Fri, 24 May 2013 - 9:58 p.m. MT
Credit: ARA Staff - American Running Association
Prescriptions for cholesterol-lowering statins are at record highs; 355 million of them were written in 2010. This remedy for heart disease, high blood pressure, and other problems linked to high LDL is a kind of modern marvel, with drugs like Lipitor, Zocor, and Crestor recording sales in the tens of billions. Eight years in a row, Lipitor has been the number-one selling drug in America. But a Canadian study published in August in JAMA reports that a healthy diet may be just as effective as statins in reducing LDL levels.
According to the study, subjects who followed a diet heavy in soy protein, nuts, grains, and other plant sterols saw a 13 to 14 percent decline in cholesterol levels after six months. These results offer hope to those at high risk of heart disease, in the form of a natural, inexpensive strategy that helps you take control of your own health. But doctors caution that diet isn’t a silver bullet cure either. Many worry that the news might encourage patients to risk their health by abandoning cholesterol-controlling drugs. Who makes the better argument, and how might both sides be reconciled to maximize efforts to reduce heart disease?
The study highlights consumption of cholesterol-lowering foods, a proactive approach, as more effective than simply avoiding certain foods (such as those high in saturated fat). But an even more controversial finding is that the authors assert it’s possible to drop LDL levels by as much as half of those seen in people who take a statin. That’s newsworthy.
There is reasonable debate on both sides here. People should not assume they can abandon their current statin—after all, the drugs work. There are decades’ worth of evidence that statins reduce heart attack risk. On the other hand, just because the clinical evidence is not currently as broadly reported for LDL-lowering foods does not mean they, too, don’t have an important role, perhaps one that will be increasingly emphasized as more studies follow.
The randomized, controlled trial in Canada looked at the dietary effect on blood lipids of cholesterol-lowering foods given at two levels of intensity. The theory behind the study was that combining foods with recognized cholesterol-lowering properties (a “dietary portfolio” in the study’s terms) has proven highly effective in lowering serum cholesterol under metabolically controlled conditions.
Over 300 participants with hyperlipidemia from four participating academic centers across Canada were assigned randomly one of three treatments lasting six months. The subjects received dietary advice on either a low saturated fat therapeutic diet (control) or a dietary portfolio, “for which counseling was delivered at different frequencies, that emphasized dietary incorporation of plant sterols, soy protein, viscous fibers, and nuts.” The “routine” dietary portfolio involved just two clinic visits over the six months, while the “intensive” dietary portfolio involved seven clinic visits over six months.
Subjects were instructed to eat a handful of nuts such as almonds or walnuts every day, and to substitute milk and meats with soy and tofu products as much as possible.
Among the 267 subjects who completed the trial, all three groups lost roughly an equal amount of weight—between about 2 pounds 10 ounces and 3 pounds 12 ounces—after six months. But those on one of the portfolio diets—intensive or routine—saw their LDL cholesterol levels decline between 13.1 percent and 13.8 percent after six months. Subjects on the low-saturated-fat diet had, on average, just a 3 percent reduction in their LDL cholesterol in the same period.
The study is certainly not the first to find that certain foods have bad-cholesterol lowering properties. Soy protein, for example, has long been reported by the American Heart Association (AHA) to reduce LDL and promote heart health.
In the late 1970s and early 1980s, the soy protein hypothesis was greatly strengthened as a result of studies that found that diets high in soy protein, replacing nearly all the animal protein, substantially reduced blood LDL cholesterol by 20 to 30 percent in severe hypercholesterolemia. Because the soy protein diets were also reduced in saturated fat and cholesterol and increased in polyunsaturated fat and because the patients also often lost weight on the dietary protocols, the results were often confounded. The authors reported that textured soy protein (50 percent soy flour, 50 percent soy protein concentrate) but not soy protein isolate (90 percent soy protein) was effective. This raised the possibilities that, rather than the soy protein itself, the non-protein components of the soy protein preparation or the effect of soy displacing cholesterol-raising fats in the diet could have had a blood cholesterol–lowering action. Results of other early studies of soy protein in hypercholesterolemic subjects showed either cholesterol reduction or no effect.
In 2000, the AHA Nutrition Committee released a scientific advisory on soy protein and cardiovascular disease (CVD). At that time, the conclusion was that “it is prudent to recommend including soy protein foods in a diet low in saturated fat and cholesterol.” Since then, many well-controlled studies on soy protein and soy-derived isoflavones substantially added to the knowledge base. For this reason, the AHA Nutrition Committee decided to reevaluate the evidence on soy protein and CVD and update its scientific advisory.
More recently, their scientific advisory reported that in the majority of 22 randomized trials, isolated soy protein with isoflavones, as compared with milk or other proteins, decreased LDL cholesterol concentrations; but the average effect was just 3 percent. This reduction is very small relative to the large amount of soy protein tested in these studies, averaging 50 grams, about half the usual total daily protein intake. No significant effects on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure were evident. Among 19 studies of soy isoflavones, the average effect on LDL cholesterol and other lipid risk factors was next to nothing.
Still, many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Soy protein has gained considerable attention for its potential role in improving risk factors for CVD. In October of 1999, the U.S. Food and Drug Administration (FDA) approved labeling for foods containing soy protein as protective against coronary heart disease. The FDA based this decision on clinical studies showing that at least 25 grams of soy protein per day lowered total and LDL cholesterol. The FDA requires for the claim that a serving contain at least 6.25 grams of soy protein, 25 percent of the necessary daily amount (25 grams), with the expectation that foods containing soy protein would be eaten at least four times per day. The FDA also stated that “the evidence did not support a significant role for soy isoflavones in cholesterol-lowering effects of soy protein.”
Using these proteins and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol will confer benefits to cardiovascular health. Soy protein also may be used to increase total dietary protein intake and to reduce carbohydrate or fat intake.
While one in about 100 people have a soy allergy, nearly one in six Americans has a high overall cholesterol level, which makes a person nearly twice as likely to suffer a heart attack or stroke as someone whose total cholesterol falls into a healthy range. LDL cholesterol is one component of this overall number. Multiple strategies are called for in the fight. Statins have a well-defined role, but perhaps an inherent limitation in that they manage or postpone the underlying causes of CVD. A permanent change in diet, looking past mere avoidance of saturated fat, will do the same—sometimes maybe even better—but without the need to ingest, not to mention pay for, medication every day for the rest of your life.
JAMA, 2011, Vol. 306, No. 8, pp. 831-839, http://jama.ama-assn.org/content/306/8/831.abstract
AHA Science Advisory: Soy Protein, Isoflavones, and Cardiovascular Health, http://circ.ahajournals.org/content/113/7/1034.full
NPR, Airtalk, Aug. 29, 2011, “Cholesterol – the good, the bad and the debate over drugs vs. diet,” http://www.scpr.org/programs/airtalk/2011/08/29/20467/cholesterol-good-and-bad/
(RUNNING & FITNEWS® September / October 2011 • Volume 29, Number 5)
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