Studies such as these, in which Harvard researchers discovered that the consumption of whole fruits such as blueberries, grapes and apples was significantly associated with a lower risk of type 2 diabetes, while more fruit juice consumption was associated with one higher risk, emphasize the dramatic difference between eating whole fruit and drinking fruit juice.

If you eat apples, your cholesterol drops compared to drinking apple juice, but you leave behind a little bit of fiber – cloudy apple juice – and it makes a difference.

In the past we only thought of fibers as a bulk material that helps with the regularity of the intestines. In fact, you can get the same laxative effect with indigestible plastic particles. Feed people a few scoops of cut polyvinyl tubing and you can increase the amount, frequency and consistency of the stool, so that fiber was seen as a similar inert, indigestible substance.

But now we know that fibers are digestible by our gut bacteria, which make it into short chain fatty acids, which have a number of health-promoting effects, such as inhibiting the growth of bad bacteria, increasing mineral absorption – for example, experimentally administered in the rectum of human body, they can stimulate calcium absorption. So much so that you can improve the bone mineral density of teenagers by giving them the fibers that naturally occur in foods such as onions, asparagus, and bananas. Our good bacteria also use fibers to maintain normal intestinal structure and function, to prevent or relieve large intestinal diarrhea and to stimulate blood flow in the large intestine up to five fold, as well as the absorption of fluid and electrolytes. The most important fuel for the cells along our colon is butyrate, which makes good bacteria from fibers. So we feed them and they feed us back immediately.

But if the only difference between fruit and fruit juice is fiber, why can't the juice industry add some fiber to the juice, sprinkle some Metamucil on it. Why can't juice with added fiber be equated with whole fruit? The reason is that we remove much more than fiber when we squeeze fruit and vegetables. We have lost all nutrients that are bound to the fiber.

Already in the 1980s, a study discovered a discrepancy with regard to the amount of fiber in carob using two different methods. There was a 21.5% gap that was not identified as fiber but non-extractable polyphenols, a class of phytonutrients that were thought to have a series of health-promoting effects. In the light of these results, it is worth noting that some of the effects associated with dietary fiber intake in plants may be due to the presence of these polyphenols.

Non-extractable polyphenols, usually ignored, constitute the majority of polyphenols in the diet. Most polyphenol phytonutrients in plants are attached to the fiber.

These so-called missing polyphenols come to our colon and are then liberated by our friendly flora, and can then be included in our system. The phytonutrients in fruit and vegetables juice is perhaps the tip of the iceberg.

Watch the video above to see all graphs, charts, images, images and quotes to which Dr. Greger refers. This is just an approximation of the audio contributed by Katie Schloer.

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