Findings from two novel studies support a critical role for polyunsaturated fatty acid (PUFAs) in maintaining the integrity of specific brain structures underlying fluid intelligence and memory and add to current evidence that omego-3 (n-3 PUFAs) and omega-6 fatty acids (n-6 PUFAs) promote healthy aging of the brain.
"These two studies highlight the importance of investigating the effects of groups of nutrients together rather than focusing on one at a time," senior author, Aron Barbey, PhD, University of Illinois Urbana-Champaign, Illinois, said in a statement.
"They suggest that different patterns of polyunsaturated fats promote specific aspects of cognition by strengthening the underlying neural circuits that are vulnerable to disease and age-related decline," he added.
The studies were published online May 11 and May 2 in Nutritional Neuroscience and Aging and Disease, respectively.
Better Problem-Solving Ability
In the first study, lead author, Marta Zamroziewicz, MD, PhD candidate, University of Illinois Urbana-Champaign, and colleagues measured six plasma phospholipid omega-3 PUFAs, fluid intelligence, and regional gray matter volume in the frontal and parietal cortices in adults aged 65 to 75 years. None of the participants was cognitively impaired.
Researchers then analyzed patterns of PUFAs in the blood and the relationship between nutrient patterns and participants' brain structure and performance on cognitive tests.
Results showed one pattern of omega-3 PUFAs made up of α-linolenic acid (ALA), stearidonic acid (SDA), and eicosatrienoic acid (ETE) was linked to fluid intelligence, which indicates a person's ability to solve problems they've never encountered before.
"Furthermore, total grey matter volume of the left FPC [frontoparietal cortex] fully mediated the relationship between precursor n-3 PUFAs and fluid intelligence," the researchers note. Frontoparietal network declines early even in health aging.
Better fluid intelligence was also predicted by both higher precursor patterns of n-3 PUFAs as well as larger volumes of the left frontoparietal cortex.
The pattern of precursor n-3 PUFAs observed in this study reflects metabolic processing of n-3 PUFAs or dietary intake of n-3 PUFA–rich nuts, seeds, and oils.
The investigators suggest that metabolic processing of n-3 PUFAs may confer neuroprotection because ALA, SDA, and ETE either possess unique neuroprotective effects or are converted to eicosapentaenoic acid (EPA), and to a lesser extent, docosahexaenoic acid (DHA).
By reducing inflation, oxidative stress, and platelet aggregation, as well as improving blood pressure and arterial compliance, "both EPA and DHA have physiological effects that can improve brain health."
Dietary Sources Not Limited to Fish
In a second study, the same group of researchers analyzed the relationship between patterns of n-3 and n-6 PUFAs, memory, and regional white matter microstructure in the same cohort of healthy older adults.
"This study revealed that memory is dependent upon a particular pattern of plasma phospholipid PUFAs which comprised a mixture of plasma phospholipid n-3 PUFAs and plasma phospholipid n-6 PUFAs," the researchers report, "and that white matter integrity of a specific white matter region, the fornix, mediates this relationship," they add.
The fornix is especially vulnerable to white matter atrophy caused by Alzheimer’s disease.
That said, "loss of white matter integrity in the fornix is amenable to lifestyle factors," the researchers write reassuringly, "suggesting the potential for intervention with nutritional factors."
Dr. Zamroziewicz noted that many factors, including physical activity and cognitive reserve, influence cognitive and brain aging, but this research suggests that nutrition may play an important role as well.
"In these two studies, we show that even when we account for factors that are known to influence cognitive and brain aging, blood levels of PUFAs are associated with particular aspects of cognitive and brain health," she told Medscape Medical News.
"Thus, nutrition may be part of a larger set of lifestyle variables that can promote healthy brain aging," she added.
The fact that omega-3 PUFAs derived from nuts, seeds, and oils appear to sustain cognitive and brain health in an aging population is important as well, she pointed out, as people in the West typically consume too little fish or fish oil to derive sufficient omega-3 PUFAs to boost brain health.
"Our work suggests that nuts, seeds, and oils could serve as an alternative to fish and fish oils in terms of providing neuroprotective omega-3 PUFAs," Dr Zamroziewicz said.
"And to provide a better balance of omega-3 to omega-6 PUFAs, increasing consumption of certain nuts, such as walnuts, and decreasing consumption of certain vegetable oils, such as soybean, safflower, and corn oil, as well as meats, is advised."
Two Studies, One Message
Commenting on the findings for Medscape Medical News, Yian Gu, PhD, assistant professor of neuropsychology, Columbia University Medical Center, New York City, felt that both studies are important in that they reinforce the same message: namely, that omega-3 PUFA is very important for the protection of the brain, especially in the elderly.
"Actually, these 2 studies actually confirm our own findings, where we also found that a dietary pattern composed of a high intake of omega-3 PUFA as well as vitamin E was related to better brain measures, including brain volume and white matter integrity," said Dr Gu. Maintaining white matter microstructural integrity might be one way in which diet exerts its beneficial effects on cognition, she added.
Dr Gu and colleagues also assessed the effects of the Mediterranean diet on brain structures and found that in their study population, participants who followed the Mediterranean diet closely had less brain atrophy — an effect similar to 5 years of aging — than those who did not follow the diet closely.
"So these studies are consistent in that they are telling us that high intake of omega-3 is important," Dr Gu emphasized. "And they are also telling us that omega-3 comes not only from fish but nuts, especially walnuts that contain high amounts of omega-3," she added.
The research was funded by a grant from Abbott Nutrition through the Center for Nutrition, Learning and Memory at the University of Illinois. The authors and Dr Gu have disclosed no relevant financial relationships.
Nutr Neurosci. Published online May 11, 2017. Abstract
Aging Dis. Published online May 2, 2017. Abstract
Medscape Medical News © 2017
Cite this: PUFAs May Help Prevent 'Brain Aging' - Medscape - May 24, 2017.