Bananas in smoothies may slash absorption of heart-healthy flavanols by 84%

Smoothies are a tasty, convenient, and nutrient-rich way to up your intake of fruits and vegetables-perfect in the morning, after a workout, or as a snack. But what if a common ingredient actually made your smoothie less healthy?

That's what researchers at UC Davis discovered through a 2023 study published in the journal Food & Function. More specifically, they found that adding a banana to your smoothie could decrease your body's absorption of heart- and brain-healthy flavanols by up to 84%.

So what does this mean for your morning smoothie? Do you need to banish bananas from your blender? We spoke with three nutritionists and dietitians to find out.

What Are Flavanols?

First things first: What are flavanols and why are they good for us? Flavanols are a subclass of flavonoids, which are naturally occurring polyphenol compounds with antioxidant, anti-inflammatory, and cardioprotective properties found in certain plant-based foods, says Morgan Walker, sports nutritionist and dietician at Lebanon Valley College.

"The antioxidant compounds can help protect the cells from damage caused by free radicals, and the anti-inflammatory properties may also lower the risk of certain chronic diseases, most notably cardiovascular disease," she explains.

Consuming more flavanols has been associated with improvements in blood pressure, vascular elasticity, insulin sensitivity, and HDL ("good") cholesterol. "Growing evidence also connects long-term flavanol intake with better cognitive outcomes, including reduced risk of cognitive decline and dementia, likely due to improved blood flow to the brain and reduced inflammatory stress," she adds.

Adding flavanols to your daily diet can be an easy approach to increasing the variety of nutrients in your diet, as well as protecting cells from the environmental stresses we all encounter every day, according to Kezia Joy, RDN, a registered dietitian nutritionist and medical advisor at Welzo, where she specializes in evidence-based nutrition guidance and metabolic health.

Common foods and beverages containing flavanols include:

• Cocoa/dark chocolate
• Black and green tea
• Apples
• Grapes
• Berries
• Red wine
• Leafy vegetables (like kale)
• Onions
• Cherries
• Pears
• Soybeans
• Citrus fruits
• Broccoli
• Asparagus

Does Blending Different Fruits Together Affect Their Nutritional Value?

In most cases, no. "Usually, blending fruits together just widens the benefits of your smoothie because each fruit has different compounds and different benefits," says Stacie Stephenson, DC, CNS, a doctor of chiropractic, a certified nutrition specialist, and a board member of The American Nutrition Association. "The more diversity of plants in your diet, the more nutritional benefits you will receive, in most cases."

Blending fruits does not inherently make them less nutritious, Walker says, but the combination of different fruits and foods can decrease the bioavailability of certain nutrients-especially polyphenols like flavanols. For example, some fruits, like bananas, contain high levels of polyphenol oxidase (PPO)-an enzyme that causes browning in bananas and other fruits. "PPO can oxidize flavanols during blending, which may reduce the amount the body can absorb," she explains.

While blending will generally change the texture of a smoothie and affect the amount of light that hits the nutrients inside it-therefore potentially affecting the amount of time the nutrients are available for absorption-most of the vitamins and minerals, as well as the fiber, are typically preserved in their original state, Joy explains.

"In general, while blending does create changes in a smoothie, the changes are usually small, and blending remains a viable option for incorporating fruits into your diet if eating whole forms of them isn't possible," she says.

Should We Stop Putting Bananas in Smoothies?

Not necessarily, says Joy. "The research allows us to consider how different combinations of fruits will impact the body's ability to absorb the flavonoid content in the fruit," she says, but the findings "don't imply that we should remove bananas from our smoothie recipes." Instead, the study suggests that if you routinely use smoothies as your primary source of flavanol-rich foods, it may be worthwhile to swap bananas for another base ingredient-like berries-that does not affect flavanol bioavailability, Walker says.

Meanwhile, for someone who enjoys the occasional banana-berry smoothie as part of an overall diet already rich in whole berries and other polyphenol-containing foods, this is a very different scenario and likely does not mean that you need to avoid bananas altogether, Walker says. "If you enjoy bananas in your smoothie, you can absolutely keep them-just pair them with other fruits like mango or pineapple where bioavailability of nutrients is not known to be impacted," she notes. "Bananas remain a good source of potassium, fiber and natural carbohydrate, which means they can continue to be part of a healthy diet when selected appropriately," Joy says.

If you're trying to increase your flavanol intake-by eating apples or berries, for example-separating these ingredients from banana-based smoothie recipes would provide the best opportunity to maximize their bioavailability, Joy explains.

What Are Some Alternatives to Bananas?

In the UC Davis study, when the researchers compared banana-based smoothies to those made with a base of mixed berries-specifically, strawberries, blueberries, blackberries, and raspberries-they found that flavanol absorption was higher in the berry smoothie.

Here are some other banana-replacement options for your smoothies:

• Cantaloupe
• Honeydew
• Pineapple
• Mango
• Peaches
• Oranges
• Dates (for sweetness)
• Coconut milk (for creaminess)
• Yogurt (for creaminess)

The primary takeaway is that if you drink smoothies to increase your flavanol intake, pay attention to which foods you're combining in order to maximize their nutritional value. Otherwise, go ahead and enjoy your banana smoothie.