Nutrition Science

Nutrition science — the study of how food affects health — is one of the most confusing and politically contested fields in science. The history of dietary guidelines is a cautionary tale: fat was demonized from the 1960s (Ancel Keys's flawed Seven Countries Study), leading to the low-fat movement and substitution of fat with sugar — which may have worsened obesity and cardiovascular health. Trans fats (introduced as a 'healthy' alternative to saturated fat) were banned 50 years later after causing millions of deaths. Robust nutritional knowledge: dietary fiber reduces colorectal cancer risk; omega-3 fatty acids reduce cardiovascular risk; vitamin D deficiency is nearly universal in Northern climates and linked to depression, immune dysfunction, and bone loss; processed foods' ultra-refined carbohydrates and additives drive obesity and metabolic syndrome; the Mediterranean diet consistently shows the strongest evidence for longevity. Less certain: specific superfoods, precise macronutrient ratios, optimal meal timing, and individual variation in response to diet.