A study published in the Current Developments in Nutrition Journal describes that a low dietary carbohydrate/fat ratio is good for cognitive health in older adults at risk for dementia.
Study: The Dietary Carbohydrate/Fat-Ratio and Cognitive Performance: Panel Analyses in Older Adults at Risk for Dementia. Image Credit: SewCreamStudio/Shutterstock.com
Background
The impact of dietary components on cognitive health has been studied widely. Typically, digestible proteins in human diets provide 10 – 20% of total energy intake, whereas digestible carbohydrates and fats give approximately 80% of total energy intake.
Dietary fibers, which are not absorbed into the bloodstream through the intestinal wall, can be converted into short-chain fatty acids by gut microbes. These fibers provide only 2% of total energy intake.
Dietary carbohydrates, proteins, fats, and fibers are humans' major energy sources. These energy categories can be divided into several subcategories, including short-chain fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, sugars, starch, and specific amino acids.
Despite the well-documented association between diet and cognitive health, evidence of the effect of each macronutrient on cognitive health is limited.
In the current study, scientists investigated whether carbohydrate and fat consumption can influence global cognition in elderly people with an increased risk for dementia.
Study design
The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) is an ongoing multicenter randomized controlled trial involving older adults without considerable cognitive impairment.
The data obtained from the trial participants with increased dementia risk was analyzed in this study.
3-day food records determined self-reported diet. Neuropsychological tests for memory, executive function, and processing speed were used to measure global cognition (primary outcome).
The ratio of carbohydrate to fat was used as the primary predictor variable and was compared with carbohydrate and fat intake separately. Secondary predictor variables were proteins and the saturated fat/total fat ratio.
Important observations
A total of 1,251 participants for whom baseline data on diet and cognition was available were included in the study.
The study analysis revealed a significant association between cognitive performance, self-reported carbohydrate, and fat consumption, and the carbohydrate/fat ratio in older adults with increased dementia risk.
While carbohydrate intake and carbohydrate/fat ratio negatively correlated with global cognition, a positive association was observed with fat intake.
These associations were more pronounced in the memory subdomain, highlighting the significance of macronutrient composition in Alzheimer's disease.
A significant correlation was observed between the carbohydrate/fat ratio and carbohydrate and fat intake. The point estimate for the carbohydrate/fat ratio fell between carbohydrate and fat. However, the carbohydrate/fat ratio was identified as the most independent predictor of global cognition.
The association between carbohydrate/fat ratio and global cognition remained stable when adjusted for several covariates, including fiber intake and proportions of fat subtypes. Total energy intake was identified as the most powerful covariate, reducing the association magnitude by 20%.
No significant association was observed between protein intake and global cognition. The saturated fat/total ratio showed a nonlinear association with global cognition.
The study population belonging to the mid-quintile (36 – 39%) showed better cognitive performance compared to those belonging to the lowest and highest quantile. A quantile refers to division of a population into five equal parts based on the distribution of values of a particular variable.
Study significance
The study finds an inverse relationship between dietary carbohydrate/fat ratio and global cognition in older adults at risk for developing dementia.
As mentioned by scientists, high-quality randomized control trials are needed to investigate whether reducing carbohydrate content or increasing the fat content in the diet can improve cognitive performance.
The study's major strength is the inclusion of the macronutrient ratio, which is a more effective measure than individual macronutrient estimates for defining the overall effect of diet on metabolism and health outcomes.
Another strength of the study is the rigorous and extensive data collection and repeated measures of study variables.
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