If I blend fruits and vegetables into a smoothie, do they lose nutrients or fibre? This is a question readers often ask me these days. The answer would be: a freshly blended smoothie ticks a lot of boxes. It’s quick to prepare, easy to consume and a versatile base for whatever fruits and veggies you have on hand.
And if blending your produce can help you eat more of it, that’s a good thing, said Kristina Petersen, an associate professor of nutritional sciences at Pennsylvania State University in the US. But are nutrients lost when fruits and vegetables are chopped into bits by a blender blade? We asked experts to help us break it down so you can get the most out of your smoothie.
Unlike juicing, blending can incorporate all of the edible parts of fruits and vegetables — including the skin, seeds and pulp — so a smoothie can be nutritionally very similar to eating the produce whole, said Mary Ann Lila, a professor of food, bioprocessing and nutrition sciences at North Carolina State University in the US.
And blending shouldn’t degrade the vitamins or minerals found in fruits and vegetables, Lila said. Nor will it immediately harm certain antioxidant and anti-inflammatory compounds, like anthocyanins and flavonols, she said.
Fruits and vegetables are also good sources of fibre, which most of us could benefit from eating more of. And whether you eat an apple whole or as part of a smoothie, “you’ve consumed exactly the same amount of fibre”, said Balazs Bajka, a gut physiologist at King’s College London in the UK.
Blending does, however, break the fibres into smaller pieces, which will affect how they move through your digestive system, he said. Some types of fibers, when chopped into bits, may disperse more quickly within your gut and slow digestion and absorption — usually a good thing — while others might lose some of the “roughage” effect that keeps things moving in your digestive tract and prevents constipation.
But there’s not much research on this topic, and specific effects may depend on the person and the fruit or vegetable. Regardless, “eating any kind of fibre is good”, Bajka said.
Processing food often disrupts its natural structure, which can lead to faster digestion and absorption. So it’s reasonable to wonder if puréeing fruit could cause a bigger spike of blood sugar, said Anthony Fardet, a nutrition scientist at the National Research Institute for Agriculture, Food and the Environment in France.
But in a few small studies that measured adults’ blood sugars after they consumed fruit blended or whole, researchers have found reassuring results. The preparation style of mango, for instance, seemed to make no difference in blood sugar response. And when researchers tested smoothies containing seeded fruits like passion fruit, raspberries or kiwi, participants had more gradual rises in blood sugars than when they ate the same fruits whole.
That result surprised Gail Rees, a senior lecturer in human nutrition at the University of Plymouth in Britain who led two of the studies. She hypothesised that mashing up the fruits’ seeds in the blender might release some fibre, protein and fat, which could slow nutrient absorption and cause a more gradual rise in blood sugars.
Beyond the fruits and vegetables you use in your smoothies, other ingredients also affect their nutritional value, Petersen said. Water is a good liquid base if you’re aiming for a light snack. For a more balanced and filling smoothie, low-fat or fat-free dairy milk or unsweetened yogurt, kefir or fortified plant-based milks can provide protein, calcium and Vitamin D, she added.
“Throw some nuts in there,” or avocado, Lila suggested. Both provide healthy fats and fibre, as do chia or flaxseeds; whole grains like millet or rolled oats are good fibre sources, too.
Smoothies also provide a great opportunity to use frozen produce, which is generally just as nutritious as when it is fresh, Lila said. She recommended storing frozen fruits and vegetables at the back of your freezer to minimise the slight thawing and refreezing that can cause nutrient losses when you open your freezer door.
Finally, keep in mind that once fruit is blended, its healthful compounds gradually become less stable, Lila said. Yesterday’s smoothie that has separated and turned a bit gray has probably lost some of its antioxidant and anti-inflammatory value, she said. For the same reason, prepackaged smoothies may not be as beneficial, she added, and they also often contain added sugars.
In other words, Lila said, enjoy your smoothie — but make it fresh each day and drink it right away.