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If they don't eat fish, vegans and vegetarians get very little EPA and DHA, the long chain omega-3 fatty acids we are told are key for maintaining cardiovascular and cognitive health. But is this a problem that needs to be fixed? And are algal omega-3 supplements the answer?
The jury on this question appeared to be out at the 6th International Congress on Vegetarian Nutrition at Loma Linda University (California) this week, in which delegates were told by successive speakers that vegans and lacto-ovo vegetarians (who don't eat fish) are significantly less likely than their non-vegetarian counterparts to develop heart disease, despite their low or zero intakes of EPA and DHA.
There is also no evidence that vegans and vegetarians are at higher risk of depression, Alzheimer's disease or other cognitive problems, delegates were told.
There are clearly independent health benefits for alpha linolenic acid (ALA) which often times get overlooked.
The cardio benefits of a vegan or vegetarian diet could be attributed to the fact that the they typically eat more fiber, less saturated fat, and fewer calories as well as consuming more cardio-protective phytochemicals, plant-based healthy fats (including the omega-3 fatty acid alpha-linolenic acid or ALA from walnuts, flaxseed and other sources), said researchers.
But should they still take EPA and/or DHA supplements? Or is eating a lot of ALA—which the body is very inefficient at converting to EPA and DHA—sufficient?
While most of the literature about the cardiovascular benefits of omega-3s is about EPA/DHA, there is some evidence that ALA has heart health benefits beyond its impact via the conversion to EPA and DHA, said Sujatha Rajaram, PhD, associate professor in the Dept of Nutrition at Loma Linda University.
"There is some evidence to suggest a role for ALA in reducing the risk of coronary heart disease and type 2 diabetes.
"There are clearly independent health benefits for ALA which often times get overlooked", added Dr. Rajaram, who has conducted several studies exploring the relative impact of walnuts (which contain ALA) versus fatty fish (which contain EPA and DHA) on biomarkers of cardiovascular risk.
Dr. Tom Sanders, a professor in the Department of Medicine at King's College in London—who also notes that arterial aging as measured by arterial stiffness "appears lower in vegans than in omnivores"—said he was not convinced that vegans and vegetarians should worry about their low or zero EPA/DHA intakes.
Meanwhile, studies suggesting that high dose DHA supplements could raise LDL cholesterol made him "a little nervous" about recommending that vegans and vegetarians rush out to buy algal DHA supplements, he said.
While some vegan and vegetarian organizations actively recommend that these groups take supplements, "present evidence does not justify advice to vegetarians and vegans to consume long-chain omega-3 fatty acids," claimed Dr. Sanders.
The vegetarian society is rather neutral on this issue, however, noting that, "If, as a vegetarian you want a source of DHA and EPA then there are a number of vegetarian supplements available."
Asked to comment on the issue, Adam Ismail, Executive Director at the Global Organization for EPA and DHA Omega-3s (GOED), told FoodNavigator-USA: "Ultimately everybody needs to know their omega-3 status, and that should guide people on whether or not they need to increase their intakes."
While vegetarians in general have lower rates of heart disease, he acknowledged, "omega-3s are important for more than just managing the heart. They are really important in reproduction and development, managing the health of your brain and eyes, and helping maintain normal inflammation. So regardless, everybody needs to get omega-3s in their diet."
He added: "Vegetarians are one of the groups that can convert short-chain omega-3s more efficiently than the rest of the population, but it ultimately comes down to your individual body which is why knowing your status is important. The most efficient way will always be to consume EPA and DHA directly."
Even if LDL is raised, it is still beneficial to take omega-3s because of the other cardio-protective changes.
Asked to comment on Sander's reference to LDL cholesterol, he said: "In general, the increase in cholesterol is usually seen in people taking very high dosages of EPA and DHA.
"In addition, omega-3s increase HDL cholesterol levels and reduce triglyerceride levels, which are beneficial effects that have to be considered in combination with an increase in cholesterol."
GOED recently commissioned a Hazard Characterization on EPA and DHA from Spherix Consulting, one chapter of which analyzed the cholesterol studies, he said.
"The basic gist is that even if LDL cholesterol is raised, it is still beneficial to take omega-3s because of the other cardio-protective changes. Also, there is research to show that your omega-3 status is a better predictor of cardiovascular mortality risk than cholesterol or other markers used in [cardiovascular disease] diagnosis."
The Spherix Consulting analysis said more research was needed, but noted that "a blood lipid profile change after consumption of fish oil that includes a shift toward increased LDL, increased HDL, and reduced triglycerides (TAGs) would still be considered a favorable outcome, as lowered HDL and raised fasting levels of TAGs are considered cardiovascular disease risk factors (Cottin, et al. 2011).
"Authoritative researchers have suggested that the reduction in TAGs may be due to reduced hepatic de novo lipogenesis which, over the long term, might contribute to lower cardiovascular risk (Mozaffarian and Wu 2011.)"
Are all n-3 fatty acids created equal? 6th International Congress on Vegetarian Nutrition (2013), Loma Linda, California