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Low glycemic load diet may improve cognitive function in older adults
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Older adults with poor glucose regulation who consume a high glycemic load diet are more likely to experience poorer cognition as measured by six cognitive domains, according to findings published in Clinical Nutrition.
“Proper blood glucose regulation is vital for brain function since the brain’s primary energy source is glucose,” Marc J. Poulin, PhD, DPhil, of the department of clinical neurosciences at the Cumming School of Medicine at the University of Calgary in Alberta, Canada, told Endocrine Today. “It follows that dysregulation of blood glucose is associated with poorer cognitive function. An effective way of managing blood glucose when glucoregulation is an issue is by consuming a diet characterized by a low glycemic load.”
Low glycemic load diets may also be associated with cardiorespiratory fitness and increased physical activity levels, the researchers noted, and their effects may be additive for cognition.
Poulin, Anna Garber, HBSc, MSc, of the Laboratory of Human Cerebrovascular Physiology at the University of Calgary, and colleagues analyzed data from 194 self-defined inactive, nonsmoking adults aged 55 to 86 years who were free of neurologic, cardiovascular, cerebrovascular and obstructive airway diseases participating in the Brain in Motion study, a quasi-experimental study assessing the effect of a 6-month aerobic exercise intervention on cerebrovascular regulation and cognitive function (mean age, 66 years; 52.6% women). The study was conducted between May 2010 and April 2016 at the University of Calgary. The study protocol included three 6-month study periods with pre-exercise, exercise and postexercise phases with five individual timepoints of data collection. Researchers assessed dietary intake via the modified National Cancer Institute Diet History Questionnaire; fasting blood samples to measure insulin, lipid profile, glucose and homeostatic model of insulin resistance; cardiorespiratory fitness via maximal aerobic capacity tests; and cognition via seven tasks evaluating six cognitive domains. Researchers used multiple linear regression models to evaluate the relationship between glycemic load and cognition by glucose regulation.
Researchers found that consuming a low glycemic load diet was associated with better global cognition in participants considered to have poor glucose regulation (n = 49), but not in participants with good glucose regulation (n = 145). Among participants with poor glucose regulation, a decrease in every 10 glycemic load units per 1,000 kcal while maintaining total energy intake was associated with an increase of 0.14 in global cognition z score (P = .008). Adjusting for age, sex, glycemic load and calorie intake explained 16.1% and 35.9% of the variance in global cognition z scores in the good and poor glucose regulation groups, respectively; further adjusting for waist to hip ratio and marital status explained 30.6% and 47.8% of the variance in scores across good and poor glucose regulation groups, respectively.
Linear regression models assessing separate relationships between glycemic load and six cognitive domains in the two subgroups found a negative association between glycemic load and figural memory in the poor glucose regulation group. For every 10-unit decrease in glycemic load per 1,000 kcal while keeping total energy intake constant, researchers observed a 0.035 decrease in figural memory z score (P < .001). Researchers found no relationship between glycemic load and the remaining cognitive domains in either the good or poor glucose regulation groups.
There were no relationships observed between glycemic load, cardiorespiratory fitness and physical activity and global cognition.
“Our results are biologically plausible, since glucose is the primary energy source of the brain, and impairments in glycemic control have been shown to impact cognitive function negatively,” the researchers wrote. “Impairments in glucose metabolism are strongly associated with brain atrophy and reduced hippocampal volumes, both of which are correlated with cognitive dysfunction or decline.”
The researchers noted that low glycemic load foods contain complex carbohydrates that take longer to digest, resulting in a gradual rise of blood glucose levels, aiding in the regulation of blood glucose at the gut level.
“The take-home message is that poorer cognitive function associated with issues in blood glucose control can arise before a clinical diagnosis of impaired glucose tolerance or type 2 diabetes, and low- [glycemic load] diets may help maintain cognitive function in such at-risk individuals,” Poulin said.
Poulin noted that the cross-sectional nature of the study limits the inferences researchers can make about cause-and-effect relations.
“Future research is needed to address if low- [glycemic load] diets improve, or at least maintain, cognitive function in poor glucoregulatory individuals,” Poulin said. “A randomized control trial or a prospective longitudinal study with multiple time-points of data collection would be appropriate in evaluating such causal relations.” – by Regina Schaffer
For more information:
Marc J. Poulin, PhD, DPhil, can be reached at the Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Room 210, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1; email: poulin@ucalgary.ca.
Disclosures: The authors report no relevant financial disclosures.
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