A review published in the special stroke issue of The Lancet Neurology says that many of the numerous studies on stroke prevention have been based on unreliable evidence. The same applies to headlines that have highlighted potential benefits of specific nutrients and foods. According to researchers, the risk of stroke is more likely to be predicted by dietary patterns and excess energy intake, i.e. overeating.
Graeme Hankey from the Royal Perth Hospital in Perth, Australia explains:
"The overall quality of an individual's diet (i.e. dietary pattern) and balance between energy intake and expenditure seem to be more important determinants of stroke risk than individual nutrients and foods."
Hankey argues that even though the benefits of fighting the two main nutritional threats, such as over-consumption of calories and salt, are well known risks that cause stroke, legislation and policies addressing the obesity and salt epidemics are nowhere near enough widespread.
Worldwide, there are currently approximately 1.46 billion overweight adults and 170 million overweight children, two-thirds of adults being in the USA. Unless the obesity epidemic is reversed, there will be a 60% clinically obese rate among men and 50% among women in the UK by 2050.
The third most common cause of mortality in developed countries is stroke, and with only limited treatment being available, it is important to prevent the risk of stroke by modifying its risk factors, such as unhealthy eating behavior. Even though it is a well-known fact that malnutrition and over-consumption of calories increase the risk of stroke, researchers have little knowledge about which particular nutrients and foods affect the risk of developing stroke.
This could be due to the fact that there are almost no randomized trials, which provide reliable evidence, and the few that have been carried out indicate that dietary supplements, such as antioxidant vitamins, B vitamins, and calcium do not lower the risk of stroke, but could actually increase the chance of a heart attack and mortality. Another explanation is that the majority of studies evaluated stroke as a single outcome, meaning that important effects of foods, nutrients, beverages, and dietary patterns on different types of stroke may have been overlooked.
Data from observational studies that do not prove cause and effect, and are therefore less reliable indicate that the risk of stroke could be reduced by low-salt - and low sugar diets that are high in potassium or other diets, such as the Mediterranean diet, which is rich in vegetables, fish, fruit, nuts and whole grains.
"Further research...to accurately assess and understand the role of nutrition in the causes and consequences of stroke will be crucial in developing and implementing strategies to minimize the global burden of stroke."
He argues that in the meantime, cutting salt intake and reducing obesity must be viewed as a critical health priority, saying:
"Unlike the tobacco and cardiovascular disease epidemic, the obesity and salt epidemics have not been reversed by public health interventions and policies aimed at individuals to change personal choice and behavior."
There have to be more improvements in public awareness in terms of food and behaviors relating to food. Targets for nutritional contents in processed foods and standards for food labeling must be set and enforced.
According to Hankey there is growing evidence that enforcing salt targets for foods could prove to be highly cost effective, for example; in the USA, if the entire population would make a small reduction of just 3g per day, the annual number of new stroke incidents could be reduced by 32,000 to 66,000.
In a concluding statement Hankey says:
"The potential effects of adopting a healthy diet policy on population health, agricultural production, trade, the global economy, and livelihoods is likely to be substantial in some countries, and the effects could be realized sooner than we think".
Written by Petra Rattue