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AST

ASPARTATE AMINOTRANSFERASE (S-AST)

Aspartate aminotransferase (AST) is an enzyme found mostly in the liver and the heart, muscle cells, red blood cells, pancreas, kidneys, and the brain. There are two genetically distinct AST isoenzymes: mitochondrial AST (mAST) and cytosolic AST (cAST). Aspartate aminotransferase has an important role in amino acid and fatty acid metabolism. The AST enzyme catalyzes the transfer of amino groups from aspartate and alpha-ketoglutarate, producing oxaloacetate and glutamate. The chemical reaction also works in the opposite direction. Oxaloacetate has a crucial role in mitochondrial energy production (citric acid cycle), urea cycle, and the breakdown and formation of glucose. The above-mentioned reaction requires bioactive vitamin B6 (pyridoxal-5-phosphate) as a cofactor.

AST levels increase in connection with cell damage. Due to this, it is used to assess damage to the liver or cardiac muscle (cardiac muscle damage is now predominantly assessed using various troponins, usually troponin-T). AST levels can also increase due to certain medications (Paracetamol and statins), chemotherapy, heavy exercise and rhabdomyolysis, acute pancreatitis or cardiac arrest.

Low AST levels sometimes occur in connection with vitamin B6 deficiency. AST may also be elevated with cholestasis (bile duct obstruction) or liver tumors and cancers. Acute viral hepatitis often causes AST levels 10 times higher compared to normal.


Elevated AST levels may also be a risk factor for future type 2 diabetes. This is particularly true if ALT levels are also elevated. Normal-weight individuals with insulin resistance often have elevated ALT levels but not AST. The AST/ALT ratio is under 1.


The AST/ALT ratio (De Ritis ratio) can be used to analyze an increase in AST levels—if the ratio is high, the increase is usually caused by tissues outside the liver. Usually, the AST/ALT ratio is slightly above 1. The highest ratio (above 2) usually involves alcoholic hepatitis. Viral, drug-induced, or autoimmune hepatitis involves an AST/ALT ratio below 1.


Typical reference range (S-AST):

  • Women: 15–35 U/l
  • Men: 15–45 U/l

Nutritional factors decreasing AST levels include:

  • Heavy coffee consumption (≥ 3 cups per day) is linked to lower AST levels, regardless of the caffeine content
  • Silymarin extract (milk thistle; 200 mg x 3/day), particularly for individuals with type 2 diabetes
  •  Silymarin may repair liver damage and is generally well-tolerated
  • Green tea extract (500 mg/day), particularly for individuals with non-alcoholic fatty liver disease
  • A comprehensive meta-analysis on rat and human tests suggests that curcumin extract (dosage ≥ 1,000 mg/day) protects the liver from damage and reduces AST levels
  • Powdered turmeric (3 g/day)
  • Alpha lipoic acid (400 mg/day) and ursodeoxycholic acid (300 mg/day), particularly for individuals with non-alcoholic fatty liver disease
  • Alpha lipoic acid (1,200 mg/day) reduces ALT and AST levels in obese individuals with NAFLD