By Jack Norris, RD
There is strong evidence that omega-3 fatty acids are useful in the prevention and treatment of heart disease. There is also some evidence that they might be important for cognitive function or useful as a treatment for depression. While short-chain fatty acids are found in a variety of plant and animal foods, fish provide the main source of the long-chain omega-3s. There are also long-chain omega-3 vegan supplements made from seaweed. Especially in the case of older vegetarians, there is a concern that an omega-3 deficiency could cause cognitive problems and omega-3 supplementation is recommended.
Background on Omega-3s
There are three important omega-3 fatty acids:
1. α-linolenic acid (ALA) is a short chain fatty acid. It is found in small amounts in animal flesh, in very small amounts in a variety of plant products, and in relatively large amounts in soy, walnuts, canola oil, camelina oil, and in flax, hemp, and chia seeds and their oils. The human body cannot make its own ALA, it is an essential fatty acid that must be obtained through the diet.
2. Eicosapentaenoic acid (EPA) is a long chain fatty acid. It is found in large amounts in fatty fish, in small amounts in eggs, and in very small amounts in seaweed. Some EPA is converted into other molecules that can reduce blood clotting, inflammation, blood pressure, and cholesterol.
3. Docosahexaenoic acid (DHA) is a long chain fatty acid. Like EPA, it is found in large amounts in fatty fish, in small amounts in eggs, and in very small amounts in seaweed. It is a major component of the gray matter of the brain, and also found in the retina, testis, sperm, and cell membranes.
All three of these omega-3 fatty acids may prevent heart arrhythmias, though ALA has been studied the least in clinical trials.
The body can convert ALA into EPA, and EPA into DHA. ALA is efficiently converted to EPA, but it may require large amounts of ALA to produce optimal amounts of DHA.
The American Heart Association (AHA) recommends that adults eat at least two servings of fatty fish a week. The AHA says that people with coronary artery disease may want to talk to their doctor about fish oil supplements, and, especially for people with high triglycerides, large doses of fish oil could help.
An ALA intake of about 2 g/day has been consistently associated with a modest lowering of heart disease risk.
There is evidence that EPA and/or DHA supplementation may improve depression and cognition, particularly in infants, children and older adults, although the results of clinical trials have been mixed.
Vegetarians and Omega-3 Status
Vegetarians, including vegans, have been shown in many studies to have lower levels of EPA and DHA than meat eaters. We do not know if lower blood DHA levels reflect lower levels in other tissues in vegetarians, though it is a reasonable assumption.
Because EPA reduces blood clotting, one way to figure out if vegetarians are getting enough EPA is to compare the blood clotting parameters of vegetarians to omnivores. Two studies have done this and found the differences to be minimal.
Vegetarians already have about a 24% lower risk of heart disease than regular meat-eaters and on average have lower triglyceride levels, and it is not clear that EPA or DHA supplementation will further reduce their risk.
In terms of depression and cognition, there has been no research on omega-3s and vegetarians, but Joel Fuhrman, MD, has a private practice seeing many long-term vegans and has observed some older vegan men with very low DHA levels and cognitive problems, so there is reason to be prudent regarding DHA in older vegans, especially men.
Improving Omega-3 Status in Vegetarians
The traditional way that vegetarians were encouraged to raise EPA and DHA levels was by increasing ALA and decreasing linoleic acid (LA), a short chain omega-6 fatty acid. Although the body can convert ALA into EPA, the enzymes that do this also convert LA into longer chain omega-6s. If there is too much LA in the diet, the enzymes can be saturated with LA and unable to convert omega-3s. An ideal ratio of omega-6 to omega-3 in the diet is thought be about 3 or 4. Vegans tend to have a ratio of 10 to 15 compared to a ratio of 6 to 10 for omnivores.
To deal with this problem, in the late 90s and 00s, vegetarian health professionals recommended increasing ALA intake and decreasing LA intake. Unfortunately, there are no long-term studies looking at the EPA and DHA levels in vegetarians who follow these recommendations. Research shows that 3 – 4 g of ALA per day per day can increase DHA levels; assuming intake of omega-6 is low.
Increasing ALA to 3 – 4 g/day has some concerns. Three studies looking at age-related eye damage and fatty acids, all coming from the Nurse’s Health Study, have associated modest ALA intakes with age-related eye problems. The ALA in these studies came mostly from animal products that were likely cooked (omega-3s are easily oxidized by heating). It is not clear that the association is causal or if the causation would apply to uncooked ALA (i.e., from plants).
Although ALA has been associated with prostate cancer risk in some studies, the association has been shown with a fair degree of certainty not to be causal.
If it weren’t for the (small chance) for potential eye problems, my recommendations would be either to add 3 g of ALA per day or to take a DHA supplement. Because of the chance for eye damage, that much ALA is not worth the risk when DHA supplements are available and more effective. Vegetarians should still add .5 g of ALA per day for its benefits on heart disease and to help increase EPA levels. Such small amounts of uncooked ALA should pose no risk to the eyes.
Following all three of these recommendations should keep vegans on par with fish eaters:
1. Take a DHA Supplement
Under 60 years old: 200 – 300 mg every 2-3 days
60+ years old: 200 – 300 mg per day
2. Do not prepare food with oils high in omega-6 such as corn, soy, safflower, sunflower, most vegetable oil blends (typically labeled “vegetable oil”) and sesame oil. Instead, use low omega-6 oils like olive, avocado, peanut, or canola.
3. On average, vegetarians meet about 50 to 60% of the daily ALA recommendations without special diet planning and should add 0.5 g of uncooked ALA daily. This would be the equivalent of:
1/5 oz *English walnuts (3 halves)
1/4 tsp of flaxseed oil
1 tsp of canola oil
1 tsp ground flaxseeds
*English walnuts are the typical walnuts for sale in grocery stores. They are distinct from black walnuts.
Too much omega-3 can result in bleeding and bruising. If you have reason to believe you have problems with easy bleeding or bruising consult a health professional before increasing your omega-3 intake.
Vegan DHA & EPA Supplements
There are now many companies offering vegan DHA supplements made from seaweed. Some of them include EPA. Some DHA can be converted into EPA and if you are supplementing your diet with .5 g of ALA, you probably do not need a DHA supplement that also contains EPA, but there’s no harm from doing so.
Vegetarian Children and DHA
There is a concern that dietary DHA may be important to developing fetuses and infants. Anthropologist John H. Langdon argues that DHA is not an essential nutrient for the brain development of infants. Pregnant women efficiently convert ALA to DHA and fetuses and infants are able to receive DHA that is released from the mother’s fat tissues and provided through the umbilical cord or breast milk. Langdon argues that in cases of very low maternal levels of DHA, infants can utilize other fatty acids for brain tissue that can later be replaced by DHA.
In a study comparing breast milk, cow’s milk formula with DHA, soy formula with DHA, and soy formula without DHA, infants who ate soy formula without DHA had indications of slower parasympathetic development, though still within the normal range.
A 1994 study measured the DHA levels in the umbilical cords of 32 infants born to vegetarian mothers compared to omnivores, and revealed no relationship between DHA and the birth weight or head circumference of the infants.
Many children have been raised vegan without supplementing with DHA, or even extra ALA, and appear to develop well. Despite this, parents of vegetarian children are encouraged to supplement their diets with DHA at 200 mg every two or three days until more is known about DHA in vegan infants.
Flax & Chia Facts
• Flaxseeds are the most concentrated source of alpha-linolenic acid (ALA), with an omega-6 to omega-3 ratio of 1:4.
• One teaspoon of flaxseed oil contains 2.5 g of ALA.
• One tablespoon of ground flaxseeds contains 1.6 g of ALA.
• If flaxseeds are not ground, they will not be digested. They can be ground in a blender or coffee grinder, and then stored in the freezer. Ground flaxseeds can be sprinkled on cereal or used in baked goods.
• Cooking flaxseed oil damages the ALA, but it can be put on warm food such as toast. Flaxseed oil should be kept in the refrigerator.
• A straight teaspoon of flaxseed oil does not taste so great. Some people use cinnamon-flavored oil, tablets, or put it on toast or salad to make it taste better.
• Chia (Salvia hispanica; also known as Salba) seed oil is a good source of ALA.
• Dried chia seeds have 5 g of ALA per ounce, although their omega-6 to omega-3 ratio of 3:1 is not nearly as good as flax.
This article is an abridged version of Omega-3 Fatty Acid Recommendations for Vegetarians which is fully annotated.
In addition to a short article I’ve written, Fish and Cardiovascular Disease, The Linus Pauling Institute at Oregon State University provides an in-depth review of omega-3s and heart disease in Essential Fatty Acids.
This article was written by Jack Norris, a Registered Dietitian and President and co-founder of Vegan Outreach. Vegan Outreach produces Why Vegan and other booklets and their Adopt a College program hands booklets to over 750,000 students every semester. In 2005, Jack was elected to the Animal Rights Hall of Fame.
Along with Ginny Messina, MS RD, Jack has written the book Vegan For Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet.