Eating resistant starch might seem counterintuitive if you have been told that a low-carb diet is healthier. However, resistant starch is an exception. It supports healthy blood sugar levels, helps with weight loss, and feeds good gut bacteria.
Read this post to learn about the science behind resistant starch, including all the health benefits and side effects. If you are interested in hacking your gut microbiome, this post is a must-read.
Health Benefits of Resistant Starch – Mechanisms
Health benefits of resistant starch are derived from many properties, including:
- By acting as a dietary fiber, resistant starch slows down digestion and absorption in the small intestine and bulks up the stool in the large intestine 
- By feeding good bacteria like Bifidobacteria in the large intestine 
- By reducing insulin resistance from inflammation 
- By being raw materials for the production of short-chain fatty acids (butyrate, acetate, propionate) and other beneficial metabolites in the large intestine 
- By stimulating fat burning and glycogen storage rather than fat storage 
- Short-chain fatty acids support intestinal barrier function (i.e., help repair leaky gut), and healthy secretions of hormones and enzymes in the gut 
Resistant Starch and Metabolic Health
1) Reduces Blood Glucose Levels After Meals
There are many ways in which resistant starch helps normalize blood glucose, including:
- By behaving like dietary fiber, it slows down carbohydrate digestion and absorption .
- By activating glycogen synthesis genes, it causes the body to store more carbohydrates in our muscles and liver (in rats) .
- By reducing insulin resistance .
Supplementing the diet with resistant corn starch controls blood glucose levels in overweight but otherwise healthy individuals .
One study found that consuming high-amylose maize resistant starch daily for six weeks improved glucose balance in 18 overweight adults. Glucose balance is the process of maintaining normal blood glucose levels .
2) Improves Insulin Sensitivity
Insulin resistance occurs when cells fail to respond to insulin, leading to high blood sugar levels, and it is associated with a higher risk of developing type 2 diabetes and heart disease.
Resistant starch intake improves insulin sensitivity and reduces the amount of insulin required to manage blood sugar in both animals and humans.
Resistant starch might improve insulin sensitivity by:
- Increasing excretion of certain bile acids into the gut, which helps decrease insulin resistance through GLP-1 [8, 9].
- Reducing fat tissue macrophages, which are immune cells that drive the development of insulin resistance [5, 3, 10, 11, 12].
- Short-chain fatty acids (fermentation products of resistant starch) signal to the brain and liver to reduce glucose production, which may improve insulin sensitivity .
- Increasing adiponectin, which improves insulin sensitivity by increasing fatty acid oxidation and inhibiting liver glucose production .
- Increasing ghrelin, which inhibits glucose-stimulated insulin secretion from the pancreas .
3) Improves Metabolic Syndrome
Metabolic syndrome or pre-diabetes is a group of factors that increase the risk of heart disease, diabetes, and stroke. Risk factors include large waistline, low HDL (high-density lipoprotein) cholesterol, high blood pressure, high triglycerides, and blood sugar levels .
In one study of 20 healthy adults, resistant starch decreased the amount of insulin needed after food intake, which helped treat metabolic syndrome .
4) May Treat Type 2 Diabetes
Type 2 diabetes occurs when individuals develop insulin resistance. It is caused by genetics, obesity, high blood glucose, and inflammation.
Resistant starch potentially reduces the risk of developing type 2 diabetes in animals and overweight adults by improving insulin sensitivity, reducing blood glucose, and reducing blood fat levels [19, 6, 12].
Supplementing the diet with resistant starch may prevent complications resulting from excess blood sugar in patients with type 2 diabetes .
One study of 56 women with type 2 diabetes found that resistant starch improved blood glucose levels, reduced toxins released by bacteria, and increased antioxidants .
Short-chain fatty acid increases glucagon-like peptide-1 (GLP-1), which is a hormone that lowers blood glucose by stimulating insulin release. GLP-1 may treat diabetes by lowering blood sugar [22, 23].
5) Helps Reduce Blood Triglycerides
One animal study found that resistant starch impaired dietary fat absorption, which prevents an increase in blood triglyceride levels after a meal. Resistant starch also induces bowel movement .
This was confirmed in both humans and rats, as resistant starch reduces triglycerides after meals .
6) Improves Cholesterol Levels
7) Helps Prevent Heart Diseases
Including resistant starch in your diet could improve heart health by lowering cholesterol levels .
In a double-blind study of 86 individuals, resistant starch type 4 reduced abnormal fat levels in the blood. Thus, including this starch in your diet could promote heart health .
The hardening of blood vessels is often a precursor to heart disease. Resistant starch potentially reduces the risk factors involved in the hardening of blood vessels in overweight individuals .
Beans, which are high in resistant starch, reduce cholesterol levels and the risk of heart disease and diabetes .
8) Slows Down Chronic Kidney Disease Progression
Chronic kidney disease is often a complication of heart disease and diabetes .
A diet with high-amylose maize starch slows down chronic kidney disease (CKD) by decreasing oxidative stress, reducing inflammation, and preventing colon lining damage in rats .
Supplementing the diet with resistant starch decreased toxic metabolite (indoxyl sulfate and p-cresol sulfate) levels in 56 CKD patients on kidney dialysis .
Resistant Starch Helps with Weight Loss and Maintenance
9) Promotes Healthy Energy Balance and Prevents Weight Gain
In obesity-prone rats, dietary resistant starch and regular exercise prevented weight gain by reducing the energy gap between the drive to eat and suppressed energy requirements .
10) Helps Burn Fat
Resistant starch helps increase fat burning by:
- Reducing fat accumulation and increasing fat oxidation after meals (both rats and humans) .
- Forcing the body to break down fat for energy by inhibiting glucose use in humans .
- Decreasing fat production in the body, while increasing the production of phospholipids, which are the main components of cell membranes .
11) Reduces Appetite
A study of 20 healthy adults found that consuming resistant starch over a 24-hour period significantly reduced the amount of food eaten. Although food intake was lower, there was no association between food consumption and how subjects rated their appetite .
Resistant Starch and Digestive Health
Prebiotics stimulate the growth of good gut bacteria (probiotics).
By increasing the number of good bacteria in the large intestine, resistant starches have several health benefits, such as improving immune function, preventing the growth of bad bacteria, normalizing energy production, and even lower cancer risks [42, 43, 44, 45].
Technical: Bacteria phyla and species changes from consumption of resistant starches in humans.
RS4 decreases Firmicutes (p<0.001) by more than 10% on average and increases Bacteroidetes (p<0.01) and Actinobacteria (p<0.05) by around 5% each, while also significantly increasing bifidobacterium .
However, this study also found a large individual variation in the changes in gut flora in response to resistant starch consumption among the 10 subjects.
The reduction of Firmicutes and increase in Bacteroidetes is associated with leanness .
13) Increases Acidity in the Stomach
14) Improves Gut Function
The short-chain fatty acid butyrate (fermentation product of resistant starch) provides energy for colon cells and is essential for promoting large bowel function. Populations at low risk of large bowel diseases have high dietary resistant starch intake and high butyrate levels .
Resistant potato starch increases butyrate concentrations in the intestines, which benefits gut microbiota. Butyrate also protects gut lining and reduces inflammation .
15) Helps Treat Diarrhea
Consuming resistant starch helps treat infectious diarrhea in both humans and animals by reducing harmful bacteria in the gut .
Resistant starch increases short-chain fatty acid concentrations, which improves the treatment of acute diarrhea in children under 5 years old .
Resistant Starch Helps with Autoimmunity
16) Helps with Leaky Gut Syndrome
Intestinal permeability, which results from a damaged intestinal barrier, affects the immune function and puts individuals at risk for other diseases like inflammatory bowel disease, celiac disease, autoimmune hepatitis, and type 1 diabetes .
Intestinal microbiota breaks down resistant starch into short-chain fatty acids (vital nutrients for gut lining cells), which reduces the disruption of tight junctions between the cells that line the colon. The colon lining is a protective barrier that allows nutrients into the colon while keeping harmful pathogens out [56, 57].
17) Reduces Inflammation and Balances the Immune System
The intestinal lining is affected by intestinal microbiota and the immune system, affecting barrier function, the composition of the microbiota, and immune balance .
Resistant starch helps balance the immune system by:
- Altering the composition of the gut bacteria [59, 60]
- Stimulating Treg, which lowers Th1, Th2, and Th17 dominance 
- Suppressing inflammatory cytokines such as IFN-gamma, increasing anti-inflammatory cytokine IL-10, and increasing PPAR-gamma through the increase in butyrate levels [61, 62]
18) Reduces Oxidative Stress
In diabetics, resistant starch consumption also protects the blood vessels from oxidative damage due to high blood sugar .
Resistant starch increases gut Lactobacillus, which produces antioxidants. Therefore, supplementing the diet with resistant starch may reduce oxidative stress and improve the function of blood vessel linings in patients with type 2 diabetes [66, 21].
19) Treats Inflammatory Bowel Disease
Resistant starch reduces the severity of inflammatory bowel disease in animals .
Isomaltodextrin, a type of resistant starch, reduces inflammation in gut diseases by suppressing pro-inflammatory and increasing anti-inflammatory proteins .
Dietary fiber like resistant starch modifies the gut microbiota and increases short-chain fatty acid production, which reduces inflammation in inflammatory bowel disease .
Resistant Starch Helps with Nutrient Absorption and Availability
20) Helps Treat Vitamin D Deficiency
Resistant starch maintains vitamin D balance in rats with type 2 diabetes by preventing urinary excretion of vitamin D-binding proteins .
21) Increases Mineral Absorption
In pigs, a diet including 16% resistant starches significantly increased the absorption of calcium and iron in the intestine .
Resistant Starch Prevents Cancer
22) Reduces the Negative Effects of Meat-Rich Diets
Red and processed meats contain a high amount of heme iron, which can increase nitroso compounds that damage DNA in the colon, thin the mucous layer, and cause cell death .
Resistant starch can mitigate these effects by :
- Protecting DNA from oxidative damage caused by the nitroso compounds
- Reducing MMP activity by increasing TIMP (inhibitor of MMP) enzyme levels, which prevents cancer growth and metastasis
- Reducing inflammation
- Reducing insulin and IGF-1 (although the effects were not statistically significant)
The health effects of resistant starch appeared to be through butyrate production and an increase in Lactobacilli bacteria .
23) Prevents and Treats Colorectal Cancer
Resistant starch prevents cancer initiation and progression .
In rats with colorectal cancer, resistant starch increased butyrate concentrations and was associated with reduced tumor incidence, number, and size .
In rats, resistant starch protected colon lining cells from DNA damage and reduced cancer-causing toxins in the gut .
24) Aids Treatment of Pancreatic Cancer
A resistant starch diet is associated with a change in the gut microbiome and a slowed pancreatic cancer tumor progression in mice .
Resistant Starch Affects Brain Function
Resistant starch exerts some of its health benefits through the gut-brain axis because the brain affects the gut bacteria and vice versa. In addition, butyrate is a substance that is absorbed through the stomach, and crosses the blood-brain barrier (read this post to learn about the health benefits of butyrate) .
Therefore, resistant starch may help with brain function. However, most research on these topics is done on animals.
25) May Increase Dopamine and Preserve Dopaminergic Neurons
This suggests that resistant starch and butyrate may help with diseases that affect dopaminergic neurons, such as Parkinson’s.
26) Other Effects on Brain Function
Mice fed with HA-7 resistant starch exhibited an increase in anxiety-like behavior .
However, these mice have significantly less cortisol level compared to mice fed with normal cornstarch.
Resistant starch also makes the brain more responsive to glucose and improves motor coordination in rats .
Limitations and Negative Effects of Resistant Starch
1) Effects Vary Among Individuals
The effects of resistant starch depend on the composition of gut microbiota, which varies among individuals. Resistant starch treatment should be personalized to maintain its beneficial effects [91, 92, 93].
2) Effects Depend on the Type of Resistant Starch
Resistant starch types 2 and 4 influence different parts of the microbiota. Specific bacterial populations can be targeted depending on the type of resistant starch .
One study found that resistant starch type 4 decreased blood glucose more than resistant starch type 2 .
Another study found that resistant starch type 4 was better at reducing oxidative stress levels than resistant starch type 2 .
3) May Cause Stomach Discomfort
Consuming too many non-digestible carbohydrates like resistant starch may cause stomach discomfort, gas, and diarrhea .
Part 2 of a 2-Part Series
This post is a continuation of a 2-part series:
Check out: the Lectin Avoidance Diet Cookbook if you have many food sensitivities, but would like to take advantage of the health benefits of resistant starch.