Surprising research reveals why you shouldn't add bananas to your smoothies

Smoothies are one of the easiest ways to pack more fruit into your day. Toss in a banana, add some berries, blend, and you have what looks like a perfectly healthy drink. But research from the University of California, Davis suggests that this popular combination may have an unexpected downside.

The issue is not that bananas are unhealthy. Instead, it comes down to how certain ingredients interact after they are blended together. In a study published in the Royal Society of Chemistry journal Food & Function , researchers found that fruits with high levels of an enzyme called polyphenol oxidase, or PPO, can sharply reduce the amount of flavanols your body absorbs from a smoothie. Flavanols are natural plant compounds linked to heart and cognitive health. They are found in foods such as apples, pears, blueberries, blackberries, grapes, cocoa, and other common smoothie ingredients. "We sought to understand, on a very practical level, how a common food and food preparation like a banana-based smoothie could affect the availability of flavanols to be absorbed after intake," said lead author Javier Ottaviani, director of the Core Laboratory of Mars Edge, which is part of Mars, Inc., and an adjunct researcher with the UC Davis Department of Nutrition. Anyone who has sliced an apple or peeled a banana has seen PPO in action. When the fruit is cut, bruised, or exposed to air, the enzyme helps trigger the browning reaction. The UC Davis team wanted to know whether that same process could also affect the nutrients people hope to get from smoothies. To test the idea, the researchers used freshly prepared smoothies made with ingredients that naturally contain different amounts of PPO. Bananas have high PPO activity, while mixed berries have low PPO activity. Participants drank a banana based smoothie, a mixed berry smoothie, and a flavanol capsule used as a control.

Key points

• The issue is not that bananas are unhealthy.
• Instead, it comes down to how certain ingredients interact after they are blended together.
• In a study published in the Royal Society of Chemistry journal Food & Function , researchers found that fruits with high levels of an enzyme called polyphenol oxidase, or PPO, can sharply reduce th…
• Flavanols are natural plant compounds linked to heart and cognitive health.
• They are found in foods such as apples, pears, blueberries, blackberries, grapes, cocoa, and other common smoothie ingredients.