Does eating meat lead to dementia?

Eating processed meat appears to increase the risk for incident dementia, regardless of the apolipoprotein E (APOE) ε4 allele, suggests a study. However, consumption of unprocessed red meat may lower such risk.

“Overall, the research adds to the growing body of evidence linking meat, especially processed meat consumption, to increased risk of a range of noncommunicable diseases,” the researchers said.

A short dietary questionnaire at recruitment and repeated 24-h dietary assessments were used to estimate meat consumption. Incident all-cause dementia, comprising Alzheimer’s disease (AD) and vascular dementia (VD), was identified via electronic linkages to hospital and mortality records.

The researchers then calculated hazard ratios (HRs) for each meta type in relation to each dementia outcome using Cox proportional hazard models and examined interactions between meat consumption and the APOE ε4 allele.

A total of 493,888 participants were included, of which 2,896 had incident all-cause dementia, 1,006 AD, and 490 VD, identified over a mean follow-up of 8±1.1 years.

Each additional 25-g/day intake of processed meat resulted in higher risks of incident all-cause dementia (HR, 1.44, 95 percent confidence interval [CI], 1.24–1.67; p_trend<0.001) and AD (HR, 1.52, 95 percent CI, 1.18–1.96; p_trend=0.001). [Am J Clin Nutr 2021;114:175-184]

On the other hand, a 50-g/day increase in unprocessed red meat intake led to reductions in risks of all-cause dementia (HR, 0.81, 95 percent CI, 0.69–0.95; p_trend=0.011) and AD (HR, 0.70, 95 percent CI, 0.53–0.92; p_trend=0.009). Of note, the linear trend for unprocessed poultry and total meat was not significant.

As regards incident VD, no statistically significant linear trends were seen. However, higher consumption of processed meat was found to increase such risk.

Furthermore, the APOE ε4 allele elevated the risk of dementia by three to six times but did not modify the interactions with diet significantly.

“In this population-based, nationwide UK Biobank cohort study, our results showed that consumption of processed meat was associated with increased risks of incident all-cause dementia and AD, while unprocessed red meat was associated with lower risks,” the researchers said.

“Related cohort studies remain few and inconsistent, and detailed knowledge of which type and amount of meat consumption would be the most influential is not clear,” they added. [J Alzheimers Dis 2019;68:711-722; BMJ 2002;325:932-933; Nutrients 2018;10:852]

The cause for the inconsistent associations between different meat types and dementia risk remains unclear, although several attempts have been made to provide an explanation.

For instance, Roberts and colleagues suggested that high protein levels in meat could explain the link between unprocessed meat intake and a lower dementia risk. Adequate protein intake has been shown to reduce the risk of mild cognitive impairment and dementia in older adults. [J Alzheimers Dis 2012;32:329-339]

A study by Piñero and Connor found high iron levels in unprocessed meat to be protective, with iron deficiency being linked to reduced cognitive and attentional processes. [Neuroscientist 2000;6:435-453]

In contrast, iron deposits in the brain may impair normal cognitive function as people age. Abnormal iron metabolism activates oxidative stress, which contributes to neurodegeneration. [Frontiers Neurosci 2018;12;632]

“On the basis of the findings of this study, more specific public health guidance could be indicated differentiating between types of meat,” the researchers said. “However, further research is recommended to confirm these results.”