HEALTH CONSCIOUS individuals may choose to leave bananas out of their morning smoothies, following findings from new research.
A study published in Food and Function last week showed that bananas reduce the amount of flavanol – a bioactive compound which promotes good heart and cognitive health – taken in by consumers by 84%.
Scientists used smoothies to investigate how polyphenol oxidase, an enzyme which causes browning when fruit and vegetables get bruised, affects the absorption of flavanols by the human body. The enzyme is particularly prevalent in bananas.
The project was led by University of California Davis Department of Nutrition, in collaboration with the University of Reading.
Gunter Kuhnle, professor of Nutrition and Food Science at the University of Reading and co-investigator of the study said: “If you don’t consume enough flavanols, it can negatively affect cardiovascular health. In older adults, a deficiency of flavanols is also linked to cognitive decline.
“So, it’s clear we need them, but the question is how best to get flavanols from the food and drinks we consume.
“Smoothies are a popular way to pack fruit and vegetables into our morning routines. We know from previous studies that flavanols can be broken down by polyphenol oxidase.
“The extent of the effect from adding a single banana was still very surprising – it had enough polyphenol oxidase to destroy the vast majority of flavanols found in the berries.
“Bananas may be ruled out of the morning smoothie if you want to boost your flavanol intake, but on their own, they are still great fruits and can play an important role in many healthy diets.”
Participants were given the following smoothie combinations: banana and berries, just mixed berries or a flavanol capsule.
Blood and urine samples were taken to identify which flavanols made it through into the individual’s body.
Researchers discovered that the levels of flavanols in the smoothie, and absorbed by the body, were markedly reduced when banana was included.
Prof Kuhnle explained: “We still know very little about food-food and food-nutrient interactions, even though they can have a huge impact on the uptake of nutrients and bioactives like flavanols.
“Here, we could show that the uptake of flavanols can vary by more than five-fold depending on the combination of foods.
“Bananas are a great ingredient in smoothies to provide a nicer texture – but they can affect flavanol uptake.
“If you want to boost your flavanol intake with a smoothie, you should combine flavanol-rich fruits like berries with foods that have a low polyphenol oxidase activity like pineapple, oranges, mango or yoghurt.”
