Pomegranate: Improved liver and metabolic health

Pomegranate (Punica granatum L.) peel extract

To examine the effects of pomegranate peel extract on liver health and metabolic risk factors in patients with non-alcoholic fatty liver disease.

The study was a randomized, double-blind, controlled design. The following outcomes were of interest:

• Gastrointestinal symptom assessment
• Fatty liver evaluated by sonography
• Blood metabolic biomarkers: Serum insulin, fasting blood glucose, triglycerides, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol
• Food intake before, during and after the study was assessed using three-day food intake diaries
• Anthropometric measures: Body mass index, waist circumference, weight
• Blood pressure
• Physical activity assessment

The treatment group received four pomegranate peel capsules daily (375 mg dried peel extract per capsule — 1500 mg daily). These were taken with breakfast and dinner for eight weeks. The control group took placebo capsules. Both groups received Mediterranean dietary advice and ate a lower calorie diet achieving a 500 kCal deficit per day.

The pomegranate extract contained a mean polyphenol content (ellagic acid)/gram of 15%.

There were 37 participants in the pomegranate group and n=37 in the placebo group analysed. Patients recruited were diagnosed with liver fibrosis and steatosis, and people were excluded if they were pregnant or lactating, had a history of high alcohol consumption or for other clinical reasons. Those with food allergy to pomegranate or herbal supplements were excluded.

The mean age of participants was 43.1 ± 8.6 years and there was a balanced distribution of participants across groups in terms of gender, body mass index and other clinical indicators. Nutritional intake was similar between the two groups over the course of the study.

The following measures decreased significantly more in the pomegranate peel group than in the placebo group: Body weight, waist circumference, fat free mass, fat mass index, total body water, and trunk fat. The data was adjusted for confounding variables of energy intake and physical activity, and the differences were still greater in the pomegranate group.

For the blood biomarkers, the following were significantly decreased in the pomegranate group: Fasting blood glucose, triglyceride to glucose ratio, total cholesterol, triglyceride, low-density lipoprotein, and cholesterol to lipoprotein ratio. Serum high-density lipoprotein levels were significantly increased in the pomegranate group. Again, adjusting for physical activity and energy intake, the changes were significant in favour of pomegranate. 

For serum insulin, the biomarkers were not significantly different between groups.

For blood pressure, there was a difference in systolic pressure between groups at baseline. There were no significant differences in blood pressure between the two groups by the end of the study.

At the end of the trial, both groups saw improvements in liver health indicators, but the pomegranate group showed a significantly greater decrease in liver stiffness compared to placebo.

Dietary supplementation with pomegranate peel extract for eight weeks along with dietary advice significantly improved liver health outcomes and improved metabolic risk factors in patients with non-alcoholic fatty liver disease. 

The effects observed included anti-obesity, glycaemic changes, lipid changes and improvements to the fatty liver status.

The study was robust with no changes in nutritional intake between the groups, suggesting that the benefits were a direct result of the pomegranate peel extract. This may be attributed to its polyphenolic composition which includes ellagic acid, gallic acid and tannins. These polyphenols can alter pancreatic lipase and other lipid enzymes to cause a decrease in serum cholesterol and triglycerides. Catechins present in the peel have also been shown to alter lipid biosynthesis and reduce fat absorption in the gut.

Although there were no changes in caloric intake, other studies had shown that pomegranate can reduce appetite through leptin regulation.

The pomegranate supplement significantly reduced fasting blood glucose levels and key lipid biomarkers, but had no effect on fasting serum insulin. It could be that although the body weights of participants ranged from normal to obese, they were not experiencing insulin sensitivity or signs of pre-diabetes.

The most clinically significant outcome was a reduction in liver stiffness in the pomegranate group. The combination of the metabolic changes already described and regulation of lipid metabolism will have worked together to reduce fat in the liver.

This was a well-executed and important study, demonstrating that pomegranate peel extract alongside a lower calorie diet and dietary advice could significantly improve liver fat status and reduce risk factors of metabolic disease. Although the authors did not report adverse events, they cited research that shows that 1500 mg of pomegranate peel daily is safe.

One of the major additional benefits is that the peel of pomegranate is a waste product of the food industry, so this therapy also provides a sustainable option.

Barghchi H, et al (2023). Pomegranate (Punica granatum L.) peel extract ameliorates metabolic syndrome risk factors in patients with non-alcoholic fatty liver disease: a randomized double-blind clinical trial. Nutr J. Aug 22;22(1):40. doi: 10.1186/s12937-023-00869-2. PMID: 37605174; https://pmc.ncbi.nlm.nih.gov/articles/PMC10464300/