Substituting just one meat dish with a plant-based alternative lowers blood ammonia toxins, researchers flag

06 May 2024 --- Reducing meat consumption can positively affect ammoniagenesis — the metabolism of glutamine to form ammonia — among adults living with a liver permanently damaged by cirrhosis. The clinical trial conducted at the US Virginia Commonwealth University’s School of Medicine and Richmond VA Medical Center includes 30 adults who usually consume a Western non-vegetarian diet.

“It was exciting to see that even small changes in your diet, like having one meal without meat once in a while, could benefit your liver by lowering harmful ammonia levels in patients with cirrhosis,” comments one of the paper’s authors, Bryan Bajaj, an expert in hepatic encephalopathy with the Richmond VA Medical Center and the VCU Stravitz-Sanyal Institute for Liver Disease and Metabolic Health.

“We now need more research to learn if consuming meals without meat goes beyond reducing ammonia to preventing problems in brain function and liver disease progression,” he adds. 

Ammonia in the blood
The chemical compound ammonia is produced by bacteria in the intestines when digesting food. It is then processed in the liver and sent to the kidney, through which it is disposed of through urine.

For patients whose livers have been severely damaged by cirrhosis, however, it can be difficult to process ammonia, leading to a dangerous rise of the toxin’s levels in the blood. This way, it can travel to the brain and impair cognitive well-being, leading to confusion and delirium. 

Even small changes in patient's diet can benefit liver health by lowering harmful ammonia levels.For the study published in Clinical and Translational Gastroenterology, the researchers separated the participants into three equal randomized groups. They were given a burger containing 20 g of protein — either meat, vegetarian or vegan. 

The scientists collected blood samples and tested for ammonia at baseline and hourly for three hours post-meal while the patients were under observation. Stool microbiome, changes in ammonia and metabolomics were compared between and within groups. 

While the stool microbiome remained the same as baseline, serum ammonia increased from baseline in the group consuming meat but not in people who received the vegetarian or vegan option. 

The participants in the meat-consuming group reported a decline in the metabolites of branched-chain and acyl-carnitines. Their lipid profile also changed, with higher sphingomyelins and lower lysophospholipids. “It can be so hard to make long-term dietary and behavioral changes. We wondered if making an occasional change could be an option for these patients. Liver patients with cirrhosis should know that making positive changes in their diet doesn’t have to be overwhelming or difficult,” Bajaj comments.

Plant-based protein
Based on the preliminary results, the study’s authors suggest that physicians encourage liver patients to switch from meat to plant-based or dairy protein sources, adding that a nutrition expert could provide the most optimal advice regarding the best foods, in particular protein, for patients living with cirrhosis.

“The main take-home message was that occasionally skipping meat from just a single meal can have benefits for patients with cirrhosis. A simple change to a patient’s diet or substituting some parts of it could be a simple and accessible method to reduce ammonia generation,” adds Bajaj. 

Meanwhile, two studies conducted last year in the US and Spain highlighted the link between the gut microbiota and non-alcoholic fatty liver disease, with experts finding that modern eating patterns are leading to fatty livers, the most common cause of liver cancer and cirrhosis. 

Another study from last year suggests that the daily intake of resistant scratch, a non-digestible fiber, acts upon the gut bacteria composition, lowering liver triglycerides and harmful liver enzymes and reducing the likelihood of developing non-alcoholic fatty liver disease.

By Milana Nikolova