Fatty acid ratio in food
Proportion of omega-3 to omega-6 fatty acids in a diet
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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).[1] 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.[2] 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.[3][4][better source needed] 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.[5]
Optimal ratio of omega−6 to omega−3 fats
The potential link between the dietary omega-6 to omega-3 ratio and human health was first noted in the late 1970s, when researchers observed unusually low rates of cardiovascular disease among Eskimo populations.[6] Researchers hypothesize that the dramatic dietary shift from an ancestral omega-6 to omega-3 fatty acid ratio of roughly 1:1 to a modern Western ratio of 20:1 or higher drives systemic inflammation and significantly elevates the risk of obesity.[7]
Increased consumption of omega-6 fats has been linked to higher rates of obesity, insulin resistance, hypertension, and coronary heart disease.[8] Evidence indicates that replacing dietary omega-6 fatty acids with plant and marine omega-3s may reduce the risk of cardiovascular disease and certain cancers due to the potential for omega-6 levels to inhibit the body's ability to synthesize and utilize omega-3s.[9] Consuming high amounts of omega-6 fatty acids may compromise cardiovascular health by displacing essential omega-3s as the two compete for the same enzymatic pathways, meaning excess omega-6 can directly interfere with omega-3 metabolism.[10] Maintaining a balanced dietary omega-6 to omega-3 ratio between 1:1 and 4:1 may optimally reduce inflammation and mitigate the risk of chronic conditions, including cardiovascular and neurodegenerative diseases.[11]
A balanced 1:1 omega-6 to omega-3 ratio is also correlated with the integrity and function of male sperm. Consequently, the highly skewed ratios typical of modern Western diets are heavily associated with impaired semen quality and increased rates of male infertility.[12] Animal models support these broader findings, demonstrating that a 1:1 ratio effectively decreases systemic and vascular inflammation in mice.[13]
To date, "no one knows what the optimal ratio in the diet is for these two families of fats."[14] 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."[14][clarification needed] It has been estimated that in developed countries, the ratio of omega−6s to omega−3s is closer to 15:1[15] 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."[16]
Despite the hypothesis that omega-6 and omega-3 polyunsaturated fatty acids competitively interact, some large-scale consortium analyses have found no evidence of a physiologically relevant interaction between the two regarding the risk of type 2 diabetes or other metabolic outcomes.[17] Several scientific advisories point out that actively reducing omega-6 intake simply to lower this ratio could inadvertently increase the risk of coronary heart disease.[18] 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.[19]
Fish
| Food | Citation | Serving size (g) | Omega−6 fatty acids (mg) | Omega−3 fatty acids (mg) | Ratio Omega−6 to omega−3 |
|---|---|---|---|---|---|
| Salmon, wild, raw | [20] | 100 | 172 | 2018 | 0.085 |
| Sardines, canned in oil | [21] | 1 can (90 g) | 3260 | 1362 | 2.4 |
| Sardines, canned in water | [22] | 1 can (90 g) | 655 | 1457 | 0.45 |
| Tuna, canned in water | [23] | 1 can (160 g) | 14 | 460 | 0.030 |
| Tuna, canned in oil | [24] | 1 can (170 g) | 4588 | 345 | 13.3 |
| Mackerel, canned | [25] | 1 can (360 g) | 357 | 4970 | 0.072 |
| Herring | [26] | 100 g | 246 | 2418 | 0.10 |
Nuts and seeds
| Food | Citation | Serving size (g) | Omega-6 fatty acids (mg) | Omega-3 fatty acids (mg) | Ratio Omega-6 to omega-3 |
|---|---|---|---|---|---|
| Almonds, dry roasted | [27] | 100 | 12065 | 6 | 2010 |
| Cashews | [28] | 100 | 7782 | 62 | 125 |
| Chia seeds | [29] | 100 | 5785 | 17552 | 0.33 |
| Coconut, raw | [30] | 100 | 366 | - | - |
| Flax seeds | [31] | 100 | 5911 | 22813 | 0.26 |
| Hazelnuts, filberts | [32] | 100 | 7832 | 87 | 90 |
| Hemp seeds | [33] | 100 | 56000 | 22000 | 2.5 |
| Macadamia nuts, dry roasted | [34] | 100 | 1720 | 259 | 6.6 |
| Pecans | [35] | 100 | 20630 | 986 | 21 |
| Pistachios, raw | [36] | 100 | 13200 | 254 | 52 |
| Poppy seed | [37] | 100 | 28291 | 273 | 104 |
| Pumpkin seeds, whole, roasted | [38] | 100 | 8759 | 77 | 114 |
| Sesame seeds, whole, dried | [39] | 100 | 21372 | 376 | 57 |
| Sunflower seeds, kernels, dried | [40] | 100 | 23048 | 74 | 311 |
| Walnuts | [41] | 100 | 38092 | 9079 | 4.2 |
| Lentils, mature seeds, cooked, boiled, without salt | [42] | 100 | 137 | 37 | 3.7 |
See also
- Monounsaturated fat
- For listings of particular classes of polyunsaturated fatty acids, see:
- 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