The news on eating a whole food, primarily plant-based diet just keeps getting better. Three new studies add more support to the idea that these kinds of foods are good for the brain. The first found that eating a diet rich in fruits and vegetables—compared to one made up mostly of processed, sweetened foods—lowers the risk of depression by 26%. The second suggests that eating a very high protein diet could actually shrink the brain and increase risk for Alzheimer’s disease. The third finds a component of extra virgin olive oil may protect against that dreaded disorder.
The depression study was part of ongoing research that examines the health of a large group of British civil service workers and was published in the British Journal of Psychiatry. Nearly 3,500 middle-aged bureaucrats were surveyed about their diet and then assessed for depression five years later.
After controlling for other factors that could affect risk like socioeconomic status and age, those who ate the most fruits, vegetables and fish were found to have a 26% lower risk of depression compared to those who ate the least.
Meanwhile, those who ate the most high-fat dairy, processed meats, fried foods and sweetened desserts saw their risk rise by more than 50%, compared to those who mainly refrained from eating these foods.
It’s possible that people eat more fatty, sweet and salty foods if they are about to get to depressed—or that the researchers missed and didn’t control for another important variable that is actually responsible for these connections. However, since there was no connection between diet and prior diagnosis of depression, this is less likely to be the case.
The Alzheimer’s studies both involved laboratory research. Previous human research has found reduced risk for Alzheimer’s amongst those who eat mainly whole grains, fruit, vegetables and fish—often called the “Mediterranean diet.”
The first study, which was published in Molecular Neurodegeneration, was conducted on genetically modified mice bred to include a human protein associated with Alzheimer’s in their brains. They were fed four different diets: ordinary mouse chow, a sort of mousy-Atkins (high protein/low carbohydrates), a high fat/low carb diet or a high carb/ low fat version.
The researchers found that the high protein and low carbohydrate diet shrunk the brain by about 5% and an important area for memory, the hippocampus, was also smaller. It’s not yet clear whether these results will apply to humans—but it does add to the data suggesting that too much meat may not be good for the brain.
The third study looked at brain cells in culture, showing that a component of extra virgin olive oil called oleocanthal can protect them from changes associated with a protein that is elevated in Alzheimer’s. Oleocanthal prevented damage to synapses, the spaces between brain cells that allow them to communicate with each other. Whether this effect can be exploited in the living brain, is not yet known.
Nonetheless, with all the data we have so far, more olives, less meat and fewer processed foods seems to be the way to go to keep the brain in good working order.