Researchers studied 1,642 Iranian adults over 50 to understand how different amino acids in the blood relate to fatty liver disease. They found that higher levels of certain amino acids—like leucine, valine, and tyrosine—were linked to signs of fatty liver. Interestingly, other amino acids like threonine and serine appeared to have a protective effect. This research suggests that the types and amounts of amino acids in our bodies might play a role in developing fatty liver disease, and that diet or other treatments targeting these amino acids could potentially help prevent or manage the condition.

The Quick Take

  • What they studied: Whether the different amino acids (building blocks of protein) in a person’s blood are connected to fatty liver disease
  • Who participated: 1,642 adults from Iran who were 50 years old or older, with an average age of about 62 years
  • Key finding: Higher levels of certain amino acids (branched-chain and aromatic types) were linked to more signs of fatty liver disease, while other amino acids (like threonine and serine) seemed to protect against it
  • What it means for you: Your amino acid levels might affect your fatty liver risk, suggesting that dietary changes focusing on protein quality could potentially help. However, this is one study in one population, so talk to your doctor before making major diet changes

The Research Details

This was a cross-sectional study, which means researchers took a snapshot in time of 1,642 people and looked at their amino acid levels and fatty liver markers all at once. They measured amino acids using a precise laboratory technique called liquid chromatography-tandem mass spectrometry, which is like a high-tech way to identify and count different amino acids in blood samples.

To determine who had fatty liver disease, the researchers used two different scoring systems (FLI and FSI) that estimate fatty liver based on blood tests and body measurements, rather than doing liver biopsies on everyone. They then used statistical analysis to see which amino acids were connected to higher or lower fatty liver scores, while accounting for other factors that might affect the results, like age, weight, diabetes, and inflammation.

Understanding which amino acids are linked to fatty liver disease is important because it could lead to new ways to prevent or treat the condition through diet. Since this study looked at a Middle Eastern population specifically, it helps fill a gap in research because most previous studies focused on other populations. The use of precise laboratory measurements of amino acids is more accurate than just looking at general protein intake.

This study has several strengths: it included a large number of people (1,642), used precise laboratory measurements of amino acids, and adjusted for many factors that could affect the results. However, because it’s a cross-sectional study (a snapshot in time), we can’t prove that amino acids cause fatty liver disease—only that they’re connected. The study was done in Iran, so results might not apply exactly the same way to other populations. The researchers also used two different scoring systems to estimate fatty liver rather than confirming it with imaging or biopsies, which is less definitive but more practical for large studies.

What the Results Show

The study found that higher blood levels of several amino acids were linked to increased signs of fatty liver disease. Specifically, branched-chain amino acids (leucine and valine) and aromatic amino acids (tyrosine, phenylalanine, and tryptophan) all showed positive associations with fatty liver markers. For example, for every unit increase in leucine levels, the odds of having a higher fatty liver score increased by about 1%. Other amino acids like alanine and glutamic acid also showed similar patterns.

Interestingly, the researchers also looked at groups of amino acids working together. They found that a combination of threonine and serine (amino acids that appeared to work as a protective group) was actually associated with lower fatty liver scores. This suggests that it’s not just individual amino acids that matter, but also how different amino acids work together in the body.

The statistical significance of these findings (with a p-value of 0.019) means there’s only about a 2% chance these results happened by random chance, which is considered reliable in scientific research.

Beyond the main findings, the research identified that certain amino acids like glycine, serine, threonine, and citrulline may have protective effects against fatty liver disease. This is important because it suggests that not all amino acids affect the liver the same way—some might actually help protect it. The study also showed that looking at patterns of multiple amino acids together (using a technique called principal component analysis) provided additional insights beyond just looking at individual amino acids alone.

Previous research in other populations has suggested that branched-chain amino acids might be involved in fatty liver disease, but the evidence has been mixed and limited in Middle Eastern populations. This study confirms and expands on those earlier findings by showing the connection in an Iranian population and by identifying which specific amino acids matter most. The finding that some amino acids appear protective is somewhat new and suggests that the relationship between amino acids and fatty liver is more complex than previously thought.

This study has several important limitations to keep in mind. First, because it’s a snapshot study (cross-sectional), we can’t determine if high amino acid levels cause fatty liver disease or if fatty liver disease changes amino acid levels. Second, the study used scoring systems to estimate fatty liver rather than confirming it with imaging tests like ultrasound or MRI, which are more accurate. Third, the study was done in Iran with people over 50, so the results might not apply the same way to younger people or people from other parts of the world. Finally, the study measured amino acids at only one point in time, so we don’t know if these patterns stay the same over months or years.

The Bottom Line

Based on this research, there’s moderate evidence suggesting that managing amino acid levels through diet might help reduce fatty liver risk. This could potentially mean focusing on protein quality rather than just quantity, and possibly eating more foods rich in protective amino acids like glycine, serine, and threonine (found in foods like bone broth, spinach, and eggs). However, these are preliminary findings from one study, so this should not replace medical advice. Anyone concerned about fatty liver disease should talk to their doctor or a registered dietitian before making significant dietary changes. The confidence level is moderate because while the findings are statistically significant, they come from a single cross-sectional study.

This research is most relevant to adults over 50, particularly those of Middle Eastern descent, who are concerned about fatty liver disease or have risk factors like obesity or diabetes. People with existing liver disease should definitely discuss these findings with their healthcare provider. However, the findings may also be relevant to younger adults and other populations, though more research is needed to confirm this. People without any liver concerns don’t need to make immediate changes based on this single study.

If someone were to make dietary changes based on these findings, it would likely take several weeks to months to see changes in amino acid levels and potentially longer (3-6 months or more) to see improvements in fatty liver markers. This is not a quick fix, and any changes should be made gradually and monitored by a healthcare provider.

Want to Apply This Research?

  • Track daily protein intake by source (plant-based vs. animal-based) and note the types of protein foods consumed, particularly those rich in protective amino acids like eggs, spinach, and bone broth. Users could rate their protein choices on a scale of 1-5 based on amino acid quality.
  • Users could set a goal to include at least one food rich in protective amino acids (glycine, serine, threonine) at each meal. For example: add spinach to breakfast, include bone broth in lunch, and eat eggs as a snack. The app could provide simple recipes and shopping lists focused on these amino acid sources.
  • Over 3-6 months, users could track changes in energy levels, digestion, and any follow-up liver function tests if their doctor orders them. The app could send monthly reminders to log protein choices and provide feedback on amino acid-rich food patterns. Users should also track any changes in weight or metabolic markers if they’re monitoring these with their healthcare provider.

This research is observational and cannot prove that amino acids cause fatty liver disease. These findings come from one study in an Iranian population and may not apply equally to all groups. This information is for educational purposes only and should not replace professional medical advice. Anyone with concerns about fatty liver disease, existing liver conditions, or considering significant dietary changes should consult with their doctor or a registered dietitian before making changes. Do not use this information to self-diagnose or self-treat liver disease.