Smoothies are one of the most popular healthy drinks in the world. Many people make them at home because they are quick, tasty, and an easy way to eat more fruit.
A common smoothie recipe often includes bananas, berries, yogurt, and other nutritious ingredients blended together into a creamy drink.
However, scientists from the University of California, Davis have discovered that one popular smoothie ingredient may quietly reduce the amount of helpful plant compounds your body can absorb.
The study, published in the Royal Society of Chemistry journal Food & Function, found that bananas may interfere with the body’s ability to absorb flavanols, important natural compounds linked to heart and brain health.
Flavanols are plant-based nutrients found in many fruits and foods. They are especially common in berries, grapes, apples, cocoa, pears, and tea. Researchers have been studying flavanols for years because they may help improve blood flow, support healthy blood pressure, and protect the brain and heart.
Health organizations such as the Academy of Nutrition and Dietetics now recommend that adults consume around 400 to 600 milligrams of flavanols per day for cardiometabolic health. Many people try to increase their flavanol intake by eating berries or drinking fruit smoothies packed with antioxidant-rich ingredients.
The problem, according to the UC Davis researchers, is not the berries themselves. The issue involves how different foods interact when they are blended together.
The scientists focused on an enzyme called polyphenol oxidase, also known as PPO. This enzyme is naturally found in many fruits and vegetables. PPO is responsible for the browning effect people often see after cutting an apple or peeling a banana.
Once fruit is exposed to air, the enzyme reacts with plant compounds and causes the brown color to appear.
Bananas contain especially high levels of PPO activity. The researchers wanted to know whether this enzyme could also affect flavanols inside smoothies.
To investigate, the research team prepared different smoothies using fruits with varying PPO levels. Bananas represented a high-PPO ingredient, while mixed berries represented low-PPO ingredients.
Participants in the study drank three different products: a banana smoothie, a mixed berry smoothie, and a flavanol capsule used as a control comparison. Researchers then collected blood and urine samples to measure how many flavanols entered the body after consumption.
The results surprised the researchers. People who drank the banana smoothie showed flavanol levels that were 84% lower than the control group. Meanwhile, participants who drank the mixed berry smoothie without bananas had flavanol levels similar to those produced by the flavanol capsule.
Lead researcher Javier Ottaviani said the team was surprised by how strongly a single banana reduced flavanol availability. The findings suggest that the way foods are combined and prepared may greatly influence how much nutrition the body actually absorbs.
The study also included another experiment. In this test, flavanols and banana ingredients were kept separate before being consumed together. Even then, flavanol levels still dropped. This suggests that the PPO enzyme may continue affecting flavanols after the smoothie reaches the stomach.
Importantly, the researchers stressed that bananas are still healthy foods. Bananas contain potassium, fiber, vitamins, and natural sweetness. They remain a nutritious part of a balanced diet.
The findings simply suggest that bananas may not be the best ingredient choice if someone specifically wants to maximize flavanol intake from berries, cocoa, grapes, or apples.
For people interested in preserving flavanols in smoothies, the researchers recommend using lower-PPO ingredients instead of bananas. Fruits such as mango, pineapple, and oranges appear to work better with berries. Yogurt may also be a good smoothie addition.
The study also highlights a larger idea in nutrition science: foods do not always act independently. The body processes nutrients differently depending on how foods are combined, cooked, or prepared.
Researchers say this area of science is becoming increasingly important because many people now focus heavily on individual nutrients without considering how foods interact inside the body.
The smoothie research also connects to broader studies on flavanols. Scientists continue studying whether flavanols may help support blood vessel health, cholesterol control, glucose regulation, and cognitive function.
Some studies involving cocoa flavanols have shown possible benefits for older adults and people with lower-quality diets, although the results remain mixed.
The researchers caution that the smoothie study was relatively small. One part included eight healthy men, while another included 11 participants. More research will be needed to confirm whether the same effects occur in larger and more diverse populations.
Nutrition experts also warn against overreacting to the findings. A banana smoothie can still be nutritious and beneficial overall. The research simply provides a practical reminder that food combinations matter.
For smoothie lovers, the message is fairly simple. If the goal is creaminess, sweetness, and potassium, bananas are still a great option. But if the main goal is boosting flavanol intake from berries or cocoa, it may be better to leave bananas out and pair those ingredients with fruits lower in PPO activity instead.
If you care about nutrition, please read studies about why vitamin K is so important for older people, and this snack food may harm your heart rhythm.
For more health information, please see recent studies about vitamin that may protect you from type 2 diabetes, and results showing this common chemical in food may harm your blood pressure.
The study was published in Food & Function.
Source: University of California, Davis.
