The hype about ALA conversion contains half-truths.
Claims that the human body cannot convert ALA into EPA and DHA in sufficient quantities to do any good is one of those half-truths that vested interests love to exploit. Humans, from fetus to old-age, are able to convert ALA to DHA, a process observed in other species as well.1 Even vegetarians do not suffer if their diets contain no additional DHA in their diets.2, 3 (Review the conversion process in the Introduction.)
Make no mistake, DHA (along with AA) is very important to the body: for brain function and development, vision, sperm counts, protection of the heart, and for anti-inflammatory action. In fact, DHA is the most abundant EFA in the brain, mothers milk, and the eyes.
EFA must be converted from ALA, otherwise life would literally cease to exist4 but that part is rarely mentioned. Instead, the trend today is to promote a fear that people must get their DHA from fish. If that were truly the case, people walking around without benefit of fish oil supplements or even access to fish and who are only able to rely on plant-based oils would be dead or very close to it. Since DHA remains in the body for only about a week,5 humans are converting what they need, when they need it.6 Some people convert more slowly while others do so rapidly. Women possess a greater capacity to convert ALA than men, no doubt to compensate for pregnancy.
One small study showed that the women involved were able to convert an average of 36% of the ALA they were given into long chain derivatives (21% EPA, 6% DPA, and 9% DHA).7 Another small study with men, showed that they converted an average of 16% of the ALA they received into long-chain derivatives (8% EPA and 8% DPA but no DHA)8 although another study did show that men do convert ALA to DHA just as well.9
Research has also proven that as quantities of dietary DHA increased, synthesis of DHA from ALA decreased but was not totally suppressed, even when the DHA levels are increased to very high concentrations. This means that the natural ability to convert ALA to DHA diminishes as more supplemental DHA is taken in but does not stop entirely. Studies conducted in Japan confirmed these findings. Ten months of feeding ALA to elderly volunteers (ages 67-91) showed serum increases of DHA. This surprised researchers since the regular intake of long-chain omega-3s from fish had been very high. The conclusion was that DHA synthesis from ALA is a continuing process and the body adjusts to fulfill essential brain functions.10
The following is but one example that gives a suitable amount of EFAs one should consume while also taking into account the currently accepted conversion rate of 1% ALA to DHA.
- One tablespoon of hempseed oil or 1 ounce of shelled hempseed per day supplies roughly 6.6 grams of omega-6 and 2.2 grams of omega-3s, which is the right amount required for a 2000-calorie diet.11
Why not flaxseed? Flaxseed has an overabundance of omega-3s and is good for a short-term treatment of an omega-3 deficiency. For long-term health maintenance, however, hemp seed or chia seed are better alternatives because they are the closest to the ratio the human body demands which is roughly 3:1 (omega-6 to omega-3). Hemp seed and chia seed have this ratio. Flaxseed has an opposite ratio of 1:3. In addition, flaxseed cannot be digested unless it is ground up, which increases the risk of oxidization. This is also true of hemp seed and the reason why both seeds need to be refrigerated. Chia seed, however, does not have this problem as it contains natural antioxidants that keep it from spoiling.12
When using plant-based oils, conversion rates increase when other nutrients are present. Although recommendations vary as to which nutrients, most agree that these are necessary to help increase the conversion of ALA to its necessary derivatives: zinc, selenium, magnesium, folic acid, and vitamins B3 (niacin), B6 and C.13, 14
Researchers have compared the effects of supplying ALA of vegetable origin with marine sources of DHA and EPA. They determined that there was very little differences between the two as far as effect on humans were concerned.15 However, it has been found that vegetable oils containing SDA (hempseed, black currant seed, and echium oils) could be more effective in increasing tissue EPA concentrations than the currently ALA-containing vegetable oils.16, 17
Medium-chain fatty acids from plant-based oils are more easily digested than long-chain fatty acids from fish, for example. When long-chain fatty acids are eaten, they must be emulsified by bile salts in the small intestine before they can be absorbed into the body. Short- and medium-chain fatty acids are absorbed directly through the portal vein to the liver, where they are immediately available to the body. Medium chain fatty acids also help increase the absorption of such nutrients as the fat-soluble vitamins A, E, D, and K as well as magnesium, calcium, carotenoids, flavonoids, and the supplemental long-chain fatty acids EPA, DHA, and GLA.18
It seems obvious that adding fish oil to an already bad diet is not the answer for preventing disease. A good diet, complete with vital nutrients, is the overall answer as well as the more immediate solution that requires the conversion of parent essential fatty acids into the components the body requires on a daily basis.
- 1Brenna. March, 2002. “Efficiency of conversion of alpha-linolenic acid to long-chain n-3 fatty acids in man.” Current Opinion in Clinical Nutrition and Metabolic Care 5(2):127-32.
- 2Kwok, Woo, Ho, and Sham. 2000. “Vegetarian and ischemic heart disease in older Chinese women.” Journal of the American College of Nutrition 19(5):622-27.
- 3Li, Sinclair, Wilson, Nakkote, Kelly, Abedin, Mann, and Turner. 1999. “Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men.” American Journal of Clinical Nutrition 69:872-82.
- 5Rose, Richard. The Hempnut Cookbook. 2004.
- 7Burdge and Wootton. 2002. “Conversion of alpha-linolenic acid to eicosapentaenoic, docosapenta-enoic and docosahexaenoic acids in young women”. British Journal of Nutrition Oct.88(4):411-20.
- 8Burdge, Jones, and Wootton. 2002. “Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men. British Journal of Nutrition Oct.88(4):355-63.
- 9Emken, Adolf, and Gulley. 1994. “Dietary linoleic acid influences desaturation and acylation of deuterium-labelled linoleic and linolenic acids in young adult males.” Biochimica et Biophysica Acta Aug.1213(3), 277-88.
- 10Willard, Harmon, Kaduce, Preuss, Moore, Robbins, and Spector. 2001. “DHA synthesis from n-3 polyunsaturated fatty acids in differentiated rat brain astrocytes.” Journal of Lipid Research 42:1368-376.
- 11Duff. May, 2005.
“Hemp Oil.” Taken from Rose, Richard. The Hempnut Cookbook. 2004.
- 12Ayerza and Coates. 2005. Chia: Rediscovering the Forgotten Crop of the Aztecs. University of Arizona Press.
- 13Dr. Alan C. Logan, http://www.genuinehealth.com/english/agh/dacl.php, during a conference call sponsored by Nutrition House, Surrey, BC, Oct. 3, 2005, 7 pm PDT
- 14Erasmus. “Optimum n-3/n-6 Ratio and Optimum Conversion.”
- 15Freese and Mutanen. 1997. “Alpha-linolenic acid and marine long-chain n-3 fatty acids differ only slightly in their effects on hemostatic factors in healthy subjects.” American Journal of Clinical Nutrition 66:591-98.
- 16James, Ursin, and Cleland. 2003. “Metabolism of stearidonic acid in human subjects: comparison with the metabolism of other n-3 fatty acids.” American Journal of Clinical Nutrition 77(5):1140-45.
- 17Surette, Edens, Chilton, and Tramposch. 2004. “Dietary Echium Oil Increases Plasma and Neutrophil Long-Chain (n-3) Fatty Acids and Lowers Serum Triacylglycerols in Hypertriglyceridemic Humans.” American Society for Nutritional Sciences Journal of Nutrition 134:1406-11
- 18PDR Health. “Medium-chainTriglycerides.”
This page was researched in November 2005.