Health officials in England have determined there is not enough evidence to support a link between diet and dementia after reviewing studies on diet, supplements like omega-3 and caffeine.
To be clear, they’re not ruling out the potential effects of diet on brain health—there’s just not sufficient evidence to show that there is a cause and effect relationship. The report, put together by the Scientific Advisory Committee on Nutrition, acknowledged that a Mediterranean diet is associated with a lower risk of cognitive impairment and dementia, but concluded that the observational model of most nutrition studies limits how much we can attribute to cause and effect.
In observational studies, researchers observe and collect data on something that is already happening—in this case, tracking the kind of food a person eats. They don’t intervene much to change people’s habits, in part because it’s not ethical to have a control group that is directed to eat unhealthy food for comparison’s sake, and in part because you can’t randomly assign something like diet. Because of the nature of an observational study, scientists can only suggest that there is an association between better brain health and a Mediterranean diet—they can’t prove that diet directly has an effect on dementia risk. For example, it could be that those who eat healthier food have other reasons their brains are not as likely to develop Alzheimer’s, like better access to health care or being less likely to smoke or be overweight.
After publishing the review, Public Health England said that following a healthy diet is still recommended, because it can help people maintain a healthy blood pressure and weight, two factors that have been shown to reduce risk of dementia.
As far as supplements and caffeine intake, the report said evidence is limited and inconclusive. In other words, there is no magic pill or amount of coffee that will or won’t improve your chances of developing dementia.
“There’s no evidence that eating a certain food, or taking a specific vitamin or supplement can affect the risk of dementia, but we do know that people who eat a Mediterranean style diet tend to have a lower risk of dementia,” said Doug Brown, Chief Policy and Research Officer at Alzheimer’s Society. “Dementia is set to be the 21st century’s biggest killer, and with no way yet to cure the condition, prevention is key.”
Both the National Health Service and Alzheimer’s Society recommend sticking to a healthy diet, despite the lack of conclusive evidence.
“We recommend eating plenty of fresh fruit, vegetables and whole grains, having fish twice a week, and using healthier fats like olive oil. It’s also a good idea to cut down on red meat, saturated fats, refined sugar and salty foods,” said Brown.
You can read the full report here.