Caroline Cassels

April 28, 2015

WASHINGTON, DC — Adherence to the Mediterranean diet (MeDi) may prevent brain atrophy in old age, new research suggests.

A large cross-sectional study by investigators at Columbia University in New York linked adherence to the MeDI to larger brain volume in an elderly population, suggesting this type of diet has the potential to prevent brain atrophy and, by extension, preserve cognition in the elderly.

"Our study suggests that adhering to MeDi may prevent cognitive decline or AD [Alzheimer's disease] by maintaining the brain structure or delaying aging-related atrophy," said study investigator Yian Gu, PhD.

Dr Gu presented the findings here at the American Academy of Neurology (AAN) 67th Annual Meeting.

Driven by Higher Fish Intake

Previous research has linked the MeDi to a reduced risk for AD and slower rates of cognitive decline in the elderly. However, Dr Gu noted that the association of this diet type to more specific brain biological markers and indicators has not been explored extensively.

She added that there is increasing use of neuroimaging biomarkers that are sensitive and allow researchers to examine preclinical changes in older individuals, including brain volume, cortical thickness, white matter integrity, and amyloid deposition. These may shed light on the link between diet and the brain from "distinct angles."

The aim of the current study was to investigate the association between adherence to the MeDi and structural MRI-based measures of both brain volume and cortical thickness among elderly individuals participating in the Washington Heights-Inwood Columbia Aging Project (WHICAP).

The study cohort included 674 multiethnic Medicare beneficiaries aged 65 years or older living in an uptown area of New York City and who had no signs of dementia.

Twenty-eight percent (n = 187) of the cohort was white, 35% (n = 235) was black, 36% (n = 239) was Hispanic, and 1.9% (13) was of "other" ethnicity.

All participants underwent high-resolution structural MRI as well as assessment of MeDi adherence based on a 61-item food-frequency questionnaire that asked participants about intake of fish, vegetables, fruits, legumes, cereals, dairy products, meat, and poultry and alcohol. A higher score (ranging from 0 to 9) indicated better MeDi adherence.

The investigators assessed intracranial volume (ICV), total brain volume (TBV), total gray matter volume (TGMV), total white matter volume (TWMV), and cortical thickness (CT).

After adjustment for age, sex, education, ethnicity, energy intake, and APOE status, the investigators found that those with higher MeDi adherence scores (5 to 9) had larger TBV (β = 13.6; P = .01), TGMV (β = 5.5; P = .03), and TWMV (β = 7.3; P = .02) compared with those with lower MeDI scores (0 to 4).

Among the 9 food components of MeDi, higher fish intake (β = 6.8; P = .01) was associated with larger TGMV, and lower meat intake was associated with both larger TBV (β = 11.1; P = .03) and TGMV (β = 7.4; P = .01). Higher fish intake was also associated with higher CT (β = 0.018; P = .04).

Participants who adhered more to a MeDI had larger brain volumes both in gray matter and white matter, said Dr Gu. She also noted that each additional higher MeDi adherence and total brain volume is equivalent to more than 1 year of aging (β for age = 2.5; P < .001).

Dr Gu noted that most of the association was driven by higher intake of fish and lower intake of meat. Potential mechanisms, she said, include anti-inflammatory and/or antioxidative effects, as well as potential slowing of the accumulation of β-amyloid or tau.

Novel Finding

Commenting on the study for Medscape Medical News, David Knopman, MD, professor of neurology at the Mayo Clinic College of Medicine in Rochester, Minnesota, said the finding that diet may influence brain volume is novel and adds a "dimension of biology" to the hypothesis that diet and brain health are linked.

"I think this is a useful and somewhat reassuring observation that diet may influence brain health," said Dr Knopman. However, he cautioned, it doesn't establish whether diet alone is responsible for this effect or whether adherence to a MeDi is a marker of general good health practices.

"The fact is that science in general has been terribly burned by conflicting claims about diet. Almost all of the studies have been observational and the possibility of causal mechanisms being something else that the diet is a proxy for is a really big issue."

However, he added, the literature about the benefits of the MeDi seem to be more than just a random observation. However, "the big question remains is it something in the diet or is the diet a proxy for something else."

Dr Knopman also advised caution in interpreting the clinical implications of the study's findings.

"There is the natural tendency by the media, but also by scientists and the lay public, to assume that the relationships translate to immediate therapeutic benefit. Any therapeutic benefit likely reflects lifelong exposure [to the MeDi] so the idea of changing one's diet at age 75 and thinking it would make much of a difference is absurd."

The authors and Dr Knopman have disclosed no relevant financial relationships.

American Academy of Neurology (AAN) 67th Annual Meeting. Abstract S36.008 Presented April 22, 2015.


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