Resistant Starch From Plants Helps Reverse Prediabetes

resistant starch

Photo credit: Judith Meskill


By Rhonda Witwer,

Consuming a plant-based diet—especially one rich in high-quality plant foods such as whole grains, fruits, vegetables, nuts, and legumes—is linked with substantially lower risk of developing type 2 diabetes. Do you ever wonder why? To me, starch was never top-of-mind to answer this question, but it turns out that the type of starch may be a key part of the answer.

Many studies show that the type of starch in plants significantly changes glucose metabolism – especially insulin sensitivity. Unprocessed foods contain a lot of resistant starch, meaning it resists digestion. Beans, peas and intact whole grains contain resistant starch, because the starch is protected by the seed or hull of the plants such that the starch is not digested in the small intestine – it reaches the large intestine and is called “resistant starch”.  Bananas and high amylose cornstarch also contain resistant starch because the plant’s starch granule resists digestion as well. Cooked and cooled foods also contain low levels of resistant starch. (See this 2015 study from Stephen O’Keefe for example.) When foods are processed, however, the starch typically becomes rapidly digestible and the resistant starch is destroyed or lost.

In short, humans used to eat a lot of resistant starch, but most of us no longer do.

Here’s how it works: Resistant starch is fermented by the microbiome or bacteria in your large intestine. A 2012 animal study by Michael Keenan and his colleagues showed that resistant starch’s fermentation changes the expression of more than 200 genes, some of which are directly connected to digestion, but some of which are directly connected to glucose and lipid metabolism.

Eight clinical studies have demonstrated that dietary consumption of resistant starch significantly improves insulin sensitivity, especially in prediabetics. It turns out that resistant starch’s fermentation makes the body’s muscles and tissues more receptive to insulin and more effective at managing glucose. Researchers are still trying to identify the exact mechanism, but increased insulin sensitivity is consistently found.

The improvement in insulin sensitivity can be impressive. In 2012, Kevin Maki and his colleagues showed that overweight men adding 15 grams of resistant starch improved insulin sensitivity by 56%. A 2016 study from Barbara Gower and her colleagues showed that insulin resistant, postmenopausal women improved their insulin sensitivity by 34% after eating 30 grams of resistant starch. Both studies fed the participants the same amount of glycemic carbohydrates as the control.

Early last year, this data was submitted to the U.S. Food and Drug Administration in a health claim petition asking for the claim that resistant starch helps to reduce the risk of type 2 diabetes. The FDA has delayed issuing its decision three times, with the most recent deadline now November 15, 2016. There is nothing to prevent them from delaying for more months if not years. Last week, a petition was launched asking the FDA to issue its ruling on this important health claim petition.

Vegetarians have been leaders in showing the advantages of plant-based diets in preventing and reversing type 2 diabetes. Your knowledge and leadership can help give credibility to a plant-based ingredient that can help to reverse prediabetes. Please sign this petition to ask the FDA to issue its ruling today. Eighty six million Americans with prediabetes will thank you for it.

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