Glycine supplements and liver markers in people with severe obesity
What it found
Two weeks of glycine supplements raised blood glycine levels and improved several liver health markers in 19 people with severe obesity.
Body weight, blood sugar, and insulin did not change.
What they found
Studies in people
Blood glycine levels rose
After two weeks, glycine levels in the blood went up by about 35%. Participants took in roughly four times more glycine than they normally got from food.
Liver markers improved
Blood fats called triglycerides fell. Two liver enzymes that signal liver stress also dropped, along with a score used to track fatty liver disease.
Waste clearance increased
Urine tests showed the body was clearing out more waste products linked to fat and protein breakdown. This suggests the liver's detox system worked better.
No change in weight
Body weight, body fat, and how the body burned energy stayed the same over the two weeks.
Blood sugar unchanged
Fasting blood sugar, insulin levels, and how the body handled a test drink all stayed the same. Measures of insulin resistance did not change either.
Antioxidant levels steady
The supplement did not raise glutathione, a key antioxidant inside red blood cells. A marker of oxidative stress in the blood also stayed the same.
What the authors conclude
- They conclude that glycine supplements corrected the glycine shortage seen in severe obesity and boosted the liver's ability to clear waste.
- They note that the improvements in liver markers suggest glycine could be studied further as a possible treatment for fatty liver disease.
- They advise that larger and longer trials are needed to confirm whether glycine truly helps the liver.
How it was done
People with severe obesity often have low levels of glycine, which the body needs to clear waste products and support liver function. The authors wanted to see if taking extra glycine could fix this shortage and help these metabolic processes.
Nineteen adults with severe obesity took glycine capsules at a dose of 100 mg per kg of body weight each day for two weeks. They kept their usual diets and had blood and urine tests before and after the treatment.
What it can’t tell you
- This trial lasted only two weeks, so it cannot show what happens when people take glycine for months or years.
- There was no comparison group taking a dummy pill, so some changes might not be caused by the glycine itself.
- The study measured blood markers rather than looking directly at the liver, so it cannot prove that liver fat actually decreased.
Who paid
- Funding
- Funded by Khoo Mentored Research Award (from the PubMed record).
- Conflicts
- Declarations. Competing interests: The authors declare no competing interests.
- Authors work at
- Singapore General Hospital, Singapore; Duke-NUS Medical School, Singapore; USDA/ARS Children's Nutrition Research Centre, USA
The paper
- Title
- Metabolic impact of dietary glycine supplementation in individuals with severe obesity
- Type
- Clinical trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Tan HC, Hsu JW, Tai ES, et al (2025). Metabolic impact of dietary glycine supplementation in individuals with severe obesity. Scientific reports. doi:10.1038/s41598-025-20511-xFree full textPubMed 41107432DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error