A four-month randomised controlled experiment in persons with non-alcoholic fatty liver disease (NAFLD) has found that consuming resistant starch on a daily basis can change gut flora composition and lower liver triglycerides and liver enzymes linked to liver injury and inflammation. The findings of the research were published in the journal Cell Metabolism.
NAFLD, which is caused by an accumulation of fat in the liver, affects around 30% of the global population. It can cause serious liver damage and worsen other disorders like type 2 diabetes and cardiovascular disease. There is currently no approved drug to treat NAFLD. To treat the disorders, doctors frequently recommend dietary adjustments and exercise.
The study was conducted by Shanghai Sixth People’s Hospital, China in partnership with Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knöll-Institute (HKI) in Germany.
“We think it would be very meaningful if we can find an effective approach, maybe through identifying new therapeutic targets, to manage NAFLD,” said Huating Li, the paper’s co-corresponding author at Shanghai Sixth People’s Hospital. Previous research results suggest that NAFLD is associated with perturbed gut microbiota. So, Li and her team wanted to investigate if resistant starch—a type of fibre known to encourage the growth of beneficial gut bacteria—could help treat NAFLD.
For the study, the team recruited 200 NAFLD patients and provided them with a balanced dietary plan designed by a nutritionist. Among them, 100 patients also received a resistant starch powder derived from maize while the other 100 received calorie-matched non-resistant corn starch as a control. They were instructed to drink 20 grams of the starch mixed with 300 ml water (1 ¼ cups) before meals twice a day for 4 months.
After the 4-month experiment, participants who received the resistant starch treatment had nearly 40% lower liver triglyceride levels compared to patients in the control group. In addition, patients who had the resistant starch treatment also saw reductions in liver enzymes and inflammatory factors associated with NAFLD. Importantly, these benefits were still apparent even when statistically adjusted for weight loss.
“Our study shows resistant starch’s impact in improving patients’ liver conditions is independent of body weight changes,” said Yueqiong Ni, the paper’s co-first author at Shanghai Sixth People’s Hospital and Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knöll-Institute (HKI) in Germany.
By analyzing patients’ fecal samples, the team found the resistant starch group had a different microbiota composition and functionality compared with the control. In particular, the treatment-group patients had a lower level of Bacteroides stercoris, a key bacterial species that can affect fat metabolism in the liver through its metabolites. The reduction in B. stercoris is strongly linked to the decrease in liver triglyceride content, liver enzymes, and metabolites observed.
“We were able to identify a new intervention for NAFLD, and the approach is effective, affordable and sustainable. Compared with strenuous exercise or weight loss treatment, adding resistant starch to a normal and balanced diet is much easier for people to follow through,” Li said.
Foods rich in resistant starch
The John Hopkins patient guide to diabetes lists the following foods as high on resistant starch:
2. Beans, peas, and lentils particularly white beans and lentils.
3. Whole grains including oats and barley.
4. Cooked and cooled rice.
How to add resistant starch to your diet
The John Hopkins Patient Guide suggests cooking starchy foods like rice, potatoes, beans, and pasta a day in advance and leaving them to cool in the refrigerator overnight. The guide notes that reheating the dishes didn’t decrease the amount of resistant starch. It advices soaking uncooked oats in yoghurt, milk or plant-based milk and refrigerating overnight. Adding lentils to a salad or soup is another idea. You can try replacing regular flour with green banana flour, plantain flour, cassava flour, or potato starch.