A listener asked me this week whether any vitamins actually remain in the fruit smoothie she prepares in the morning. This is an excellent question, because in recent years, smoothies have become a symbol of health on one hand, while on the other hand, they face quite a bit of criticism: They contain a lot of calories, a lot of fruit, sometimes a lot of natural sugar, and there are also those who claim that vitamins are destroyed the moment the blender is turned on. So, what really happens inside the glass?
One of the claims against smoothies is that vitamins are "destroyed" immediately after blending, but this is inaccurate. It is true that some vitamins, especially vitamin C and some B–complex vitamins, are sensitive to light, oxygen, and heat. During blending, greater contact occurs between the fruit or vegetable and oxygen, because the food tissues break down and the surface area exposed to the air increases. Therefore, the longer the smoothie sits, especially if it is exposed to air, light, or heat, a gradual breakdown of some of the sensitive vitamins begins.
But it is very important to understand: This does not happen in seconds. If you drink the smoothie immediately after preparation, or within a short time, most of the vitamins and minerals are still present in it almost in their entirety. In other words, a smoothie prepared and consumed in the morning right after preparation can still be an excellent source of vitamin C, additional vitamins, minerals, fiber, and antioxidants.
What is the most sensitive and degrades the fastest? Studies examining the preservation of vitamin C in plant foods and juices found that degradation is primarily affected by storage time, temperature, and exposure to oxygen and light. For example, in a study published in Food Chemistry, it was emphasized that oxygen is a central factor in the degradation of ascorbic acid, meaning vitamin C. Studies on smoothies and processed vegetables also found that a low storage temperature reduces the degradation rate of vitamin C, compared to storage at room temperature.
What does not degrade? Not all nutritional components are equally sensitive. Minerals such as calcium, iron, magnesium, and potassium are not "destroyed" during blending. They are not delicate vitamins that break down in light or oxygen, and therefore they remain in the smoothie even after blending. Dietary fiber does not disappear either. Unlike juice, where the fiber is strained out and a significant portion of the fruit and vegetable's benefit is lost, in a smoothie, all components remain inside the glass. Many antioxidants also continue to be present, although some can change over time.
Air exposure time: The problem begins primarily when the smoothie sits for hours in a transparent bottle, on the counter, in the car, or in a warm bag. In such a situation, there is a combination of time, light, heat, and oxygen, and these are the conditions that are less favorable for sensitive vitamins. Therefore, the simple recommendation is to prepare and drink close to the time of preparation. If you want to take a smoothie on the go, it is preferable to keep it in a well–sealed bottle, filled to the top to reduce contact with air, and refrigerated as much as possible. This way, you get the great benefit of the smoothie without losing much of its nutritional value.
Why are smoothies considered healthy anyway? Despite the calorie count, smoothies can be an excellent nutritional tool, provided they are used correctly. The problem begins when a smoothie turns into a giant dessert containing four fruits, dates, peanut butter, granola, and honey, and is then treated as if it were just a "small drink." In such cases, it can easily reach the calorie count of a full meal, and sometimes even more. But a balanced smoothie, which contains one or two fruits, vegetables, leafy greens, and an addition of protein or high–quality fat, can be a wonderful solution for people who do not manage to eat enough fruits and vegetables during the day.
Vitamin concentration: Smoothies composed of leafy greens, fresh fruits, and vegetables provide a handsome amount of important vitamins. Vitamin C, for instance, is important for the proper functioning of the immune system, collagen production, and the absorption of plant–based iron. Vitamin A, which comes in some foods in the form of beta–carotene, is important for vision, skin, and the immune system. Vitamin K, found primarily in leafy greens, is important for blood clotting and bone health.
For people who do not eat enough vegetables or fruits, a smoothie can be a convenient way to bridge the gap. Not everyone will sit down in the morning to eat a large bowl of leafy greens, cucumber, apple, kiwi, and parsley, but many will agree to drink all of it in a single glass. From a nutritional standpoint, this is a significant advantage. Of course, it is still advisable to eat whole vegetables and fruits during the day as well, but a smoothie can be an excellent addition and not a total substitute for all regular eating.
Easier absorption: When we drink a smoothie, we consume the food when it is already well–blended. The significance is that part of the mechanical breakdown process of the food has already been done for us. This does not mean that a smoothie is always "healthier" than eating a whole fruit or vegetable, but there are situations where blending can improve the availability of some components. For example, components found inside the cell walls of the plant can be released better when the food is blended. This is one of the reasons why some studies have found that the mechanical processing of vegetables and fruits can improve the availability of certain antioxidants.
And what is the reason this can help? In real life, we do not always chew well enough. Many people eat quickly, talk while doing so, swallow relatively large pieces, and thus some of the plant components are less exposed to digestion. The smoothie bypasses part of this problem. On the other hand, there is also a disadvantage to this: It is very easy to quickly drink a large amount of fruit without feeling that we have eaten a lot. Therefore, it is important to treat a smoothie as a meal or as part of a meal, and not as a "free drink."
Balance between protein and fat: When you add tahini, yogurt, almonds, nuts, soy milk, yogurt protein, or enriched plant–based milk to a smoothie, you get a more balanced combination of carbohydrates, proteins, and fats. This not only adds important nutritional values such as calcium, iron, zinc, and magnesium, but also affects the absorption rate of the sugars in the fruits.
Fruit on its own is not "bad", but when you blend several fruits together and drink them quickly, the sugar is absorbed faster compared to the slow eating of a whole fruit. The addition of protein and fat slows gastric emptying, moderates the absorption rate, and can help prevent an excessively sharp rise in blood glucose levels. Therefore, a smoothie that contains only fruits and orange juice is very different from a smoothie that contains fruit, leafy greens, yogurt or soy milk, and a tablespoon of tahini or a few almonds.
Long–term satiety: A smoothie that also contains fat and protein can lead to a more moderate rise in blood sugar levels, and consequently to a longer feeling of satiety. This is particularly important for people with a tendency to get hungry quickly after sweet meals, for people with prediabetes or insulin resistance, and also for anyone trying to lose weight who feels that a smoothie "opens up their appetite" instead of satisfying it.
Everything depends on the composition. A small smoothie containing vegetables, one fruit, yogurt or soy milk, and a tablespoon of tahini or a few nuts can be an excellent light meal. In contrast, a giant smoothie based on several fruits, dates, juice, honey, and granola is a completely different story. It might contain vitamins, but it can also contain a very large amount of sugar and calories.
The bottom line: Smoothies do not lose their vitamins immediately after blending. If you drink them close to preparation, most of the nutritional value is preserved.