Writing in Prostaglandins, Leukotrienes and Essential Fatty Acids, scientists from Michigan State University, Oregon State University, and the University of BC-Okanagan (Canada) presented data from animal studies that they claim is evidence “for concern due to excessive long chain omega-3 PUFA intakes”.
“The disparity between data discussed in this review and calls for the establishment of DRI [dietary reference intakes] for [long chain omega-3 PUFA] are striking,” they wrote.
“While calls for increasing intake of [long chain omega-3 PUFA] have been made based on epidemiological associations for decreased risk of [cardiovascular disease], there is currently a dearth of validated biomarkers of intake, biological effect, and disease risk associated with high dietary [long chain omega-3 PUFA] intakes.
“However, as there are insufficient data to establish an upper level where toxic effects of [long chain omega-3 PUFA] might be observed, the practice has been deemed as safe.”
The reviewers added that, while data supporting the beneficial effects of omega-3s has been used as justification for the establishment of a DRI for both EPA and DHA, recent studies into atrial fibrillation and prostate cancer have raised concerns over omega-3s, and could be used to establish tolerable upper limits (TUL).
“Use of the IOM DRI framework, guided by validated biomarkers of exposure and risk, could assist our understanding of upper limits for [long chain omega-3 PUFA] intake and potential disease risk associated with overconsumption,” they concluded.
Harry Rice, PhD, V.P., Regulatory & Scientific Affairs for the Global Organization for EPA and DHA Omega-3s (GOED), reacted strongly to the review’s conclusions, and told us that he took exception to the article for many reasons, but two in particular:
“First, while no one can deny that animal research is part of the totality of any body of available scientific evidence, its direct relevance to humans is questionable. How many times has something looked promising in an animal model, but failed miserably in humans? Second, omega-3 intake in the US is so low that it seems futile to make an issue out of excessive intakes.
“To put this into perspective, according to a recent analysis using data from NHANES, daily EPA and DHA intake (food and dietary supplements) in the U.S. in the highest consumers (males of 51+ years) at the 90th percentile is 69 mg and 234 mg, respectively. The combined total is just 1/10 of the FDA daily limit of three grams, which was based on a 1989 report. In the unlikely event intakes should approach the three gram limit, there is recent evidence that much higher levels can be consumed without adverse health effects.
“In 2011, the Norwegian Scientific Committee for Food Safety (VKM) reported that it was not possible to identify clear adverse effects from EPA and DHA up to the dosage of 6.9 g/day,” added Dr Rice.
“In 2012, the European Food Safety Authority (EFSA) reported that supplemental intakes of EPA and DHA combined at doses up to 5 g/day do not raise safety concerns.
“Also, GOED's commissioned safety evaluation from 2012 identified no appropriate studies to define specific intake levels or intake/response relationships that could be used to define a tolerable upper intake level.”
Source: Prostaglandins, Leukotrienes and Essential Fatty Acids
Published online ahead of print, doi: 10.1016/j.plefa.2013.09.011
“Immunomodulation by dietary long chain omega-3 fatty acids and the potential for adverse health outcomes”
Authors: J.I. Fenton, N.G. Hord, S. Ghosh, E.A. Gurzell