Higher dietary intake of total flavonols and individual flavonol components was linked to slower cognitive and memory decline in older adults, a longitudinal study showed.
Total flavonol intake was associated with less decline in global cognition (β=0.004, 95% CI: 0.001-0.006), according to Thomas Monroe Holland, MD, MS, of Rush University Medical Center in Chicago, and coauthors.
Slower declines in episodic, semantic, and working memory were also related to overall flavonol intake. The associations were independent of cardiovascular conditions and lifestyle factors, the researchers reported in Neurology.
The findings suggest that specific diet choices could lead to a slower rate of cognitive decline, Holland noted. “Something as simple as eating more fruits and vegetables and drinking more tea is an easy way for people to take an active role in maintaining their brain health,” she said in a statement.
Flavonols are a type of flavonoid, a group of phytochemicals found in plant pigments. Previous research has shown that a high intake of flavonols was linked to a lower risk of Alzheimer’s dementia.
The mechanisms behind these relationships are not fully understood. The anti-inflammatory characteristics of flavonols may decrease the amplitude or duration of neuroinflammation, Holland and co-authors suggested. Furthermore, the antioxidant characteristics of flavanols can prevent or reduce oxidative stress from reactive oxygen species and free radicals, they noted.
In this study, Holland and his colleagues evaluated 961 people without dementia at baseline who participated in the Project Rush Memory and Aging, an ongoing community-based prospective cohort. The participants were followed for 6.9 years.
The sample was predominantly female (75%), white (98%), and had an average educational level of 15 years and an average starting age of about 81. Overall, 22% had at least one APOE4 alleles and 42% reported a history of smoking.
The researchers assessed diet using a validated semi-quantitative food frequency questionnaire and measured cognitive performance annually with a battery of 19 standardized tests. They adjusted the findings for age, sex, education, APOE4cognitive activity in old age, physical activity and smoking.
The study looked at both the total intake of flavonoids and the intake of four components: kaempferol, quercetin, myricetin, and isorhamnetin. Kale, beans, tea, spinach and broccoli were the main foods that contributed to kaempferol in the study. Tomatoes, kale, apples, and tea were the main contributors of quercetin; tea, wine, kale, oranges, and tomatoes for myricetin; and pears, olive oil, wine, and tomato sauce for isorhamnetin.
The mean intake of total flavonols was 9.6 mg/day. In adjusted models, total flavonol intake was associated with a slower decline in the following domains:
- Episodic memory β=0.004, 95% CI 0.002-0.006
- Semantic memory β=0.003, 95% CI 0.001-0.007
- Perceptual speed β=0.003, 95% CI 0.001-0.004
- Working memory β=0.003, 95% CI 0.001-0.005
Total flavonol intake was not associated with changes in visuospatial ability.
Among individual flavonol constituents, kaempferol (β=0.01, 95% CI 0.006-0.02) and quercetin (β=0.004, 95% CI 0.0005-0.007) were associated with cognitive impairment slower overall. Myricetin and isorhamnetin were not associated with global cognition.
The study has several limitations, Holland and his colleagues noted. The sample population was white, highly educated, and from the Midwest. Additionally, dietary intake was recorded using self-reported food frequency questionnaires. Residual confusion may also have played a role in some factors.
The study was supported by the National Institutes of Health, the National Institute on Aging and the USDA Agricultural Research Service.
The researchers did not report any relevant disclosures.