Diets rich in protein and anti-inflammatory foods may guard against cognitive decline

A recent Nutrients journal study evaluates the effects of a protein-enriched diet (PED) and an anti-inflammatory diet (AID) on cognitive impairment (CI) in older adults in China.

 Study: Anti-Inflammatory Diet and Protein-Enriched Diet Can Reduce the Risk of Cognitive Impairment among Older Adults: A Nationwide Cross-Sectional Research. Image Credit: Ruslan Huzau / Shtuterstock.com

The connection between diet and dementia

Age-related CI in older adults can range from mild CI to severe dementia. Recently, the Lancet Commission concluded that diet and nutrition could delay or prevent 40% of dementia worldwide through the actions of specific dietary compounds.  

Beta-carotene, for example, is crucial in maintaining mental health, whereas polyphenols have a neuroprotective effect, and omega-3 fatty acids positively affect CI. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are also crucial for brain structure and function.

The Dietary Inflammatory Index (DII) assesses dietary inflammation by calculating the correlation between systemic pro-inflammatory cytokine levels and nutrients. To this end, diets with a higher pro-inflammatory dietary potential have been linked to a higher incidence of dementia.

Previous studies have documented the beneficial effects AID’s on mental health disorders. Protein intake has also been linked to better cognitive performance.

The protein-enriched Mediterranean diet is associated with healthy neurocognitive aging in the older population; however, these results remain inconclusive, as some studies have not identified a significant relationship between protein intake and cognitive function. Moreover, previous studies have constructed a systematic PED and studied its association with CI.

About the study

Since the role of AID and PED on CI remains unclear, constructing two dietary indices for AID and PED and measuring their relationship with CI is essential. To this end, the current study included a cohort of older adults from the China Longitudinal Health and Longevity Survey (CLHLS) to assess the effects of AID and PED on CI.

The study cohort comprised 8,692 adults 60 years of age or older. The anti-inflammatory foods included fruits, vegetables, legumes, tea, and nuts. Protein-rich food sources included eggs, fish, meats, dairy products, and bean products.

Binary logistic regressions and restrictive cubic splines were used to explore the linear and non-linear relationships. Sensitivity and subgroup analyses established robustness.

Study findings

Older adults with higher PED and AID scores were less likely to suffer from CI, and the relationship between AID, PED, and CI was linear. Subgroup and sensitivity analyses also provided significant credibility to the findings. Taken together, these results have important implications for future management of CI from a dietary and nutritional perspective.

CI was different among females and males, consistent with prior research. AID and PED scores were also different across genders. Gender differences in CI could be attributed to gender differences in dietary intake or smoking habits.

The incidence of CI in older adults was found to decrease, thus suggesting that the combined effect of lifestyle factors plays a beneficial role and that diet could be a promising approach for delaying or preventing CI.

In addition to diet, some digestive problems and malabsorption could also be related to CI. For example,  malabsorption of vitamin B-12 has been shown to alter cognitive performance and lead to some intestinal disorders.

In older people, the incidence of folate deficiency is high due to poor intestinal malabsorption and reduced dietary intake. Low folate levels have been linked to depression, mild CI, and dementia, especially Alzheimer’s. In the current study, the protective effect was more significant when the consumption of AID and PED was greater than three units. Thus, over three protein-rich and anti-inflammatory foods should be consumed regularly to prevent CI. A higher consumption of these foods linearly reduces the risk of CI; however, excessive consumption cannot be recommended due to issues related to digestion and absorption.

Conclusions

Increased consumption of AID and PED was associated with a reduced risk of CI among older adults in China. Nevertheless, a fundamental limitation of the current study is the self-reported data regarding CI, which could be subject to bias. Furthermore, causality could not be established due to the cross-sectional nature of the study.

Given the linear relationship between these diets and CI, the optimal dosage of PED and AID remains to be determined. Thus, future cohort studies are needed to determine the precise dosage recommendations for these two dietary patterns.