Some, but not all, observational studies — those in which individuals are observed or certain outcomes are measured, without treatment — have shown that the Mediterranean diet is associated with a lower risk for dementia. These studies compared cognitively normal people who ate a Mediterranean diet with those who ate a Western-style diet, which contains more red meat, saturated fats and sugar.
Evidence supporting the MIND diet comes from observational studies of more than 900 dementia-free older adults, which found that closely following the MIND diet was associated with a reduced risk of Alzheimer’s disease and a slower rate of cognitive decline.
Not all studies have shown a link between eating well and a boost in cognition. Overall, the evidence suggests, but does not prove, that following a Mediterranean or similar diet might help reduce the risk for Alzheimer’s dementia or slow cognitive decline. To find out more, scientists supported by NIA and other organizations are conducting clinical trials—considered the gold standard of medical proof—to shed more light on any cause and effect. (See a list of trials currently recruiting participants at the end of this article.)
While scientists aren’t sure yet why the Mediterranean diet might help the brain, its effect on improving cardiovascular health might in turn reduce dementia risk. Two recent studies suggest that, as part of this diet, eating fish may be the strongest factor influencing higher cognitive function and slower cognitive decline. In contrast, the typical Western diet increases cardiovascular disease risk, possibly contributing to faster brain aging.
In addition, the Mediterranean diet might increase specific nutrients that may protect the brain through anti-inflammatory and antioxidant properties. It may also inhibit beta-amyloid deposits, which are found in the brains of people with Alzheimer’s or improve cellular metabolism in ways that protect against the disease.
Studies that observed changes in thinking of people who ate the Mediterranean or MIND diet suggest it might help the brain. For example:
- In one observational study of 116 cognitively normal adults, those who followed a Mediterranean diet had thicker cortical brain regions than those who did not. These brain regions shrink in people with Alzheimer’s, so having thicker regions could mean cognitive benefit.
- A follow-up observational study showed lower glucose metabolism and higher levels of beta-amyloid protein — both seen in Alzheimer’s — in people who did not follow the Mediterranean diet closely, compared to those who did.
- An analysis of diet and other factors found that, after an average of 4.5 years, people who adhered most closely to the MIND diet had a 53% reduced rate of Alzheimer’s disease compared to those who did not follow the diet closely.
- In a similar study, following the MIND diet was associated with a substantial slowing of cognitive decline during an average of almost 5 years.
- The Age-Related Eye Disease Studies originally looked at diet and eye disease. Further analysis by the researchers showed that people who followed the Mediterranean-style diet had a lower risk of developing cognitive problems while maintaining a higher level of cognitive function.