Berry smoothies are a great way to start your day. Strawberries, blueberries and other members of the berry family are packed to the brim with healthy nutrients such as flavanols. But new research suggests that if you use some common smoothie ingredients alongside them, you may have been unknowingly depriving yourself of all the benefits on offer.
A new study published in the Royal Society of Chemistry’s journal Food And Function by researchers at the University of California suggests that using ingredients which contain polyphenol oxidase—an enzyme commonly found in fresh produce that is responsible for turning some fruits and vegetables brown when you slice them—can significantly limit the absorption of flavanols in the body.
That’s not good news because flavanols are highly beneficial for your health. These powerful antioxidants have been found to help improve brain function and lower blood pressure. In fact, the US industry body, the Academy of Nutrition and Dietetics issued a guideline in 2022 which recommended that everyone should try to consume 400 to 600 milligrams of flavanols a day (190g of blueberries contain 10 milligrams).
In the study, healthy male participants were instructed to drink one of two smoothies: one made with just a banana and the other made with berries, alongside a capsule containing flavanols only. Researchers analyzed their blood and urine samples, and found that participants who drank the banana smoothie had almost 84% lower levels of flavanols in their body than the berry group. Such a significant drop cannot be entirely ascribed to chance or measurement error.
It’s a small and preliminary study, and more research is needed to understand the complex interactions of different nutrients in the human body. However, the researchers noted that it’s a clear indication that we may need to rethink how we make our smoothies.
To reap all the health benefits from flavanol-rich fruits and vegetables, you may wish to consider mixing them with ingredients that are low in polyphenol oxidase, which includes yogurts, oranges, mangoes and pineapples.
At the same time, you shouldn’t be ditching smoothies with fruit and vegetables high in the enzyme. Bananas and apples remain great smoothie ingredients with their own unique health benefits to offer. They contain many essential vitamins and antioxidants, and are particularly rich in fiber that feeds healthy gut bacteria.
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Anna Gora is a health writer and certified PT with more than a decade’s experience in the fitness industry. She provides online health coaching to people as part of the UK’s Healthier You: NHS Diabetes Prevention Programme and has a master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol. As well as Coach, Anna also contributes to sister site Fit&Well and science news website Live Science.