Vitamin, Diet Link to Stroke Risk Assessed
By Kristina Fiore, Staff Writer, MedPage Today|
Published: December 12, 2011
There's little that individual vitamins and nutrients can do to prevent stroke, but overall healthier diets may lower the risk, an Australian researcher found.
In a review, neither antioxidant vitamins nor B-vitamins were associated with stroke prevention, but a healthy diet, such as the Mediterranean diet, did appear to diminish risk, Graeme Hankey, MD, of Royal Perth Hospital in Australia, reported in The Lancet.
"The overall quality of an individual's diet and balance between energy intake and expenditure seem to be more important determinants of stroke risk than individual nutrients and foods," he wrote.
Hankey reviewed the literature on individual vitamins, nutrients, foods, and overall diets and their effects on stroke risk.
· Neither antioxidant vitamins nor B-vitamins were associated with stroke prevention, but a healthy diet, such as the Mediterranean diet, did appear to diminish risk.
· Two popular healthy diets -- the DASH diet (which focuses on reducing hypertension) and the Mediterranean diet -- have been shown to reduce stroke risk, and the latter has also been shown to diminish heart disease and death.
Vitamins & Minerals
Randomized trials have shown that beta-carotene, the biologically active metabolite of vitamin A, won't prevent stroke; in fact, it appears to up the risk of all-cause and cardiovascular death.
Similarly, large randomized controlled trials have shown that vitamins C and E won't prevent stroke, either, Hankey reported, adding that vitamin E may even increase the risk of death.
Calcium could also increase the risk of stroke, and trials have shown that it may increase the risk of heart attack by 31%.
While B-vitamins reduce stroke risk, he found, in places with low folate intake, treating deficiency may lower stroke risk. Similarly, vitamin D deficiency is also associated with a higher stroke risk, as well as other related factors such as hypertension and cardiovascular disease.
The relationship between stroke risk and sodium and potassium intake is a bit clearer; high salt intake -- about 5 g per day -- has been associated with a 23% increased risk of stroke in observational studies, and also carries clear heart disease risk, Hankey said.
At the same time, upping potassium intake could diminish risk, he reported. Studies have shown a 21% lower risk of stroke with a higher intake of the mineral, and the benefits may come through its ability to help lower blood pressure.
Patients who eat a lot of fat overall don't appear to be at a heightened risk of stroke, Hankey reported. In fact, a high intake of the vilified trans- or saturated fats doesn't appear to up the risk.
But polyunsaturated omega-3 fatty acids from marine life have been shown to reduce the risk of heart events and death, and those found in plants have been shown to diminish stroke risk.
Eating lots of carbohydrates has been associated with other poor outcomes that could be related to stroke risk, such as higher blood sugar levels and increased body weight, but high fiber intake appears to lower risk factors such as blood pressure and cholesterol.
Hankey added that there are no ties between protein and stroke.
When it comes to specific foods, a few have been repeatedly linked with a lower risk of stroke, such as chocolate, coffee, and tea.
Cocoa, for instance, may be protective via its antihypertensive or anti-inflammatory properties, Hankey wrote.
One major stroke risk trial, INTERSTROKE, found that greater intakes of fish and fruit were each associated with a lower risk of stroke, while a handful of observational studies have shown that eating too much meat may up the risk of ischemic stroke.
It's not clear, however, whether the type of meat, be it red or processed, for instance, has a specific effect on stroke risk, he added.
Finally, while not directly related to stroke risk, sugary drinks have been linked with several other risk factors, including adiposity, metabolic syndrome, diabetes, and heart disease. But whole grains, on the other hand, can protect against heart events.
There have been some conflicting results as to whether a "healthy" diet can diminish stroke risk -- depending on how that diet is defined, Hankey wrote.
The Women's Health Study, which defined a healthy diet as one with high fiber, folate, and omega-3 intake paired with low consumption of bad fats, was associated with a higher risk of stroke over 10 years, but the Nurses' Health Study and the Health Professionals' Follow-Up found that a diet high in fruits, vegetables, and fiber and low in fat and red meat was associated with a lower risk of stroke.
Yet other studies have shown that unhealthy "Western" diets are clearly associated with an increased risk of stroke, Hankey reported.
Two popular healthy diets -- the DASH diet (which focuses on reducing hypertension) and the Mediterranean diet -- have been shown to reduce stroke risk, and the latter has also been shown to diminish heart disease and death.
Though overnutrition has clearly been associated with an increased risk of stroke -- likely through its effects on obesity, hypertension, hyperlipidemia, and diabetes -- poor nutrition can also play a role in risk, Hankey wrote.
Observational studies have suggested that malnutrition in the first year of a woman's life may ultimately be associated with a greater risk of stroke in her offspring, and malnutrition in childhood can up the risk of stroke later in life as well.
Hankey noted that findings of the many studies on stroke risk are diverse because the majority of them are epidemiological and subject to limitations.
Thus, he called for further research to improve the quality of evidence relating to the association of nutrients, foods, and dietary patterns with stroke risk.