I hear from lots of people every day who are concerned about how their diet is affecting their health.

They need answers based on facts, in other words, from the peer-reviewed medical literature and that is what I'm here for.

Welcome to the Nutrition Facts podcast. I'm your host Dr. Michael Greger.

You may have heard about a study suggesting that an enzyme in

bananas that turns bananas brown can partially destroy a class of nutrients

found in foods like berries. So should you stop putting bananas in your smoothies? Here are some answers.

We all know there are recommended daily intakes of essential nutrients like vitamins to prevent deficiencies,

but recently the first dietary recommendation for a bioactive food compound was published.

Bioactive food compounds are not necessary for basic human needs but may have health benefits.

For example, plant metabolites known as flavonoids.

Flavonoids are a type of polyphenol, which are of which the most commonly consumed one is these

flavin thralls, also known as just flavenals.

A review of the literature suggests that it didn't take a 400 to 600 milligrams a day of these

flabinals will be beneficial for cardiovascular

protection such as potential for improving blood pressure, cholesterol, blood

sugars, right? Now note that this is specifically a food guideline, not a supplement guideline, though really

it's actually more like a beverage guideline since if you look at the primary sources it's really a tea green or black is the easiest way to reach those levels though there's certainly some in a variety of berries and cocoa.

However, done, done, done, done, there's an enzyme called polyphenyl oxidase that can break down these wonderful polyphenols like flabenoids.

That is what makes certain fruits of vegetables brown when you cut them such as bananas and potatoes. Now why would a plant do that to itself?

Well apparently it is a defense mechanism.

It's part of the plant's immune system.

And when exposed to oxygen, what happens is that polyphenol

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