Eating more indigestible starch reduces the high amount of fat in the liver in people with fatty liver disease. This is because their intestinal flora improves as a result, according to Chinese research see this week in the scientific journal Cell Metabolism. If mice with fatty livers receive intestinal bacteria from these treated people, their liver becomes smaller and the amount of fat in it decreases.
Not only alcoholics get fatty liver, also people who do not drink alcohol excessively, often due to an unhealthy lifestyle. Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and affects more than a quarter of the world’s population. In the Netherlands, 2.5 million people have it. In one in three patients, the disease develops into a serious liver inflammation, non-alcoholic steatohepatitis (NASH), which can lead to liver damage and liver cancer. There is no cure for the disease yet, so scientists are looking for ways to inhibit the condition. One of those ways is through gut bacteria.
Unripe bananas
Resistant starch cannot be digested into sugars in the human small intestine. The right enzymes are missing for this. In the large intestine, these indigestible fibers are food for beneficial intestinal bacteria. There are different types of resistant starch, including grains, seeds, unripe bananas, legumes and raw potatoes, but also boiled and then cooled potatoes, rice and pasta.
For four months, 99 Chinese adults with non-alcoholic fatty liver disease drank a large glass of water with 20 grams of powdered indigestible starch from a certain type of corn (high-amylose corn) twice a day before meals. A similar group of other patients was given plain starch. In addition, all participants received dietary advice from a nutritionist.
After four months, the amount of triglycerides in the liver was almost 40 percent lower in the treatment group than in the control group. MRI scans revealed that there was markedly less fat in the liver and around other organs. All kinds of inflammatory values and liver enzymes had also improved, a sign that the damage to the liver had reduced.
An improvement of 40 percent is impressive, says Stijn Meijnikman, liver researcher at the University of California in San Diego (USA) and not involved in this study. He is deeply impressed by the scope of the study. “Part of the improvement in liver fats is due to weight loss. The group that received resistant starch lost more weight during the study than the control group. It is good that the researchers have corrected for this. Their analysis shows that almost 6 percent of the drop in liver fats occurs independently of weight loss.”
In the treated participants, the composition of the intestinal bacteria had also changed, in contrast to the control group. Specifically, the bacterial strain Bacteroides stercoris was less present. The breakdown products of this strain of bacteria have an unfavorable effect on fat metabolism in the liver, the researchers have shown.
Improved composition
And conversely, a test with mice shows that the beneficial effects on liver fats indeed occur thanks to the improved composition of the intestinal bacteria. Mice that were fed food high in fat and cholesterol for weeks so that their livers became fatty, received fecal transplants from the treated patients or from the control group. The mice that received the treated faeces lost more weight, got smaller and less fatty livers and less inflammation.
Resistant starch could be a simple treatment for non-alcoholic fatty liver disease, the researchers conclude. And the findings could help develop new treatments that favorably affect the microbiome.
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