Alanine Aminotransferase (ALT)

What is Alanine Aminotransferase (ALT)?

Alanine aminotransferase (ALT) is an enzyme mostly found in the liver but is also present in other tissues like the heart, kidneys, and muscles. Aminotransferases are enzymes involved in the metabolism of amino acids, the building blocks of proteins. ALT is one of two clinically important aminotransferases. The other is aspartate aminotransferase^[1].

Because ALT is predominantly found in the liver, high levels can indicate liver damage because it is released into the blood when injury occurs.

What Are Normal ALT Levels?

The normal range for ALT can vary from lab to lab, but generally, a normal reference range is:

Data collected from Forth customers shows the average ALT levels according to age and sex:

What Causes High ALT?

A high ALT level could indicate liver damage because ALT is released into the blood when liver cells are damaged. There are several ways the liver can become damaged causing an increase in circulating ALT levels, including:

• Increased alcohol consumption

  Serum ALT levels are raised in moderate drinkers^[3]. Raised ALT levels can suggest liver damage has occurred because of chronic alcohol use. In most cases, it means that the liver is inflamed^[4].

• Medicines

  Drugs including non-steroidal anti-inflammatory drugs(NSAIDs), antibiotics, and herbal remedies have all been associated with elevated ALT levels or liver damage^[5].

• Non-alcoholic fatty liver disease (NAFLD)

  Some research shows that NAFLD can increase ALT levels^[6].

• Obesity

  Obese groups tend to have higher liver enzyme levels, including ALT^[7]. Some people may be able to naturally lower their ALT levels through weight loss.

• Viral hepatitis

  Mild rises in ALT are linked to viral hepatitis^[8] whereas levels over 1000 IU/L suggest acute viral hepatitis^[9].

Does exercise cause high ALT?

When you exercise for long periods or at high intensities, your muscle fibres can tear, releasing many compounds into the blood including liver enzymes like ALT. When this happens, it’s not usually linked to liver injury but a sign that your muscles are repairing themselves.

Exercise-induced muscle damage causes elevated ALT levels. Research shows that for at least 7 days following strenuous exercise like weightlifting, ALT and AST levels remained high^[10].

Several factors contribute to high ALT levels after exercise:

• Intensity and duration of exercise

• Type of exercise

• Where you are on your fitness journey e.g. trained or untrained

• Protein intake

Symptoms of High ALT

You may not experience any symptoms associated with high ALT levels but you may notice signs of liver damage. They include:

• Generally feeling unwell

• Tiredness

• Weight loss

• Muscle wasting

• Feeling or being sick

• Blotchy red palms

• Disrupted sleep

• Itchy skin

• Yellowing of the skin or whites of the eyes (jaundice)

• Swollen legs, ankles, or feet

• Muscle cramps

• Hair loss

Some liver conditions may not cause any symptoms, like non-alcoholic fatty liver disease, or may return normal ALT levels. So, an ALT test may form part of a wider investigation to rule out certain liver diseases.

Managing Your ALT Levels

If your ALT levels are raised, you may need to work with your doctor to identify the underlying cause. However, there are a few things you can try to help bring your ALT levels back within a normal range.

Assess your alcohol consumption

Alcohol abuse is one of the three major causes of liver disease^[11]. So, if you are a drinker, one of the most effective things you can do is lower your alcohol intake. High ALT and AST levels can indicate advanced alcoholic liver disease^[12] and abstaining from alcohol is considered one of the best ways to improve your liver enzyme levels.

Try drinking coffee

Interestingly, several studies have found that coffee may have a protective benefit for the liver and reduce liver enzyme levels^[13]. A study published in 2020 found that regular coffee drinkers had lower liver enzyme levels compared to non-coffee drinkers. For those who had been regular coffee consumers for at least 5 years, their blood ALT levels were significantly better^[14].

As a general rule, it is advised that you should not consume more than 400 mg of caffeine per day. That’s approximately 4 to 5 cups per day^[15].

Weight loss

Obesity is associated with elevated ALT levels. Some research shows that losing weight can be beneficial for lowering blood ALT. In one study, ALT levels were normalised in 66.7% of people following a 6-month weight loss intervention^[16].

Adjust your training program

Monitoring your biomarker levels, including ALT, can help you adapt your training and identify if you are overtraining. You should schedule adequate rest periods following training to allow your muscles to recover and ensure your energy intake and energy output are balanced.

Try folic acid supplements

Some research has found a link between a higher dietary intake of folate and normal ALT levels^[17]. Some good sources of folate are:

• Liver (to be avoided if pregnant)
• Broccoli
• Brussels sprouts
• Leafy green vegetables
• Chickpeas
• Fortified breakfast cereals^[18]

Adjust your diet
Non-alcoholic fatty liver disease is caused by a build-up of fat in your liver and is often associated with obesity. As well as weight loss and regular exercise, changing your diet to ensure it is balanced and healthy can help to prevent or manage the condition^[19].

You can:

• Swap saturated and trans fats for monounsaturated and polyunsaturated fats
• Eat at least two portions of fish per week
• Increase your consumption of fruit and vegetables, aiming for at least 5 portions per day
• Swap fizzy or sweet drinks for water
• Eat fibre-rich wholegrains
• Choose lean meats over processed or fatty cuts
• Choose healthier snacks like nuts and seeds over cakes, biscuits, and crisps

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.