Genetic risk for Alzheimer's disease may be modified by higher meat intake

Older people with a genetic risk of Alzheimer's disease did not experience the expected increase in cognitive decline and dementia risk if they consumed relatively large amounts of meat. This is shown in a new study from Karolinska Institutet published in JAMA Network Open. The results may contribute to the development of more individually tailored dietary advice.

APOE is a gene that affects the risk of Alzheimer's disease. In Sweden, approximately 30 per cent of the population are carriers of the gene combinations APOE 3/4 or APOE 4/4. Among people with Alzheimer's disease, those with these genotypes account for nearly 70 per cent.

When the Swedish Food Agency presented an overview of research on the link between diet and dementia last year, more research was requested to assess a possible link between meat consumption and the development of dementia.

This study tested the hypothesis that people with APOE 3/4 and 4/4 would have a reduced risk of cognitive decline and dementia with higher meat intake, based on the fact that APOE4 is the evolutionarily oldest variant of the APOE gene and may have arisen during a period when our evolutionary ancestors ate a more animal-based diet."

Jakob Norgren, first author, researcher, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet

The study followed more than 2,100 participants in the Swedish National Study on Aging and Care, Kungsholmen (SNAC-K) for up to 15 years. All were aged 60 or older and had no diagnosis of dementia at the start of the study. The association between self-reported diet and cognitive health measures was analyzed, adjusting for age, sex, education and lifestyle factors.

At lower meat intake, the group with APOE 3/4 and 4/4 had more than twice the risk of dementia than people without these gene variants. However, the increased risk of cognitive decline and dementia in the risk groups was not seen in the fifth of participants who consumed the most meat. Their median consumption is estimated at approximately 870 grams of meat per week, standardised to a daily energy intake of 2,000 calories.

'Those who ate more meat overall had significantly slower cognitive decline and a lower risk of dementia, but only if they had the APOE 3/4 or 4/4 gene variants,' says Jakob Norgren. He continues:

'There is a lack of dietary research into brain health, and our findings suggest that conventional dietary advice may be unfavourable to a genetically defined subgroup of the population. For those who are aware that they belong to this genetic risk group, the findings offer hope; the risk may be modifiable through lifestyle changes. '

The study also shows that the type of meat is important.

'A lower proportion of processed meat in total meat consumption was associated with a lower risk of dementia regardless of APOE genotype,' says Sara Garcia-Ptacek, assistant professor at the same department, who together with senior lecturer Erika J Laukka is the study's last author.

The findings also extend beyond brain health. In a follow-up analysis, the researchers observed a significant reduction in all-cause-mortality in carriers of APOE 3/4 and 4/4 with higher consumption of unprocessed meat.

However, the study is observational and needs to be followed up with intervention studies that can better demonstrate causal relationships.

'Clinical trials are now needed to develop dietary recommendations tailored to APOE genotype,' says Jakob Norgren. He continues:

'Since the prevalence of APOE4 is about twice as high in the Nordic countries as in the Mediterranean countries, we are particularly well suited to conduct research on tailored dietary recommendations for this risk group.'

The research was funded by, among others, the Swedish Alzheimer's Foundation, the Swedish Dementia Foundation, the Emil and Wera Cornell Foundation, the Leif Lundblad family and other philanthropists, the Swedish Research Council and FORTE.