Banana smoothies may reduce flavanol benefits of berries
Does your smoothie deliver all the health benefits you expect?
Smoothies have become a popular way to increase fruit and vegetable consumption, offering a convenient source of vitamins, minerals, fibre, and antioxidants. However, emerging research suggests that the ingredients you choose can significantly influence how well your body absorbs beneficial plant compounds.
Why Flavan-3-ols absorption matters?
Flavan-3-ols are naturally occurring polyphenols found in foods such as cocoa, berries, apples, grapes, pears, and tea. Evidences have linked these compounds with several health benefits, including:
- Improved cardiovascular function
- Enhanced cognitive performance
- Better blood vessel health
- Antioxidant and anti-inflammatory effects
As many people fail to meet recommended fruit and vegetable intake, smoothies are frequently recommended as a practical way to increase flavanol consumption. However, little was previously known about how smoothie preparation influences flavanol absorption.
What is Polyphenol oxidase?
Polyphenol oxidase (PPO), an enzyme naturally present in certain fruits such as bananas, is responsible for the browning seen when fruits like bananas and apples are cut or blended. This enzyme supposedly hypothesized to degrade beneficial flavan-3-ols before or during digestion.
A recent study by scientists of University of California, investigated whether smoothies prepared with fruits containing different levels of polyphenol oxidase (PPO) affect the bioavailability of flavan-3-ols. The study tested whether preventing banana and flavan-3-ols from mixing before consumption would improve absorption. The test products included three flavan-3-ol delivery methods:
- Banana Smoothie (High PPO)
- Naturally rich in polyphenol oxidase
- Standardized flavan-3-ol content
- Mixed Berry Smoothie (Low PPO)
- Low PPO activity
- Similar flavan-3-ol dose
- Flavan-3-ol Capsule (Control)
- Standardized cocoa flavanol extract
- Consumed with milk
The findings provide valuable insights for consumers, nutritionists, and food manufacturers seeking to maximize the nutritional value of smoothies.
Banana smoothies dramatically reduce flavanol absorption
The most striking finding was the substantial reduction in flavanol bioavailability after consuming banana smoothies. In smoothies prepared with bananas,
- Peak flavanol metabolite concentration decreases by approximately 84%
- Overall flavanol exposure decreases by more than 80%
In contrast, the mixed berry smoothie produces flavanol absorption levels similar to the capsule control.
Berry smoothies preserved antioxidant availability
Unlike bananas, berries contain very low levels of polyphenol oxidase.
As a result:
- Flavan-3-ol metabolites remain high
- Bioavailability is comparable to the control capsule
- No significant loss of antioxidant absorption
This supports the berry-based smoothies as an effective vehicle for delivering dietary flavanols.
Polyphenol oxidase degrades flavanols quickly
Laboratory experiments demonstrated that flavan-3-ols rapidly disappeared after mixing with blended bananas.
As observed:
- A flavanol half-life of approximately 10 minutes
- Significant preservation occurs when PPO inhibitors are added
This confirms that the enzyme, not another property of bananas, is primarily responsible for flavanol degradation.
The effect continues during digestion
Even when flavan-3-ols and banana are consumed separately, absorption remained significantly lower than the control. In addition, banana PPO remains active under simulated stomach conditions, suggesting the enzyme continues breaking down flavanols after ingestion.
Polyphenol oxidase levels differ greatly between fruits
When PPO activity was measured across various fruits and vegetables.
High PPO foods included:
- Bananas
- Apples
- Pears
- Beet greens
Low PPO foods included:
- Strawberries
- Blueberries
- Kale
- Pineapple
- Oranges
These differences may help explain why some smoothie combinations preserve antioxidants better than others.
What is the right way to consume smoothies?
People preparing smoothies at home may maximize flavanol intake by:
- Choosing berries instead of bananas when antioxidant intake is the priority
- Drinking smoothies immediately after preparation
- Including fruits naturally low in PPO
For Nutrition Professionals
Dietitians can incorporate right smoothies’ recipe into evidence-based dietary recommendations, particularly for individuals seeking cardiovascular or cognitive benefits from flavanol-rich foods.
For Food Manufacturers
Companies producing ready-to-drink smoothies may benefit from:
- Selecting ingredients with lower PPO activity
- Optimizing processing methods that reduce enzymatic degradation
- Evaluating flavanol retention during manufacturing
These approaches could improve the nutritional quality of commercial products.
Future Insights
It is important to pay attention on the right food preparation methods, considering the right dietary interventions. While bananas remain a nutritious fruit rich in potassium, fiber, and essential nutrients, their naturally high polyphenol oxidase activity appears to substantially reduce the absorption of flavan-3-ols when blended into smoothies. Further, studies may be carried out to study the effects of the dietary foods on women and children, combining different fruit combinations and evaluating the long-term health outcomes.
As nutrition science continues to evolve, these studies remind us that the interactions between foods can significantly influence the nutrients our bodies ultimately absorb, not just the nutrients listed on the label.
