A wall of nutritional supplements can be incredibly seductive. The little jars with multisyllabic, unpronounceable technical names that often combine letters and numbers: CoQ10, L-carnitine L-tartrate, methylsulfonylmethane. The pictures of molecules and all the trappings of science. The cartoon-sized tubs of protein powder and the aggressive packaging. The tanned, rippling, bulging models. The delicious pictures of guilt-free “healthy” cookies and candy bars. The promise of massive gains. The nutritional-supplement industry—which includes vitamins, minerals and supplements—produced $32 billion in revenue in 2012. According to the Nutritional Business Journal, that figure is expected to double by 2021 . Everyone wants an edge, something a little extra. If you train hard, sleep well and eat right, why shouldn’t you also take supplements? The problem is many of the claims made about supplements are not supported by science, and we don’t yet understand how our b...