Dietary flavanols restore hippocampal-dependent memory in older adults with lower diet quality and habitual flavanol consumption

Dietary flavanols are food constituents found in certain fruits and
vegetables that have been linked to cognitive aging. Previous studies
suggested that consumption of dietary flavanols might specifically be
linked to the hippocampal-dependent memory component of cognitive aging
and that memory benefits of a flavanol intervention might depend on
habitual diet quality. Here, we tested these hypotheses in the context of
a large-scale study of 3,562 older adults, who were randomly assigned to a
3-y intervention of cocoa extract (500 mg of cocoa flavanols per day) or a
placebo [(COcoa Supplement and Multivitamin Outcomes Study) COSMOS-Web,
NCT04582617]. Using the alternative healthy eating index in all
participants and a urine-based biomarker of flavanol intake in a subset of
participants [n = 1,361], we show that habitual flavanol consumption and
diet quality at baseline are positively and selectively correlated with
hippocampal-dependent memory. While the prespecified primary endpoint
testing for an intervention-related improvement in memory in all
participants after 1 y was not statistically significant, the flavanol
intervention restored memory among participants in lower tertiles of
habitual diet quality or habitual flavanol consumption. Increases in the
flavanol biomarker over the course of the trial were associated with
improving memory. Collectively, our results allow dietary flavanols to be
considered in the context of a depletion–repletion paradigm and suggest
that low flavanol consumption can act as a driver of the
hippocampal-dependent component of cognitive aging.