Why It Matters
The ALT to AST ratio compares blood levels of alanine aminotransferase (ALT), which is mostly liver‑specific, to aspartate aminotransferase (AST), which is found in liver and other tissues. (source).
Low ALT/AST Ratio: Compromised Hepatic Capacity
A low ALT/AST ratio can indicate various physiological and nutritional factors affecting liver health. Physiologically, a low ratio may result from reduced liver enzyme production due to liver damage or dysfunction. From a nutritional perspective, inadequate intake of nutrients essential for liver function, such as antioxidants and amino acids, can contribute to an imbalance in ALT/AST levels (source, source, source, source).
Potential Performance Impact
- Reduced liver enzyme production impairing amino acid metabolism and energy availability
- Compromised detoxification capacity slowing recovery between training sessions
Optimization
Drink black coffee. Coffee consumption has been associated with lower AST levels (source). Black coffee is high in polyphenols which exert antioxidant properties that mediate liver enzymes, including AST (source).
Protocol: Drink coffee as desired.
Active recovery. Intense exercise has been shown to negatively affect AST levels (source). An intense exercise bout can induce microscopic tears in the muscle fibers, releasing AST into the bloodstream (source). Recovery days allow these levels to return to a normal state.
Protocol: Prioritize techniques to enhance recovery capacity, such as low-intensity movement and mobility, at least twice a week.
Supplement with milk thistle. Supplementation with milk thistle has been shown to benefit AST concentrations (source). Milk thistle's flavonoid content, particularly Silymarin, exhibits antioxidant and anti-inflammatory properties that help lower liver enzymes, including AST (source).
Protocol: Supplement with at least 420 mg of milk thistle daily.
High ALT/AST Ratio: Hepatic Metabolic Stress
A high ALT/AST ratio may indicate physiological stress on the liver, as ALT and AST are primarily found in the liver. AST is also present in other organs like the heart and muscles. Nutritionally, excessive alcohol consumption, a diet high in saturated fats, and lack of antioxidant-rich foods may contribute to liver stress and an elevated ALT/AST ratio (source, source, source, source).
Potential Performance Impact
- Increased liver stress reducing metabolic waste clearance during high-output training
- Impaired nutrient processing diminishing fuel availability for sustained performance
Optimization
Limit sugar intake. Sugar intake has been shown to increase ALT concentrations (source). Consuming excess sugar, particularly fructose, has been associated with increased liver fat accumulation, decreasing liver efficiency and negatively affecting function (source). Decreasing sugar intake can help relieve liver stress and decrease ALT concentrations.
Protocol: Monitor and limit excess added sugar intake.
Maintain an athletic body composition. As body fat increases, so do ALT levels (source, source). Body fat is associated with increased cholesterol levels, which is also associated with increased ALT levels (source, source). Cholesterol is metabolized in the liver (source). These findings suggest that body fat increases liver stress through increased cholesterol metabolism. Reducing body fat can positively affect cholesterol levels and decrease stress on the liver, leading to improved ALT concentrations (source).
Protocol: Maintain a high-performance diet and exercise program that supports a body composition of no more than 15% body fat for men and 20% for women.
Avoid coffee. Coffee consumption has been associated with lower AST levels (source). AST levels are reduced with coffee consumption due to its polyphenol content, which exerts antioxidant properties that mediate liver enzymes (source).
Protocol: Monitor and limit coffee intake.
