Bananas Cut Antioxidant Uptake in Berry Smoothies, Study Finds

Researchers at the University of California, Davis conducted a blinded, controlled trial to examine how adding banana to a berry‑based smoothie affects the absorption of flavonols, a class of antioxidants linked to heart, brain and vascular health. Eight volunteers drank a berry smoothie with a flavonol supplement, and a second group drank the same drink with a banana added. Blood tests showed that the participants who consumed the banana‑containing smoothie had about 84 % lower levels of flavonol metabolites than those who drank the banana‑free version. The reduction is attributed to polyphenol oxidase (PPO), an enzyme abundant in bananas that reacts with flavonols and degrades them before the body can absorb them. When the enzyme’s activity was blocked in the laboratory, the loss of flavonols was much smaller. The researchers therefore recommend preparing berry smoothies without banana if the goal is to maximise antioxidant intake, or to consume banana separately from flavonol‑rich fruits.

The study’s participants were all male and the sample size was small, so further research is needed to confirm the findings across broader populations.