By Sandee LaMotte, CNN
(CNN) — Eating a high-quality plant-rich diet that includes whole grains, vegetables and fruits may prevent cognitive impairment — even when people start that diet in their late 50s and 60s, according to a new study.
“It’s never too late to start eating healthy to lower the risk of Alzheimer’s disease and related dementias,” said senior author Unhee Lim, a professor of population sciences at the University of Hawaii Cancer Center in Honolulu, in an email.
Older adults who cut many unhealthy foods from their diet over a decade had a 11% lower risk of Alzheimer’s and dementia when compared with adults whose diets didn’t change, Lim said.
However, people who increasingly ate more unhealthy plant-based options, such as refined grains and foods with added sugars, were about 25% more likely to develop some type of dementia at the end of 10 years, she said.
“The findings suggest that both plant-predominant eating and high diet quality help protect brain function as we age,” said Dr. David Katz, a specialist in preventive and lifestyle medicine who was not involved with the study. Katz founded the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.
What is a ‘healthy’ plant-based diet?
The basic definition of a plant-based diet is broad, simply requiring a person to prioritize eating more plant foods than animal products such as meat, milk and eggs. Under that umbrella, a person could call themselves a vegan and yet subsist on sugary, fat-filled, ultraprocessed foods known to harm health.
Breakfast, for example, could be an ultraprocessed frozen waffle or pancake with fake maple syrup. Lunch could include a fast-food veggie burger high in sodium, french fries or onion rings dripping in saturated fat, and a fruit-based soda packed with sugar. Dinner could include refined-grain white flour pasta with high-sugar tomato sauce, followed by ultraprocessed cookies or cake — all plant-based, but none good for your brain’s health.
The new report, published Wednesday in the journal Neurology, tried to tease apart how the quality of a plant-based diet would impact dementia risk. The study included nearly 93,000 people with an average age of 59 and a diverse mix of ethnicities: African American, Japanese American, Latino, Native Hawaiian and White. All participants were asked about their diets at the start of the study. Ten years later, a smaller group of just over 45,000 people reported on their diet a second time.
The research team scored diets on three tiers of quality. Eating saturated animal fats, dairy, eggs, seafood and meat was the lowest tier. A tier up was less healthy plant-based foods such as refined grains, fruit juices, potatoes and added sugars.
Why are fruit juices and potatoes considered less healthy? Potatoes are high in starch, which quickly turns into glucose in the blood, potentially triggering blood sugar spikes. In addition, frying potatoes or adding sour cream and butter adds excessive calories, unhealthy fats and sodium.
Drinking fruit juice such as apple or orange, for example, floods the blood with fructose, a sugar found naturally in fruits and some vegetables. Eating a whole apple or orange, on the other hand, doesn’t spike blood sugar levels in the same way because the fiber i