It`s the latest in a series of studies showing that a healthy diet can preserve health, including brain health.

This one`s a little different because it doesn`t seem to show that adding fish to the diet makes any difference. It`s not clear why, but it adds another piece of evidence in favor of dumping junk food and turning instead to fresh salads dressed with olive oil, plenty of fresh fruit, hummus, beans and pasta.

Everyone`s brain shrinks as they get older. This study, published in the journal Neurology, found that people in their mid-70s who ate a Mediterranean-style diet lost less brain mass than people who ate a diet more typical of their native Scotland.

"We found that lower adherence to the Mediterranean diet was associated with greater three-year reduction in total brain volume," Michelle Luciano of the University of Edinburgh in Scotland and colleagues wrote.

The team used a group of Edinburgh residents who were born in 1936 and have been followed ever since. For this round, the volunteers filled out a food diary and then many of them agreed to have a series of magnetic resonance imaging (MRI) scans of their brains.

The study took them from age 70 to around 76 and the MRIs allowed the researchers to see just when and how their brains changed as they moved from late middle age into early old age. About 400 of the volunteers made it through two MRIs over three years.

Those who ate more fruits, vegetables, olive oil and the like, and less fried food, red meat and cheese had less brain shrinkage, the team found. On average, their brains shrank at about half the rate that would normally be expected over three years for people this age, they said.

"In our study, eating habits were measured before brain volume was, which suggests that the diet may be able to provide long-term protection to the brain," Luciano said in a statement. "Still, larger studies are needed to confirm these results."

People got points for light to moderate drinking-- in this case about a third of drink a day to no more than three drinks a day on average for men and two for women.

Dr. David Knopman, a professor of neurology at the Mayo Clinic in Minnesota who was not involved in the study, said this could translate to real-life benefits.

"Loss of brain volume is an inevitable part of the aging process," Knopman told NBC News.

"A bigger brain is in general better for you because at least in late life, it makes a person more resistant to the effects of brain diseases," he added. "People who have bigger brains in general can tolerate more brain pathology, more brain disease, than those who have smaller brains. So the reduced loss in the people who adhered to the Mediterranean diet in general would be expected to protect them from developing dementia."

Everyone who took part in the study was healthy and living independently, and the study was not designed to show whether healthier eating reduced the risk of dementia. But other studies have shown that good diets can prevent Alzheimer`s and other types of dementia.

A 2015 study done at Columbia University also found that people who ate Mediterranean diets had bigger brains. But it also found this may have been caused in part because people who ate Mediterranean diets also are more fish and less of other types of meat.

The Edinburgh team didn`t find any effect from eating meat or fish, and they found education did not seem to matter, either.

Previous research has linked a Mediterranean diet to a reduced risk of heart disease and some cancers, as well as stroke and to a longer life in general.

"People who eat healthy are often healthier in many other respects," Knopman pointed out.

"They`re much less likely to be obese, they`re much less likely to have diabetes, hypertension, much less likely to smoke, more likely to exercise. And they`re probably more likely to adhere to good health behaviors in general."

But a series of studies done in Spain finds the effects are clear even when people are already starting out with healthier diets. The team in Barcelona adds extra olive oil and nuts to the standard diets of Spaniards and finds the benefits on heart health and brain health are clear.

The Edinburgh study only asked people once - when they were 70 - what they ate. So it`s not entirely clear if it takes a lifetime of eating better to help the brain.

/NBCnews/

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