Dumping on Omega-3's It was a long, tough fight for those of us who helped shove the neglected Omega 3 (3) fats out of nutrition's gray zone into their rightful place as pivotal players. But no sooner was I settling into complacency, when odd and scary reports began drifting in. A series of articles in '93 and '94 medical journals warned that "high levels" (in the diet and in the blood) of the primary essential Omega-3 fat - alpha linolenic acid (ALA) - were associated with men's risk of developing advanced prostate cancer. Soon, newspapers and popular magazines were trumpeting the dangers of consuming vegetable oils high in ALA. The basic study, however, had specifically found animal fats from red meats to be the chief culprits. [E. Giovannucci, et al., Journal of the National Cancer Institute, Vol. 85, No. 19, Oct. 6, 1993.] It depended solely on statistical analyses of food-frequency questionnaires, filled out in 1986 by over 47,000 men initially free of diagnosed cancer. By the beginning of 1990, follow-up questionnaires to the men revealed 300 cases of prostate cancer, 126 of these advanced. From the men's reported food intakes, researchers concluded "animal fat, especially fat from red meat, is associated with an elevated risk of advanced prostate cancer." Then comes the truly strange part: the actual fatty acid they found to be "most strongly related to risk" was alpha-linolenic. That's because, believe it or not, they said red meat is "relatively high" in Omega-3 ALA and low in the primary essential Omega-6 - linolenic acid. Or stated another way, "animal fat is a relatively good source of alpha-linolenic acid but a poor source of linolenic acid" I beg your pardon, Dr. Giovannucci et al. Red meat (beef, pork and lamb) and its fat are poor sources of Omega-6 linolenic, but are far poorer sources of ALA! Consult any reliable fatty acid table: typical cuts of beef, lamb, and pork contain from 2 to 13 times more Omega-6 linolenic than Omega-3 ALA. (Note: Pork products contain about five times more Omega-6 linolenic than lamb or beef, but still only a smidgen of ALA.) In other words, the researchers goofed on their basic premise. Their tangled statistical analyses of the diets reported some years earlier "proved" that the fat in red meat responsible for advanced prostate cancer was Omega-3 ALA, when there's little of it in red meats, and so much less of it than Omega-6 linolenic. Moreover, they did not include Omega-6 arachidonic acid content of red meats - a puzzling oversight. The actual sources of Omega-3 ALA in the diets of the men with advanced prostate cancer probably would have been, typically, soy oil in salad dressings and cooking oils - but the researchers explicitly stated it was not ALA from vegetable sources but only ALA from animal products that was associated statistically with prostate cancer. Great statistics! Incidentally, the calculated levels of Omega-3 ALA in the diets, according to the researchers, ranged from low to moderate. By my standards, based on work by careful scientists, even the highest levels were very low! In contrast, Omega-6 linolenic acid intake (from salad dressings, mayonnaise, grains, etc., as well as from red meat) tended to be high, as is typical in U.S. diets. A high Omega-6, low Omega-3 intake ratio admittedly is a recipe for trouble, including cancer. Dr. Stephen C. Cunnane of the University of Toronto in his chapter in Flaxseed in Human Nutrition (AOCS Press, 1995) questions the interpretation given to the data, in light of "strong evidence that ALA is not cancer promoting in animals" and that "lean cuts of red meat contain almost undetectable ALA." Processed red meats, i.e., sausage, lunch meat, etc., contain more fat, more ALA, but also more Omega-6 linolenic - again, about 6 to 8 times more linolenic than ALA.  This muddled study, full of
contradictory, oddly conceived
conclusions, did not deserve the
hoopla it got. Nobody in the press
apparently checked it against food
tables but swallowed it whole, issuing
wholesale warnings about red meat
and/or ALA. I remember in 1981 a
similar to-do in medical journals
about ghastly consequences of taking
more than 100 to 300 I.U. of vitamin
E. A nurse friend cautioned me
sternly about it. For years afterwards
I'd see anti-vitamin E admonitions in
the medical media. I'll bet those
doctors (and their patients) are sorry
now, what with all the current kudos
(finally!) in medical literature for
vitamin E as a heart-saving, primo
antioxidant.
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