April 25, 2012 â€" A large, prospective study of Swedish men and women has found that those who consumed low-fat dairy products had a lower risk for stroke than those who consumed full-fat dairy foods.
The study, by Susanna C. Larsson, PhD, from the Karolinska Institutet, Stockholm, Sweden, and colleagues, is published online April 19 in Stroke.
"Full-fat dairy foods may counteract a potential beneficial effect of dairy consumption on stroke by increasing total and low-density lipoprotein cholesterol concentrations," Dr. Larsson told Medscape Medical News.
The benefits of low-fat dairy foods may relate to the vitamins and minerals they contain, such as calcium, potassium, magnesium, and vitamin D. "It is possible that vitamin D in low-fat dairy foods may explain in part the observed lowered risk of stroke in this study because of its potential effect on blood pressure," she noted.
"We controlled for other known risk factors for stroke and the results persisted. Still we cannot entirely exclude the possibility that unknown risk factors for stroke may in part have accounted for the observed association," Dr. Larsson said.
"But doctors can tell their patients to consume the low-fat dairy foods instead of high-fat dairy foods," she said.
Potential Mechanisms
"There are potential biological mechanisms by which low-fat dairy foods could reduce the risk of stroke, for example by lowering blood pressure," Dr. Larsson said. "However, few studies had examined the potential association between low-fat dairy food consumption and stroke risk. Therefore, we examined this association in a large cohort of women and men."
Dr. Larsson and her team followed 74,961 Swedish adults aged 45 to 83 years from 1998 through December 2008.
The adults, who were participants in the Swedish Mammography Cohort and the Cohort of Swedish Men studies, filled out a questionnaire that asked them about education, weight, height, smoking, physical activity, aspirin use, history of hypertension and diabetes, family history of myocardial infarction before age 60 years, alcohol consumption, and diet.
They also reported their level of physical activity and exercise in the year before they were enrolled in the studies. Their intake of dairy foods was assessed by using a self-administered food-frequency questionnaire.
During a mean follow-up of 10.2 years, the researchers observed 4089 strokes (1680 in women and 2409 in men), including 3159 cerebral infarctions, 583 hemorrhagic strokes, and 347 unspecified strokes.
The study showed that the more low-fat dairy food consumed, the lower the risk for total stroke and cerebral infarction.
Compared with women and men in the lowest quintile of low-fat dairy food consumption (0 servings per day), those in the highest quintile (4 servings per day) had a 12% lower risk for total stroke (95% confidence interval [CI], 3% - 20%; P for trend = .03), and a 13% lower risk for cerebral infarction (95% CI, 2% - 22%; P for trend = .03).
After adjustment for age; sex; smoking status; education; body mass index; physical activity; aspirin use; history of hypertension; diabetes; family history of myocardial infarction; and intake of total energy, alcohol, coffee, fresh red meat, processed meat, fish, fruits, and vegetables, the relative risks for the highest vs the lowest quintile of low-fat dairy consumption were 0.88 (95% CI, 0.80 - 0.97) for total stroke and 0.87 (95% CI, 0.78 - 0.98) for cerebral infarction.
No association was observed between consumption of full-fat milk, cheese, yogurt, or other dairy products and stroke risk.
An "Exciting Study"
Medscape Medical News asked Rachel K. Johnson, PhD, RD, Bickford Professor of Nutrition and professor of medicine at the University of Vermont, Burlington, to comment on this study.
"This is an exciting study that reinforces the role of low-fat dairy products in lowering the risk of stroke," she said.
"It is important to note that it was low-fat dairy foods and beverages such as low-fat milk, low-fat yogurt, cottage cheese, and low-fat cheese that provided the protection against stroke," Dr. Johnson, who is also a spokesperson for the American Heart Association, said.
Unknown, however, are what components of the low-fat dairy foods were protective, she added.
"It may be the calcium, vitamin D, potassium or the magnesium, all of which are known to lower blood pressure and thus the risk of stroke. So it's important to consume low-fat dairy foods, because vitamin and mineral supplements may not provide the same protection," Dr. Johnson said.
The study was funded by the Swedish Council for Working Life and Social Research and the Swedish Research Council. Dr. Larsson and Dr. Johnson have disclosed no relevant financial relationships.
Stroke. Published online April 19, 2012. Abstract
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