The resistant starch-enriched flour was also associated with a “small but significant” 1% increase in fat-free mass in people with or without metabolic syndrome, according to findings published in Molecular Nutrition & Food Research.
The study was conducted in Hutterite communities in Eastern South-Dakota. Hutterites are an interesting population because they are culturally homogeneous Caucasians of Central European ancestry. Their diets are typically high in protein, fat, and salt, but low in fiber compared with the RDA levels, explained the researchers. In addition, the incidence of metabolic syndrome in the population is higher than the national average (46.5% vs 34%, respectively).
Metabolic syndrome (MetS) is characterized by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type-2 diabetes and cardiovascular diseases.
“Fiber is an important class of dietary constituent implicated in the prevention of MetS,” wrote the researchers, led by Dr Moul Dey. “Currently, fewer than 3% of Americans, including the Hutterites, meet the daily-recommended intake of dietary fiber of 25–38 g/day in age 50-plus adults.
“Wheat-based menus are routine in a western-style diet, and a simple exchange of regular wheat flour in a daily domestic or commercial kitchen (such as in a restaurant) with RS4-enriched wheat flour might be an effective way to increase fiber intake and promote a healthier dietary lifestyle.”
The study used resistant starch type 4 (Fibersym) and flours from Kansas-based MGP Ingredients, which also provided the majority of the financial support.
Dr Dey and her co-workers recruited 86 Hutterites with or without MetS to participate in their double blind, placebo-controlled, cluster cross-over study. Participants were randomly assigned to use either the RS4-enriched flour (30% v/v) or regular flour for their food preparation, which included bread, noodles, maultaschen, and dumplings.
Starches can be divided into three groups: rapidly digestible starch (RDS, digested within 20 minutes), slowly digestible starch (SDS, digested between 20 and 120 minutes), and resistant starch (RS). The latter is not digested but is fermented in the large intestine and has 'prebiotic' properties.
Resistant starch can be further divided into four types – RS1, RS2, RS3, and RS4 – based on the properties that render them indigestible.
Resistant starch can be found naturally in cold cooked potatoes, pasta and rice as well as baked beans and lentils.
After 12 weeks of intervention, the results indicated that use of the resistant starch-enriched flour led to average reductions in total cholesterol and non-HDL cholesterol or 7.2% and 5.5%, respectively, in the people with MetS. A 13% reduction in HDL cholesterol levels was also observed.
Body composition improvements in the non-MetS participants, with significant reductions observed for waist circumference and percent body fat (2.6% and 1.5%, respectively), compared with the regular flour group.
Commenting on the potential mechanism, Dr Dey and her co-workers said that the benefits of resistant starch consumption could be linked to the prebiotic activity, selectively enhancing the growth of select gut microbial populations, which in turn produce short chain fatty acids, including butyrate, “which is associated with higher insulin sensitivity and improved glycemic control”, they added. Mechanistic studies are already underway, confirmed the researchers.
Improving public health
“We conclude that we have presented results suggesting that RS4-enriched diet may be effective for reducing pathophysiological consequences in individuals with MetS,” they wrote.
“Synergistic risk reduction of multiple comorbidities for CVD by RS4 may potentially contribute to improved management of major public health issues. Our results also indicate that unrestricted dietary interventions with potentially better adaptability over long-term, could be an effective strategy for health promotion.”
Source: Molecular Nutrition & Food Research
Published online ahead of print, doi: 10.1002/mnfr.201300829
“Resistant starch type 4-enriched diet lowered blood cholesterols and improved body composition in a double blind controlled cross-over intervention”
Authors: S.N. Nichenametla, L.A. Weidauer, H.E. Wey, T.M. Beare, B.L. Specker, M. Dey