Red-meat consumption linked to increased stroke risk

Pauline Anderson

December 30, 2010

Stockholm, Sweden - Women who consumed at least 102 g of red meat a day had a 42% higher risk of cerebral infarction than those who ate 25 g or less daily in a new analysis [1].

The findings "suggest that consumption of red and processed meats may increase risk of cerebral infarction," the authors, led by Dr Susanna C Larsson, (National Institute of Environmental Medicine, Stockholm, Sweden), conclude.

"These findings merit confirmation in additional large, prospective studies and in experimental studies on possible biological mechanisms," they add.

The study was published online December 16, 2010 in Stroke.

The prospective population-based study included 34 670 Swedish women aged 49 to 83 years who were part of the Swedish Mammography Cohort study and completed a diet and lifestyle questionnaire in 1997.

In addition to providing information on education, weight, height, smoking, physical activity, aspirin use, medical history, family history of MI, and alcohol consumption, study subjects also reported how often they consumed various food items, including meat.

For the study, researchers grouped meats into red meat, fresh meat, and processed meat such as sausage, hot dog, salami, ham, and liver pâté. Red meat was the sum of fresh and processed meat.

Over a mean follow-up of 10.4 years, there were 1680 incident strokes: 1310 cerebral infarctions, 154 intracerebral hemorrhages, 79 subarachnoid hemorrhages, and 137 unspecified strokes.

Compared with women in the lowest quintile of red-meat consumption, the multivariable relative risk (RR) of cerebral infarction for women in the highest quintile was 1.22 (95% CI 1.01-1.46; p=0.04). The association between red meat and cerebral infarction was stronger when the first three years of follow-up were excluded (RR 1.35, 95% CI, 1.10-1.66; p=0.005)

Among those who had never smoked and who did not have diabetes, there was a 68% increased risk of cerebral infarction among the biggest meat eaters compared with those who ate the least.

The researchers found no significant association between fresh meat consumption and the risk of intracerebral hemorrhage or subarachnoid hemorrhage. Poultry was not associated with risk of any stroke subtype or total stroke.

Possible mechanisms

The authors cited several possible mechanisms for the association between meat consumption and cerebral infarction. At least one previous study has shown that the risk of hypertension, which is implicated in stroke, is higher among meat eaters.

Red meat contains saturated fat and cholesterol, which have also been linked to poor cardiovascular health. Red meat is also rich in heme iron, a nutrient known to catalyze the formation of hydroxyl radicals, which are powerful pro-oxidants.

Commenting on this research, Dr Thomas W Wolever (University of Toronto, ON) agreed that the high heme iron content of red meat could be a factor in the association between this type of meat and some types of stroke.

"High hemoglobin, high iron, is associated with cardiovascular disease, but it's unclear whether that's because the blood becomes more viscous when there are more red cells or whether it's because the iron itself is a kind of pro-oxidant that causes oxidative stress and that would promote atherosclerosis."

Another possible factor is sodium. The association between meat and cerebral infarction in this study was stronger for processed meat than for fresh meat. Processed meats are high in sodium, which could at least partly account for the study's findings, said the authors.

The study findings are not that surprising, Wolever added, given the fact that stroke and coronary heart disease share so many of the same risk factors, including metabolic syndrome and insulin resistance as well as hypertension. All these factors are associated with red-meat intake, he said.

Wolever noted the small number of hemorrhagic strokes in the study and wondered whether this would limit its statistical strength. "There were so few bleeds that probably the study had no power to pick it up."

Also, he said, if meat and protein are associated with excess blood clotting, "then maybe you don't get bleeds because the blood doesn't clot."

Wolever also commented that the highest level of meat consumption in the study (102 g daily) is not all that high. He pointed out that women generally eat less meat than men.

And while many aspects of the North American diet have been linked to increased risks for cardiovascular disease and cancer, this diet has also been associated with longevity and good health, he said.

"Some people would say that the fact we can live long enough to get strokes is a testament to how good our diet is."

He cautioned that the associations uncovered by the study do not prove causality, "athough, being a vegetarian, it would be tempting to think they did."

 The authors report no conflicts of Interest .

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