A scientist said bananas ‘kill’ the benefit of blueberries. Is that true?

A claim circulating online suggests that adding bananas to a blueberry smoothie “kills” the health benefits of the berries by reducing their polyphenol content. The assertion, made by health‑content creator Patrick of FoundMyFitness, hinges on the presence of polyphenol oxidase—an enzyme abundant in bananas—that supposedly breaks down the antioxidant compounds known as polyphenols found in blueberries. Patrick cites a 2023 study that measured blood levels of flavanols, a specific class of polyphenols, after participants consumed banana smoothies with added flavanols versus mixed‑berry smoothies with the same additive, reporting lower flavanol concentrations in the banana group. However, the study never actually combined bananas and blueberries, involved only eight subjects, and focused on flavanols rather than the anthocyanins that dominate blueberry polyphenols and are most linked to health benefits.

Experts caution against over‑interpreting the study’s findings. Dr. Joe Schwarcz of McGill University notes that while polyphenol oxidase can affect the antioxidant capacity of certain compounds, the research did not test the banana‑blueberry pairing directly and its tiny sample size limits statistical power. Moreover, blueberries contain anthocyanins—far more abundant and biologically relevant than flavanols—so the measured reduction in flavanol absorption does not necessarily reflect a loss of the berries’ key nutrients. The study’s funding by Mars, a company that markets flavanol supplements and chocolate, adds another layer of complexity to its relevance. Registered dietitians Alyssa Northrop and Sheri Gaw emphasize that nutrient interactions like those described are common but generally minor in the context of an overall diet; they argue that encouraging fruit consumption, even with bananas, outweighs concerns about marginal polyphenol loss.

In practical terms, the consensus among the consulted scientists and nutritionists is that the modest enzymatic effect of bananas on blueberry polyphenols should not deter people from enjoying the popular fruit combination. Bananas contribute valuable nutrients such as potassium, vitamin B6, vitamin C, manganese, magnesium, and dietary fiber, and they improve the texture and palatability of smoothies, potentially increasing overall fruit intake. Given that many individuals fall short of the recommended five daily servings of fruits and vegetables, the addition of a banana—despite any slight reduction in specific antioxidant levels—represents a net positive for most diets. The broader takeaway is to focus on dietary variety and consistency rather than micromanaging individual food pairings, as the cumulative benefits of a diverse, plant‑rich diet far exceed the nuanced biochemical interactions within a single smoothie.

⚡ Effects Interpreter