The Fatty Acids
This article discusses how much fat should be included in someone's diet:
Fat in Vegan Diets: How Low Should You Go? by Virginia Messina, MPH, RD
- Saturated Fats
- Trans Fats
- Monounsaturated Fats
- Polyunsaturated Fats
- PUFA Conversion Pathways
- Replacing saturated fats with polyunsaturated fats reduces the risk of heart disease (5) .
- Found in high amounts in animal products; also in high amounts in coconut, palm, and palm kernel oils.
- Found mostly in foods made with partially hydrogenated oils, including margarines, shortening, commercial frying fats, crackers, cookies, and other snacks. Check label.
- The consensus among nutritional professionals is that large amounts of trans fats increase the risk of heart disease and many other diseases.
- A 2008 review (4) of trans fats and cardiovascular health found:
- Five meta-analyses of controlled dietary interventions have examined the relationship between trans fatty acids intake and blood lipid levels and consistently report a worsening of blood lipid profiles with increasing trans fatty acid intakes, with a dose-response relationship evident.
- Four cohort studies report on the association between trans fatty acid intake and incidence of cardiovascular disease. They consistently found that larger amounts of trans fats (about 4 to 6 grams per day) increased heart disease rates by about 25% in comparison with the lowest amounts (about 1 to 2 grams per day).
- Vegetable based trans fats were found to be more harmful than animal-based (those found naturally in ruminent animal products).
- Also see 2010 Trans Fats Update.
- Earth Balance is a vegan margarine that contains omega-3s, no hydrogenated oils, and is available at many natural foods stores.
- Also known as omega-9 fats, n-9, or oleic acid.
- Improve cholesterol levels when replacing saturated fats.
- Abundant in olive oil, canola oil, high oleic sunflower oil, hazelnut oil, high-oleic safflower oil, and almond oil.
- Olive oil is not as refined as other oils, making it a reliable source of vitamin E and possibly other healthy components. If you do not like the taste of olive oil in some dishes, try other oils made of high MUFA.
- Avocados and many nuts (almonds, cashews, filberts/hazelnuts, macadamias, peanuts, and pecans) are high in MUFA. Because nuts are high in nutrients and other protective compounds, you can benefit from eating them on a daily basis.
- In one study, eating nuts (including peanuts (2)) five or more times per week reduced heart disease by about 50% (3).
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.
The following is a list of the notable PUFAs:
- 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 animal flesh. It is also found in very small amounts in leafy green vegetables and other plant foods.
- There is evidence in humans that STA is more readily converted to EPA than is ALA.
- Echium plantagineum is a abundant souce of STA.
- Here are some studies on STA:
- 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.
- EPA is found mainly in fatty fish who get their EPA from seaweed. Vegan EPA supplement are now available. EPA is also present 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.
- DPA has not been studied like EPA and DHA because it is not as prevalent in fish oil and isolated supplements have not been readily available – it is not known if it has any unique functions. A 2011 review (supported by Meat and Livestock Australia) says, "The literature on n-3 DPA is limited, however the available data suggests it has beneficial health effects. In vitro n-3 DPA is retro-converted back to EPA (7)."
- DHA is found in seaweeds and fatty fish. Vegan DHA supplements are available. DHA 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.
LA is the most prevalent omega-6 fatty acid in plant foods and found in most vegetable oils, especially corn, sunflower, "vegetable," soy, safflower, and sesame oils.
GLA is found in evening primrose oil, borage oil, black current oil, and breast milk.
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.
AA is found in meat and peanut oil, and is also made from DGLA. AA is converted into series 2 and 4 eicosanoids. (Cats cannot convert LA to AA, which is why they must have AA supplemented in their diet if they are on a vegan diet.)
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.
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 and ALA compete for D6D. Too much LA will saturate this enzyme and prevent adequate ALA from being synthesized into EPA and DHA and thus increase inflammation from a lack of the series 3 eicosanoids.
However, a 2012 meta-analysis of studies on LA and inflammation found that in the recommended amounts, 3 - 10% of calories, LA did not increase markers of inflammation. Increased LA decreased EPA levels, but did not descrease DHA (1). A study from 1992 (6), vegans ate 9-10% of their calories as LA and, of course, had no natural dietary source of DHA. Whether large amounts of LA harm the DHA status of vegans has yet to be determined.
1. Johnson GH, Fritsche K. Effect of Dietary Linoleic Acid on Markers of Inflammation in Healthy Persons: A Systematic Review of Randomized Controlled Trials. Journal of the Academy of Nutrition and Dietetics. 2012 Jul;112(7):1029-41. | link
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. Booker CS, Mann JI. Trans fatty acids and cardiovascular health: translation of the evidence base. Nutr Metab Cardiovasc Dis. 2008 Jul;18(6):448-56. Epub 2008 May 12. | link
5. Mozaffarian D, Micha R, Wallace S. Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Med. 2010 Mar 23;7(3):e1000252. Review. | link
6. Sanders TA, Roshanai F. Platelet phospholipid fatty acid composition and function in vegans compared with age- and sex-matched omnivore controls. Eur J Clin Nutr. 1992 Nov;46(11):823-31. | link
7. Kaur G, Cameron-Smith D, Garg M, Sinclair AJ. Docosapentaenoic acid (22:5n-3): a review of its biological effects. Prog Lipid Res. 2011 Jan;50(1):28-34. Epub 2010 Jul 23. Review. | link