Smoothies, a popular choice for a speedy breakfast or a nourishing snack, can be a convenient way to incorporate more fruits and vegetables into our diet. But while the individual fruits in smoothies are well-studied (and are good for you), the combination of fruits is less studied.
In a new study, scientists found that adding bananas to a berry smoothy reduces the flavanols, a group of bioactive compounds good for your health, by 84% — hinting that ideally, you wouldn't mix the two fruits.
First of all, we should say that there's more to healthy nutrition than flavanols. This is just one component that makes berries healthy, there are plenty of other things to consider. But if you want to optimize your nutrition, it's something you can consider.
Researchers used smoothies to test how different levels of polyphenol oxidase (an enzyme found in many fruits and vegetables) affects the absorption of flavanols by the body. Flavanos are a natural compound commonly found in foods and drinks that can reduce inflammation and protect your vascular (blood system).
“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,” Gunter Kuhnle, one of the study authors, said in a news release.
The right smoothie
This is where bananas come in.
When we peel a banana or cut an apple, the fruit turns brown very fast. This happens because of polyphenol oxidase (PPO), an enzyme naturally present in those foods. In their study, the researchers wanted to know whether drinking a smoothie made with different fruits containing PPO affected the amount of flavanols available to the body.
To find out, they gave volunteers a smoothie with banana and berries, a smoothie just with berries, or just a flavanol capsule by itself (the control group). The researchers then took blood and urine samples to measure how many flavanols were present after taking the smoothie or capsule. They found flavanol levels were reduced when bananas were included.
“We were really surprised to see how quickly adding a single banana decreased the level of flavanols in the smoothie and the levels of flavanol absorbed in the body,” Javier Ottaviani, study author, said in a news release. “This highlights how food preparation and combinations can affect the absorption of dietary compounds in foods.”
The researchers said that people who are trying to consume flavanols should consider making smoothies by combining flavanol-rich fruits such as berries, pineapple, and oranges. The findings don’t mean bananas are not a good fruit to eat alone or in smoothies, they clarified, but bananas may affect flavanol update very significantly. It is further worth noting that the study was conducted among a relatively small sample of people, and only men, so effects may be different depending on the person.
Next, they hope their study can lead others to look at how other foods are prepared and the effect of flavanols. For example, Ottaviani said tea is a big source of flavanols, and depending on how it’s prepared, a different amount of flavanols would be available for absorption. “This is certainly an area that deserves more attention,” he added.
The bottom line: if you really want to optimize your smoothie, put the berries in and save the banana for later. It'll increase your flavanol intake.
The study was published in the journal Food & Function.