Foods that are common in a Mediterranean diet, including a tomato, pistachios, avocado, fish, bread and oil. A new study finds that following a Mediterranean diet could benefit people with varying genetic risk for Alzheimer’s disease.BOBBI LIN/The New York Times News Service
Many observational studies have linked a Mediterranean diet to better cognitive health.
The gold standard eating pattern has been tied to a slower rate of cognitive decline and a lower dementia risk.
It’s also the only dietary pattern demonstrated in a long-term randomized controlled trial to improve cognitive function in older adults.
Now, new research suggests that people at high genetic risk for Alzheimer’s disease may benefit the most by following a Mediterranean diet.
Here’s what to know about the study, plus key Mediterranean diet components to include in your regular menu.
The link between genetics and ‘sporadic’ Alzheimer’s disease
Sporadic Alzheimer’s disease, the most common type, develops later in life and is not directly tied to family history. Rather, it’s due to an interaction between genetics, the environment and lifestyle factors.
Apolipoprotein E (APOE) is a gene that’s associated with varying risks of Alzheimer’s disease (AD), depending on the variant of the gene a person has. Each person inherits two copies of the APOE gene, one from their mother and one from their father.
The APOE4 variant is the strongest genetic risk factor for late-onset AD.
People who carry one copy of the variant have a three- to four-fold greater risk of developing AD. People who have two copies have an eight- to 12-fold higher risk compared to those who don’t.
In the brain, APOE4 promotes the accumulation of sticky beta-amyloid plaques, impairs glucose regulation and the removal of cholesterol and fats, and promotes inflammation.
About the new study
For the study, published Aug. 25 in the journal Nature Medicine, researchers investigated whether following a Mediterranean diet could benefit people with varying genetic risk for AD.
The team also looked at how adherence to the diet influenced dementia-related blood metabolites, small molecules produced during metabolic processes in the body.
To do so, the researchers analyzed data from 4,215 women who were part of the U.S. Nurses’ Health Study and followed for 34 years (1989 to 2023). On average, participants were 57 years old when the study began.
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To verify their findings, the researchers examined data for 1,490 male participants of the U.S. Health Professionals Follow-Up Study, followed from 1993 to 2023.
Dietary information, collected routinely throughout the study, was used to calculate participants’ Mediterranean Diet (MedDiet) index scores, a higher score indicating greater adherence to the diet.
Participants’ blood samples were analyzed for 401 metabolites. A subset of 1,037 women also underwent regular telephone cognitive testing to assess cognitive function.
MedDiet score components
MedDiet scores ranged from zero to nine based on participants’ regular intake of nine dietary components.
Higher intakes of vegetables (excluding potatoes), whole fruit, nuts, whole grains, pulses (e.g., kidney beans, chickpeas, lentils) and fish were each given one point.
So was a higher intake of monounsaturated fat (e.g., olive oil, avocado, almonds, peanuts) compared to saturated (animal) fat.
One point was given for consuming less red and processed meat. One point was also assigned if alcohol intake was between 5 and 15 g per day. One standard drink (5 ounces of wine, 12 ounces of 5 per cent beer or 1.5 ounces of 40 per cent spirits) contains 15 g of alcohol.
Mediterranean diet most protective for highest risk group
Overall, individuals who closely adhered to a Mediterranean diet had a significantly lower risk of dementia and better cognitive function.
The greatest benefit of the Mediterranean diet, however, was seen in people with the highest genetic predisposition to AD.
For people with two copies of the APOE4 gene, every one-point increase in the MedDiet score was associated with a 35 per cent lower risk of dementia.
Among individuals with one copy of the gene, every one-point increase in the MedDiet score was associated with a 4 per cent reduced dementia risk.
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The protective association between adherence to the Mediterranean diet and dementia risk was also observed in the Health Professionals Follow-Up Study participants.
Significant patterns were identified between 49 dementia-related metabolites and APOE4, especially in people with two copies of the gene.
The results also revealed that specific components of the Mediterranean diet – nuts, fruit and monounsaturated fat – were strongly associated with protective metabolite patterns.
How a Mediterranean diet may stave off dementia
Mediterranean diet-derived metabolites may influence metabolic pathways in the brain and, in so doing, reduce the risk of cognitive decline and dementia, especially in individuals carrying two copies of the APOE4 gene.
The researchers found, for example, cognitive benefits associated with betaine, a phytochemical plentiful in beets, spinach and whole grains, in people at high genetic risk for AD. Betaine is thought to protect the brain by removing toxic compounds, supporting blood flow and reducing inflammation and oxidative stress.
A higher intake of anti-inflammatory carotenoids, found in red, yellow, orange and dark green vegetables and fruits, has also been associated with slower cognitive decline, especially in APOE4 carriers.
The new study findings add to growing evidence that a healthy diet is an important tool for preventing of dementia, even for those with a high genetic predisposition.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD
