Study finds plant-based diets lower dementia risk

By Stephen Beech

Healthy plant-based diets lower the risk of dementia, according to new research.

And it's never too late to turn vegan or vegetarian, as dementia risk is reduced even among those who adopt a plant-based diet in their sixties, say scientists.

But the study, published in the journal Neurology, also showed that it's not just about going meat-free as eating an unhealthy plant-based diet is associated with a higher risk of Alzheimer’s disease and other forms of dementia.

The American research team found that people who changed their diets to be more unhealthy over 10 years had a higher risk of dementia during the study, while people whose diets changed to be less unhealthy had a lower risk.

They say adopting a plant-based diet - even over the age of 60 - and refraining from low-quality plant-based diets are associated with a lower risk of all forms of dementia.

The researchers looked at three plant-based diets.

The overall plant-based diet prioritises eating more plant foods than animal products such as meat, milk and eggs, without looking at quality.

The healthy plant-based diet prioritizes healthy plant foods such as whole grains, fruits, vegetables, vegetable oils, nuts, legumes and tea and coffee.

The unhealthy plant-based diet includes less healthy plant foods like refined grains, fruit juices, potatoes and added sugars. Researchers did not look at vegetarian or vegan diets.

Researchers say the study does not prove that eating a higher quality plant-based diet causes a lower risk of dementia, it only shows an association.

Study author Dr. Song-Yi Park said: “Plant-based diets have been shown to be beneficial in reducing the risk of diseases like diabetes and high blood pressure, but less is known about the risk of Alzheimer’s disease and other dementias.

“Our study found that the quality of a plant-based diet mattered, with a higher quality diet associated with a reduced risk, and a lower quality diet associated with an increased risk.”

The research involved 92,849 people with an average age of 59 at the start of the study.

It included white, African American, Japanese American, Latino and Native Hawaiian participants.

The participants were followed for an average of 11 years, during which 21,478 developed Alzheimer’s disease or another related dementia.

Participants completed food questionnaires at the start of the study.

Researchers determined how well people’s diets resembled the overall plant-based diet, the healthy plant-based diet and the unhealthy plant-based diet, by reviewing how many healthy and less healthy plant foods they ate, as well as animal fats, meat, dairy, eggs, fish and seafood.

Participants were each given three scores based on how closely they followed the three plant-based diets.

The research team then ranked the participants into five subgroups for each of the three diet scores.

After adjusting for factors including age, physical activity and diabetes, the findings showed that when comparing people based on their score for the overall plant-based diet, the top subgroup who ate the most plant foods had a 12% lower risk of dementia compared to the lowest subgroup.

When people were compared based on their score for the healthy plant-based diet, the top subgroup had a 7% lower risk compared to the lowest subgroup.

And when compared based on their score for the unhealthy plant-based diet, the top subgroup who ate the most unhealthy plant foods had a 6% higher risk of dementia than the lowest subgroup.

Among a smaller group of 45,065 participants who reported their diet again after 10 years, 8,360 participants later developed dementia.

Researchers looked at diet changes over time.

When compared to people whose diets didn’t change, people whose diets changed the most toward following an unhealthful diet had a 25% higher risk of dementia while those whose diets changed the most away from following an unhealthful diet had an 11% lower risk.

Park, from the University of Hawaii, Honolulu, said: “We found that adopting a plant-based diet, even starting at an older age, and refraining from low-quality plant-based diets were associated with a lower risk of Alzheimer’s and other dementias.

“Our findings highlight that it is important not only to follow a plant-based diet, but also to ensure that the diet is of high quality.”