Emerging Benefits

There are several areas of benefits that do not yet have sufficient evidence to be established or verified.  It is not a coincidence that these areas are strongly correlated with type 2 diabetes and other aspects of metabolic syndrome. Existing evidence suggests that benefits exist in the following areas:

Kidney Health

One human study (Sirich CJ ASN 2014) suggests that resistant starch assists in reducing the blood levels of p-cresol sulfate and indoxyl sulfate, compounds believed to be toxic in individuals with impaired kidney function. This may occur because the nitrogen-related compounds are captured by the bacterial mass and excreted through the intestines instead of being disposed through the kidneys. This may not present problems in healthy individuals, but is definitely a problem in individuals with kidney disease. Animal studies have also found the same benefit: Kiefer FASEB J 2015, Vaziri PO 2014.

Another study found a similar effect with the combination of probiotics (Yakult® beverage) with the prebiotic fiber, galacto-oligosaccharide: (Nakabayashi NDT 2011).

Two studies have shown that high levels of resistant starch protected kidney function and improved Vitamin D metabolism in the kidneys in animal models of type 1 and type 2 diabetes. As a result, circulating levels of serum 25-hydroxycholecalciferol (25-hydroxy Vitamin D) were significantly increased. Koh JN 2014, Smazal JN 2013

Inflammation

Two clinicals have shown reduced inflammation following very high levels of resistant starch consumption.  Additional research is needed to identify the extent and potential for resistant starch to reduce inflammation.

  • Dr. Stephen O’Keefe’s study included an entire diet swap, so the results cannot be isolated to one dietary component. While resistant starch was a major focus of the study, dietary fat and protein was also reduced in the two week diet swap. O’Keefe NC 2015 found reduced mucosal inflammation in the cells of the colon wall after African-Americans living in Pittsburgh ate a South African diet very high in resistant starch (38 grams/day). Reciprocally, South Africans eating the American diet had increased colonic inflammation after two weeks.
  • Dr. Denise Robertson’s study fed British adults with well-controlled type 2 diabetes high quantities of unmodified RS2 resistant corn starch (40 grams/day) and found a reduction in obesity-associated inflammation independent from any changes in body fat volume. Bodinham EC 2014.

Eye Health

Three animal studies from Allen Taylor and his colleagues at Tufts University compared the effects of resistant starch versus highly digestible starch on eye health in rodent models. They found significantly reduced age-related glycation end-products (AGEs) in the eyes. AGEs are a major biomarker for age-related macular degeneration. Their papers attribute the benefits to reduced glycemic index without seeming to consider the well-established fermentation metabolic effects.  Uchiki AC 2012, Weikel IOVS 2012, and Rowan IOVS 2014.

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