September 12, 2023 – A daily smoothie has transformed Lindsey Seegers’ life. After doctors said her long-term disability from COVID would be the new normal, she sought out an expert in alternative medicine, known as a naturopath. One of her recommendations: a smoothie for breakfast, packed with berries, banana, cashew milk, MCT coconut oil and other ingredients.
“As a foodie, I hated the idea of drinking a meal. I’d rather be munching and enjoying an avocado toast. But it really helped me feel so good,” said Seegers, director of a San Diego nonprofit. While there’s no evidence that smoothies can cure long-term COVID (none, as far as we know), she started feeling better after just a few weeks.
But new research suggests that if you drink a smoothie for certain perceived health benefits, combining certain fruits could backfire.
Focus on Flavanols
The research, in the journal Food & Function, specifically looked at the flavanol content of certain fruits. It turns out that a banana and berry smoothie may not have as many health benefits as you think. When you combine fruits high in enzymes that turn fruit brown when exposed to oxygen, such as bananas, with fruits high in beneficial plant compounds known as flavanols, such as berries, the flavanol content decreases rapidly. After 30 minutes, the amount of one flavanol decreased by 80%.
Flavanols, also known as flavan-3-ols, are a common type of flavonoid – plant compounds that have been shown to promote health. Last year, for the first time, the Academy of Nutrition and Dietetics established guidelines for the consumption of flavanols, after reviewing the available research. The group found that these compounds, found in tea, apples, berries, grapes, red wine and cocoa, promote cardiometabolic health.
“If you want to increase your intake of flavanols through smoothies, you shouldn’t combine flavanol-rich ingredients like berries with fruits that turn brown easily when you cut them,” says the study’s lead author, Javier Ottaviani, PhD. director of the Core Laboratory of Mars Edge, part of Mars Inc., and adjunct investigator at the University of California, Davis, Department of Nutrition. “That could destroy the flavanol.”
This effect doesn’t just happen in smoothies, he said. “Anytime you crush or destroy the structure of the fruit, which allows contact between the enzyme and flavanols, it will lead to that loss.” For example, avocados also contain the enzyme, so you can expect reduced flavanol levels in guacamole.
The bigger picture
This may sound like a recipe for disaster, but don’t give up on your regular smoothie (or guacamole) just yet.
“The last thing we want is for people to think, ‘Oh, if I make a smoothie, it’s not going to be healthy,’” says Mary Ann Lila, PhD, director of the Plants for Human Health Institute at North Carolina State University. . A smoothie is an extremely healthy way to get all the bioactive compounds in the fruit, she said, as long as you drink it right away. “If the integrity of the bioactives is destroyed, you will see that. If I left my smoothie there and it turned brown, I wouldn’t drink it.”
Additionally, Ottaviani’s advice only applies if you specifically want to increase your flavanol intake through smoothies. Most people don’t have to do that. A varied diet — especially with a daily cup of green or black tea, which contains more than half the recommended flavanols — can offset a banana’s flavanol-killing power. And bananas offer some impressive benefits on their own.
“If you add the banana to your smoothie, you get potassium and phosphorus. Maybe not as many flavanols,” says Wintana Kiros, a clinical dietitian in the Washington, DC area. ‘But if you eat different foods at lunch or dinner, you eat them throughout the day. The all-or-nothing mentality is the problem.”
The lead author of the study agrees. “Bananas remain a great fruit,” says Ottaviani. “You can still use them for smoothies. The most important thing is that you eat a balanced diet.”
Just get your flavanols somewhere else.
Where smoothies go wrong
While you probably don’t need to worry about the flavanol content of your smoothie, it should is possible to drink a smoothie that will be counterproductive.
For example, too much fruit can lead to problems. “A big problem with smoothies is the total amount of calories and sugar. We certainly want you to eat fruit, but not overconsume it,” says Joanne Slavin, PhD, professor of food science and nutrition at the University of Minnesota. “For most people, when they start mixing it, it becomes a lot of calories.”
A related mistake: omitting important nutrients. “Especially for people on a low-calorie diet, a smoothie should be a meal replacement if it contains protein,” Slavin said. She has conducted research into the power of proteins in smoothies. Together with the fiber in fruit, proteins can keep you feeling satisfied for longer.
Store-bought smoothies can also pose a problem. For starters, you have no control over how much sugar is added. Furthermore, nutrients and bioactive compounds are not affected by processing at home, Lila says. “But they can be affected by commercial processing, if they use heat or add additives to them.”
Secrets of a nutritious – and delicious – smoothie
So you’re ready to take out the blender. What should go in it? Aim for a mix of nutrients. “I recommend a cup of berries, a cup of spinach, and Greek yogurt or protein powder,” Kiros said. “You need a fiber source, a fat source and a protein source.”
Also, don’t be afraid to be a little creative. Here are some ideas:
- Fruits of course. Frozen fruit is especially good here. It helps thicken the smoothie and may contain more bioactive compounds than fresh fruit because it is frozen at maximum freshness. Lila chooses blueberries in her own morning smoothie. Her research has shown that daily consumption can reverse a decline in the thinking skills of the elderly. But don’t limit yourself to the usual banana and berries – go tropical by adding pineapple and mango, or try peach, melon or kiwi.
- Surprise: Vegetables. You get more bioactive substances with less sugar when you add vegetables to your smoothie. Avocado, for example, provides a creamy texture, mild flavor and healthy fat. Lila recommends mixing kale with yogurt or a dash of juice before adding the other ingredients – the plant-based flavor blends in right away. Kiros has spinach. And Seegers, the foodie who was so reluctant to drink her breakfast, adds frozen carrots.
- Protein, for sure: If you’re tired of the usual yogurt and milk, try adding kefir, cottage cheese or ricotta, tofu, peanut powder, your favorite nut butter, edamame, canned white beans, or seeds like chia, flax, and pumpkin.
- Tasty extras: “To be healthy, it has to be something you want to consume,” Lila said. “I believe in making things tasty.” That could mean a drizzle of honey or maple syrup, spices like cinnamon, nutmeg and cardamom, cocoa powder or vanilla extract. Seegers is a big fan of frozen cubes of ground ginger.
Seegers has even become a big fan of smoothies in general. “I can’t throw away the smoothies,” she said. “They are my thing now, this is my life.”