Combination of specific ingredients in smoothies can significantly influence the body’s reception of essential nutrients.
Recent findings from researchers highlight how the enzyme polyphenol oxidase (PPO) found in select fruits, such as bananas, may hinder the absorption of beneficial flavanols, particularly when blended with flavanol-rich elements like berries. The study recommends opting for ingredients exhibiting lower PPO activity, such as pineapple or oranges, when creating smoothies to enhance flavanol absorption.
Published in the Royal Society of Chemistry’s journal Food and Function, the study investigated the impact of varying levels of polyphenol oxidase (PPO), an enzyme found in numerous fruits and vegetables, on the absorption of flavanols in food. Flavanols, beneficial for heart and cognitive health, naturally occur in commonly used smoothie ingredients such as apples, pears, blueberries, blackberries, grapes, and cocoa.
Lead author Javier Ottaviani, the director of the Core Laboratory of Mars Edge at Mars, Inc., and an adjunct researcher with the UC Davis Department of Nutrition, highlighted the study’s aim:
“We aimed to comprehend, on a practical level, how a prevalent food and its preparation, like a smoothie based on bananas, could affect the availability of flavanols for absorption post-consumption.”Javier Ottaviani
When someone slices an apple or peel a banana, these fruits tend to brown quickly due to the presence of polyphenol oxidase (PPO), an enzyme naturally occurring in these foods. This browning process occurs upon exposure to air, cutting, or bruising. The researchers delved into whether freshly made smoothies containing various PPO-rich fruits affected the body’s access to flavanols.
Bananas and berries
In the study, participants were given a banana-based smoothie, known for its naturally high PPO activity, and a blend of mixed berries, which boast naturally low PPO activity. As a control, participants also ingested a flavanol capsule. Researchers then analyzed blood and urine samples to gauge the presence of flavanols in the body post-consumption of both smoothie variations and the capsule. The results showed that individuals who consumed the banana smoothie had an 84% reduction in flavanol levels in their bodies compared to the control group.
“We were genuinely surprised to witness how swiftly the addition of a single banana diminished the flavanol levels in both the smoothie and the body’s absorption of flavanols. This underscores the impact of food preparation methods and ingredient combinations on the absorption of nutritional elements within foods.”Javier Ottaviani
Notably, the Academy of Nutrition and Dietetics advised a daily intake of 400 to 600 milligrams of flavanols for optimal cardiometabolic health last year. Ottaviani suggested that individuals aiming for this flavanol intake should consider creating smoothies by pairing flavanol-rich fruits like berries with other ingredients exhibiting low PPO activity, such as pineapple, oranges, mangoes, or yogurt.
While acknowledging bananas as an excellent fruit for consumption or inclusion in smoothies, Ottaviani advised against combining them with flavanol-rich fruits like berries, grapes, and cocoa. This also applies to other fruits and vegetables with high PPO activity, such as beet greens.
The study’s findings may spark further investigations into the preparation of various foods and their impact on flavanols. Ottaviani highlighted tea as a significant dietary source of flavanols, emphasizing that varying preparation methods could result in differing flavanol availability for absorption.
“This area certainly warrants more attention within the realm of polyphenols and bioactive compounds,”Javier Ottaviani
Flavan-3-ols are bioactive compounds found in a variety of fruits and vegetables (F&V) that have been linked to positive health benefits. Increasing habitual flavan-3-ol intake is challenged by the generally low consumption of F&V. While smoothies are a commonly endorsed, consumer-accepted means to increase the daily intake of these important foods, fruits used for smoothie preparation can have a high polyphenol oxidase (PPO) activity and thus potentially affect the content and bioavailability of flavan-3-ols. To assess whether or not consuming freshly prepared smoothies made with different PPO-containing fruit impacts the bioavailability of the flavan-3-ols, a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control). The peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L−1, which was similar to the levels detected after the intake of the low PPO drink. In contrast, the intake of the high PPO drink resulted in a Cmax of 96 ± 47 nmol L−1, 84% lower than that obtained after capsule intake. In a subsequent study (n = 11), flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented. In this context, plasma flavan-3-ol levels were still reduced, suggesting an effect possibly related to post-ingestion PPO activity degrading flavan-3-ols in the stomach. There was a substantial range in the PPO activity detected in 18 different fruits, vegetables and plant-derived dietary products. In conclusion, 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 both at home and in industrial settings.