The biological effects of the ω-3 and ω-6 fatty acids are mediated by their mutual interactions, but it is unclear whether the dietary ratio of omega-3 fatty acids and omega-6 fatty acids is important for human health.
Ratio of omega-6 to omega-3 fats in the diets of hunter-gatherers
It has been claimed that among hunter-gatherer populations, omega-3 fats and omega-6 fats are typically consumed in roughly a 1:1 ratio. At one extreme of the spectrum of hunter-gatherer diets, the Greenland Inuit, prior to the late Twentieth Century, consumed a diet in which omega-6s and omega-3s were consumed in a 1:2 ratio, thanks to a diet rich in cold-water fish (which are a rich source of omega-3s) and completely devoid of omega-6-rich seed oils.
To date, "no one knows what the optimal ratio in the diet is for these two families of fats." Susan Allport writes that the current ratio in Japan is associated with a very low incidence of heart and other diseases. A dietary ratio of 4:1 produces almost a 1:1 ratio of highly unsaturated fatty acids (HUFAs) in cell membranes."
Andrew Stoll, who advocates the consumption of the two fats in a 1:1 ratio, states, "Once in the body, omega-3 and omega-6 fatty acids follow parallel pathways, continually competing with each other for chemical conversion to various structures and molecules inside and outside the cells. Given this mechanism, it makes sense that the two fats might be required in approximately equal amounts."
Both Stoll and Allport assert that present-day diets in the developed world have departed dramatically from this ratio. It has been estimated that in developed countries, the ratio of Omega-6s to Omega-3s is closer to 15:1 Another estimate is that "[t]he diet consumed by the typical American tends to contain 14 - 25 times more omega-6 fatty acids than omega-3 fatty acids."
^Marventano, S; Kolacz, P; Castellano, S; Galvano, F; Buscemi, S; Mistretta, A; Grosso, G (2015). "A review of recent evidence in human studies of n-3 and n-6 PUFA intake on cardiovascular disease, cancer, and depressive disorders: does the ratio really matter?". International journal of food sciences and nutrition. 66 (6): 611–22. doi:10.3109/09637486.2015.1077790. PMID26307560.
^"Populations maintaining historic omega-6 to omega-3 ratios (approximately 1 to 1) are protected from many of the scourges of the modern age." Source: Andrew Stoll, The Omega-3 Connection. New York: Simon and Schuster, 2001, p. 43.
^William Lands, Fish, Omega-3 and Human Health. Urbana, Illinois: APCS Press, 2005, p. 10.
^ abSusan Allport, The Queen of Fats: Why Omega-3 Fats Were Removed From the Western Diet and What We Can Do to Replace Them. Berkeley: University of California Press, 2007, p. 115.
^Andrew Stoll, The Omega-3 Connection. New York: Simon and Schuster, 2001, p. 40.