A recent study published in the British Medical Journal doubts the benefits of consuming omega-3 fatty acids. Despite vast research showing a reduced number of deaths from cardiovascular disease due to consumption of omega-3. Dr Mike Knapton of the British Heart Foundation isn't convinced. Reuters reports:
"People should not stop consuming omega-3 fats or eating oily fish as a result of this study," he said in a statement issued by the foundation.
"Until now, medical research has demonstrated a benefit from omega-3 fats in protecting people from heart and circulatory disease. This systematic review of numerous studies concludes that there is no clear evidence either way," he added.
Dr. Fuhrman says this does little to alter his conviction that for those who are deficient in omega-3 fatty acids, getting more from diet or supplementation is beneficial:
Interesting study, it shows that higher fish intake or use of fish oil did not significantly affect mortality one-way or the other. I guess we would expect to find that. Fish and fish oil are over-hyped as being such wonder foods that will make everyone live longer.
But now let's put this in perspective. Giving B12 to the entire population will not have a significant effect on lifespan either, but give B12 to those B12 deficient people and it will be very significant for them.
This study specifically excluded those studies that checked and monitored blood levels of omega-3 fats. Those studies that do monitor such levels definitely show a strong relationship between fatal heart attacks and omega-3 fatty acid levels in the blood.1
Since most people are not deficient in these fatty acids, taking more is not protective, but in a vegan population who does not eat any fish, a certain percent will be deficient in DHA. DHA deficiency is an important thing to avoid; it can lead to depression, dementia and later life neurological deterioration. And this study did not show fish or fish oil would not increase lifespan in a vegan population or a group documented to be low in omega-3 fatty acids, which has already been demonstrated in other studies.
So this finding takes the edge off all the high intake of fish and fish oil hype, but it does not make it less important to make sure that a deficiency does not exist in anything (including long chain omega-3's) and it is still important to take a supplement or to have ones blood drawn to make sure your level is adequate.
So even if this study is correct and that eating fish or taking fish oil or (vegan) DHA supplement does not have a significant effect on longevity for most people, there are still other good reasons to assure nutritional adequacy with supplementation. Epidemiological data indicate decreased plasma DHA interacts with genetic and other environmental influences to predispose people to dementia. Approximately 40% of fatty acid phospholipids in the brain are DHA. Individuals with dementia have lower plasma phospholipid DHA levels in the brain compared to controls. Prospective studies have reported consumption of at least 1 fish serving per week decreases risk of Alzheimer's disease by 60%. Preliminary data suggest that after adjustment for age, gender, apoE genotype, and homocystine levels, the top quartile of plasma DHA of approximately 2.7 or more servings of fish/week or 180 mg or more DHA/day is associated with 50% decreased risk of dementia.
1. N Engl J Med 2002;346:1113-8). Albert et al.
Here are some additional resources:
Tully AM; Roche HM; Doyle R; et al. Low serum cholesteryl ester-docosahexaenoic acid levels in Alzheimer's disease: a case-control study.Br J Nutr. 2003; 89(4): 483-9.
Myers RH, Schaefer EJ, Wilson PW, et al. Apolipoprotein E epsilon4 association with dementia in a population-based study: The Framingham study. Neurology. 1996;46: 673-677.
Soderberg M, Edlund C, Kristensson K, et al. Fatty acid composition of brain phospholipids in aging and in Alzheimer's disease. Lipids. 1991; 26: 421-425.
Conquer JA, Tierney MC, Zecevic J, et al. Fatty acid analysis of blood plasma of patients with Alzheimer's disease, other types of dementia, and cognitive impairment. Lipids. 2000; 35: 1305-1312.
Schaefer E. Omega-3 fatty acids and dementia. Presented at the omega-3 fatty acids: Recommendations for therapeutics and prevention symposium. May 21, 2005. New York.