Questions and Answers about Omega-3 Fatty Acids for Vegans
By Reed Mangels, PhD, RD
Omega-3 fatty acids are showing up in all sorts of products. I took a quick trip down the aisles of a grocery store and a natural foods store and found cereals, soymilk, pasta, snack bars, and even peanut butter proudly proclaiming "contains omega-3 fatty acids." Labels and ads trumpet, "Omega-3 DHA is an important brain nutrient," and "Omega-3s may reduce the risk of heart disease." Are these claims real or are they hype? Should vegans be concerned about omega-3 fatty acids? We'll look at these questions and more.
What are omega-3 fatty acids?
Omega-3 fatty acids are polyunsaturated fatty acids—building blocks of fats. They differ from other fatty acids because of the number of carbons that they contain and where double bonds are located. The omega-3 fatty acids that are most important nutritionally are alpha-linolenic acid, docosahexaenoic acid, and eicosapentaenoic acid (DHA and EPA for short).
Why are omega-3 fatty acids important?
Our bodies cannot make alpha-linolenic acid, so it is essential for us to get it from our diet. We can make DHA and EPA from alpha-linolenic acid, although there are some questions about how efficient this process is. Some have suggested that DHA should be considered an essential fatty acid.1 Recent research on omega-3 fatty acids has centered on the following areas:
Pregnancy and Breastfeeding
A higher intake of omega-3 fatty acids in pregnancy may slightly reduce the risk of having a premature baby.2 In addition, DHA is essential for normal brain development3 and appears to play a role in the development of the infant's vision. The amount of DHA in a woman's diet determines the amount of DHA that appears in her breastmilk.
A number of studies have found that risk of death from heart disease is lower in people with higher intakes of omega-3 fatty acids. Omega-3 fatty acids may also reduce risk of stroke and reduce elevated blood pressure.4 (For more information on omega-3 fatty acids and heart disease, see the Nutrition Hotline column in Issue 1, 2005, of Vegetarian Journal, which is available at <www.vrg.org/journal/vj2005issue1/2005_issue1_hotline.php>.
People with clinical depression tend to have lower blood concentrations of omega-3 fatty acids than non-depressed controls. In some studies, one gram of EPA (either with or without DHA) has been used, along with antidepressants, to treat people with depression.5
EPA and DHA appear to have some benefits for those with rheumatoid arthritis, including reduction of morning stiffness and pain relief. They may be beneficial in other conditions like Crohn's disease, Alzheimer's disease, and asthma, but there is not yet enough research in these areas to make recommendations.6,7
Which foods contain DHA and EPA?
Vegetarian diets contain low levels of EPA and DHA, mainly from dairy products and eggs; vegan diets do not normally contain EPA or DHA. The only plant sources of EPA and DHA are microalgae and sea vegetables. Sea vegetables are not a concentrated source of these omega-3 fatty acids and do not provide significant amounts of omega-3 fatty acids for most people. Fish, especially fatty fish, do have DHA and EPA. This is not because the fish produce these fatty acids but because the fish eat microalgae containing DHA and EPA. A vegan DHA made from microalgae has been developed and is being added to some foods and used to make supplements.
Must we get DHA and EPA from food, or can our bodies produce these omega-3 fatty acids?
Do vegans get enough DHA and EPA? Our bodies are able to produce some DHA and EPA from alpha-linolenic acid, but we are not very efficient at this production. The rate of conversion is low in women and very low in men.3 Vegans who do not use DHA supplements or eat DHA-fortified foods must rely on conversion of alpha-linolenic acid to DHA and EPA. Some studies have found that blood levels of EPA and DHA are lower in vegans and vegetarians than in meat-eaters.8,9 Whether or not these lower levels have health consequences is not known. The concentration of DHA in breastmilk from vegan women is lower than that in lacto-ovo vegetarians or non-vegetarians.10,11 Milk EPA concentration can be increased if dietary alpha-linolenic acid intake increases, but milk DHA content remains unchanged.12
How can vegans maximize DHA and EPA production?
- Include sources of alpha-linolenic acid in your diet on a regular basis. Major sources include ground flaxseed, flaxseed oil, canola oil, soy products, hemp products, and walnuts. Green leafy vegetables, sea vegetables, and pecans also provide smaller amounts of alpha-linolenic acid. (See Table 1, below.)
- Whole flaxseeds are not well digested, so the alpha-linolenic acid that they contain is not available to us. If you are using flaxseeds as a source of alpha-linolenic acid, be sure to use ground or milled flaxseeds or flaxseed oil.
- Avoid trans fats since they interfere with EPA and DHA production. Trans fats are found in foods containing hydrogenated fat, like margarine and commercial cookies and crackers.
- Use less sunflower, safflower, corn, and sesame oil and more canola and olive oil to promote DHA and EPA production. Sunflower, safflower, corn, and sesame oil are high in linoleic acid, an omega-6 fatty acid that can interfere with DHA and EPA production.
TABLE 1: Alpha-Linolenic Acid in Foods
|Food, Serving Size||Alpha-Linolenic Acid (Milligrams/Serving)|
|Breakfast cereal containing flax and/ or hemp, 1 serving*||400-1,000|
|Broccoli, cooked, 1 cup||190|
|Cabbage, cooked, 1 cup||165|
|Canola oil, 1 teaspoon||400|
|Collards, cooked, 1 cup||180|
|Flaxseed oil, 1 teaspoon||2,400|
|Flaxseed, ground, 1 teaspoon*||570|
|Hot cereal containing flax, 1 serving*||450|
|Kale, cooked, 1 cup||130|
|Pasta containing flax, 1 serving*||600|
|Peanut butter containing flaxseed oil, 2 Tablespoons||11,000|
|Pecans, 1/4 cup||240|
|Snack bar containing flax and/or hemp, 1 bar*||400-2,100|
|Soybean oil, 1 teaspoon||300|
|Soybeans, cooked, 1/4 cup||320-510|
|Soymilk, 1 cup||210|
|Soy nuts, 1/4 cup||725|
|Tempeh, 3 ounces||120|
|Tofu, 1/2 cup||400|
|Walnuts, 1/4 cup||2,270-2,700|
|Walnut oil, 1 teaspoon||470|
* Flaxseed should be ground or milled; otherwise little or no alpha-linolenic acid will be absorbed.
Sources: Composition of Foods. USDA Nutrient Data Base for Standard Reference, Release 18, 2005, and manufacturers' information.
Vegan DHA and DHA + EPA Supplements
- O-Mega-Zen 3 300 mg DHA/capsule - www.nutru.com
- Dr. Fuhrman's DHA Purity 175 mg DHA/0.5 ml - www.drfuhrman.com/shop/DHA.aspx
- Vegan Omega-3 DHA 200 mg DHA/capsule - www.devanutrition.com
- V-Pure Omega-3 135 mg DHA + 37.5 mg EPA/capsule - www.water4.net
What about supplements of omega-3 fatty acids?
Alpha-linolenic acid supplements produce a small increase in blood EPA concentrations but do not increase concentrations of DHA in the blood.13 These results have led some researchers to recommend direct supplementation with DHA for some groups with increased needs for EPA and DHA (pregnant and breastfeeding women) or with a risk for low conversion of alpha- linolenic acid to EPA and DHA (people with diabetes, premature infants).8,14 DHA supplements can increase blood concentrations of both DHA and EPA.
Supplements with both EPA and DHA also are effective in increasing blood levels of EPA and DHA.15
What amount of omega-3 fatty acids do we need?
There is limited storage of omega-3 fatty acids in our bodies, so these fatty acids should be a regular part of the diet.15 When you are thinking about the amount of omega-3 fatty acids that you should be getting, one key question is whether you are relying on alpha-linolenic acid being converted to EPA and DHA or taking a direct source of DHA.
If you are a vegan relying only on alpha-linolenic acid as the source of omega-3 fatty acids, approximately 1-2 percent of calories should come from alpha-linolenic acid.15 For the typical adult man, this would be 2,200-5,300 milligrams (2.2-5.3 grams) of alpha-linolenic acid; for the typical adult woman, 1,800-4,400 milligrams (1.8-4.4 grams). Very active and heavier people as well as pregnant and lactating women should strive for the higher end of the range; smaller and more sedentary people should aim towards the lower end.
If you are using a supplement or foods that contain DHA or EPA on a daily basis, strive for the adequate intake for alpha-linolenic acid established by the Institute of Medicine of 1.6 grams per day for men and 1.1 grams per day for women.3
There is no Recommended Daily Allowance (RDA) for EPA or DHA, but the American Heart Association recommends 500-1,800 milligrams (0.5-1.8 grams) per day of DHA and/or EPA to significantly reduce the risk of death from heart disease.17 This level seems appropriate for people with a family history of heart disease, although there have been no studies examining whether DHA supplements further reduce the risk of death from heart disease in vegans.
Because of DHA's role in infant development, several groups2,18 have suggested that pregnant and lactating women get 200-300 milligrams (0.2-0.3 grams) of DHA daily from fortified food or supplements. Can someone get too much of the omega-3 fatty acids? There is not enough information available to set a safe upper limit for omega-3 fatty acids. The Food and Drug Administration (FDA) says up to 3 grams (3,000 milligrams) per day of EPA + DHA is generally recognized as safe.19 DHA and EPA may have negative effects on the immune system and may inhibit blood clotting, so supplementation should only be done with caution. More is not necessarily better.
Men at risk for prostate cancer should not use high amounts of alpha-linolenic acid since one study found that those men whose diets were highest in alpha-linolenic acid had an increased risk of developing advanced prostate cancer.20 The other omega-3 fatty acids, EPA and DHA, were associated with lower prostate cancer risk.
Sample Menu That Provides At Least 4,400 Milligrams of Alpha-Linolenic Acid Daily - DAY 1
- 1 bagel with jelly
- 1 medium orange
- 1 cup cold cereal
- 1 cup enriched soymilk
- Hummus sandwich made with:
- Hummus (3/4 cup chickpeas and 2 teaspoons tahini)
- 3 slices of tomato
- 2 slices of whole wheat bread
- 1 medium apple
- 1 cup of cooked pasta with
- 1/4 cup marinara sauce
- 1/3 cup carrot sticks
- 1 cup cooked broccoli sautéed in 1 teaspoon canola oil
- 1 whole wheat roll
- A juice pop made with 1 cup frozen grape juice
- 1/2 cup trail mix (mix of dates, raisins, and at least 3 Tablespoons of walnuts)
- 1 cup enriched soymilk
Sample Menu That Provides At Least 4,400 Milligrams of Alpha-Linolenic Acid Daily - DAY 2
- 1 serving hot cereal containing milled flaxseed with:
- 3 Tablespoons wheat germ
- 1/4 cup raisins or dates
- 1 ounce chopped walnuts
- 1 cup diced cantaloupe
- 1 cup enriched soymilk
- Burrito made with:
- 1 whole wheat tortilla
- 1/2 cup black beans
- 1 Tablespoon salsa
- 1 ounce lowfat tortilla chips with:
- 1/4 cup salsa
- Stir-fry made with:
- 1/2 cup diced tofu
- 1 cup vegetables
- 2 Tablespoons soy sauce
- 1 1/2 cups cooked quick brown rice
- 1 teaspoon canola oil
- 3 graham crackers
- 6 ounces calcium-fortified vegetable juice
- 3 cups popped popcorn with:
- 1 Tablespoon Vegetarian Support Formula nutritional yeast
- 1 cup enriched soymilk
What's the bottom line?
The topic of omega-3 fatty acids, like many topics in nutrition, is fluid. Recommendations change as new studies provide more information. Based on what we know today, here's what you need to remember:
- Alpha-linolenic acid is an essential fatty acid; that means we need to obtain it from food or supplements. To prevent deficiency, vegan adults should have 1-2 percent of calories from alpha-linolenic acid 2,220-5,300 milligrams of alpha-linolenic acid for the typical adult man, 1,800-4,400 milligrams for the typical adult woman.
- Good sources of alpha-linolenic acid include ground flaxseed, flaxseed oil, canola oil, soy products, hemp products, and walnuts. Table 1 provides information about the amount of alpha-linolenic acid in various foods.
- Vegan pregnant and breastfeeding women, people at risk for heart disease or high blood pressure, and people with diabetes are the groups most likely to benefit from supplements of DHA. Approximately 500-1,800 milligrams of DHA has been recommended to reduce the risk of heart disease17; 200-300 milligrams of DHA is suggested for pregnant and breastfeeding women.2,18
1 Gebauer SK, Psota TL, Harris WS, Kris-Etherton PM. 2006. N-3 fatty acid dietary recommendations and food sources to achieve essentiality and cardiovascular benefits. Am J Clin Nutr 83(suppl):1526S-35S.
2 Jensen CL. 2006. Effects of n-3 fatty acids during pregnancy and lactation. Am J Clin Nutr 83(suppl):1452S-57S.
3 Williams CM, Burdge G. 2006. Long-chain n-3 PUFA: plant v. marine sources. Proc Nutr Soc 65:42-50.
4 Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington: National Academies Press, 2002.
5 Sontrop J, Campbell MK. 2006. Omega-3 polyunsaturated fatty acids and depression: A review of the evidence and a methodological critique. Prev Med 42:4-13.
6 Johnson EJ, Schaefer EJ. 2006. Potential role of dietary n-3 fatty acids in the prevention of dementia and macular degeneration. Am J Clin Nutr 83(suppl):1494S-98S.
7 Calder PC. 2006. N-3 polyunsaturated fatty acids, inflammation, and inflammatory diseases. Am J Clin Nutr 83(suppl):1505S-19S.
8 Davis BC, Kris-Etherton PM. 2003. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr 78(suppl):640S-46S.
9 Rosell MS, Lloyd-Wright Z, Appleby PN, et al. 2005. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr 82:327-34.
10 Sanders TAB, Reddy S. 1992. The influence of a vegetarian diet on the fatty acid composition of human milk and the essential fatty acid status of the infant. J Pediatr 120:S71-77.
11 Uauy R, Peirano P, Hoffman D, et al. 1996. Role of essential fatty acids in the function of the developing nervous system. Lipids 3:S167-S76.
12 Francois CA, Connor SL, Bolewicz LC, Connor WE. 2003. Supplementing lactating women with flaxseed oil does not increase docosahexaenoic acid in their milk. Am J Clin Nutr 77:226-33.
13 Harper CR, Edwards MJ, DeFilipis AP, Jacobson TA. 2006. Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans. J Nutr 136:83-87.
14 Geppert J, Kraft V, Demmelmair H, Koletzko B. 2005. Docosahexaenoic acid supplementation in vegetarians effectively increases omega-3 index: a randomized trial. Lipids 40:807-14.
15 Arterburn LM, Hall EB, Oken H. 2006. Distribution, interconversion, and dose response of n-3 fatty acids in humans. Am J Clin Nutr 83(suppl):1467S-76S.
16 WHO/FAO (World Health Organization/Food and Agriculture Organization). Diet, Nutrition and the Prevention of Chronic Diseases. WHO Technical Report Series 916. (Geneva: World Health Organization, 2003.)
17 Kris-Etherton PM, Harris WS, Appel LJ. 2002. AHA Scientific Statement. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation 106:2747-57.
18 Melina V, Davis B. The New Becoming Vegetarian. Summertown: Book Publishing Company, 2003.
19 Department of Health and Human Services, U.S. Food and Drug Administration. Substances affirmed as generally recognized as safe: menhaden oil. Federal Register. June 5, 1997. Vol. 62, No. 108: pp 30751-30757. 21 CFR Part 184 [Docket No. 86G-0289]. Available at <frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=1997_register&docid=fr05jn97-5>.
20 Leitzmann MF, Stampfer MJ, Michaud DS, et al. 2004. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr 80:204-16.Reed Mangels, PhD, RD, is one of The Vegetarian Resource Group's Nutrition Advisors. She is the co-author of Simply Vegan.