Americans have relied on federal dietary guidelines with assurance that the recommendations apply to everyone. Today we have the allure of the personalized diet based on genetic markers, lifestyle information, cholesterol data, gut microbiome and chronic disease.

One popular genetic test, performed on yours truly, showed genetic predispositions to red meat and fast food, even proposing sensitivity to caffeine, but not offering specific diet or medical advice.

According to an article by Jamie Ducharme in Time magazine, people following the same diet can have markedly different results. Our meta...