’t,” one can’t assume that the multivitamin (not a combination of factors) was fully responsible. Surveys show that supplement users tend to practice other healthy habits, too—eating lots of vegetables, shunning cigarettes and exercising regularly—so it’s hard to tease out a single protective factor.
This is why diet/disease links found in observational studies must be confirmed in controlled randomized clinical trials. In these “gold-standard” investigations, researchers deliver specific nutrient doses to one group and placebo “sugar supplements” to another (neither the subjects nor the investigators know who’s getting what) to test whether a supplement is really responsible for observed benefits.
The Bottom Line: Supplement makers don’t have to say how scientifically conclusive their studies are.