Key Findings:
There has been attention paid recently to the overwhelming changes that have occurred in omega 3 and 6 intakes over the last generation. In the hunter-gather time (40,000 or so years ago), the omega 6 to 3 ratio in the diet was relatively equal. Our genetics evolved basis this type of intake. Modern diets post the agricultural and industrial revolutions have dramatically modified the ratio such that many diets have a ratio of 16 to 1. Contributing to this trend is both lower levels of omega 3 intakes and dramatic increases in omega 6 intakes. As the ratio of omega 6 to 3 has increased, so has the prevalence of chronic disease including heart disease, diabetes, cancer, obesity and high blood pressure. The authors make a strong argument for the need to return to ratios that more closely resemble those of our ancestors.
ABSTRACT:
BACKGROUND: The consumption of omega-3 (n-3) and omega-6 (n-6) essential fatty acids in Western diets is thought to have changed markedly during the 20th century. OBJECTIVE: We sought to quantify changes in the apparent consumption of essential fatty acids in the United States from 1909 to 1999. DESIGN: We calculated the estimated per capita consumption of food commodities and availability of essential fatty acids from 373 food commodities by using economic disappearance data for each year from 1909 to 1999. Nutrient compositions for 1909 were modeled by using current foods (1909-C) and foods produced by traditional early 20th century practices (1909-T). RESULTS: The estimated per capita consumption of soybean oil increased >1000-fold from 1909 to 1999. The availability of linoleic acid (LA) increased from 2.79% to 7.21% of energy (P < 0.000001), whereas the availability of alpha-linolenic acid (ALA) increased from 0.39% to 0.72% of energy by using 1909-C modeling. By using 1909-T modeling, LA was 2.23% of energy, and ALA was 0.35% of energy. The ratio of LA to ALA increased from 6.4 in 1909 to 10.0 in 1999. The 1909-T but not the 1909-C data showed substantial declines in dietary availability (percentage of energy) of n-6 arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Predicted net effects of these dietary changes included declines in tissue n–3 highly unsaturated fatty acid status (36.81%, 1909-T; 31.28%, 1909-C; 22.95%, 1999) and declines in the estimated omega-3 index (8.28, 1909-T; 6.51, 1909-C; 3.84, 1999). CONCLUSION: The apparent increased consumption of LA, which was primarily from soybean oil, has likely decreased tissue concentrations of EPA and DHA during the 20th century. (Authors Abstract)