Alanine aminotransferase (ALT) is an enzyme routinely measured in blood tests, often as part of a liver function panel. ALT acts as a marker that offers insight into the health of certain cells, primarily in the liver. While most discussions focus on elevated ALT levels, a low reading occasionally prompts questions about increasing this enzyme. Understanding ALT’s normal function provides the necessary context to interpret both low and high test results.
What Alanine Aminotransferase Is
ALT is a protein that speeds up specific chemical reactions, primarily concentrated within liver cells. Smaller amounts are also present in other tissues, including the kidneys, heart, and skeletal muscles. ALT’s function involves transferring an amino group from the amino acid L-alanine to alpha-ketoglutarate, forming pyruvate and L-glutamate. This metabolic step is part of the alanine cycle, which aids in the body’s energy production and amino acid processing. The presence of ALT in the bloodstream is usually low because it is contained within cells to perform its function.
Understanding Low ALT Levels
Low levels of ALT are generally not a sign of a significant health concern and often reflect a healthy liver. However, a very low reading can occasionally indicate a specific nutritional deficiency or other underlying medical conditions. The enzyme requires pyridoxal 5-phosphate, the active form of Vitamin B6, to function correctly. A deficiency in Vitamin B6 can lead to a low reading because the enzyme cannot perform its reaction efficiently during the lab assay.
Low ALT levels can also occur in individuals with severely reduced muscle mass, such as the elderly, since muscle tissue is a secondary source of the enzyme. Paradoxically, advanced liver disease may also result in a low reading because the mass of functional liver cells producing the enzyme is significantly reduced. In these limited contexts, a low reading may be a signal that further investigation is appropriate.
Strategies for Addressing Low ALT
Raising a low ALT level is typically only considered when a health professional confirms a Vitamin B6 deficiency. Correcting this deficiency is the direct method to normalize the enzyme’s activity. The most sensible first step is dietary intake, focusing on foods naturally rich in Vitamin B6. Excellent sources include:
- Fish like salmon and tuna
- Poultry
- Chickpeas
- Potatoes
- Bananas
If dietary changes are insufficient, a healthcare provider may recommend a Vitamin B6 supplement. A modest daily dose, such as 30 milligrams of pyridoxine hydrochloride, can help normalize ALT levels in deficient individuals. It is important to consult with a physician before starting supplementation, as high doses of B6 can lead to nerve problems.
The Context of High ALT
While low ALT is rarely an issue, the enzyme is primarily measured because elevated levels indicate cellular damage. Since ALT is highly concentrated in the liver, a sudden release into the bloodstream most commonly signifies liver cell injury or inflammation. Common causes include non-alcoholic fatty liver disease, alcohol-related liver disease, and viral hepatitis. Certain medications, such as some pain relievers and cholesterol-lowering drugs, can also temporarily elevate ALT levels.
When ALT levels are high, it suggests the enzyme has leaked out of compromised cell membranes. This elevation may be accompanied by symptoms such as fatigue, nausea, or jaundice (a yellowing of the skin and eyes). Other causes of elevated ALT not directly related to the liver include muscle injury, extreme exercise, or heart failure, as these tissues also contain the enzyme. For any persistently high reading, medical follow-up is necessary to identify the source of the cellular damage and determine the appropriate course of action.