Bananas and the Hidden Cost of Smoothie Convenience
What you blend into a smoothie matters just as much as what you blend it with. A recent study published in the Royal Society of Chemistry’s journal Food and Function highlights a surprising factor in nutrient absorption: the enzyme polyphenol oxidase (PPO), naturally present in many fruits and vegetables, can influence how well flavanols are taken up by the body. Flavanols are bioactive compounds linked to heart and brain health, commonly found in apples, pears, blueberries, blackberries, grapes, cocoa, and other smoothie staples.
What the Research Found
Led by Javier Ottaviani, the study compared two smoothie formats to see how preparation and ingredients affect flavanol availability. One smoothie featured banana—an ingredient with relatively high PPO activity—while the other used mixed berries, which have lower PPO activity. Participants also took a flavanol capsule to serve as a comparison. After consumption, researchers measured flavanol levels in blood and urine to gauge absorption.
The results were striking: those who drank the banana-based smoothie had an 84% lower level of flavanols in their system compared with the control capsule. The takeaway isn’t that bananas are unhealthy, but that including high PPO ingredients can markedly reduce the body’s ability to absorb these beneficial compounds when mixed with other foods rich in flavanols.
Why PPO Matters for Nutrient Absorption
PPO is the enzyme responsible for browning when fruits are cut or bruised. In the context of a smoothie, PPO can react with oxygen and other components, altering how polyphenols like flavanols are available for absorption. When a banana is blended with flavanol-rich ingredients, the enzyme activity may degrade or modify flavanols, making them harder for the body to utilize. This does not mean smooth move toward “bad” smoothies, but it does suggest that some fruit combinations can optimize or hinder nutrient uptake.
Flavanols: Benefits and Practical Guidance
Flavanols are part of the larger polyphenol family and are associated with cardiovascular and cognitive health benefits, including improved blood flow, potential memory support, and reduced inflammation with regular intake. The Academy of Nutrition and Dietetics has suggested a daily target in the hundreds of milligrams range to support cardiometabolic health through flavanol intake.
To maximize the health impact of flavanols in smoothies, researchers suggest pairing flavanol-rich fruits with ingredients that exhibit low PPO activity. Examples include pineapple, oranges, mango, or yogurt. These pairings can help preserve flavanols as they travel through the digestive system, increasing the likelihood of absorption.
Practical Smoothie Tips for Health-Conscious Eaters
- Prefer berry-forward smoothies when your goal is flavanol intake, or add a non-PPO-rich base like yogurt or citrus to balance flavors.
- Avoid blending high-PPO ingredients with large amounts of flavanol-rich foods in a way that could reduce absorption.
- Consider stirring in a flavanol-rich supplement or adding a cocoa product to boost intake without overwhelming the blend with PPO-heavy fruits.
- Be mindful of overall ingredient variety; the goal is a tasty smoothie that also respects nutrient bioavailability.
More Research on Food Preparation
Ottaviani notes that this line of inquiry could extend beyond smoothies. Tea, for instance, is a major flavanol source, and brewing methods might influence how much of these compounds are accessible to the body. The study calls for more exploration into how everyday food preparation affects nutrient absorption, an area that could guide dietary recommendations and product development in the future.
As researchers continue to unravel the complexities of polyphenols and bioactive compounds, the practical message remains clear: how you prepare and combine foods can subtly shift the health benefits you expect from them. For those tracking flavanol intake, choosing fruit pairings with lower PPO activity and being mindful of high-PPO ingredients can help maximize the nutritional payoff of smoothies.
Funding for the study came from Mars, Inc., reflecting ongoing interest in how cocoa flavanols affect human health. The collaboration spans several universities and industry partners, underscoring a growing focus on translating lab findings into real-world dietary guidance.
