LONDON – Researchers believe they have uncovered a key piece of the puzzle in the connection between diet and dementia.
They linked a specific dietary pattern to blood markers of inflammation. In addition, they showed that in elderly adults who followed such a dietary pattern, brain gray matter volume was less, and they had worse visuospatial cognitive function.
"We found that people who consume less omega 3, less calcium, vitamin E, vitamin D, and vitamin B5 and B2 have more inflammatory biomarkers," study investigator Yian Gu, PhD, Columbia University and the Taub Institute for Research on Alzheimer's Disease and the Aging Brain, New York City, told Medscape Medical News.
An inflammatory dietary pattern, said Dr Gu, "is bad for both the brain and cognition."
The study was presented here at the Alzheimer's Association International Conference (AAIC) 2017.
Evidence cited by Dr Gu suggests that dietary factors such as fish, nuts, omega-3 polyunsaturated fatty acids, and folate, as well Mediterranean-type diets, are associated with lower risk for Alzheimer's disease (AD) and better brain health in the elderly. Other evidence, she said, shows that many foods and nutrients modulate inflammatory processes.
Other studies have linked chronic inflammation to an increased risk for AD. Dr Gu's group previously showed an association between increased C-reactive protein (CRP) and interleukin-6 (IL6) levels and worse cognition and smaller brain volumes.
But none of this research addressed whether diet affects brain and cognitive health by modulating inflammation.
"No study has formally tested whether the relationship of diet with cognition, or with the brain, is actually because of inflammation," said Dr Gu.
The new cross-sectional study included 330 elderly adults from the Washington Heights–Inwood Community Aging Project imaging study. In these participants, researchers carried out structural MRI scans and measured levels of the inflammatory biomarkers CRP and IL6.
Study participants completed a 61-item food frequency questionnaire that asked about nutrient intake during the past year.
From this information, the researchers used a statistical model to create the inflammation-related nutrient pattern (INP).
"The INP is basically a linear combination of 24 nutrients, each with a different weight on the INP," said Dr Gu. "For example, omega-3 is negatively 'loaded' – which is similar to 'correlated' – on this pattern. Lower consumption of omega-3 will contribute to a higher INP score."
Study participants also underwent neuropsychological testing that assessed memory, language, executive speed, and visuospatial function. From these test scores, the researchers calculated a composite mean cognition score for each participant.
The study showed that the INP was positively correlated with CRP level (P = .009) and IL6 level (P < .0001).
Those with fewer years of education had a relatively high INP. The INP was higher for African Americans (P < .0001) and Hispanics (P = .003) compared to whites.
The analysis uncovered a significant association between INP and visuospatial function (P = .015) and total gray matter volume (P = .002) after adjusting for age, sex, race/ethnicity, APOE4 status, calorie intake, body mass index, and vascular comorbidity.
The researchers determined that having a smaller brain gray matter volume might help explain why those who consume more inflammatory nutrients have worse visuospatial cognition.
This study is important because "now you have a linkage to measurable biological differences," said Keith Fargo, PhD, director of scientific programs at the Alzheimer's Association.
"If your cognition is poor, we know something has to be going on. But it's sort of a black box; it's not clear what's going on. Now, though, you can measure the level of these proteins in the body."
These new findings suggest that interventions that decrease inflammatory markers may be helpful. "It gives us some ideas of what pathways might be involved," said Dr Fargo.
Once that is known, it may be possible to intervene, not just through a healthier diet but perhaps also with medications. "At least, there may be some targets to work with," said Dr Fargo.
No Dietary Recommendations
Commenting on the findings for Medscape Medical News, David Knopman, MD, professor of neurology, Mayo Clinic, Rochester, Minnesota, who chaired a press briefing featuring Dr Gu's research, said that because it is a cross-sectional study, it cannot be used to make dietary recommendations.
It is possible the study's observations are not directly linked to diet, said Dr Knopman. "They could be due to the socioeconomic context of those diets that reflect a lifelong exposure to either poor or better health, which could in turn affect brain volume and cognition."
Although Dr Gu and her colleagues controlled for numerous potential confounding factors, they could not adjust for "residual confounding," said Dr Knopman.
"If you don't ask a zillion questions about what the study participants' lifestyle was like all their life – which, of course, you can't do because they don't remember – you don't know that you've gotten rid of all the confounding."
Dr Knopman also cautioned that diet studies "are the worst in terms of replication of results."
Neither Dr Gu not the commentators have disclosed any relevant financial relationships.
Alzheimer's Association International Conference (AAIC) 2017. Abstract P2-552, presented Monday July 17, 2017.
Medscape Medical News © 2017
Cite this: Inflammatory Dietary Pattern Linked to Brain Aging - Medscape - Jul 17, 2017.