Dietary patterns and over eating could be a more important factor in stroke risk than consuming individual nutrients and foods, many of whose purported benefits are based on unreliable evidence, a renowned stroke expert suggests.
In the review of evidence linking nutrition and the risk of stroke, Professor Graeme Hankey, a neurologist at Royal Perth Hospital in Western Australia, said that although malnutrition and overeating were known to increase the risk of stroke, more evidence was needed to elucidate which nutrients, foods and dietary patterns were linked to stroke risk.
“The overall quality of an individual’s diet (ie, dietary pattern) and balance between energy intake and expenditure seem to be more important determinants of stroke risk than individual nutrients and foods,” Professor Hankey said.
In the review, published in The Lancet Neurology, he warned that most studies were epidemiological and prone to substantial “methodological challenges of bias, confounding, and measurement error.”
The few randomised trials showed dietary supplementation with antioxidant vitamins, B vitamins, and calcium did not lower the risk of stroke, he said.
“Indeed, calcium might increase the risk of myocardial infarction, and β-carotene, vitamin A, and vitamin E might increase mortality,” he said.
Most studies had also assessed stroke as a single outcome, potentially missing important effects of nutrients, foods, beverages, and dietary patterns on specific stroke subtypes.
“Less reliable data suggest that a lower risk of stroke could be associated with diets that are low in salt and added sugars, high in potassium, and contain the ingredients of a Mediterranean diet,” he said.
The two main “nutritional threats” to stroke risk were over-consumption of calories and salt, he said, arguing that wider legislation and policies were needed to tackle the obesity and salt epidemics.
“Population-wide salt-reduction programmes that are led by governments and engage with industry to remove salt at its source could be highly cost effective, he said.”
Modest, population-wide reductions in dietary salt of up to three grams per day were expected to reduce the annual number of new cases of stroke by 32,000 to 66,000, Professor Hankey concluded.