Some fruits used in smoothie blends – such as bananas – can have a high polyphenol oxidase (PPO) activity, which affects the content and bioavailability of flavan-3-ols.
US-based researchers compared the effects of consuming different fruits in combination and found that the peak plasma concentration (Cmax) of flavan-3-ol metabolites was 84% lower in subjects who consumed flavan-3-ols alongside high-PPO fruit.
“Bioavailability of flavan-3-ols, and most likely other dietary polyphenol bioactives, can be reduced substantially by the co-ingestion of high PPO-containing products, the implications of which are of importance for dietary advice and food preparation,” they wrote in the journal Food and Function.
The findings could also be of interest to functional drink manufacturers, including commercial smoothie brands.
Cmax of flavan-3-ol metabolites 84% lower for high-PPO drink
Study participants either consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink), or flavan-3-ols in a capsule format (control).
The Cmax of flavan-3-ol metabolites was 84% lower among those who consumed the high-PPO drink than that obtained after capsule intake. The Cmax of flavan-3-ol metabolites after capsule intake was similar to the levels detected after intake of the low-PPO drink.
In a follow-up study, flavan-3-ols were co-ingested with a high-PPO banana drink without mixing the two before consumption. Plasma flavan-3-ol levels remained reduced, suggesting an effect possibly related to post-ingestion PPO activity degrading flavan-3-ols in the stomach.
The research, which was funded with a grant from Mars, detected a substantial range in PPO activity in 18 different fruits, vegetables, and plant-derived dietary products.
Dietary flavan-3-ols linked with positive health benefits
Dietary flavan-3-ols – bioactive compounds that are found in tea, apples, pears, berries, and chocolate or cocoa products – have been linked to a lower risk of developing chronic diseases such as cardiovascular disease, metabolic disorders, and cancer.
Last year, the US-based Academy of Nutrition and Dietetics published a guideline – the first of its kind – after an expert panel concluded that there was “moderate evidence” to show that flavan-3-ol intakes of 400-600 mg per day offer cardiometabolic protection.
Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said: “Don't mix bananas with berries if you want to have the benefit of flavanols.”
“Flavanols can reduce the risk of heart disease and cognitive decline – you should try to get between 400 and 600 mg per day. It's easy to achieve this by some small changes to the diet, but you need to be careful what foods you mix.”
“Combining berries (a great source of flavanols) with bananas (a staple of smoothies) might not be a good idea: the enzymes in the banana break down the flavanols and none ends up in your stomach – or your body.”
The study authors concluded: “This study highlights that consideration needs to be given not only to the types of fruits and vegetables and plant-based products to recommend to increase intake, but also how they are prepared, stored, and consumed as part of a regular meal in order to maximise their potential to support health.”
Commenting on the study, Mars Edge, the entrepreneurial division of Mars that specialises in promoting health through targeted nutrition, said: “Smoothies and juices made with flavanol-rich foods such as apples, berries and cocoa flavanol supplements, including our CocoaVia supplement, have become a popular way for people to increase their intake of flavanols. But it is important to consider the combination of ingredients. For example, combining high-flavanol fruits such as berries in a smoothie with low-PPO foods including pineapple, oranges, and mango will help to maintain the level of dietary flavanols available.”