A whole foods, plant-based diet provides adequate quantities of omega 3 essential fatty acids. Supplements are unnecessary and may be harmful. The alleged health benefits of omega 3 supplements is largely marketing hype and recent research has even questioned the long standing dogma that omega 3 supplements are heart protective. Humans are able to efficiently utilize the type of omega 3’s found in plants. However, excessive dietary omega 6’s inhibits the conversion of these plant omega 3’s into DHA and EPA long chain omega 3’s. Therefore, the ratio of omega 6’s to omega 3’s in the diet may be more important than the total amount of omega 3’s.
Our solution to ensuring optimal omega 3 function is to avoid vegetable oils completely, moderate consumption of most nuts and avocados and consume generous quantities of green leafy and other vegetables. Flaxseed and chia seeds are extremely rich sources of omega 3 fats and the addition of small amounts of these foods to your diet will ensure that your omega 3 intake is more than adequate.
It is often stated that we need fats in our diet and that there is no such thing as a no fat diet. While this is true, adding vegetable oils and high fat foods to the diet is not necessary. All whole plant foods contain small amounts of fats and the diet we advocate provides approximately 10% of calories from the fat, a fair proportion of which are essential fatty acids. This easily meets the human requirement for essential fatty acids (there is no absolute requirement for other fats in the diet).
There are two classes of fatty acids which are essential nutrients – omega 3 and omega 6 fatty acids, and these can only be synthesized by plants. All of the omega 3 oils in the food chain originate from plants. Both plant-based and omnivorous diets provide plenty of omega 6 fats so there is no hype and few supplements for this type of essential fat. While most people equate omega 3’s with fish, they are widely present in plants, with some plants being very rich sources. However the omega 3 fatty acids in plants are present as alpha-linolenic acid (ALA) while the active form in humans and other animals are the longer chain EPA and DHA.
CLASS PLANT FORM ANIMAL FORM
Omega-6 linoleic acid (LA) arachidonic acid (AA)
Omega-3 alpha-linolenic acid (ALA) eicosapentaenoic acid(EPA)
docosahexaenoic acid (DHA)
AA and EPA/DHA are substrates for cell membrane components and a large group of signaling molecules called eicosanoids that have powerful local effects in many different organs. The omega 6’s tend to promote inflammation and blood clotting and over production is associated with chronic disease whereas the omega 3’s tend to have the opposite effect. The AA found in animal products is one of the features that makes these foods pro-inflammatory. The anti-inflammatory, anti-thrombotic effect of omega 3 derived molecules provides a theoretical framework for therapeutic use of EPA/DHA supplements, although clinical trials with these supplements have found limited benefits.
We have an enzyme that can convert the ALA (from plants) into the EPA and DHA (active form) with reasonable efficiency. The problem is that this same enzyme also processes the other class of essential fatty acids, the omega 6 fatty acids, and the two classes of fatty acids are said to “compete” for this enzyme. An overload of omega 6’s will therefore reduce the activation of plant omega 3’s. We actually need more dietary omega-6s than omega-3s but not too much more. It is recommended that the current vegetarian and vegan intake (13:1) be reduced to 4:1 or less. This ratio is more important than the actual quantity of omega 3 fats in the diet.
The usual Australian diet is low in vegetable sources of omega 3’s and has huge quantities of omega 6s from vegetable oils. The solution is to avoid vegetable oils completely, moderate your intake of most nuts and avocados (which are high in omega 6’s) and to eat generous quantities of green leafy and other vegetables. Flaxseed, chia seeds and hemp seeds are extremely rich sources of omega 3 fats and the addition of small amounts of these foods to your diet will ensure that your omega 3 intake is more than adequate. Walnuts are a moderately rich source of omega 3’s. Eat the whole seed rather than just the oil – flaxseed for example is also rich in other substances known to promote health such as lignans.
Omega 6 : omega 3 ratios of common foods:
Peanut no omega 3
Sunflower oil very high
Olive oil 13:1
Hemp seed 3:1
Canola oil 2:1
Green leafies* 1:1
Chia seed 1:3
Flax seed 1:4
*Green leafy vegetables are low in fat therefore it takes a lot of them to have a meaningful effects on your omega 3 intake.
You may read that our bodies cannot efficiently convert the plant omega 3 (ALA) into the animal (long-chain) omega 3 (EPA and DHA found in fish and lean meats). If this were true then it would make us obligate carnivores like cats who lack the ability to utilize plant forms of the omega 6 fatty acids and therefore must obtain arachidonic acid from meat. There is another viewpoint from which to consider the apparent inefficiency of EPA and DHA production in the human body and that is that we are not cold water fish. Our cell membranes are not meant to contain high levels of EPA and DHA except for a few special cell types. Creating abnormally high levels of any nutrient or substrate within the body always has consequences. High intakes of ALA from plants is safe because the body can choose how much to convert into EPA and DHA.
There is emerging evidence that there are health risks associated with high intakes of long chain omega 3s. There is an increased risk of diabetes associated with both fish oil supplements and high consumption of fish. Clinical trials of fish oil supplements have also found an increased risk of prostate cancer (see Sorongon-Legaspi et al 2013). High doses of fish oils inhibit the function of platelets (involved in blood clotting) and therefore increase the risk of serious haemorrhages.
The long standing belief that fish oil supplements reduce heart risk has been refuted by several recent studies including this one, n–3 Fatty Acids in Patients with Multiple Cardiovascular Risk Factors, published in the New England Journal of Medicine. The evidence for any other significant benefits from taking fish oil supplements is also becoming weaker.
If you do choose to take a DHA/EPA omega 3 supplement you can use microalgae derived DHA. Fish oil is a concentrated source of fat soluble persistent organic pollutants such as PCBs. Dr Michael Greger discusses this in his blog on fish oils.
See related pages:
- The Risk and Prevention Study Collaborative Group. (2013). n–3 Fatty Acids in Patients with Multiple Cardiovascular Risk Factors. New England Journal of Medicine, 368(19), 1800-1808 – “…there was no significant benefit of n−3 fatty acids in reducing the risk of death from cardiovascular causes”
- Hooper, L., et al. (2006). Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ, 332(7544), 752-760 – “…omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer”.
- Kaushik, M., et al. (2009). Long-chain omega-3 fatty acids, fish intake, and the risk of type 2 diabetes mellitus. American Journal of Clinical Nutrition, 90(3), 613-620 – “…higher fish and long-chain omega-3 fatty acid consumption appears to be associated with a modestly but significantly higher incidence of T2DM”
- Simopoulos, A. P. (2008). The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases. Experimental Biology and Medicine, 233(6), 674-688.
- Sorongon-Legaspi, M. K., Chua, M., Sio, M. C., & Morales, M., Jr. (2013). Blood level omega-3 Fatty acids as risk determinant molecular biomarker for prostate cancer. Prostate Cancer, 2013, 875615.
- Welch, A. A., et al. (2010). Dietary intake and status of n-3 polyunsaturated fatty acids in a population of fish-eating and non-fish-eating meat-eaters, vegetarians, and vegans and the product-precursor ratio [corrected] of alpha-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. American Journal of Clinical Nutrition, 92(5), 1040-1051.
Last updated 29 August 2017