Liver enzymes are proteins within liver cells that help the organ perform its metabolic functions. Blood tests measure the levels of these enzymes in the bloodstream as an indicator of liver health. Elevated levels suggest the liver may be experiencing stress or damage, prompting a closer look at its condition.
The Key Liver Enzymes
A liver function panel measures several proteins to create a picture of liver health. The most frequently analyzed are Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). ALT is involved in converting proteins into energy, while AST helps metabolize amino acids. Because ALT is found in highest concentrations within the liver, its presence in the blood is considered a more specific marker of liver issues.
Other enzymes provide additional context. Alkaline Phosphatase (ALP) is another protein found in the liver’s bile ducts, but also in bone. To determine if an elevated ALP level is related to the liver, it is often assessed alongside Gamma-Glutamyl Transferase (GGT). GGT is a sensitive marker for bile duct issues and liver cell damage. Analyzing these enzymes together allows for a more precise understanding of potential liver distress.
The Link Between Fatty Liver and Elevated Enzymes
The development of fatty liver disease begins with the accumulation of excess fat, particularly triglycerides, inside liver cells, a condition called steatosis. This buildup is often a consequence of metabolic issues like insulin resistance, which disrupts the normal processing and storage of fats. In this initial stage, the liver becomes enlarged with fat deposits, but it may not yet be inflamed, and enzyme levels can sometimes remain within a normal range.
As fat continues to accumulate, it can cause significant stress to the liver cells. This process, known as lipotoxicity, generates reactive oxygen species that damage cellular structures, including the cell membrane and mitochondria. This cellular stress can trigger the body’s inflammatory response, recruiting immune cells to the liver. The presence of both excess fat and inflammation is a more advanced condition known as non-alcoholic steatohepatitis (NASH).
The inflammation characteristic of NASH is what directly leads to higher enzyme readings. When liver cells become inflamed and damaged, their outer membranes lose integrity. This compromised barrier allows the enzymes concentrated inside—such as ALT and AST—to leak out of the cells and spill into the bloodstream. Therefore, elevated enzyme levels are a direct indicator of the cellular injury and inflammation caused by that fat, not a measure of the amount of fat in the liver.
Interpreting Enzyme Levels
When reviewing blood test results, it is important to compare them to the laboratory’s specific reference range, as these can vary. A common reference range for ALT is approximately 7 to 56 units per liter (U/L), while for AST it is often around 10 to 40 U/L.
The relationship between AST and ALT levels can provide further insight. In cases of non-alcoholic fatty liver disease, ALT levels are typically higher than AST levels, resulting in an AST/ALT ratio of less than 1. In contrast, an AST/ALT ratio greater than 2 is more suggestive of alcoholic liver disease. As fatty liver disease progresses and fibrosis (scarring) develops, the AST/ALT ratio may rise and eventually exceed 1.
Enzyme levels alone do not provide a complete diagnosis. They are one part of a larger clinical picture and do not always correlate directly with the severity of underlying liver damage. For instance, a person could have significant liver fibrosis with only mildly elevated enzymes. These tests are a signal for further investigation, which may include imaging studies to determine the full extent of liver health.
Lowering Liver Enzymes Through Lifestyle Management
The primary strategy for lowering elevated liver enzymes is to address the root cause: the excess fat and inflammation in the liver. Managing the underlying fatty liver disease through sustainable lifestyle changes reduces stress on liver cells and allows them to heal.
Weight management is a central component of this process. Losing even 3-5% of total body weight can significantly reduce the amount of fat stored in the liver. To resolve the inflammation associated with NASH, a greater weight loss of 7-10% is often recommended. This weight loss should be gradual, as rapid weight loss can sometimes worsen inflammation.
Adopting a balanced diet is fundamental to reducing liver fat. A Mediterranean-style diet, rich in fruits, vegetables, whole grains, and healthy fats like olive oil, is often recommended. It is also beneficial to limit the intake of processed foods, especially those high in added sugars, fructose, and saturated fats. Reducing consumption of sugary drinks, red meats, and refined carbohydrates can help improve insulin resistance and decrease the fat burden on the liver.
Regular physical activity works alongside diet to improve fatty liver disease. The recommendation is at least 150 minutes of moderate-intensity aerobic exercise, such as brisk walking or cycling, spread throughout the week. Combining aerobic activity with resistance training two or three times a week can further help reduce liver fat and improve insulin sensitivity.
Finally, avoiding alcohol is an important step. Even in non-alcoholic fatty liver disease, alcohol consumption can add further stress to the liver and contribute to damage. Limiting or eliminating alcohol allows the liver to focus on healing and regeneration without the burden of processing additional toxins.