Bananas in Smoothies May Block Key Heart and Brain Nutrients, Study Finds

A recent study from UC Davis suggests that bananas may not be the best choice for health-focused smoothies. Researchers found that adding a banana can cut the body's absorption of flavanols by up to 84%. These compounds, found in foods like berries and dark chocolate, are linked to better heart health, blood pressure, and cognitive function.

Flavanols belong to a group of plant compounds called flavonoids, known for their antioxidant and anti-inflammatory effects. They are found in foods such as cocoa, tea, apples, berries, and leafy greens. Higher intake has been associated with improved blood pressure, vascular health, insulin sensitivity, and even sharper thinking.

The UC Davis study highlighted that bananas contain very few flavanols—only about 2–5 mg per 100 g. More importantly, they are rich in polyphenol oxidase, an enzyme that breaks down flavanols during blending. This reaction drastically reduces how much the body can actually use. In contrast, foods like blueberries, strawberries, apples, and dark chocolate contain far more bioavailable flavanols—up to 10 times the amount—thanks to compounds like epicatechin. For those relying on smoothies as a key source of flavanols, the study recommends swapping bananas for alternatives. Options like cantaloupe, honeydew, pineapple, or yogurt won't interfere with absorption. Even coconut milk or dates can work as a base. The goal is to separate flavanol-rich ingredients, such as berries or green tea, from bananas to maximise their benefits. However, the findings don't mean bananas must be avoided entirely. Occasional banana-berry blends are fine if the overall diet includes plenty of whole berries, apples, or other polyphenol-rich foods.

The research clarifies that blending itself doesn't destroy nutrients, but certain combinations can limit their benefits. By choosing banana-free bases for smoothies, people can better absorb the flavanols that support heart and brain health. Small changes in ingredients could make a noticeable difference in long-term well-being.