Dietary Impact on Cholesterol (Published July 28, 2003)

A small, one month study was published in last week's Journal of the American Medical Association. It demonstrated that a diet enriched with fiber and soy protein lowered total and “bad”, or LDL cholesterol, as much as a first generation statin, lovastatin. The media has characterized this as a debate of diet versus drug therapy. In my estimation, assessment of the meaning of this report should not be viewed in that light.

This small study involved 46 men and women with high cholesterol levels. Total cholesterols were between 250 and 260 mg/dL and LDL cholesterols of greater than 160 mg/dL. Sixteen ate the vegetarian diet for one month, 16 consumed a very low-fat diet, and 14 ate the low-fat diet and took 20 milligrams of lovastatin (now available generically) every day for a month.

The fiber-rich vegetarian diet included eggplant, okra, soy protein, almonds, margarine containing plant sterols, barley and psyllium - foods that have demonstrated the ability to lower cholesterol. The study was funded in part by the Canadian government and the Almond Board of California.

The vegetarian group showed an average decrease of 28.6 percent in their LDL cholesterol, the "bad cholesterol.” That was similar to the 30.9 percent reduction seen in the low-fat diet plus statin group. The low-fat diet-only group only had an 8 percent decrease.

But remember that this diet was prepackaged and provided to patients. With that caveat then, these data are not new. What is new is the direct comparison with a first generation, but nonetheless excellent, statin. At the National Institutes of Health during the 1960s, even before I got there, the metabolic wards demonstrated that tight dietary measures produced excellent cholesterol lowering. Our patients ate only that which was provided by our NIH dieticians. These approaches were necessary because our then available medications were quite intolerable or toxic. One can fairly evaluate lipids results only if there is no weight loss, which commonly occurs with extreme diets. The reason is that weight loss spuriously lowers blood fats, which return to true values when weight stabilizes. But the levels of lipid lowering were comparable to those in this recent study, and comparable to the cholesterol lowering ability of the low doses of the first generation statin.

The first statin drug was released in 1987 and changed everything. Because of their potency and safety, statins made strict dietary adherence less of a factor in lipid lowering. Statins are more effective but costlier and potentially riskier than adopting a strict vegetarian diet. But statins provide benefits that curiously have not been associated with blood fat lowering directly. There seem to be blood vessel protection characteristics, stroke prevention, and reduction in inflammatory markers of cardiovascular risk. Also, as has been getting increased attention, there may be some protection against Alzheimer's and osteoporosis. These data are very preliminary and must be interpreted with great caution until validating trials are completed.

Note that increasing data is being accrued demonstrating that statins are protective even if the baseline cholesterol levels are “average”. Note that I did not say “normal”. The accepted average levels of blood fats in the United States may indeed be too high when compared to populations with low incidence of cardiovascular diseases.

So remember that this is not a debate over diet versus drug treatments. These treatments are complementary. Dietary therapy is the basis of front line management. In the absence of a cardiovascular event, dietary and nutritional approaches may be all that is needed. The difficulty with extreme diets is long-term compliance. I have told my lecture audiences that radical diets may not make you live longer, but it sure will seem longer. But if the tolerated diet does not control the blood fats, or if a cardiovascular event has already occurred, then pharmacologic therapy needs to be strongly considered.



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