Does Adding a Banana to a Smoothie Lower Antioxidants?

Many people consider bananas to be the GOAT ingredient for smoothies. Not only are bananas a healthy way to add a rich, creamy texture and loads of natural sweetness to a smoothie, they’re also jammed with vitamins, minerals and fiber. But recent research has many people wondering if it’s time to ditch this popular, affordable and nutritious fruit. 

Why, you ask? A study published in Food & Function suggests that bananas may make your smoothie less nutritious by inhibiting the absorption of health-promoting flavanols from other fruits, especially berries. Yes, you heard that right. But before you scratch bananas off your grocery list, there’s more to the story. To find out whether you really need to say goodbye to your go-to smoothie ingredient, we asked the experts for their take on the study. Here’s what they told us.

Should You Be Concerned About Bananas in Your Smoothies?

If you’re wondering what potentially makes bananas problematic for smoothies, the culprit is an enzyme in bananas called polyphenol oxidase (PPO). This enzyme, also found in apples and avocados, is what makes these fruits turn brown after you peel or cut them. It also happens to break down a particular class of antioxidants, called flavan-3-ols, found in many fruits and veggies, including berries. While flavan-3-ols don’t get much press, they are antioxidant powerhouses that are particularly beneficial for heart and brain health.  

To find out if the PPO in bananas might inhibit the absorption of berries’ flavan-3-ols, researchers fed eight healthy men two different smoothies at different points in time. The first was a flavan-3-ol-rich banana-based smoothie, and the second was a flavan-3-ol-heavy mixed berry smoothie. For a point of comparison, they also conducted a separate control intervention in which they gave the volunteers a flavan-3-ol capsule to measure the impact of pure flavan-3-ols on their blood levels of these beneficial compounds. After each intervention, the researchers measured flavan-3-ol metabolites in the volunteers’ blood. Their findings: the volunteers’ flavan-3-ol metabolite levels were 84% lower after drinking the banana smoothie than after they consumed the control capsule. However, after drinking the mixed berry smoothie, their flavan-3-ol metabolite levels were similar to their levels from the flavan-3-ol capsules. 

The results may appear clear, but it’s important to consider the study as a whole before assuming you shouldn’t add bananas to your smoothie, says Melissa Jaeger, RD, LD. 

“The study had several limitations, including a small sample size and an all-male participant group, making it difficult to draw broad conclusions,” she says.

Based on a growing body of research, eating foods that provide 400 to 600 milligrams of flavan-3-ols per day may support cardiometabolic health through potential improvements in blood pressure, blood sugar and cholesterol levels. But flavan-3-ols aren’t the only beneficial compounds fruits and vegetables provide. “While there may be a slight difference in your absorption of one particular type of flavanol when you mix bananas and berries in your smoothie, you are still getting a ton of nutrition into your body by eating a couple of types of fruit,” says Gretchen Wallace, M.S., RD. And while bananas may limit absorption of one specific compound, they still provide a wide range of vitamins, minerals and antioxidants plus fiber.

Since only about 1 in 10 U.S. adults eat enough fruits and vegetables to begin with, dietitians agree that focusing too much on the action of one individual nutrient isn’t the most helpful strategy. “Nutrient interactions like this are common,” says Jaeger. “For example, iron and calcium or zinc and copper also compete for absorption.” Because of the sheer number of potential competing nutrients in our foods, hyperfocusing on which fruits or vegetables you’re pairing together in one smoothie, meal or snack isn’t the best way to ensure you’re getting the nutrients your body needs to thrive. Instead, the trick is to eat a variety of plant foods to help you get the nutrients you need from lots of sources.

What Are Flavanols?

Flavanols are a group of health-promoting compounds in many plant foods. They are part of a bigger family of phytochemicals called flavonoids, which fall under an even larger umbrella of antioxidants called polyphenols.  Flavanols are found in foods like broccoli, apples, grapes, tomatoes, kale, olives and citrus fruits, as well as beverages, such as tea and red wine. Eating an abundant variety of flavanol-rich foods is associated with multiple health benefits, including a lower risk of cancer and cardiovascular disease and improved insulin secretion. One way they are believed to do this is by protecting our cells from free-radical damage and oxidative stress, which, if unchecked, can lead to a long list of chronic illnesses.

Strategies to Increase Flavanols

Because flavanols are found in a variety of plant foods, smoothies aren’t the only way to get your fill. Try some of these dietitian-approved strategies for a big flavanol boost:

• Brew Your Tea Longer. Green and black teas are loaded with disease-preventing flavonoids. To get even more of these healthy compounds from your cup, steep your tea longer. Research shows that black tea has the highest polyphenol content after 15 minutes of steeping, while green tea reaches its maximum at around 10 minutes. If you prefer weaker tea, you can add a little extra water to your tea after brewing to dilute it.
• Choose Non-Alkalized Cocoa Powder. Cocoa is an incredible source of flavanols, particularly flavan-3-ols, but mostly if you use non-alkalized cocoa. Research has found that alkalized cocoa powder has just 20% of the flavan-3-ols in non-alkalized cocoa. And you don’t need much cocoa, either. “It only takes a small amount, such as a teaspoon, of cocoa or cacao powder to deliver benefits,” says Avery Zenker, RD. 
• Boost Flavor with Onions. Whether they’re red or white, all onions are loaded with flavanols, Jaeger recommends stirring onions into sauces or soups or sprinkling them onto tacos for extra flavor and nutrition. 
• Don’t Peel Your Apples. Apples are rich in quercetin, a flavanol that is linked to better cognitive health. However, almost all of it is in their skin, so don’t peel away those antioxidants!

Our Expert Take

One recent study found that an enzyme in bananas may block the absorption of health-promoting compounds called flavanols from other fruits in smoothies. But before you swear off bananas, dietitians say that just because bananas may reduce the absorption of one beneficial compound, it hardly means you should exclude them from your diet or your smoothies. After all, bananas offer plenty of health benefits, including a variety of antioxidants, vitamins, minerals and fiber. 

The truth is, there are lots of compounds in our foods that block the absorption of important nutrients. We just never hear about them, because it’s not a problem in the overall scheme of a healthy, balanced eating pattern. In the end, nutrition isn’t about micromanaging each meal and snack. It’s about aiming for a wide range of nutrients and health-promoting compounds from a broad variety of foods, all fruits and veggies included!