2024-01-15 23:00:00
Mixed fruit drinks, or smoothies, are considered a convenient way to stock up on nutrients, particularly antioxidants. However, new research shows that to really benefit from them, it is better not to combine the ingredients haphazardly.
Mixed fruit drinks being can be composed as desired, you may be tempted to put together in your blender an apple, red fruits, a kiwi, an avocado, or even a little greenery (sprouted seeds, broccoli, etc.), for example. And above all add a banana, popular as much for the taste as for the texture. But what if such a mix was a mistake? This is what a study published in August 2023 in the journal Food and Function (1) suggests, which warns of the action neutralizing an enzyme present in abundance in bananas vis-à-vis flavanols, a category of antioxidants particularly well represented in red fruits, cocoa, grapes, but also broccoli or spinach.
Flavanols: random bioavailability
Flavanols, also called “catechins”, are key players in the fight against free radicals. They contribute to counteract the deleterious effects of oxidative stress , and are particularly recognized for their positive effects on memory (2) and cardiovascular health (3). When a person ingests foods rich in flavanols, traces of them are found in the blood 3 to 8 hours later (depending on whether the meal is liquid or solid), in the form of different metabolites. However, the bioavailability of these flavanols remains difficult to quantify, because it is highly dependent on other food constituents with which they are ingested – the so-called«matrix effect » food. A recent study (4) suggests, for example, that the simultaneous presence of proteins of fibers and of minerals would have a limiting effect on the bioavailability of flavonoids, while lipids, digestible carbohydrates (as opposed to fiber, which are indigestible carbohydrates), vitamins, alkaloids and carotenoids would favor it.
Banana, enemy of flavanols
The richness in antioxidants of red fruits (raspberries, strawberries, blackberries, blueberries, etc.) has been widely praised in recent years; it is therefore not surprising that a public increasingly concerned about their health took hold of it. We still need to have an idea of the true impact of these antioxidants, particularly flavanols, on human biochemistry.
Nutrition researchers interested in the bioavailability of polyphenols therefore offered volunteers a berry smoothie (strawberries, blueberries, blackberries and raspberries, plus almond milk and yogurt), or the same smoothie with the addition of a banana, or a flavanol capsule. The berry smoothie and the capsule resulted in approximately the same increase in blood levels of flavanol metabolites. But among the participants who consumed the smoothie with banana, the researchers noted a spectacular drop of 84% in blood levels of flavanol metabolites .
According to the authors, this drop in the absorption of flavanols is directly attributable to the polyphénoloxydase (PPO), which would degrade flavanols as soon as they arrive in the stomachpreventing them from being subsequently used in the digestive tract, mainly by intestinal bacteria – as is the case in the absence of PPO.
PPO is not specific to bananas, since it is found in many fruits and vegetables, but it is in bananas that the concentration of this enzyme is highest : 3,258 KU/100 g (enzyme unit). For comparison, it goes down to 1,600 in beet leaves, 570 in apples, 150 in pears and 24 in avocados.
To make a smoothie rich in antioxidants, choose the following fruits and vegetables:
Strawberries Blueberries Blackberries Raspberries Cherries Grapes Broccoli Spinach leaves
You can also add spices such as cinnamon or ginger, which are also rich in antioxidants.
Conclusion and practical advice
If the interactions between natural food components are extremely complex and still little known, it nevertheless appears justified, in the light of this study, to forgo incorporating a banana (and to a lesser extent an apple or a pear, or even an avocado) to a smoothie made from red fruits so as not to reduce antioxidant properties of the latter. The authors assume that this limiting effect of banana on the bioavailability of flavanols most likely extends to other polyphenols antioxidants (flavones, anthocyanidins, resveratrol, phenolic acids, lignans, etc.).
The impact of this discovery can be significant, not only for the preparation of homemade smoothies, but also for commercial products. For those who want to benefit from the nutritional benefits of bananas (source of fiber, potassium, vitamins and minerals), it would be better to consume them separately, a few hours away from foods rich in antioxidants.
Under no circumstances can the information and advice offered on the Alternative Santé site replace a consultation or diagnosis made by a doctor or health professional, the only ones able to adequately assess your state of health.
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