'Compelling results': Resistant starch may aid weight management via gut microbiome modulation

Writing in Nature Metabolism​, China- and Germany-based scientists reported that the resistant starch (Ingredion’s Hi-Maize) led to significant increases in levels of three bacterial species in the gut: Bifidobacterium adolescentis​, Bifidobacterium longum​ and Ruminococcus bromii.​

“The increased abundance of B. adolescentis​ strongly correlated with decreased BMI and VFA, suggesting its role in RS’s weight-loss benefits,” the researchers wrote.

The five types of resistant starch ​

Resistant starch is undigested in the upper intestine but is fermented by gut microbes in the large intestine and therefore acts a prebiotic.

There are over 200 human clinical trials using resistant starch—the majority derived from maize, potato, acorn and sago—to address digestibility, immune health, insulin and glycemic response, colonic health and fermentation, satiety and weight management.

There are five types of resistant starch: RS1 and RS2 are not digestible due to their structure; starch is protected by either cell walls or by the granule and is not accessible to the intestinal enzyme.

For RS3 and RS4, starch is modified (cooking and cooling = retrogradation for RS3 and chemically for RS4), making it undigestible and resistant to the attack of intestinal enzymes.

RS5 is a specific complex with starch and lipid, thus preventing granule dissolution during cooking.

The new study used Ingredion’s Hi-Maize 260 resistant starch, which is RS2. The company provided the ingredients used in the study but did not provide any funding or other contribution. 

'Compelling results'

Megan DeStefano, senior director of strategic growth at Ingredion, welcomed the study's findings.

"The clinical study published in Nature Metabolism​ underscores the importance of understanding the intricate relationship between nutrition, gut health, glucose metabolism and overall well-being," she told NutraIngredients-USA. "As the global obesity epidemic escalates, concerns related to metabolic health are more relevant than ever.

"It’s encouraging to see how Hi-Maize resistant starch showed such compelling results in the study related to glucose metabolism and its significance in weight management. The reduction in fat mass, waist circumference and inflammation markers help paint a full picture of how resistant starches like Hi-Maize may benefit metabolic health. Looking bigger picture, this research provides additional support to the significant body of evidence for benefits of consuming resistant starch.”

Study details​

The randomized placebo-controlled crossover trial recruited 37 overweight and obese people (average age 33) and randomly assigned to receive either the resistant starch supplement (40 g of RS per day) or an energy-matched control supplement (Ingredion’s AMIOCA cornstarch, 0 g of RS) for eight weeks. This was followed by a four-week washout period before the participants crossed over to the other intervention for another eight weeks.  Participants consumed one sachet twice a day.

Results showed that eight weeks of resistant starch supplementation led to an average weight loss of 2.8 kg compared to no change when consuming the cornstarch control supplement.

In addition, the resistant starch supplement was associated with significant reductions in fat mass and waist circumference, with these improvements being seen as early as the second week of the intervention.

The researchers also reported significant reductions in pro-inflammatory cytokines such as serum tumor necrosis factor (TNF-α) and interleukin (IL)-1beta  for the resistant starch intervention, as well as significant increases in the daily excretion of non-esterified fatty acids, triglycerides and total cholesterol compared to the cornstarch (CS) intervention.

“As there was no significant difference in fat intake during the RS and CS consumption, these results suggested that the RS intervention may decrease lipid absorption from the diet,” the researchers wrote.

Analysis of the gut microbiota revealed significant increases in B adolescentis​, B. longum​ and R. ​bromii, while decreases were recorded for four species—Alisipes putredinis, Bacteroides vulgatus, Odoribacter splanchnicus ​and Parabacteroides merdae.​

"Participants with B. adolescentis​ in their gut microbiome at baseline exhibited a greater decrease in fat mass after RS treatment," the researchers reported. "Furthermore, we transmitted the beneficial effects of RS on host obesity and glucose metabolism in mice via human microbiota engraftment, reinforcing our hypothesis that RS-induced changes in the microbiota can drive beneficial host outcomes."

The study concluded: "As RS occurs naturally in foods and can also be added to daily diets, our findings provide a pragmatic lifestyle to treat obesity and its related metabolic disorders. Manipulating the gut microbial composition through diet may represent a strategy for modifying host energy balance to promote health."

Source: Nature Metabolism​
Published online ahead or print, doi: 10.1038/s42255-024-00988-y​
“Resistant starch intake facilitates weight loss in humans by reshaping the gut microbiota”
Authors: H. Li, et al.