by J. Raloff
Fish oil is a dietary wonder. It appears to lower the chances not only of developing breast cancer and autoimmune disease but of having heart attacks. It's one of the few substances known to lower concentrations of triglycerides, or fatty substances that pose a cardiovascular risk, in the blood.
Yet many physicians have been reluctant to advocate consuming fish oil in large quantities because this natural fat has the drawback of increasing the proportion of cholesterol shuttled through the blood in low-density lipoproteins (LDLs), another major risk factor for heart disease.
Now, a Canadian study appears to have found a way to redeem fish oil's therapeutic promise -- by marrying it to garlic, a food previously shown to possess a mild propensity for lowering LDL cholesterol.
Bruce J. Holub and Adam J. Adler of the University of Guelph in Ontario randomly assigned a dozen men each to three daily treatments: 900 milligrams of garlic (in the form of three sugar-coated pills), 12 grams of fish oil (in 1-gram capsules), or a combination of the two. A fourth group received garlicfree sugar pills and capsules of a vegetable oil.
The volunteers, each about 45 years old, appeared healthy. However, Holub observes, on the basis of their blood lipids -- principally their concentrations of triglycerides and LDL cholesterol -- each man faced a moderately high risk of heart disease.
Over the 12-week trial, LDL cholesterol concentrations dropped, as expected, by about 14 percent in men taking garlic only, the researchers report in the February American Journal of Clinical Nutrition. Similarly, fish oil capsules reduced a man's triglycerides by some 37 percent, but at the expense of increasing LDL cholesterol concentrations by 8.5 percent.
However, among men getting both fish oil and garlic, triglyceride concentrations fell some 34 percent and LDL cholesterol dropped 9.5 percent.
Currently, Holub says, people at risk of heart disease often receive advice to modify their diet -- specifically to lower their consumption of saturated fats and cholesterol and increase their intake of vegetables and fiber. If this doesn't reduce their blood lipids sufficiently, the next step is usually prescription drugs.
"We'd like to change that approach," he says. Before switching patients to expensive drugs, he thinks, physicians "should consider nutritional supplements that have been shown effective and safe," like this garlicfish oil combination.
"I find this pairing really exciting," says nutrition scientist Penny M. Kris-Etherton of Pennsylvania State University in State College. Not only does it erase the LDL concern that has dimmed fish oil's cardiovascular prospects, she says, it indicates that even for people who follow today's conventional dietary guidelines, "there is more that can be done."
Indeed, she argues, this study ushers in the prospect that other foods beneficial to the heart -- such as tofu, oat bran (SN: 2/1/97, p. 71), or insoluble fiber -- might be added to fish oil and garlic or taken in new combos as improved, natural strategies to fight heart disease.
David G. Robertson of Emory University in Atlanta expresses more tempered enthusiasm. An endocrinologist whose research focuses on cutting heart disease risks, he notes that the magnitude of changes seen in this fairly short trial is "impressive" for nondrug therapies but still leaves lipid concentrations "at least 15 percent above where they ought to be." Such nutritional supplements may still need to be coupled with some drug therapy, he cautions.
Moreover, says Robertson, fish oil and garlic supplements can be as costly as prescription drugs.
Adler, A.J., and B.J. Holub. 1997. Effect of garlic and fish-oil supplementation on serum lipid and lipoprotein concentrations in hypercholesterolemic men. American Journal of Clinical Nutrition 65(February):445.
Kris-Etherton, P.M., T.D. Etherton, and S. Yu. 1997. Efficacy of multiple dietary therapies in reducing cardiovascular risk factors. American Journal of Clinical Nutrition 65(February):560.Further Readings:
Fackelmann, K.A. 1988. Heart studies add to fish-oil controversy. Science News 134(Nov. 26):343.
Harris, W.S., et al. 1990. Fish oils in hypertriglyceridemia: A dose-response study. American Journal of Clinical Nutrition 51(March):399.
Hunninghake, D.B., et al. 1993. The efficacy of intensive dietary therapy alone or combined with lovastatin in outpatients with hypercholesterolemia. New England Journal of Medicine 328(April 29):1213.
Radack, K.L., C.C. Deck, and G.A. Huster. 1990. N-3 fatty acid effects on lipids, lipoproteins, and apolipoproteins at very low doses: Results of a randomized controlled trial in hypertriglyceridemic subjects. American Journal of Clinical Nutrition 51:599.
Raloff, J. 1997. FDA allows heart health claims for oats. Science News 151(Feb. 1):71.
______. 1997. FDA helps you identify heart-y oats! Science News Online (Jan. 25).
______. 1996. More on those "really bad" LDLs ... and the role of triglycerides. Science News Online (Sept. 21).
______. 1996. Fat: If you can't bear to pare it. Science News 149(Feb. 17):108.
______. 1993. Fish oil may ward off 'sudden death.' Science News 144(Dec. 4):380.
______. 1992. Cancer-fighting food additives. Science News 141(Feb. 15):104.
______. 1990. Beyond oat bran. Science News 137(May 26):330.
______. 1989. Fish oil lowers even normal blood pressure. Science News 136(Sept. 16):181.
______. 1989. Fish oil slows some developing cancers. Science News 135(June 24):390.
______. 1988. No fault fat: More praise for fish oil. Science News 134(Oct. 8):228.
Wickelgren, I. 1989. Revealing the finicky functions of fish oil. Science News 135(March 25):183.Sources:
Bruce J. Holub
Department of Human Biology and Nutritional Sciences
University of Guelph
Guelph, Ontario N1G 2W1
Penny M. Kris-Etherton
Pennsylvania State University
College of Health and Human Development
126 Henderson Building South
University Park, PA 16802
David G. Robertson
Division of Arteriosclerosis and Lipid Metabolism
1639 Pierce Drive
Atlanta, GA 30322