In the news: Flavonols May Slow Memory Decline; Caffeine Unlikely a Risk for DED

The last edition of EduFacts for 2022 covers recent findings on flavonoids and cognition, caffeine and dry eye. Best wishes for a happy, healthful holiday season from all of us at ScienceBased Health!

Dietary Flavonols May Slow Memory Decline

Higher intake of total flavonols and certain types of flavonols may slow the rate of cognitive decline according to a study published in Neurology(1).

Flavonols, which have anti-inflammatory and antioxidant properties, are one type of flavonoid found in various fruits, vegetables, tea, and wine. This study focuses on flavonols as a group and on the major individual flavonols: kaempferol, quercetin, myricetin and isorhamnetin.

The study included 961 participants (60-100 years) with no signs of dementia who were followed for an average of 7 years. Diet was assessed yearly using a validated semi-quantitative food frequency questionnaire. Cognitive performance was also assessed annually with a battery of 19 standardized tests such as recalling lists of words, and remembering numbers and putting them in correct order.

An overall global cognition score summarizing the 19 tests was used to determine rates of cognitive decline. The average score ranged from 0.5 for those with no cognitive impairment to 0.2 for mild impairment to -0.5 for those with Alzheimer’s.

After adjusting for an array of confounding factors including APOE-ɛ4, the global cognitive score for those consuming the most total flavonols (about 15 mg a day) declined 0.4 units per decade more slowly than those who consumed the least flavonols (about 5 mg daily). The highest intake was associated with less decline in multiple cognitive domains: episodic memory, semantic memory, perceptual speed, and working memory.

For individual flavonols, the highest vs. lowest intake of kaempferol resulted in a 0.4 units per decades lower rate of cognitive decline. For quercetin the rate was 0.2 units slower. A 0.3 units per decade slower rate of decline was observed for myricetin, while isorhamnetin was not associated with global cognition.

While these findings do not prove that flavonols directly cause slowing of cognitive decline, they are consistent with previous research reporting a link between cognition and flavonoids. Additionally, flavonols are known to be cytoprotective, including neurons. Thus, an impact of these bioactive plant compounds on cognition is plausible.

Caffeine Not Likely a Risk Factor for DED

Should curtailing caffeine be included as one of the modifiable risk factors for DED? While the literature has been unclear about the effects of caffeine on the ocular surface, caffeine stimulates the CNS by antagonizing adenosine receptors – receptors that are present in the eye and could possibly affect lacrimal gland secretion.

The results of the first large cohort study to examine the relationship between caffeine intake and DED suggest that caffeine is not a DED risk factor in the general public(2).

DED was assessed in 85,302 participants (59% females) using the Women’s Health Study defined criteria. Dietary caffeine was calculated from the intake of coffee, tea, cola, and energy drinks.

The mean caffeine intake was 285 mg/day. After adjusting for demographics, BMI, smoking status, and alcohol intake, higher caffeine intake was associated with a 3% decreased risk of a clinical diagnosis of DED per 100 mg caffeine daily (p < 0.0005).

When also adjusting for 48 comorbidities of DED, no significant effect of caffeine was observed.

None of the beverages were significantly linked with the risk of DED, when correcting for intake of other caffeinated beverages, demographics, smoking status, alcohol intake, and all comorbidities.

References

1. TM Holland, et al. Association of dietary intake of flavonols with changes in global cognition and several cognitive abilities. Neurol. Epub Nov. 22, 2022.
2. MS Magno, et al. The relationship between caffeine intake and dry eye disease. Cornea. Epub Jan, 2022.