Only two essential fatty acids are known to be essential for humans: alpha-linolenic acid (an omega−3 fatty acid) and linoleic acid (an omega−6 fatty acid). Closely related, these fatty acids act as competing substrates for the same enzymes. The biological effects of the ω−3 and ω−6 fatty acids are largely mediated by essential fatty acid interactions. The proportion of omega−3 to omega−6 fatty acids in a diet may have metabolic consequences. Unlike omega−3 fatty acids and omega−6 fatty acids, omega−9 fatty acids are not classed as essential fatty acids because they can be created by the human body from monounsaturated and saturated fatty acids, and are therefore not essential in the diet.

Ratio of omega−6 to omega−3 fats in the diets of hunter-gatherers It has been claimed that among hunter-gatherer populations, omega−6 fats and omega−3 fats are typically consumed in roughly a 1:1 ratio.Andrew Stoll, The Omega-3 Connection. New York: Simon and Schuster, 2001, p. 43. "Populations maintaining historic omega-6 to omega-3 ratios (approximately 1 to 1) are protected from many of the scourges of the modern age." At one extreme of the spectrum of hunter-gatherer diets, the Greenland Inuit, before the late 20th century, consumed a diet with twice as much omega−3 as omega−6, thanks to a diet rich in cold-water fish (a rich source of omega−3s) and completely devoid of omega−6-rich seed oils.William Lands, Fish, Omega-3 and Human Health. Urbana, Illinois: APCS Press, 2005, p. 10.

Optimal ratio of omega−6 to omega−3 fats To date, "no one knows what the optimal ratio in the diet is for these two families of fats."Susan 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. Science writer 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."

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."

According to a 2009 review by the American Heart Association, instead of avoiding ω−6 fats, the ω−6:ω−3 ratio should be decreased by consuming more ω−3 fats. The conversion rate of linoleic acid (LA) into arachidonic acid is very low with a diet high in linolenic acid.

The maximum ω−6:ω−3 ratio allowed in dog food by the AAFCO is 30:1.

Fish

Food Citation Serving size (g) Omega−6 fattyacids (mg) Omega−3 fattyacids (mg) RatioOmega−6 toomega−3Salmon, wild, raw10017220180.085Sardines, canned in oil1 can (90 g)326013622.4Sardines, canned in water1 can (90 g)65514570.45Tuna, canned in water1 can (160 g)144600.030Tuna, canned in oil1 can (170 g)458834513.3Mackerel, canned1 can (360 g)35749700.072Herring100 g24624180.10

Nuts and seeds

Food Citation Servingsize (g) Omega-6 fattyacids (mg) Omega-3 fattyacids (mg) RatioOmega-6 toomega-3Almonds, dry roasted1001206562010Cashews100778262125Chia seeds1005785175520.33Coconut, raw100366 - -Flax seeds1005911228130.26Hazelnuts, filberts10078328790Hemp seeds10056000220002.5Macadamia nuts, dry roasted10017202596.6Pecans1002063098621Pistachios, raw1001320025452Poppy seed10028291273104Pumpkin seeds, whole, roasted100875977114Sesame seeds, whole, dried1002137237657Sunflower seeds, kernels, dried1002304874311Walnuts1003809290794.2Lentils, mature seeds, cooked, boiled, without salt100137373.7

See also Monounsaturated fat For listings of particular classes of polyunsaturated fatty acids, see: Polyunsaturated fat Omega−3 fatty acid Omega−6 fatty acid Omega−9 fatty acid Conjugated linoleic acid Essential fatty acid – for biochemistry of most polyunsaturated fats Essential fatty acid interactions – for the interactions between ω-6 and ω-3 fatty acids Unsaturated fat Israeli paradox

References