How Eating Less Protein Can Help a Weak Liver
People whose liver does not work well may lower their chance of getting liver cancer, or slow the disease, by simply eating less protein.
Liver Cancer Is a Big Problem
Liver cancer is one of the deadliest cancers in the United States. Only about 22% of patients live five years after diagnosis. In 2025, more than 42,000 new cases and 30,000 deaths were expected.
Many adults also have liver problems that raise cancer risk. Around one out of four U.S. adults has fatty‑liver disease, and conditions like viral hepatitis or heavy drinking can lead to cirrhosis, which makes cancer more likely.
Why Protein Can Be Trouble
When the body breaks down protein, it creates nitrogen. The liver normally changes this nitrogen into a harmless substance called urea, which we pee out. If the liver is damaged, it can’t turn the nitrogen into urea fast enough.
Instead, the nitrogen becomes ammonia, a toxic chemical that can hurt the brain and other organs.
Ammonia May Feed Tumors
Scientists wondered whether the build‑up of ammonia actually helps liver tumors grow. To test this, they gave mice liver tumors and then turned off the genes that let the liver process ammonia in half of the animals.
The mice that could not handle ammonia collected high levels of the toxin. Their tumors grew larger and the mice died sooner than the mice with normal ammonia processing.
Further tests showed that the extra ammonia was turned into building blocks (amino acids and nucleotides) that cancer cells need to multiply.
Low‑Protein Diet Slows Tumor Growth
Next, the researchers asked if eating less protein could lower the amount of nitrogen that becomes ammonia. They fed one group of mice a normal diet and another group a low‑protein diet.
The low‑protein mice had much slower tumor growth and lived far longer than the mice that ate regular amounts of protein.
For people with a healthy liver, a high‑protein diet is usually fine because the liver can safely turn ammonia into urea. The new findings matter most for those whose liver is already damaged.
Talk to a Doctor Before Changing Your Diet
Doctors usually tell cancer patients to eat enough protein to keep muscle strong during treatment. Changing protein intake without medical advice could be risky.
Always discuss any diet changes with a healthcare professional who knows your specific liver health.