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Processed Meats Linked to Increased Stroke Risk

Barbara Boughton, Medscape

August 19, 2011 — The largest study to date on the relationship of stroke to red meat consumption suggests higher intake of processed meat, but not fresh red meat, is associated with an increased risk for stroke, including cerebral infarction.

In the study of 40,291 Swedish men, there were 2409 cases of stroke during 10 years. The researchers found that the relative risk for stroke for those who had the highest intake of processed meat compared with those who at the least amount of processed meat was 1.23 (95% confidence interval, 1.07 – 1.40; P = .004).

Men who ate more fresh red meat also had an increased risk for stroke, but the association was not significant. Processed meat was associated with a significantly increased risk for cerebral infarction (relative risk, 1.18; 95% CI, 1.01 – 1.38; P = .03) but not with hemorrhagic stroke.

The findings suggest meats that consumers often think are healthier, such as low-fat deli turkey, ham, and bologna, may actually increase the risk for stroke if intake is high enough, the study authors note.

The strengths of the study include its large number of subjects and a relatively large number of cases of stroke during an extended period of follow-up, said Susanna Larsson, PhD, of the Karolinska Institute in Stockholm, Sweden, and the lead author of the study.

“Yet because of the prospective nature of the study we can never know if another health behavior other than red meat consumption increased the risk for stroke,” Dr. Larsson told Medscape Medical News.

For instance, those who had the highest intake of both fresh red and processed meat had a higher body mass index — although the researchers adjusted for this variable in their calculations.

The study is published in the August issue of the American Journal of Clinical Nutrition.

Are Sodium, Nitrites the Culprits?

Subjects in the study were drawn from the Cohort of Swedish Men, initiated in 1997, when all men aged 45 to 79 years residing in 2 counties of central Sweden received a questionnaire that included 350 questions about diet and lifestyle.

Among those who completed the questionnaire, men with a history of stroke, heart disease, or cancer at baseline were excluded. Cases of stroke were ascertained through Swedish hospital and death registries.

Diet was assessed through 96 questions on a food-frequency questionnaire, which asked participants to report how often they had consumed fresh red meat and processed meat and other foods in the past year.

The researchers also collected data on body mass index, aspirin use, history of diabetes and hypertension, alcohol consumption, and family history of heart disease, as well as subjects’ smoking history and level of physical activity. The researchers adjusted for all these potential confounders, Dr. Larsson said.

The investigators speculate that sodium in processed meats, which can contribute to the development of hypertension if intake is high enough, might contribute to a higher risk for stroke by promoting vascular stiffness or oxidative stress.

Nitrites used as preservatives may also contribute to increased stroke risk. Because there was no association between fresh red meat and stroke in the study, it’s unlikely that heme iron or cholesterol in processed meats could explain the findings, the investigators note.

Findings Should Be Taken Seriously

Although the study contradicts some previous studies on the relationship between processed red meat and stroke, the statistical power of the study was robust enough to be taken seriously, commented Robert Eckel, MD, past president of the American Heart Association and professor of medicine at the University of Colorado School of Medicine, Denver. Dr. Eckel was not associated with the study.

Further, Dr. Eckel noted that it’s difficult to assess how processed meat contributes to stroke risk.

“It’s hard to know whether to blame the salt, the preservatives, or the nitrite in the preservatives for the increased risk of stroke seen in this study,” he said. The results of the study should also be interpreted with some caution because it relied on a survey and assessed association, not cause and effect, he said.

Dr. Eckel pointed out that the group with the highest intake of processed meat in the Swedish study also had a healthier diet overall, including more fruit, vegetables, and whole grains.

“It suggests that the effects of processed meat may confound the benefit of a heart-healthy diet,” he said.

Dr. Eckel does not believe the study should change physicians’ advice to their patients regarding a heart-healthy diet. However, it might be wise to ask patients about their intake of processed meat and their overall diet and activity level, he said.

The study was funded by research grants from the Swedish Council for Working Life and Social Research and the Swedish Research Council/Committee for Infrastructure. Drs. Larsson and Eckel have disclosed no relevant financial relationships.

Am J Clin Nutr. 2011;94:417-421. Abstract

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