A Mediterranean-style diet rich in oily fish, fresh vegetables and nuts could help cut the risk of dementia.
New studies presented at the Alzheimer's Association International Conference in London examined links between diet and dementia and found following a nutrient-rich diet helps keep the brain healthy.
In a study on almost 6000 people led by the University of California, scientists found those who stuck closest to a Mediterranean or similar diet over a year were 30-35 per cent less likely to have low scores on cognitive tests than those who did not.
This was even after taking into account factors such as smoking, exercise, overall health and socio-economic status.
Co-author Claire McEvoy said the benefits of healthy eating seem to exist on a sliding scale.
"Even moderate adherence to these high-quality dietary patterns showed a protective association with cognitive function," she said.
Dr Maria Carrillo, chief science officer for the Alzheimer's Association, said the study showed changing your dietary pattern "really is quite impactful".
She told Fox Business: "You can change your trajectory of cognitive decline if you are adherent, for example, to Mediterranean diets or other diets low in saturated fats, low in processed flour and processed sugar.
"Good fats are important. Fats found in fish and good meats, as opposed to red meats, are all very good for your brain."
She said another study from Columbia University had shown poor nutrition may increase inflammation in the body and lead to brain shrinkage.
"People that perhaps eat a lot of junk food and processed foods may end up having less brain cognition over time as they age and may actually have smaller brains."
A Mediterranean diet includes vegetables, fruit, nuts, seeds, fish, olive oil and whole grains, while being low in red and processed meat and with alcohol kept to a minimum.
People considered to get maximum benefit from the diet have less than one alcoholic drink a day for women, or one to two for men.
They also eat several servings of fruit and vegetables per day, one serving of wholegrains and up to four servings of fish per week.
Another study on more than 2,200 older adults, from the Karolinska Institute in Sweden, found people who stuck to a Nordic diet that consists of non-root vegetables, fruit, fish and poultry enjoyed a better cognitive status than those who ate a less healthy diet.
And another study on more than 7000 people in the US found older women who ate diets traditionally thought of as heart-healthy, such as a Mediterranean diet, were less likely to develop dementia.
