Hold The Banana!

Bananas are a healthy fruit for most people (there is such a thing as a banana allergy, so we can’t extend it to all people, but certainly most people).

Full of fiber, carbs for energy, vitamins and minerals, and a stack of nutritious phytochemicals.

One thing we will quickly say as a small counterpoint, which isn’t the main point of today’s article but is worth mentioning: the claim of bananas being “a good source of potassium” is true but greatly overstated; they’re not even in the top 10 of fruits for potassium; just, it was mentioned in a popular TV show, referenced in another popular TV show, and then the English-speaking world never let it go.

But that’s just a minor “not quite as good as people make it out to be” thing, rather than an actual negative.

So, what’s the problem with bananas?

It’s about polyphenol oxidase (PPO)

Researchers (Dr. Jodi Ensunsa et al.) found that adding bananas to berry smoothies drastically reduced flavanol absorption, with blood levels dropping by about 84% compared with a flavanol capsule or a low-PPO berry smoothie.

Quick recap on what flavanols are: flavanols are a kind of polyphenolic plant compounds linked to cardiovascular and cognitive health, that are found in foods like blueberries, blackberries, grapes, apples, pears, tea, and cocoa.

See for example: Are You Getting The Right Kinds Of Flavonoids? ← flavanols are a kind of flavonoid

Why bananas had this effect: bananas contain high amounts of polyphenol oxidase (PPO), which (as you might have guessed) mediates the oxidation of polyphenols; it’s the enzyme responsible for the browning of cut fruit, and the researchers believe PPO breaks down flavanols before your body can absorb them.

What the study tested: healthy participants consumed:

• a banana-based smoothie with high PPO activity
• a mixed berry smoothie with low PPO activity
• a flavanol capsule control

What they saw in the results: the berry smoothie produced flavanol absorption similar to the capsule control, while the banana smoothie produced much lower levels of flavanol metabolites in blood samples.

Also! A surprising follow-up finding: even when flavanols and banana were kept separate until consumption, absorption was still reduced, suggesting that PPO continues degrading flavanols in the stomach after ingestion.

You can read the paper in full, here: Impact of polyphenol oxidase on the bioavailability of flavan-3-ols in fruit smoothies: a controlled, single blinded, cross-over study

Quick note before we move on: no, the study doesn’t mean bananas are unhealthy; bananas still provide many wonderful nutrients; it’s just that they don’t pair well with flavanol-rich foods if maximizing flavanol intake is your goal 🙂

Want to learn more?

On a similar topic (it has many important bits of information like the one we discussed today), you might like to check out:

Make Your Vegetables Work Better Nutritionally

As for why you might want to favor getting it from food if you can, then while the title says “vitamins”, this book discusses an assortment of vitamins, minerals, and other nutrients; the “other nutrients” category including amino acids (branched chain and essential), prebiotics and probiotics, and triglycerides of various kinds:

Eat Your Vitamins – by Mascha Davis, RDN ← see our review, here

Take care!