Transcript: Juicing Removes More Than Just Fiber
Studies like this, in which Harvard researchers found the consumption of whole fruits such as blueberries, grapes, and apples was significantly associated with a lower risk of type 2 diabetes, whereas greater fruit juice consumption was associated with a higher risk, highlight the dramatic difference between eating whole fruits and just drinking fruit juice.
If you eat apples, your cholesterol drops, compared to drinking apple juice, but leave just a little of the fiber behind—cloudy apple juice—and it makes a difference.
We used to just think of fiber as just a bulking agent that help with bowel regularity. In fact you can get the same laxative effect with indigestible plastic particles. Feed people a couple spoonfuls of sliced polyvinyl tubing and you can increase stool bulk, frequency and consistency, so fiber was viewed as a similarly inert, indigestible substance.
But now we know fiber is digestible, by our gut bacteria, who make short chain fatty acids out of it, which have a number of health promoting effects, such as inhibiting the growth of bad bacteria, increasing mineral absorption—for example, experimentally infused into the rectum of the human body, they can stimulate calcium absorption. So much so you can improve the bone mineral density of teenagers just by giving them the fiber naturally found in foods like onions, asparagus, and bananas. Our good bacteria also use fiber to maintain normal bowel structure and function, preventing or alleviating colonic-based diarrhea, and stimulating colonic blood flow up to five-fold, as well as fluid and electrolyte uptake. The major fuel for the cells that line our colon is butyrate, which our good bacteria make from fiber. So we feed them and they feed us right back.
But if the only difference between fruit and fruit juice is fiber, why can’t the juice industry just add some fiber back to the juice, sprinkle in a little Metamucil. Why can’t juice with added fiber be equated with whole fruit? The reason is because we remove a lot more than fiber when we juice fruits and vegetables. We lost all the nutrients that are bound to the fiber.
Way back in the 80’s a study found a discrepancy as to the amount of fiber in carob using two different methods. There was a gap of 21.5% that was identified not as fiber but nonextractable polyphenols, a class of phytonutrients thought to have an array of health-promoting effects. In the light of these results, it is worth noting that some of the effects associated with the intake of dietary fiber in plants may actually be due to the presence of these polyphenols.
Nonextractable polyphenols, usually ignored, are the major part of dietary polyphenols. Most polyphenol phytonutrients in plants are locked to the fiber.
These so-called missing polyphenols make it down to our colon and are then liberated by our friendly flora, and can then get absorbed into our system. The phytonutrients in fruit and vegetable juice may just be the tip of the iceberg.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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