Omega-3 fatty acids

Omega-3 fatty acids are a family of polyunsaturated fats that play roles in cell membranes, the brain, the eyes and the cardiovascular system. Of the three main types, one is found widely in plant foods, while the other two are found mainly in oily fish and in the microalgae that fish ultimately obtain them from. For this reason, omega-3 intake is often discussed in relation to vegan diets.

Types of omega-3

• Alpha-linolenic acid (ALA) is a short-chain omega-3. It is an essential fatty acid, meaning the body cannot make it and it must come from food. ALA is found in a number of plant foods.
• Eicosapentaenoic acid (EPA) is a long-chain omega-3 involved in producing signalling molecules that affect inflammation and blood clotting.
• Docosahexaenoic acid (DHA) is a long-chain omega-3 that is a major structural component of the brain and the retina.

The body can convert ALA into EPA and, to a lesser extent, DHA. However, this conversion is limited. Studies report that only a small percentage of ALA is converted, with conversion to DHA especially low; women of reproductive age appear to convert somewhat more efficiently than men. Conversion may also be affected by genetics and by the amount of omega-6 fats in the diet, since the two families share the same enzymes.

Recommended intakes

The US Institute of Medicine has set adequate intakes (AIs) for ALA of 1.6 g/day for adult men and 1.1 g/day for adult women, as reported by the NIH Office of Dietary Supplements. No US intake level has been set for EPA and DHA.

EFSA has set an adequate intake of 250 mg/day of EPA plus DHA for adults, with an additional 100–200 mg/day of DHA advised during pregnancy and breastfeeding.

ALA sources

ALA-rich plant foods include:

• ground flaxseed (linseed) and flaxseed oil;
• chia seeds;
• hemp seeds and hemp oil;
• walnuts;
• rapeseed (canola) oil;
• soya beans and tofu, in smaller amounts.

Whole flaxseeds may pass through the gut undigested, so they are usually eaten ground. Flaxseed oil is not suitable for high-heat cooking. A tablespoon of ground flaxseed or a small handful of walnuts each day is a commonly suggested way to contribute towards ALA needs.

Algae oil

Fish do not make EPA and DHA themselves; they accumulate them by eating microalgae, directly or through the food chain. Algae oil supplements are produced by cultivating these microalgae and extracting the oil, providing a direct, vegan source of DHA and often EPA. Algae oil is also used in some fortified foods and in infant formulas.

Algae oil supplements avoid the use of fish and do not carry the same concerns about marine pollutants as some fish oils. Some studies have found that algae-oil DHA raises blood DHA levels in a way comparable to fish oil. Supplements should be checked for vegan capsules, as some use gelatin (see hidden animal ingredients).

Should vegans supplement?

Health organisations differ on whether routine EPA/DHA supplementation is necessary for vegans. Vegans and vegetarians typically have lower blood levels of EPA and DHA than fish eaters, but the clinical significance of this is not fully established. Common recommendations include:

1. Eat a reliable source of ALA every day.
2. Prefer oils lower in omega-6, such as rapeseed oil, over large amounts of sunflower or corn oil.
3. Consider an algae-oil supplement, particularly during pregnancy, breastfeeding, infancy and older age, when DHA may be especially important.

The Vegan Society suggests that vegans may wish to consider an algae-derived DHA and EPA supplement in addition to eating ALA-rich foods.

Safety

Omega-3 supplements are generally well tolerated. High doses can affect blood clotting, so people taking anticoagulant medication or preparing for surgery should seek medical advice. EFSA has stated that long-term intakes of EPA and DHA supplements up to about 5 g per day do not raise safety concerns for adults.

This article is for general information. Individuals should consult a doctor or registered dietitian for personal advice.

See also

• vegan pregnancy and children
• vegan diet and health
• meal planning