NEW YORK (Reuters Health) - An isocaloric diet high in animal or plant protein appears to reduce liver fat in patients with non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes, according to new findings.
"High-protein diets (30% energy from protein, 40% from carbohydrates, 30% from fats) with a favorable fatty acid composition potently reduced liver fat content in patients with type 2 diabetes and fatty liver independently of protein origin or body weight changes," lead author Dr. Mariya Markova of the German Institute of Human Nutrition Potsdam-Rehbruecke in Nuthetal told Reuters Health by email.
The findings were published online October 17 in Gastroenterology.
Diets high in animal protein, carbohydrates and saturated fat increase liver fat, Dr. Markova and her team note, while there is evidence from small studies that a diet high in protein may reduce it.
In the current study, 37 diabetes patients with NAFLD were assigned to one of two isocaloric high protein diets for six weeks. Eighteen patients ate animal protein (AP) and 19 consumed plant protein (PP).
Intrahepatic lipids (IHL) were reduced by 48% in the AP group and 35.7% in the PP group after six weeks, both statistically significant decreases. Nine patients (three from the AP group, six from the PP group) had IHL levels below 5.56%, meaning they no longer had NAFLD.
Each group had a 50% reduction in fibroblast growth factor 21 (FGF21), and this reduction correlated with reductions in IHL. Study participants on either diet also had reductions in inflammatory markers and hepatic enzymes, increases in insulin sensitivity, and reductions in serum keratin 18.
"We could show that keeping a healthy diet rich in proteins as well as more unsaturated fats for 6 weeks leads to a large decrease of liver fat together with further improvements in metabolism without caloric restriction," Dr. Markova said. "For this period we did not observe any adverse effects. We thus support this type of diet for the treatment of diabetes patients."
While consuming protein is especially important to prevent loss of muscle mass and sarcopenia in older adults, high-protein diets should not be recommended for people with severe kidney disease, she added.
"We need larger and longer intervention studies in order to confirm the results of the present study and to elucidate the long-term effects of high-protein diets of plant or animal origin," Dr. Markova said.
She noted that the diet should be tested in younger people, because participants in the study were over 60 years old, on average.
"The effect might be most pronounced in diabetes patients and might differ in non-diabetic obesity," she added. "Further research is needed to investigate the metabolic mechanisms that are involved."
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