A couple more great papers just released show that resistant starch is probably going to be the gold standard for all prebiotic research. Researchers love Hi-Maize, mostly because they get it for free from Ingredion, but also because it works. It's a great product, still being sold as a cooking ingredient, and easy for people to buy. Presently, there are two good suppliers: King Arthur Flour and Honeyville.
The best thing about Hi-Maize is that you can cook with it, so the sky's the limit for how to get this into your diet. Raw potato starch and Banana Flour are great prebiotics, too, but must be consumed raw/unheated.
Resistant starch lowers postprandial glucose and leptin in overweight adults consuming a moderate-to-high-fat diet: a randomized-controlled trial (Maziarz et al., 2017).
Abstract of the paper:
High-amylose maize resistant starch type 2 (HAM-RS2) stimulates gut-derived satiety peptides and reduces adiposity in animals. Human studies have not supported these findings despite improvements in glucose homeostasis and insulin sensitivity after HAM-RS2 intake which can lower adiposity-related disease risk. The primary objective of this study was to evaluate the impact of HAM-RS2 consumption on blood glucose homeostasis in overweight, healthy adults. We also examined changes in biomarkers of satiety (glucagon-like peptide-1 [GLP-1], peptide YY [PYY], and leptin) and body composition determined by anthropometrics and dual-energy x-ray absorptiometry, dietary intake, and subjective satiety measured by a visual analogue scale following HAM-RS2 consumption.
Using a randomized-controlled, parallel-arm, double-blind design, 18 overweight, healthy adults consumed either muffins enriched with 30 g HAM-RS2 (n = 11) or 0 g HAM-RS2 (control; n = 7) daily for 6 weeks. The HAM-RS2 and control muffins were similar in total calories and available carbohydrate.
At baseline, total PYY concentrations were significantly higher 120 min following the consumption of study muffins in the HAM-RS2 group than control group (P = 0.043). Within the HAM-RS2 group, the area under the curve (AUC) glucose (P = 0.028), AUC leptin (P = 0.022), and postprandial 120-min leptin (P = 0.028) decreased independent of changes in body composition or overall energy intake at the end of 6 weeks. Fasting total PYY increased (P = 0.033) in the HAM-RS2 group, but changes in insulin or total GLP-1 were not observed. Mean overall change in subjective satiety score did not correlate with mean AUC biomarker changes suggesting the satiety peptides did not elicit a satiation response or change in overall total caloric intake. The metabolic response from HAM-RS2 occurred despite the habitual intake of a moderate-to-high-fat diet (mean range 34.5% to 39.4% of total calories).
Consuming 30 g HAM-RS2 daily for 6 weeks can improve glucose homeostasis, lower leptin concentrations, and increase fasting PYY in healthy overweight adults without impacting body composition and may aid in the prevention of chronic disease. However, between-group differences in biomarkers were not observed and future research is warranted before specific recommendations can be made.
My impression: This study observed 11 people who supplemented with 30g (about 3TBS) of Hi-Maize daily, comparing them with 7 people who changed nothing in their diet. The folks taking the Hi-Maize showed changes related to hunger/satiety hormones (PYY and leptin) as well as blood glucose.
The test subjects were overweight, but otherwise healthy. The study designers did not include a pre-test acclimation period, which seems to be required for gut health research, but maybe there is something more to the story than gut bacteria, as the next paper describes:
Resistant starch can improve insulin sensitivity independently of the gut microbiota (Bindels et al., 2017).
Abstract of the paper:
Obesity-related diseases, including type 2 diabetes and cardiovascular disease, have reached epidemic proportions in industrialized nations, and dietary interventions for their prevention are therefore important. Resistant starches (RS) improve insulin sensitivity in clinical trials, but the mechanisms underlying this health benefit remain poorly understood. Because RS fermentation by the gut microbiota results in the formation of physiologically active metabolites, we chose to specifically determine the role of the gut microbiota in mediating the metabolic benefits of RS. To achieve this goal, we determined the effects of RS when added to a Western diet on host metabolism in mice with and without a microbiota.
RS feeding of conventionalized mice improved insulin sensitivity and redressed some of the Western diet-induced changes in microbiome composition. However, parallel experiments in germ-free littermates revealed that RS-mediated improvements in insulin levels also occurred in the absence of a microbiota. RS reduced gene expression of adipose tissue macrophage markers and altered cecal concentrations of several bile acids in both germ-free and conventionalized mice; these effects were strongly correlated with the metabolic benefits, providing a potential microbiota-independent mechanism to explain the physiological effects of RS.
This study demonstrated that some metabolic benefits exerted by dietary RS, especially improvements in insulin levels, occur independently of the microbiota and could involve alterations in the bile acid cycle and adipose tissue immune modulation. This work also sets a precedent for future mechanistic studies aimed at establishing the causative role of the gut microbiota in mediating the benefits of bioactive compounds and functional foods.
My impression: This study used mice who were devoid of gut bacteria. They fed the mice Hi-Maize and FiberSym (an RS4 product) and observed how they responded. The germ-free mice had many of the same responses to resistant starch as did normal mice, indicating that the "magic" in RS is not all from your gut flora.
This is good news, because it means that everybody should see some benefits from increasing RS in their diet, even people whose gut bacteria has been wiped out by antibiotics and years of food abuse.
Prebiotics are powerful and important. Learn to eat fiber rich foods and take a supplement if your diet lacks the amount of fiber you need. We should strive to eat 30-50 grams of fiber daily, yet most of us eat less than 15g. A spoonful or two of a fiber supplement, a simple cooking ingredient...untouched by Big Pharm, and as cheap as it ought to be, is all you need.