Elevated CRP Can Foil Dietís Ability to Lower Cholesterol

June 20, 2005

(University Park, Pa) — Trying to lower your LDL-cholesterol through modest changes alone may not work for individuals with have high levels of C-reactive protein (CRP) — a marker in blood for inflammation that is strongly associated with heart disease — according to a recent Penn State study.

Kirsten Hilpert, a doctoral candidate in the nutrition option of Penn Stateís Integrative Biosciences program, conducted a small study of the Step 1 dietís effect on men and women with moderately elevated cholesterol. She found that those who also had elevated CRP levels couldnít lower their LDL-cholesterol numbers with the Step 1 cholesterol-lowering diet, even when soy protein — a food with an approved heart health claim from the U.S. Food and Drug Administration Ė was added to the diet.

The National Cholesterol Education Program Step 1 diet, the first level of treatment for high cholesterol, is a low-fat diet that restricts total fat to 30 percent of calories with saturated fat less than 10 percent.

—Although there are specific dietary factors like soy that have been shown to lower blood cholesterol, not all people experience this benefit,— Hilpert says. “Our study suggests that if your CRP is elevated, you may not be able to reap the full benefit of the Step 1 Diet with or without soy.”

The study is detailed in a paper, “Lipid Response to a Low-Fat Diet with or without Soy Is Modified by C-Reactive Protein Status in Moderately Hypercholesterolemic Adults,” published in a recent issue of the Journal of Nutrition. Hilpertís co-authors are Dr. Penny Kris-Etherton, distinguished professor of nutrition, and Dr. Sheila West, assistant professor of biobehavioral health.

Hilpert points out that, in recent studies, other researchers noticed that only individuals with low CRP levels experienced significant reductions in total cholesterol when consuming the DASH diet, a low-fat, low sodium diet shown to reduce high blood pressure.

The Penn State researchers decided to see if CRP status had the same effect when subjects consumed a cholesterol-lowering diet. Their study is among the first to test whether or not CRP status can predict a personís lipid response to a cholesterol-lowering diet including soy.

The researchers recruited 32 older, overweight people with moderately elevated cholesterol. The participants included 14 men and 18 women, six of whom were receiving hormone replacement therapy. Their LDL cholesterol was in the 124 to 211 mg/dl range.

For three weeks, each participant ate only foods on the National Cholesterol Education Program Step 1 diet prepared in the research kitchen. For the next six weeks, they were fed the Step 1 diet plus 25 grams of soy protein or milk protein, after which their blood samples were drawn. The participants then took a two-week break and ate their usual diet before returning to eating only foods from the research kitchen.

In the final six weeks of the study, the participants again ate the Step 1 diet with either soy or milk protein added. Those that had had soy protein in the earlier six-week phase received milk protein and vice versa, after which their blood samples were drawn again.

Analysis of the participantsí blood samples showed that the Step 1 diet only lowered LDL-cholesterol in people with low CRP levels. LDL-cholesterol levels in those who had elevated CRP were, in fact, increased even further as the result of the diet. Adding soy or milk protein to the Step 1 diet did not affect either cholesterol or CRP levels.

“These results suggest that habitual consumption of a Step 1 diet may beneficially affect individuals with CRP levels less than 3.5 mg/L, the median level of the study, and may have deleterious effects in patients with elevated levels,” Hilpert says. “If these results are confirmed in other studies, the next question is whether lowering CRP will improve diet response.”

Funding from Protein Technologies International, now known as The Solae Company, supported the study.

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Editors: Hilpert can be reached at (814) 863-0926 or kfc107@psu.edu.  For additional information, please contact Barbara Hale in the Penn State Office of Science and Research Information at (814) 865-9481 or bah@psu.edu.