An Orange a Day Keeps Stroke Away (CME/CE)
However, total flavonoid intake didn't predict ischemic stroke risk in the multivariate-adjusted model ( P =0.36 for trend).
These results suggested "that flavanones may be another important cardioprotective constituent of citrus fruits," Cassidy's group wrote.
"However, in a population-based study like ours, it is impossible to disentangle the relative influence of all the constituents of citrus fruits."
An impact from flavanones is plausible, they noted, pointing to experimental evidence that two flavanones, naringenin and hesperetin, act on neuroprotective pathways with effects on nitric oxide release.
A trend appeared for the flavones at the highest intake level of more than 3 mg per day compared with the lowest at less than 1 mg per day, but the difference wasn't statistically significant (adjusted relative risk 0.88, 95% CI 0.72 to 1.08).
The same was true for anthocyanins (blueberries were the main source) and flavan-3-ols (predominantly consumed from tea).
Individual flavonoids are likely to differ in benefits because of different mechanisms through their specific structural characteristics, the researchers noted.
They cautioned that residual or unmeasured confounding was possible despite the detailed adjustment used in the study.
Another limitation is that the actual flavonoid content in foods consumed may have differed from levels recorded because of wide variability based on where the food was grown and during what season and how it was cultivated and processed.
Randomized trials are needed to test flavanone and citrus foods for reduction of ischemic stroke risk, the group concluded.
Cassidy and a co-author reported having received funding from Unilever Research and GlaxoSmithKline to conduct trials and experimental studies on flavonoid-rich foods in the past.