New thesis on how different macronutrients in the diet affect the elderly’s cognition and risk of dementia

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It is unclear how the proportions between carbohydrates and fat in the diet affect cognitive ability and the risk of dementia in the elderly. Some promising pilot studies on the ketogenic diet (strict carbohydrate restriction) have increased interest in the research area, but there has been a lack of knowledge as to whether it may also be justified to investigate moderate carbohydrate restriction in future randomized trials. In these observational studies on elderly people with risk factors for dementia, we have investigated the relationship between different macronutrients in the diet and results on cognitive tests. In addition, we investigated whether APOE genotype, an important risk factor for Alzheimer’s disease, influences the relationship between diet and cognitive ability. The most common variant APOE3 confers normal Alzheimer’s risk while APOE4 increases and APOE2 reduces the risk.

What are the main results?

A lower proportion of carbohydrates compared to fat was associated with better cognitive ability in the group as a whole. Further analyzes showed that association was driven by the APOE34/44 subgroup, and analyzes of BMI, blood pressure, and blood lipids did not indicate an unfavorable association with a lower carbohydrate-to-fat ratio for them. Analyzes for protein, fiber and fat types showed that the relationship with cognitive ability was also affected by APOE. Our results support published hypotheses that APOE4, compared to APOE3, would entail poorer adaptation to diets high in carbohydrates and plant sources. In addition, we found that the insulin status of the participants affected the results. One conclusion is that within the field cognitive health can it be justified to prioritize intervention studies with moderate carbohydrate restriction, rather than the ketogenic diet which can be expected to be more complicated and reach a more limited target group.

How can that knowledge benefit people/contribute to improving people’s health?

The results justify that future dietary research and guidelines focus more on understanding the changing needs of different subgroups, rather than an average need in the population. APOE4 is overrepresented in the Nordic countries, where the gene variant is found in about 25% of the population but in ≈75% of people diagnosed with Alzheimer’s. Better understanding of specific dietary needs of that group could potentially lead to better cognitive health for them in the future.

What are you going to do now? Will you continue to do research?

Yes absolutely! This is a very interesting area to work on and fortunately we have been given the resources to follow up the results in a randomized study among individuals with a prodromal Alzheimer’s diagnosis. It would also be interesting to use existing databases to replicate the results and extend the analyzes to wider age groups and health aspects.