Background: The worldwide diversity of dietary intakes of n-6 and n-3 fatty acids influences tissue compositions of n-3 long-chain fatty acids (LCFAs: eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) and risks of cardiovascular and mental illnesses.

Objective: We aimed to estimate healthy dietary allowances for n-3 LCFAs that would meet the nutrient requirements of 97-98% of the population.

Design: Deficiency in n-3 LCFAs was defined as attributable risk from 13 morbidity and mortality outcomes, including all causes, coronary heart disease, stroke, cardiovascular disease, homicide, bipolar disorder, and major and postpartum depressions. Dietary availability of n-3 LCFAs from commodities for 38 countries and tissue composition data were correlated by best fit to each illness in deficiency risk models.

Results: The potential attributable burden of disease ranged from 20.8% (all-cause mortality in men) to 99.9% (bipolar disorder). n-3 LCFA intake for Japan (0.37% of energy, or 750 mg/d) met criteria for uniformly protecting >98% of the populations worldwide. n-3 LCFA intakes needed to meet a tissue target representative of Japan (60% n-3 in LCFA) ranged from 278 mg/d (Philippines, with intakes of 0.8% of energy as linoleate, 0.08% of energy as alpha-linolenate, and 0.06% of energy as arachidonic acid) to 3667 mg/d (United States, with 8.91% of energy as linoleate, 1.06% of energy as alpha-linolenate, and 0.08% of energy as arachidonic acid).

Conclusions: With caveats inherent for ecologic, nutrient disappearance analyses, a healthy dietary allowance for n-3 LCFAs for current US diets was estimated at 3.5 g/d for a 2000-kcal diet. This allowance for n-3 LCFAs can likely be reduced to one-tenth of that amount by consuming fewer n-6 fats.