In recent years, I have been taking DHA, a long-chain, omega-3 fatty acid, as a supplement form in the hopes of preventing dementia and have been recommending others do the same. I have recently changed my thinking about taking this supplement.
UPDATED: November 6, 2019
I have been recommending others take a DHA supplement, largely on the basis of reports in the medical journals, such as these:
Journal of Nutrition. 2010 Apr; 140(4): 869–874. DHA May Prevent Age-Related Dementia. Greg M. Cole* and Sally A. Frautschy
Monday, October 28, 2019. News & Perspective Drugs & Diseases CME & Education Academy Consult Video From Medscape Family Medicine. DHA and Dementia: Preserving Cognition in the Aging Patient. Authors: Sally A Frautschy, MS, PhD; Greg M Cole, PhD
The reports like those above are filled with suggestions that DHA might be of some value in brain function, but none present ironclad research proving a solid connection between DHA deficiency and dementia in vegans. Very importantly, no study conclusively demonstrate that DHA supplementation will prevent or reverse dementia in vegans. Several authors of these reports, like Greg Cole, PhD cited above, have received money from companies that make DHA supplements and cannot be regarded as unbiased researchers.
As you will see in this brief video, I have changed my thinking about taking this supplement due to (1) the lack of solid scientific evidence of dementia prevention in vegans through DHA supplementation and (2) concern over increased cancer risk:
The most worrisome reason that I have stopped taking DHA supplements and no longer recommend that others ingest this substance is that researchers at the Fred Hutchinson Cancer Research Center and others have found, in a subset of men, a strong link between high levels of DHA in their blood and tissues and the development an aggressive form of prostate cancer.
Here's what the recent studies show on the effects of DHA:
British Journal of Nutrition
14 November 2012 , p. 1721
JNCI: Journal of the National Cancer Institute
JNCI: Journal of the National Cancer Institute, Volume 105, Issue 15, 7 August 2013, Pages 1132–1141
Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial
Theodore M. Brasky, Amy K. Darke, Xiaoling Song, Catherine M. Tangen, Phyllis J. Goodman, Ian M. Thompson, Frank L. Meyskens, Jr, Gary E. Goodman, Lori M. Minasian, Howard L. Parnes, et.al.
Canadian Urological Association Journal
Can Urol Assoc J. 2013 May-Jun; 7(5-6): E333–E343.
"Furthermore, the presence of long chain n-3 PUFA (DHA and EPA) in the prostate cell’s beta-oxidative metabolic process leads to the formation of lipid hydroperoxides in the microenvironment of the cell; this can generate reactive species.55–56 With chronic exposure to these reactive molecules, the prostate cell can become dysplastic and develop into an aggressive cell.
Prostate Cancer and Prostatic Diseases
55. Liu Y. Fatty acid oxidation is a dominant bioenergetic pathway in prostate cancer. Prostate Cancer Prostatic Dis. 2006;9:230–4.
International Journal of Cancer
56. Federico A, Morgillo F, Tuccillo C, et al. Chronic inflammation and oxidative stress in human carcinogenesis. Int J Cancer. 2007;121:2381–6.
Lemaitre RN, Tanaka T, Tang W, et al. Genetic Loci Associated with Plasma Phospholipid n-3 Fatty Acids: A Meta-Analysis of Genome-Wide Association Studies from the CHARGE Consortium. PLOS Genet. 2011;7:e1002193. doi: 10.1371/journal.pgen.1002193.
From these studies, I conclude that, although loading up the tissues with pre-formed DHA from supplements may superficially seem to make some sense, apparently “leapfrogging” over the body’s natural enzymatic processes that normally make EPA and DHA from alpha-linolenic acid in our food, and just saturating the prostate cells with pre-formed DHA through supplementation may make the prostate cells unstable and start the cascade towards prostate cancer development in some men.
Whether there is any adverse effects of DHA supplementation upon women is not known at this time, but because “Do no harm” applies to dietary advice, as well, in view of the concerning evidence above, I can no longer recommend that people — especially men — take DHA supplements.
The safest course is to regularly consume walnuts, ground flax and chia seeds and dark green leafy vegetables in smoothies, salads and porridge - while avoiding omega-6 heavy vegetable oils and processed foods — and to let our body make our own DHA.
Science dictates that when newer knowledge is gained that make old concepts obsolete, the previous beliefs must be left behind. My thinking on DHA has certainly evolved on this subject and, as a result, (and with my uncle dying of prostate cancer), I am leaving the algae-derived DHA capsules behind.
To your good health and happiness,
Dr. Michael Klaper