The fruits and vegetables in smoothies determine the level of healthy flavanols. However, added bananas, for example, can significantly reduce the amount of flavanols absorbed by the body. So what should a smoothie consist of to get as many flavanols as possible?
In a new study involving researchers from the University of California, Davis, the bioavailability of flavanols in freshly made fruit smoothies was examined using the enzyme polyphenol oxidase. The results are published in the journal “Food & Function”.
Apples, pears, blueberries, blackberries, grapes, and even cocoa are common ingredients in smoothies, all of which contain so-called flavanols. These are known to be particularly beneficial for cardiac and cognitive health.
Link between polyphenol oxidase and flavanols
However, an enzyme called polyphenol oxidase, found in many fruits and vegetables, affects how much flavanols are absorbed by the body, the team explains.
Polyphenol oxidase is also the reason why some fruit (e.g. apples and bananas) turn brown very quickly after cutting. If fruit with polyphenol oxidase is exposed to the air, cut or squeezed, this typical browning occurs.
Polyphenol oxidase affects bioavailability of flavanols
To determine how the consumption of freshly prepared smoothies made from different fruits with polyphenol oxidase affects the bioavailability of the flavanols, participants were instructed to consume two different smoothies, the researchers report.
One smoothie was banana-based and had high polyphenol oxidase activity, while the other smoothie was made with mixed berries, which are naturally low in polyphenol oxidase activity. The control group took a flavanol capsule.
“We tried to understand, on a very practical level, how a common food and a food preparation like a banana-based smoothie could affect the availability of flavanols that are absorbed after consumption,” study author Javier Ottaviani explained in a press release.
84 percent fewer flavanols from bananas
The team used blood and urine samples to determine how much flavanols were in the body after ingesting smoothies and capsules. It turned out that participants who had consumed the banana smoothie had 84 percent fewer flavanols in their bodies than the control group.
“We were really surprised at how quickly adding a single banana reduced the flavanol content in the smoothie and the amount of flavanols absorbed by the body. This shows how the preparation and combination of foods can affect the absorption of dietary components,” reports Ottaviani.
Ingest as many flavanols as possible through smoothies
To get as many flavanols as possible from smoothies, Ottaviani advises combining flavanol-rich fruits like berries with other ingredients that also have low polyphenol oxidase activity. Such ingredients can be, for example, pineapple, oranges, mango or yoghurt.
On the other hand, the expert recommends not combining smoothies with bananas or other types of fruit and vegetables with high polyphenol oxidase activity with fruits rich in flavanol, such as berries, grapes and cocoa. (as)
