Could polyphenol intake affect Alzheimer’s disease risk?

The intake of certain polyphenols may be tied to a reduced risk of Alzheimer’s disease and related dementias (ADRDs) particularly in Black individuals, according to a study from the US presented at Nutrition 2022.

The researchers analysed Medicare claims data of 14,500 individuals enrolled in the Southern Community Cohort Study which includes a large cohort of low-income individuals (>50 percent) and African American participants (~65 percent). Validated food frequency questionnaires and polyphenol databases were used to assess dietary intake of polyphenols which included total polyphenols and four major classes of polyphenols (flavonoids, phenolic acids, stilbenes, and lignans) and their 29 subclasses.

Over 4 years of follow-up data, 1,402 incident cases of ADRD were diagnosed. The median age at dietary survey was 62 years and 73 years at ADRD diagnosis. Individuals diagnosed with ADRD were more likely to have lower educational and household income levels than those without ADRD, regardless of ethnicity.

Median intake of total polyphenols significantly differed according to participant ethnicity, with the highest intake documented in Whites (1,118 mg/day), followed by other ethnicities (846 mg/day) and Blacks (570 mg/day).

Overall, total polyphenol intake did not appear to affect the risk of ADRD in any of the ethnic groups. However, the intake of two subclasses of flavonoids* – flavanols and theaflavins – was associated with a reduced risk of ADRD in Black participants (hazard ratio [HR], 0.72, 95 percent confidence interval [CI], 0.57–0.91; p_trend=0.03; p_linearity=0.015 and HR, 0.66, 95 percent CI, 0.53–0.83; p_trend=0.02; p_linearity=0.006, respectively). [Nutrition 2022, abstract OR21-04-22]

Tea consumption* was also inversely associated with the risk of ADRD in Black participants (HR, 0.69, 95 percent CI, 0.55–0.86; p_trend=0.02; p_linearity=0.005).

There was also a trend toward a lower risk of ADRD with red wine consumption* among White participants (HR, 0.69, 95 percent CI, 0.48–0.99; p_trend=0.74; p_nonlinearity=0.047).

“Polyphenols are the most abundant dietary antioxidants found mainly in fruits, vegetables, and beverages such as wine, tea, or coffee,” presented study author Jae Jeong Yang, PhD, a statistical analyst from Vanderbilt University Medical Center (VUMC), Nashville, Tennessee, US.

They may be effective in protecting against ADRD due to their anti-inflammatory properties, or through modulating cellular signalling processes or altering the gut microbiome, Yang added.

Yang acknowledged that the single, self-report of polyphenol intake presented a limitation as did the lack of information on genetic data and disability.

“[Nonetheless,] our findings indicate beneficial associations of certain dietary polyphenols and polyphenol-rich tea for the prevention of ADRD among low-income Black Americans,” she said.

“Black Americans and people with low socioeconomic status are disproportionately affected by the disease but have been largely underrepresented in epidemiologic studies,” remarked study co-author Assistant Professor Danxia Yu, also from VUMC.

“Identifying modifiable factors for the prevention of ADRD among low-income people of different races and ethnicities is a critical public health issue,” she pointed out.

“Our findings provide a strong piece of epidemiologic evidence on ADRD prevention through dietary modification,” said Yang. “Our findings [also] highlight the importance of healthy diets that could potentially benefit everyone to eventually reduce the health burdens and disparities posed by ADRD,” she said.