High red meat intake may up risk of cognitive impairment
High intake of red meat during midlife was associated with a greater risk of cognitive impairment later in life among Chinese adults, according to data from approximately 20 years of follow-up of the Singapore Chinese Health Study (SCHS) cohort.
“Diet is one of the modifiable risk factors for delaying the onset of cognitive impairment,” stated the researchers led by Professor Koh Woon-Puay from the Duke-NUS Medical School, Singapore. “[Our study showed that] substitution of red meat intake with poultry or fresh fish/shellfish was associated with reduced risk [of cognitive impairment].”
Compared with participants with the lowest quartile of red meat intake (9.50 g/day), those in the highest intake quartile (53.58 g/day) were 16 percent more likely to have cognitive impairment (adjusted odds ratio [OR], 1.16; p-trend=0.009), after taking into account of various potential confounders such as age, gender, education, physical activity, smoking status, alcohol consumption, comorbidities, and dietary pattern. [Eur J Nutr 2019;doi:10.1007/s00394-019-02031-3]
The excess risk for cognitive decline remained regardless of whether the red meat was fresh (OR, 1.15; p-trend=0.05) or preserved (OR, 1.15; p-trend=0.02).
In contrast, high intake of fresh fish/shellfish was associated with a reduced risk of cognitive impairment (OR, 0.88; p-trend=0.03). The reverse was true for intake of fish/shellfish in preserved form (OR, 1.19; p-trend=0.01).
On the other hand, there was no significant association between poultry intake and the risk of cognitive impairment.
Interestingly, the risk of cognitive impairment was reduced by 15 percent when one daily serving of red meat was replaced with fresh fish/shellfish (OR, 0.85, 95 percent confidence interval [CI], 0.72–1.01) and by 27 percent when replaced with poultry (OR, 0.73, 95 percent CI, 0.59–0.90).
“Substitution of red meat with poultry or fresh fish/shellfish may reduce the risk and is worth being tested in experimental studies,” noted Koh and co-authors.
Based on the differences in SM-MMSE* scores between the participants in the highest and the lowest intake quartile, the difference for fresh fish/shellfish intake corresponds to 0.88 year younger cognitive function, while the differences for preserved fish/shellfish and red meat correspond to 1.13 year older and 0.87 year older cognitive function, respectively.
As adjustment for components of red meat such as haem iron, saturated fat, and total cholesterol did not attenuate the observed relationship between red meat and risk of cognitive decline, the researchers believed that these components were not the factors mediating the association.
Other dietary factors such as nitrite in preserved meat may promote oxidative stress and inflammation associated with cognitive impairment, while polyunsaturated fatty acids in fresh fish/shellfish may be responsible for the protective effect against cognitive decline, suggested the researchers.
“Further studies are needed to confirm the findings in other populations and explore the potential underlying mechanisms,” said Koh and co-authors.
The epidemiological study involved 16,948 participants (mean age 53.5 years, 59.2 percent women) in the SCHS who were assessed on dietary habit at baseline using the 165-item semiquantitative food frequency questionnaire. They were followed up over three visits, in which the third visit (about 20 years later) entailed an assessment of cognitive function using SM-MMSE.
“Since the MMSE questionnaire is generally a screening tool, our study does not directly address the relation of meat intake with dementia or Alzheimer’s disease. Second, dietary factors were also evaluated only once at baseline and we did not have information on potential changes in diet during the follow-up,” pointed out the researchers on the potential limitations of the study.