Fat
Below is a quick summary about fats that gives basic recommendations. For a more comprehensive discussion see The Challenge of Defining Optimal Fat Intake by Virginia Messina, MPH, RD, and Making Sense of Fats and Oils by Brenda Davis, RD.
Whole Foods Market has a good summary about cooking oils. They include a chart showing the fatty acid components, smoke points, and best oil for various uses.
Here is another chart showing the fatty acid breakdown of many higher-fat plant foods.
There are two main types of PUFAs: omega-3s (aka n-3) and omega-6s (aka n-6). Both n-3s and n-6s can be further divided into short chain and long chain.
The short chain n-3, alpha-linolenic acid (ALA), and the short chain n-6, linoleic acid (LA) are considered "essential," because the body cannot make them. Other PUFAs are not considered essential because most people's bodies can produce them from LA or ALA. However, in recent decades there has been a debate about whether the body can produce enough long-chain n-3s, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) out of ALA.
Chart 1 below shows the order in which LA and ALA are converted into longer chain fatty acids and then into eicosanoids. Eicosanoids act like hormones with a direct effect on a wide range of physiological actions, including blood pressure, blood clotting, stomach secretions, cholesterol synthesis, respiratory muscle contraction, and effects on the immune and nervous systems. Many eicosanoids have opposing actions and, therefore, a balance of eicosanoids is needed to create optimal health.
Chart 1: PUFA Sources and Pathways
In the chart above, "D6D" represents the enzyme that changes ALA and LA into other fats. The reactions that convert LA into ALA compete for D6D. Because modern day diets are high in LA, LA wins this battle much of the time and people end up with too many of the series 2 and 4 eicosanoids. Series two and four are only considered "bad" because we tend to get too many; they are also necessary, but only in moderate amounts. Because many people eat fish that contain EPA and DHA, their diets make up for the low conversion of ALA into EPA and DHA. Vegetarians, however, not only do not eat fish, they also tend to have high intakes of LA because it is found in many vegetable oils.4 This can result in higher blood clotting which is a risk for heart attack and stroke.6
The following is a list of the notable PUFAs.
- Surette ME, Edens M, Chilton FH, Tramposch KM. Dietary echium oil increases plasma and neutrophil long-chain (n-3) fatty acids and lowers serum triacylglycerols in hypertriglyceridemic humans. J Nutr. 2004 Jun;134(6):1406-11. Abstract.
- Miles EA, Banerjee T, Calder PC. The influence of different combinations of gamma-linolenic, stearidonic and eicosapentaenoic acids on the fatty acid composition of blood lipids and mononuclear cells in human volunteers. Prostaglandins Leukot Essent Fatty Acids. 2004 Jun;70(6):529-38. Abstract.
- James MJ, Ursin VM, Cleland LG. Metabolism of stearidonic acid in human subjects: comparison with the metabolism of other n-3 fatty acids. Am J Clin Nutr. 2003 May;77(5):1140-5. Abstract.
Alpha-linolenic Acid (ALA or LNA) - short chain; 18:3(n-3)
ALA is found mainly in the oil of flaxseeds, hemp seeds, walnuts, rapeseed (canola oil), camelina (aka Gold of Pleasure), chia seeds, and soybeans, and in some animal products. Also found in very small amounts in leafy green vegetables and other plant foods. ALA reduces blood clotting, improves artery flexibility, and may also reduce heart arrhythmias. ALA shows a strong association with reduced cardiovascular mortality rates, including those from heart attack and stroke. Much of this may be due to its incorporation into cell membranes.
Stearidonic Acid (STA) - short chain; 18:4(n-3)
Croda Health Care has developed a product called Incromega V3 which contains stearidonic acid (STA). It may be released in the USA soon (as of June 2007). There is evidence in humans that STA is more readily converted to EPA than is ALA. The STA in Incromega V3 is derived from the seed of the plant Echium Plantagineum. You can read more about it in this news story.
Here are some studies on STA:
Eicosapentaenoic Acid (EPA) - long chain; 20:5(n-3)
EPA is found mainly in fatty fish (from eating seaweed). A vegan EPA supplement is available from Switzerland (will ship to the USA). Also in irish moss and wakame, but the ratio of iodine to EPA is much too high to make these foods a recommended source. Some EPA is converted into series 3 eicosanoids which can reduce inflammation, blood pressure, and cholesterol.
Docosahexaenoic Acid (DHA) - long chain; 22:6(n-3)
DHA is found in seaweeds and fatty fish. Vegan DHA supplements are available. It is a major component of the gray matter of the brain, retina, testis, sperm, and cell membranes. Low levels of DHA have been associated with depression. DHA can be converted into EPA at a rate of about 10%.5
Linoleic Acid (LA) - short chain; 18:2(n-6)
LA is the most prevalent omega-6 in plant foods and found in most vegetable oils (especially corn, sunflower, "vegetable," soy, and safflower oils).
Gamma Linolenic Acid (GLA) - short chain; 18:3(n-6)
GLA is found in evening primrose oil, borage oil, black current oil, and breast milk.
Dihomo Gamma Linolenic Acid (DGLA) - long chain; 20:3(n-6)
DGLA is made from GLA. Some DGLA is converted into series 1 eicosanoids which are considered good and so some people try to boost their DGLA through GLA supplements.
Arachidonic Acid (AA) - long chain; 20:4(n-6)
AA is found in meat and peanut oil, and is also made from DGLA. AA is converted into series 2 and 4 eicosanoids which are considered bad. (Cats cannot convert LA to AA, which is why they must have AA supplemented in their diet if they are on a vegan diet.)
Vegetarians should consume omega-3 fats and limit omega-6 fats.
A panel of experts on omega-3 fats has recommended an n-3 intake for nonvegetarians of about 1.3% of calories.7 They recommended an additional 300 mg/d of DHA for pregnant and lactating nonvegetarians. Limiting n-6 intake and increasing intake of ALA to 1.5% of calories will enhance conversion of ALA to EPA and DHA; however, it can sometimes take a few months of following these recommendations to build up DHA. Based on the Recommended Dietary Allowance (RDA) for caloric intake (and subtracting .5% of kcal for usual ALA intake without any supplementation), the following amounts of ALA should be added to the diet:
| age (years) |
ALA (g/day) |
flaxseed oil (rounded teaspoons) |
| 0.5-6 |
.9 - 2.0 |
.5 |
|
> 7 |
2.2 - 3.3 |
1 |
|
PregnantA |
||
| 2nd Trimester |
An extra .3 |
An extra .5 |
|
3rd Trimester |
An extra .3 |
An extra .5 |
|
LactatingA |
extra .6 |
extra .5 |
|
A - Pregnant and lactating women should consider replacing the extra .5 teaspoon of flaxseed oil with 300 mg (.3 g) of DHA because infants have more difficulty converting n-3s. |
||
People with diabetes do not efficiently convert ALA to EPA and DHA and should replace .3 grams of ALA with 300 mg of DHA per day.
Parents with prematurely-born infants should contact a health professional about supplementing their diets with essential fatty acids.
Limit omega-6 Fats
Limiting omega-6 intake is important for maximizing the conversion of omega-3s into EPA and DHA. You should aim for an omega-6 to omega-3 ratio of 4:1 or less. The following sources of n-3s are followed by their approximate ratio of omega-6 to omega-3:
| omega-3 source | approx. n-6:n-3 ratio |
| flaxseeds/flaxseed oil | 1:4 |
| chia seeds | 1:3 |
| canola oil | 2:1 |
| english walnutsA | 4:1 - 5:1 |
| walnut oil | 5:1 |
| soybean oil | 7.5:1 |
| black walnuts | 10:1 |
| AEnglish are the typical walnuts found in most grocery stores. | |
Only the top three foods (flax, chia, and canola) fall below the recommended ratio of n-6:n-3. This means that other foods will not help decrease the ratio to 4:1, though walnuts will not harm the ratio much while providing a good source of omega-3s.
Flaxseed oil goes a long way in correcting the imbalance in a typical vegetarian diet, but you should only take the recommended amounts.
If you prefer oils on foods such as bread, choose raw olive or raw canola oil to minimize your n-6:n-3 ratio.
Flax Oil
- Flaxseeds are the most concentrated source of ALA.
- 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, there is a chance they will not be digested. They can be ground in a blender (works best with a large amount) 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, tablets, or put it on toast or salad to make it taste better.
Camelina Oil
- Camelina oil is an oil that has an n-3:n-6 ratio of about 2:1 (ref). The USDA does not list camelina oil in their nutrient database.
- Medline lists one study using camelina oil, Effect of alpha-linolenic acid-rich Camelina sativa oil on serum fatty acid composition and serum lipids in hypercholesterolemic subjects (Metabolism. 2002 Oct;51(10):1253-60). In this study, camelina oil fared better than canola (aka rapeseed) and olive oil on LDL cholesterol levels and in increasing EPA and DHA levels.
- More information can be found at Canpressco.com.
Chia
- Chia (Salvia hispanica; also known as Salba) seed oil is a good source of ALA but not available everywhere.
- Dried chia seeds have 5 g of ALA per ounce.
Hemp Oil
- Hemp seed oil is also a good source but not available everywhere.
DHA and EPA: Should Vegans Supplement?
You can see from Chart 1 (above) that DHA is a number of steps away from ALA. We know that most people convert some ALA all the way into DHA. A recent study on vegans and vegetarians by Rosell MS, et al. (Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr. 2005 Aug;82(2):327-34) showed the following fatty acid levels in blood:
| Meat Eaters | Vegetarians | Vegans | |
| Number of participants | 196 | 231 | 232 |
| EPA (mg/l) | 23 | 14 | 8 |
| DHA (mg/l) | 53 | 31 | 16 |
The differences among diet groups were all statistically significant. It is not clear whether these lower blood levels in vegetarians and vegans is a problem. Length of time since becoming a vegetarian or vegan did not affect blood levels, indicating that once someone becomes vegetarian or vegan for a short time, their levels stabilize. Unfortunately, omega-3 intake was not measured in this study so there is no way to compare EPA and DHA levels in vegetarians who supplement their diet with ALA.
There is some research showing that it takes 4 months of supplementing the diet with extra ALA (e.g., through flax, canola, etc.) before significant amounts of DHA are produced. Older people and diabetics tend to have a harder time converting ALA into DHA. It is possible that people who eat fish regularly for most of their lives have a harder time converting ALA into DHA because their bodies are not used to needing this conversion process.
Note that it is easier for the body to convert ALA into EPA and if you supplement with DHA, your body can convert some of it (about 10%) into EPA. If you are supplementing your diet with both ALA (through flax or canola) and DHA, EPA levels should probably be fine. However, there is now an EPA/DHA supplement available from Switzerland and they ship to the U.S. (see list below)
While many vegetarians have obviously survived just fine without taking EPA or DHA supplements, some might have become depressed or had other problems from low DHA levels. We don't know whether all vegetarians or vegans should supplement with DHA for optimal health, although some do.
To be safe, I now take one bottle of Omega-Zen-3 at a rate of 300 or 600 mg/day until the bottle is gone at least once a year. Because it is not clear that the lower blood levels in vegans is a problem, I only take it once a year to replenish my stores. However, I do not know how long my stores stay replenished.
If a vegan is suffering from depression, I, and some other health professionals, recommend a supplementation of 300 mg/day indefinitely.
Vegan EPA/DHA supplements:
- Water4Life V-PURE vegan EPA & DHA
supplement.
90 vegetable capsules per bottle
25 mg EPA and 90 mg DHA per capsule.
Now available in the USA from Pangea.
- NuTru's O-Mega-Zen3
In vegetable-based gelcaps; 300 mg of DHA per capsule.
Available from Pangea and Vegan Essentials.
- Deva Vegan Omega-3 DHA
In vegetable-based gelcaps; 200 mg of DHA per capsule.
Available from VegetarianVitamin.com
- Dr. Fuhrman's
DHA Purity - Dr. Fuhrman takes much care to prevent rancidity.
- Genestra Neurogen DHA
Marketed by Seroyal out of Toronto Ontario. Call 800-263-5861. 100 mg DHA per capsule.
- Neuromins© DHA is available at most health food stores, but it comes in gelatin capsules.
Other Resources
Another good article is Questions and Answers about Omega-3 Fatty Acids for Vegans (p. 22 - 26) by Reed Mangels, PhD, RD. It basically says the same things as I say here but if you are looking for another source check it out.
Footnotes
1. Mahan LK, Escott-Stump S. Krause's Food, Nutrition, & Diet Therapy, 10th ed. Philadelphia, PA: W.B. Saunders, Co., 2000.
2. Personal communication with Gary Fraser of the Adventist Health Study. October 22, 2001.
3. Fraser GE. Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. Am J Clin Nutr. 1999 Sep;70(3 Suppl):532S-538S.
4. Roshanai F, Sanders TA. Assessment of fatty acid intakes in vegans and omnivores. Hum Nutr Appl Nutr. 1984 Oct;38(5):345-54.
5. Conquer JA, Holub BJ. Supplementation with an algae source of docosahexaenoic acid increases (n-3) fatty acid status and alters selected risk factors for heart disease in vegetarian subjects. J Nutr. 1996 Dec;126(12):3032-9.
6. Mezzano D, Munoz X, Martinez C, Cuevas A, Panes O, Aranda E, Guasch V, Strobel P, Munoz B, Rodriguez S, Pereira J, Leighton F. Vegetarians and cardiovascular risk factors: hemostasis, inflammatory markers and plasma homocysteine. Thromb Haemost 1999 Jun;81(6):913-7.
7. Artemis P. Simopoulos, MD, Alexander Leaf, MD, Norman Salem, Jr, PhD. Workshop on the Essentiality of and Recommended Dietary Intakes for Omega-6 and Omega-3 Fatty Acids. National Institutes of Health (NIH) in Bethesda, Maryland, USA, April 7-9, 1999.