Processed meat linked to increased stroke risk

Barbara Boughton

August 19, 2011

Stockholm, Sweden - The largest study to date on the relationship between stroke and red-meat consumption suggests that higher intake of processed meat—but not fresh red meat—is associated with an increased risk of stroke, including cerebral infarction[1].

In the study of 40 291 Swedish men, there were 2409 cases of stroke over 10 years. Researchers found that the relative risk of stroke for those who had the highest intake of processed meat compared with those with the lowest intake was 1.23 (95% CI 1.07-1.40, p=0.004).

Men who ate more fresh red meat also had an increased risk of stroke, but the association was not significant. Processed meat was associated with a significantly increased relative risk of cerebral infarction (1.18, 95% CI 1.01-1.38, p=0.03), but not hemorrhagic stroke.

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

The strengths of the study include its large number of participants as well as a relatively large number of cases of stroke over a long follow-up period, said lead author Dr Susanna Larsson (Karolinska Institute, Stockholm, Sweden).

"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," Larsson said in an interview.

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 2011 issue of the American Journal of Clinical Nutrition.

Are sodium, nitrites the culprits?

Study participants were drawn from the Cohort of Swedish Men, initiated in 1997, when all men aged 45 to 79 residing in two 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, as well as other foods, over the past year. Analyses were adjusted for other stroke risk factors.

Investigators speculate that sodium in processed meat, which can contribute to the development of hypertension if intake is high enough, might contribute to a higher risk of 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 is unlikely that heme iron or cholesterol in processed meat could explain the findings, investigators note.

Findings should be taken seriously

Although the study contradicts previous findings of the relationship between processed meat and stroke, the statistical power of the study was robust enough to be taken seriously, commented Dr Robert Eckel (University of Colorado School of Medicine, Denver), who was not associated with the study.

Further, Eckel noted that it is 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 should also be interpreted with some caution because it relied on a survey and assessed association, not cause and effect, he said.

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 fruits, vegetables, and whole grains.

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

Eckel does not believe the study should change physicians' advice to patients regarding a heart-healthy diet. However, it might be wise to ask patients about their intake of processed meat, as well as 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. Larsson and Eckel do not report any relevant financial relationships.


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