Why Probiotics May Often Not Be Enough for Healthy Microbiomes: The Necessity of Prebiotics Like Resistant Starch

by Paul Fassa
Health Impact News

One of the latest nutritional discoveries that only recently began gaining good press and widespread awareness is something called resistant starch, or sometimes known as safe starch.

This is a food quality, and it’s not relegated to one food – several different foods fall into this category.

Resistant starch has been studied with increasing awareness of its ability to serve as a prebiotic, a fermentation fiber food source for friendly bacteria in the intestinal or gut flora. The results of an enhanced microbiome, in turn, lead to greater immunity to disease and improved overall health.

Several different carbohydrate plant foods contain resistant starch. And some are enhanced with resistant starch by cooling after cooking.

If it were not for the increased awareness of the microbiome’s friendly bacteria content and function over the past couple of decades, this resistant starch research information would probably still be under the radar of nutritional health awareness.

Growing Awareness of “Prebiotics”

It has been suggested that the lack of experiencing optimum results from probiotic supplements or fermented foods may be due to a lack of fertile prebiotic accumulation in the large intestine. This can be remedied by increasing the consumption of resistant starch.

The term ‘resistant starch’ applies to carbohydrate foods that resist rapid digestive conversion to glucose.

In other words, food creating less glycemic index spikes.

Resistant starch foods pass through the small intestines as a soluble fiber that accumulates as a gel in the large intestine to help friendly bacteria thrive.

This soluble fiber gel doesn’t remain there forever, of course. It’s just considerably slower to digest than most other carbs. There is evidence it helps remove toxins and cellular waste debris from the bowel during its slow digestive process.

Officially, resistant starch is “the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals.” Instead of being cleaved in twain by our enzymes and absorbed as glucose, resistant starch (RS) travels unscathed through the small intestine into the colon, where colonic gut flora metabolize it into short chain fatty acids. Thus, it’s resistant to digestion by the host. (Source)

This slow digestive fermentation process in the colon produces short chain fatty acids, mainly acetate, butyrate, and propionate.

Acetate and butyrate are incorporated into other fatty acids and help produce cholesterol, which is not the source of obesity or poor heart health but is vital for human health.

Propionate mainly produces glucose in the liver.

But the combined synergistic effects of these short-chain fatty acids have even more health-increasing and disease-preventing benefits.

Short chain fatty acids from resistant starch’s colon fermentation also protect the colon against cancer. Colon cancer is the among the highest occurring malignancies in the Western world. This prebiotic fermentation of intestinal flora, with resistant starch soluble fiber, contributes mightily to resisting colon cancer.

The resultant short-chain fatty acids nip cancer cells before they colonize and metastasize while inhibiting inflammation.

There have been many studies demonstrating this.

A large review study, Mechanisms linking dietary fiber, gut microbiota, and colon cancer prevention, can be accessed here.

A roundworm (Caenorhabditis elegans) study, considered a practical animal model for human research, has demonstrated resistant starch’s potential for obesity reduction by reducing intestinal fat deposits. (Study abstract)

At first, resistant starch foods were relegated to only those starchy foods that were once cooked then cooled by refrigeration. Those cooked potatoes used in potato salad, cooked pasta converted to cold pasta salads, and rice used for cold rice puddings were the bedrock of resistant starch.

Better to use pure maple syrup instead of refined sugar for that tasty rice pudding by the way. And best to ensure your foods are not influenced in any way by GMOs or pesticides, especially glyphosate-based herbicides, such as Roundup.

Various studies have determined some other choices of resistant starch either raw, cooked, or cooked then cooled:

Legumes or beans are naturally resistant to rapid glucose conversion. Raw beans soaked overnight, boiled, then cooled for use in salads provides even more resistant starch
Barely ripened bananas raw or plantains cooked provide resistant starch
Raw seeds and nuts
Unrefined grains, especially steel cut oats, traditional ancient grains such as kamut or einkorn, and even true sourdough bread minimally fermented 24 hours contribute to short chain fatty acid production

Regardless of how many studies that have been done regarding resistant starch, fermenting, and safe carbohydrates, the overall scientific consensus has not been completely established. This is based on not being able to catalog every type of food and its influence on producing short-chain fatty acids and the gut microbiome.

It’s wiser to take advantage of what is known so far, as a study published in the May 2015 edition of the International Journal of Obesity states:

In conclusion, it is evident that the administration of FCs [fermentable carbohydrates] and their breakdown products, SCFAs [short chain fatty acids], have positive effects on host physiology. (…) Here, we propose that SCFAs have a number of metabolic processes, which are activated in parallel, that affect energy homeostasis and appetite regulation. (Source)

All the negative press around carbohydrates assumes that the processed junk, passed off as food in the common Western diet, is the same as traditional foods that demand a little more work with their preparation.

Refined carbs, modern mass production bread making, and refined sugars are the actual culprits, offering consumer convenience and longer shelf life for processed food manufacturers.

A little more discernment and extra effort at acquiring and preparing foods that offer resistant starch is a major step toward better overall health.

Published on July 9, 2018

2 Comments

Paul Fassa October 6, 2018 at 9:09 am - Reply

Hi Rhonda,

This is Paul Fassa, the one who wrote this article.

Thanks for trying to link the source of your correction, but I was blocked from access to that site. Don’t know why really – seems like my computer or internet service considered it a dangerous site. So as yet, I can’t say thanks for the correction. Do you have a safer source?

I go by the sources that are available to me. I’m not a biochemist or biologist. If those sources miss the mark, so do I. I usually cross reference sources against other articles or studies. Maybe this time I didn’t do enough.Then again, maybe there was a typo.

Regarding the "omission", none of the sources I had used mentioned anything about FDA approval. The idea of this article was to point out how a starchy carbohydrate food could become helpful as a prebiotic. I don’t think FDA approval or disapproval would matter to most HIN readers. It certainly doesn’t matter to me.

Rhonda Witwer October 4, 2018 at 11:32 am - Reply

Thanks for a good article. However, there are two major mistakes – Resistant starch is insoluble fiber, not soluble fiber as you wrote. It is fermented like some soluble fibers but is really insoluble. Many researchers now refer to resistant starch as the third type of dietary fiber (in addition to soluble and insoluble). It is more valuable to move away from the limiting soluble and insoluble definitions (which are not meaningful in relation to their health effects) toward describing dietary fibers by their main mechanisms: bulking, viscosity and fermentation. Bulking fibers (like wheat bran and cellulose) hold a lot of water and physically provide bulking but are not fermented. Viscous fibers (beta-glucan and psyllium) lower glucose and cholesterol absorption because they thicken the chyme or contents of the intestinal tract. Fermenting fibers (resistant starch, inulin, beta-glucan) feed the intestinal bacteria and trigger specific health benefits.

The second major omission is the fact that resistant starch has been approved by the US Food & Drug Administration for its benefit of improving insulin sensitivity and reducing the risk of type 2 diabetes. No other fiber can make this claim (approved as a qualified health claim in Dec of 2016). Resistant starch’s fermentation changes the expression of >200 genes in the large intestine, some of which are directly connected to insulin sensitivity. Improved insulin sensitivity can be seen hours after someone eats resistant starch (without weight loss or exercise). This is a HUGE benefit, as 84 million American adults (34%) are prediabetic, (with similar rates around the world according to the International Diabetes Federation). This benefit should change the way we eat. Before processed foods, people routinely consumed 30-50 grams of resistant starch/day but now we’re getting only 5 grams. The link to improved metabolism and improved insulin sensitivity should be a major part of your story, but was somehow left out.

If you want to see the evidence, visit http://www.ResistantStarchResearch.com.