More Evidence Links Red Meat to Stroke Risk

Pauline Anderson

January 24, 2012

January 24, 2012 — A new study again has found that higher consumption of both processed and unprocessed red meat is associated with a higher risk for stroke, whereas intake of poultry was associated with a reduced risk.

Dr. Adam Bernstein

"This study adds to a large and growing body of literature on the relationship between red meat and chronic disease," study author Adam M. Bernstein, MD, research director of the Wellness Institute at the Cleveland Clinic, Ohio, told Medscape Medical News.

Previous literature linked red meat with an increased risk for coronary heart disease, diabetes, total mortality, weight gain, and some cancers. "So here we have a number of reasons that one could reduce or eliminate red meat from the diet and find alternative, healthier sources of protein," Dr. Bernstein added.

The study was published online December 29 in Stroke.

Red Meat Risks

The analysis looked at 2 well-known cohort studies, the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS), in which for several years participants regularly filled out food frequency questionnaires. Study participants were asked how often on average during the previous year they had consumed certain units or portion sizes of foods, with answers ranging from "never" to "greater than 6 times per day."

Researchers calculated cumulative average intake of major dietary protein sources by taking the mean of all reported food intakes to the beginning of a 2-year follow-up interval, and then divided participants into quintiles of average intake. They obtained information on stroke from medical charts and identified deaths from state vital records.

During 2,041,679 person-years of follow-up, from 1980 to 2006, in the NHS, and 833,660 person-years of follow-up, from 1986 to 2008, in the HPFS, the researchers found 1397 documented strokes in men and 2633 strokes in women.

After adjusting for dietary and nondietary cardiovascular disease risk factors, high intake vs low intake of red meat was associated with a higher risk for total stroke.

Table. Risk for Total Stroke by Intake of Red Meat

Intake Relative Risk 95% Confidence Interval P
Processed red meat (per 1 serving per day) 1.32 1.11 - 1.57 .01
Unprocessed red meat (per 1 serving per day) 1.16 1.00 - 1.33 .05

Poultry consumption was associated with a lower total stroke risk, with the relative risk for 1 serving per day in pooled analysis being 0.77 (95% confidence interval, 0.62 - 0.95; P = .02).

These associations were independent of other major protein sources, fruits and vegetables, and other stroke risk factors. The findings were similar for ischemic and hemorrhagic stroke.

When participants lowered their consumption of red meat from baseline, the risk for stroke was significantly reduced. For example, compared with those with an increase of 0.6 servings per day during follow-up, men with the greatest decrease (median for quintile of change, −0.93 servings per day) had a 21% reduction in risk (risk for stroke, 0.79; 95% confidence interval, 0.62 - 0.99).

Protein Substitutions

Although there was no significant association between increasing intakes of fish, dairy, or legumes and the risk for stroke, there was an association when some of these protein sources took the place of red meat.

For example, by substituting 1 serving of red meat with a serving of nuts or fish, the stroke risk was reduced by 17%, and by replacing the red meat with low-fat dairy, the risk went down by 11%. Substituting 1 serving of red meat with a serving of poultry resulted in a 27% reduction in stroke risk.

When substituting these foods, it is possible to maintain energy balance by, for example, eating nuts or yogurt instead of bacon at breakfast, or yogurt or nuts in a salad instead of a hamburger at lunch or dinner, said the authors.

What is not clear right now is the mechanism by which red meat may raise stroke risk. The recent focus on saturated fat "may not be the entire story," said Dr. Bernstein. He added that preservatives such as nitrates and nitrites found in processed meats may play a role, as could the sodium content and relatively high iron levels, which may cause inflammation leading to vessel injury.

"Simply...choosing a low-fat red meat may not in and of itself lower one's risk of stroke; it looks like it may be that what we call the 'whole protein package' ups the risk," he said.

In the case of dairy products, it could be their relatively high levels of potassium, magnesium, and calcium, all of which "have helpful benefits for vasculature," said Dr. Bernstein. As for poultry, the contributing factors are less clear, but it could have something to do with how this meat is prepared and cooked, he said.

Still Noteworthy

Asked by Medscape Medical News to comment on the study, Vineeta Singh, MD, associate professor, Neurology, University of California at San Francisco, and a member of the American Academy of Neurology, said she is not sure it adds much to what is already known about cardiovascular-related risks of red meat.

"I think they simply agreed with previous studies in terms of increasing the overall risk of cardiovascular diseases."

However, the study is still noteworthy, she said. "When you're counseling your patients on stroke risk, at least you can make a strong argument about eating healthy and substituting red meat with poultry or other non–red meat options."

Dr. Singh stressed that the study showed correlation, not causation, and that red meat was also associated with smoking and other unhealthy lifestyle habits. "All this study is saying is that there is a positive correlation," and may not provide "the complete picture" of stroke risk, she said.

Although a "big positive" about the study was the "sheer number" of participants, they were mostly physicians and nurses, and thus they may not be typical stroke patients, said Dr. Singh.

This study was supported by the National Institutes of Health, US Department of Health and Human Services. Dr. Bernstein was supported through the Harvard Human Nutrition Program. Dr. Singh has disclosed no relevant financial relationships. Disclosure information for the other authors is available in the original article.

Stroke. Published online December 29, 2011. Abstract

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