U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. is right about one thing: chronic disease is on the rise in America, and the food system is at least partly responsible. But his “Make America Healthy Again” campaign stumbles by relying on weak evidence to target specific foods.Take seed oil. Kennedy has labeled oils from sunflower, safflower, and canola seeds as “poison” and a driving force behind the obesity epidemic. The concern stems from their high levels of omega-6 fatty acids, compared with the omega-3s found in olive oil. Some studies have linked a higher omega-6-to-omega-3 ratio to poorer health outcomes.What is the problem? Most of these studies are not designed to prove cause and effect. Seed oils are common in processed and fast foods because they are ch...