"Dementia is one of the world’s leading causes of death, and there is no simple cure. Even the newest Alzheimer’s drugs are not suitable or safe for everyone, and people with the APOE ε4 gene variant, a major genetic risk factor related to cholesterol processing, can face higher treatment risks, making prevention especially important.

Meat is a controversial food, and it’s often linked to concerns about long-term disease burden, including heart disease and possibly dementia, so guidelines commonly recommend limiting it and especially processed meat (eg, cured meats/sausage).

This new long term Swedish study is important because it suggests diet may not affect everyone the same way. Over 15 years, higher total unprocessed meat intake was associated with slower cognitive decline and roughly half the dementia risk in APOE ε4 carriers (one or two copies), compared with their lower meat intake counterparts.

This pattern was not seen in people without APOE ε4. In contrast, higher processed meat intake was linked to worse outcomes. The results suggest that when it comes to reducing the risk of developing dementia, diet advice may need to be tailored to genetics."

"This new published study provides interesting evidence regarding an association between diet and cognitive health in a relatively small cohort of 2,157 older adults from Sweden, studied over 15 years.  The study adds to a growing literature that links specific aspects of diet to brain health, brain ageing, cognition and risk of dementia. The significant findings relate to the quarter of the cohort that has an increased risk of dementia, due to genetic variants in a gene called APOE.

Whilst it is possible that increased meat consumption directly caused a decreased risk of dementia in genetically predisposed people, in such a cohort of aged individuals, there may be other factors at play.   For example, it is possible that those who consumed more meat had other lifestyle (environmental exposure) factors in common that independently reduced the risk of dementia.

Nevertheless, these findings should be followed up in larger cohorts internationally (to see whether the findings are robust across countries outside Sweden), particularly from the perspective of the effects of diet and nutrition on the ageing brain.  Key questions relate to how diet may slow brain ageing, boost brain health, and delay dementia. It is possible that key dietary factors are acting on the gut microbiome (the trillions of microbes that inhabit the gastrointestinal system), which in turn signals to the brain, to enhance brain health over time, via what we call the ‘microbiota-gut-brain axis’.

If we can carry out more discovery research to work out exactly how this might happen, we could then develop new approaches to slow brain ageing, enhance brain health, and delay onset and progression of dementia."

"This very interesting paper builds on the association of a specific gene, Apolipoprotein E epsilon 4 (APOEε4), with red meat eating. We all have a variety of apolipoprotein E, which we inherit from each parent. Over 60% of us have the 3/3 variant, about 25% have 3/4 and 2% have 4/4.  One copy of APOEε4 increases risk of Alzheimer’s 2-5 times, depending on race, and 4/4 10 times or more. The authors cite evidence that there was a period in evolution when humans were hypercarnivorous, which coincides with when APOEε4 was the predominant variant.

Using data from a Swedish national study (SNAC-K) of data from 2157 adults aged 60 or older followed up for 15 years, Norgren and colleagues found that people who were APOEε3/4 or 4/4 who were in the top 20% for unprocessed red meat consumption had better cognitive trajectories and lower dementia risk than people who ate less meat.

There was no benefit for people with other APOE profiles. Processed meat had negative effects. The authors concede this was a limited sample in one country. They conclude that dietary advice may need to be tailored to genetic profiles. These results contradict current advice to adhere to a Mediterranean style diet rich in legumes, vegetables, grains, nuts (almonds and walnuts), extra virgin olive oil and fish and less amounts of red meat."