Assuring Neurological Health in Later Life

By Joel Fuhrman, M.D.

Maintaining An Optimal Omega-3 Index Is Crucial, Especially For Vegetarians and Vegans!

Low blood levels of the long-chain omega-3 fatty acids, EPA and DHA, have been associated with higher risk of heart disease and cancer. In randomized prevention trials, consumption of fish or fish oil (about 1 gram per day) has been demonstrated to reduce heart disease mortality as well as total mortality. Omega-3 fatty acids also have demonstrated protection against neurological disease such as depression and dementia.1

Scientists call the amount of EPA and DHA in red blood cell membrane the omega-3 index. This number is measurable in a blood test, and research has documented that an index number of 4% places people at higher risk, whereas an index score of 8% gives significant protection against heart disease.

There are clear benefits to a diet that has less, rather than more, fish, such as reducing breast cancer incidence, 2 and there are drawbacks to consuming fish oil, such as slightly increasing your risk of cerebral hemorrhage. However, those not eating fish, especially vegetarians and vegans, have been shown to have unfavorably low levels of EPA and DHA, which can lead to neurological problems in later life.

About half or less of the fat in fish oil consists of EPA and DHA. So a one-gram capsule of fish oil contains about 400 to 500 mg of EPA and DHA. The question then remains if supplementation with a lower dose of non-fish, algae-derived DHA is sufficient to optimize this omega-3 index for those not eating large amounts of fatty fish or taking fish oil. Recently, a randomized, placebo-controlled study showed that 100 mg of DHA daily increased the omega-3 index from 4.8 (poor) to 8.4 (optimal) percent, demonstrating that even a relatively low dose of pure DHA taken daily is as effective as a much higher amount of fish oil.3

Only a very small amount of pure DHA is needed to optimize the omega-3 index, so this can be achieved without consuming huge amounts of rancid fish oil or flaxseed oil. I recommend that people eating vegan, near-vegan, or flexitarian diets consume 100-200 mg of DHA per day to assure nutritional adequacy of these beneficial fats. Consumption of flaxseed oil can’t assure such benefits as the conversion from short chain (alpha linolenic acid, ALA) into the longer chain EPA and DHA is inefficient and varies greatly from person to person. Only 2-5% of alpha linolenic acid (from flaxseed) is converted to DHA, and flaxseed oil is about half alpha linolenic.4 That means for every 1000 mg flax oil capsule, only about 1.5 mg to 2.5 mg of DHA is generated. An optimal omega-3 index is not generally achieved with flaxseed oil supplementation. It would be foolish to take in large amounts of flaxseed oil in an attempt to achieve adequate omega- 3 status, especially because a high amount of alpha linolenic acid is linked to prostate cancer.5


1. Young G; Conquer J. Omega-3 fatty acids and neuropsychiatric disorders. Reprod Nutr Dev. 2005 Jan-Feb;45(1):1-28.

2. Stripp C; Overvad K; Christensen J; et al. Fish intake is positively associated with breast cancer incidence rate. J Nutr. 2003;133(11): 3664-3669. J Urol 2004 Apr;171(4):1402-7.

3. Geppert J; Kraft V; Demmelmair H; Koltzko B. Docosahexaenoic acid supplementation in vegetarians effectively increases omega-3 index: a randomized trial. Lipids. 2005 Aug;40(8):807-14.

4. Burdge GC; Calder PC. Conversion of (alpha)- linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reprod Nutr Dev. 2005 Sep-Oct;45(5):581-585. Davis BC; Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr. 2003 Sep;78(3 Suppl):640S-646S.

5. Brouwer IA; Katan MB; Zock PL. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr. 2004;134(4):919-22.

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