Tag Archives: Essential fats

Omega 3 Essential Fatty Acids

A whole foods, plant-based diet can provide all the essential fats we need. These are the omega-6 and omega-3 groups of polyunsaturated fatty acids. There is no dietary requirement for other polyunsaturated fats, monounsaturated fats or saturated fats other than as an energy source. Omega-6 fats (linoleic acid) are plentiful in our diet. It’s the omega-3 group that has become a nutrient of concern.

Essential fatty acid requirements

Human requirements for omega-6 and omega-3 fats are uncertain because deficiency states are rarely seen. Dietary requirements are given as an ‘adequate intake’ rather than a minimum requirement. Adequate intake is used when an RDI cannot be determined and is based on an average intake of an apparently healthy population. [see Nutrient Reference Values: Fats: Total Fats & Fatty Acids for Adequate Intake (AI) recommendations]

The ratio of omega-6 to omega-3 fats is more relevant than the absolute amount of each, and herein lies the problem. The modern food supply is overloaded with omega-6 fats and often low in omega-3 fats with ratios of 15-20:1. The optimal ratio of 6’s to 3’s is generally considered 4:1 or less. Many foods promoted as ‘good fats’ have an overabundance of omega 6’s. (See our FAQ What are good fats?).

Omega 6:3 ratios of common foods

*Green leafy vegetables are low in fat therefore it takes a lot of them to have a meaningful effect on your omega 3 intake.

Fatty Acid Chemistry

Plants provide linoleic acid (omega-6) and alpha-linolenic acid (ALA)(omega-3). Our cells have enzymes that convert these to arachidonic acid (AA)(omega-6 fat), EPA (omega-3) and DHA (omega-3). (Cats are carnivores and lack this enzyme). Arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are substrates for cell membranes, and a large group of signalling molecules called eicosanoids that have powerful local effects in many different organs. Omega-6 fats are essential for inflammatory processes and blood clotting. Omega-3 fats are required in smaller amounts and are often considered anti-inflammatory, but this is an oversimplification.

Is there a dietary requirement for DHA?

The efficiency of the human enzyme that initiates the conversion of plant-based omega-3 (alpha-linolenic acid) into the long-chain forms (EPA, DHA) has been called into question. Only a few percent of plant-based ALA is converted to DHA. Estimates of the conversion rate vary widely and are found to increase when requirements are greater, such as during pregnancy. Omega-3 and omega-6 fats are processed by the same enzyme, and an excessive dietary intake of omega-6 fats reduces the conversion of omega-3s despite the enzyme having a greater affinity for omega-3s. Theoretically, flooding the body with excess omega-3 fats might also impair arachidonic acid production. We are confident that a plant-based diet with a reasonable omega-6 to omega-3 balance will allow the body to make just the right amount of AA, EPA and DHA to meet its needs. The body controls DHA levels through a feedback mechanism that suppresses one of the steps in the DHA synthesis pathway (EPA -> DPA), ensuring that it does not produce more DHA than it needs. We can push DHA to much higher levels than the body would produce by eating fish or taking supplements.

No absolute requirement for DHA has been established. The controversy is over whether taking preformed DHA (from fish or microalgal supplements) leads to better health outcomes.

Measuring omega-3 in the food and the body

Dietary analysis is unreliable for measuring dietary intake of omega-3 because food composition tables do not have an omega-3 value for many foods, thus underestimating true intake.

Blood tests for omega-3 levels are popular and often offered by the same corporate groups that sell omega-3 supplements. Test results are presented as a numeric value and compared to a reference range and suggest an optimal level of the omega-3 index between 8-12%. As of December 2024, we have not found any scientific rationale for these suggested ‘optimal’ levels.

Risks and benefits of omega-3 supplementation

Heart disease: Several meta-analyses and reviews have failed to find a protective effect of omega-3 supplementation on cardiovascular disease (e.g. The Risk and Prevention Study Collaborative Group, 2013 ). Some studies have observed better health outcomes in people who eat fish. However, this is probably because of what fish replaces, e.g. Red meat and because fish intake is often an indicator of a healthy diet and lifestyle.

Omega-3 supplementation is associated with an increase in atrial fibrillation, a common heart arrhythmia that can lead to stroke (see Gencer et al 2021).

Brain health: Having failed to protect the heart, omega-3 supplements are now being promoted for brain health. The brain preferentially takes up omega-3 fats and concentrates them in cell membranes. In this regard, omega-3s are essential for brain health, but more may not be better. Although the brain contains a lot of DHA (4g), the daily uptake of DHA from the blood is only 4mg. The issue of EPA/DHA supplementation is controversial among plant-based advocates. The research is mired in conflicts of interest, small changes of low clinical significance, and research subjects with poor-quality baseline diets.

Diabetes: There is an increased risk of diabetes in those who take fish oil supplements or eat fish.

Prostate cancer: Fish oil supplementation and fish intake is associated with an increase in prostate cancer risk. It’s possible that some of this risk may be attributable to the high levels of PCBs and other organic pollutants found in fish and fish oil supplements (see Sorongon-Legaspi et al 2013)

Premature birth: There is evidence that DHA supplements given to women with singleton pregnancies from 12 weeks reduce the risk of premature birth. The author wonders whether this effect is offsetting the high arachidonic acid intake of omnivores.

Bleeding disorder: Very high intakes of oily fish, such as the traditional Inuit diet, or excessive intake of supplements cause prolonged bleeding times due to impairment of blood clotting.

Osteoporosis: Some studies report that high blood DHA levels are associated with osteoporosis (see Li et al 2024). Others report healthier bones in subjects with a lower (more favourable) ratio of Omega-6 to Omega-3 in their blood. In the latter, the plant-based omega-3 (alpha-linolenic acid) was associated with a lower rate of bone loss (see Feehan et al 2022).

Take home points

  • Dietary omega-3 requirements are controversial among plant-based advocates.
  • Blood tests are not clinically useful because there is no evidence-based reference range.
  • Omega-3 brain research is mired by conflicts of interest and clinically insignificant results.
  • Humans can synthesize EPA and DHA (and arachidonic acid) in adequate amounts provided dietary essential fatty acids are in reasonable balance.
  • EPA and DHA supplements may be harmful, particularly in higher doses.
  • Dietary strategies can ensure that essential fatty acid needs are met.
  • A microalgael DHA supplement may be appropriate in some situations. A smaller dose may be a safer option.

Dietary strategies for adequate omega-3

  • Minimise intake of vegetable oils, particularly polyunsaturated oils such as sunflower oil, a common ingredient in plant milks and other processed foods.
  • Eat nuts, seeds and avocados in small quantities, and shift your diet towards the lower fat end of the whole plant macronutrient spectrum, tubers, whole grains and legumes.
  • Include some high omega-3 nuts/seeds with your meals, for example, flax or chia seed. Leafy green vegetables provide some omega-3 fats.
  • If you choose to eat higher quantities of nuts, seeds and avocados, include plenty of moderate to high omega-3 plants.
  • See our FAQ: What Are Good Fats?

 

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Resources

Peer-reviewed articles

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Page created 22 June 2013
Last updated 23 December 2024 (major revision); minor revision 26 January 2025