The Smoothie Debate
I want to credit the inspiration for this blog post to my very excellent and brilliant colleague Dr. Udo Obodo, whom I collaborate with at the School of Medicine. She is constantly engaging and inspiring me with new ideas— this time, asking whether we should be placing bananas in our berry smoothies?!! A seemingly simple question— until digging into the research. A novel and thought provoking article was published in the journal Food & Function finding that the addition of bananas, which contain the enzyme polyphenol oxidase (PPO), to smoothies will reduce the availability (and therefore absorption) of healthy compounds called flavenols, found in foods like berries and cocoa, with the conclusion being that perhaps we should not be adding bananas to our smoothies. For some important background and clarification:
PPO is found in many plants that we consume, not just bananas, including apples, pears, and avocados. So mixing these items in your smoothies could yield similar results!
PPO served a very important evolutionary role in these plants! The reactive ortho-quinones (o-quinones) produced by PPO is highly toxic to invading bacteria and fungi, by protein cross-linking, membrane disruption, and oxidative stress. The polymerization of the o-quinones produces the dark pigments (melanins) that darken the fruit.
The highly reactive quinones rapidly turn into inert melanin and are therefore non-toxic to humans in normal consumption amounts.
Polyphenols are naturally occurring antioxidant compounds found in plant-based foods like vegetables, fruits, coffee and tea. Flavonoids are the largest and most common type of polyphenols, and include the flavanols and the anthocyanins. These very important molecules have been show to prevent malignant tumors, diabetes mellitus, cardiovascular disease, and other critical illnesses!!
Researchers in the Food & Function study above concluded that, “…bioavailability of flavanols, and most likely other dietary polyphenol bioactives, can be reduced substantially by the co-ingestion of high PPO-containing products.”
There were a few critical limitations in the study, though:
1) The study only included 8 subjects. Difficult to draw definitive conclusions from this small sample size.
2) The study was funded by a company that sells flavanol supplements, introducing a definite potential conflict of interest.
And there is also the very important consideration of the comparative health of a banana/berry/cocoa smoothie, even if there is some reduction in the polyphenols, compared to “smoothies” found in fast-food chains, budget smoothie bars, or grocery store shelves, where a long shelf-life may be prioritized— since these may contain high-fructose corn syrup, thickening agents, emulsifiers, corn starch, chemical additives, and petroleum-derived artificial dyes!! Yikes!
Of course, bananas always taste great alone too! Here’s to fresh fruit, and gratitude to the organic farmers producing such wonderful, natural treats.
