A study in JAMA Open Network indicates that increased meat intake could reduce cognitive decline—but only for individuals possessing a particular version of the APOE gene. This gene regulates fat and cholesterol processing, existing in three primary forms: ε2, ε3, and ε4.
Everyone inherits two copies of the APOE gene, creating six possible combinations. The ε4 variant is the strongest known genetic risk factor for Alzheimer’s disease, with people who carry one copy facing a 3-fold increased risk, and those with two copies facing up to a 12-fold increased risk.
Researchers analyzed data from 133,771 participants in the UK Biobank, tracking their dietary habits and cognitive function over time. They found that higher meat consumption was associated with slower cognitive decline, but only in people with the APOE ε4 gene variant.
Individuals with this gene who ate more meat performed better on tests of fluid intelligence, showing a higher ability to solve new problems and think abstractly. For participants with other APOE genotypes, higher meat intake showed no protective effect.
Researchers proposed a hypothesis rooted in human evolution, suggesting that the APOE ε4 variant is the ancestral form of the gene. This means that it’s the version our earliest human ancestors carried, and their brains may have adapted to thrive on meat-derived nutrients like vitamin B12, iron, zinc, and complete proteins.
As humans migrated and diets diversified, newer variants emerged and became more common. These variants may be better suited to plant-heavy or mixed diets, whereas people who carry the ε4 variant may be evolutionarily “wired” to benefit from meat in ways that other genotypes aren’t.
The research is observational, meaning it shows an association, not direct cause and effect. The researchers can’t say definitively that meat causes cognitive protection in ε4 carriers, only that there’s a significant correlation worth exploring further.
For the roughly 25% of people who carry the APOE ε4 variant, this research shows that meat may play a more important role in brain health than previously thought. However, for others, different dietary patterns may be more beneficial.
According to the researchers, the next step is to conduct further studies to confirm the findings and explore the potential mechanisms by which meat consumption affects cognitive decline in ε4 carriers. This could involve examining the effects of specific nutrients found in meat, such as vitamin B12 and iron, on cognitive function.