Aspartate aminotransferase is an enzyme involved in the balance of proteins (amino acids). Levels of this molecule in the body can be used as a sign of liver disease and other health problems.
People go to their doctor to get their AST tested as part of a standard panel. Almost always, the results are not scrutinized, even though we know that you can be healthier and live longer when your results lie within optimal ranges. When I used to go to doctors and tried to discuss my results, they had no clue what these meant from a health perspective. All they cared about was whether they could diagnose me with some disease.
Read more to learn more about the function of AST, its associated diseases, and how to raise and lower levels of this molecule.
What is Aspartate Aminotransferase (AST)?
Aspartate aminotransferase (AST), also known as SGOT, is an enzyme that breaks down proteins for energy. It is found mainly in the liver and heart, but also in many other tissues, including the muscles, red blood cells, kidneys, and the brain. When any one of these tissues is damaged or diseased, AST is released into the blood [1, 2].
AST levels are often measured to check overall liver health. However, as mentioned above, increases in AST levels can also be due to damage to other organs, such as the heart, kidneys, or muscles. Therefore, AST is often paired with other tests in order to determine the specific location of the problem.
The rest of the article will elaborate on the function of this protein, how different levels of this enzyme may impact your health, and how it can serve as a marker for the disease.
Function
Aspartate aminotransferase is one of the key enzymes involved in the aspartate (amino acid) pathway. At a macro level, this pathway impacts the overall metabolism of amino acids and fats (fatty acids). The aspartate pathway also has partial roles in detoxification (urea cycle) and glucose production (gluconeogenesis) [3, 4].
At a micro level, the direct chemical reaction that aspartate aminotransferase accelerates is the conversion of an amino acid (aspartate) and acid (alpha-ketoglutarate) to a different acid (oxaloacetate) and amino acid (glutamate). This conversion is vital for other metabolic processes such as the urea cycle, glucose generation, and glucose breakdown (glycolysis) [3, 4].
Normal AST Levels
Normal healthy levels of this protein in your blood range from 5 to 40 U/L [2, 5].
There may be some lab-to-lab variability in ranges due to differences in equipment, techniques, and chemicals used.
There are a variety of health problems that are associated with higher than normal levels of AST, and this will be elaborated further below [5].
Low AST Levels
Low AST levels are expected and normal – they are just uncommon in the general population. The reference ranges are based on where 95% of the healthy population falls into, which means that there are 5% of the people who are healthy and not within the reference range!
However, in rare cases, low AST may signal vitamin B6 deficiency, because the AST enzyme requires vitamin B6 to function. Vitamin B6 deficiency is uncommon, but it’s more likely to occur in the elderly, alcoholics, and people with underlying health conditions such as liver, kidney, or inflammatory diseases [6, 7].
AST may also be low in chronic kidney disease, unrelated to vitamin B6 levels [8, 7, 9, 10].
Finally, hormone replacement therapy can decrease AST levels [11].
Increasing AST
Low values are normal and generally don’t require any action or intervention.
If you have an underlying condition that may be affecting your AST, work with your doctor to treat it!
If your vitamin B6 is on the low side:
- make sure your diet is healthy and well balanced and contains enough of all essential vitamins and nutrients, especially vitamin B6 [6]
- avoid smoking, as smoking can further decrease it [12]
Studies suggest that supplementation with vitamin B6 may help increase AST in the elderly [5].
High AST Levels
A high AST (above 40 U/L) can signal a problem with the liver, heart, or muscles.
However, a variety of factors can affect an AST result including age, diet, exercise, and the drugs and supplements a person is taking. That’s why a result that’s higher than normal, doesn’t necessarily mean that you have a health condition that needs treatment. A doctor will interpret an elevated AST result, taking into account your medical history, symptoms, and other test results.
Causes of High AST
Causes shown here are commonly associated with high AST levels. Work with your doctor or another health care professional to get an accurate diagnosis.
1) Muscle Damage
Muscle damage causes AST to leak from muscles into the blood. Muscle damage can be due to various causes, including strenuous exercise, injury, seizures, burns, or muscle diseases [13, 14, 15, 16, 17].
2) Heart Attack
Heart attack or heart failure can also result in AST leaking from the heart muscle into the blood [18, 19].
3) Liver Damage or Disease
Damage to the liver due to various liver diseases increases AST. These diseases include fatty liver, viral hepatitis, infections that affect the liver (e.g. mononucleosis), or liver cancer [20, 21].
In addition, AST also increases when there’s liver damage due to toxins such as lead, mercury, or pesticides [22, 23, 24].
There are many drugs that can increase AST by causing liver damage, but this usually only happens in a small percentage of the people taking the drug. The same applies to natural products and supplements. That’s why it’s important to tell your doctor about all of the drugs and/or supplements you are taking.
Drugs and supplements that can increase AST include:
- NSAIDs like ibuprofen (Advil) [22]
- Blood pressure medications [1]
- Opiates [25]
- Anti-seizure medications [26]
- Chemotherapy agents [27]
- Kava [28]
4) Chronic Alcohol Abuse
Chronic alcohol abuse increases AST levels [29].
5) Anorexia
Studies report that AST levels are abnormally high in over half of the people who have anorexia, mainly due to weight loss and fasting [30].
6) Pancreatitis
AST increases with severe Inflammation of the pancreas (pancreatitis) [31].
7) Gallbladder Attack
A gallbladder attack can cause both mild and short-liver sharp (up to 100 fold) increases in AST [32].
8) Abnormal Destruction of Red Blood Cells
Rupture of red blood cells (hemolysis) releases AST from blood cells [33]. There are many different conditions that can cause abnormal destruction of red blood cells, including autoimmune disease, malaria, and an enlarged spleen.
Lowering AST
The most important thing is to work with your doctor to find out what’s causing your high AST and to treat any underlying conditions. The additional lifestyle changes listed below are other things you may want to discuss with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes.
Liver Health
If your liver health is compromised:
- Over-consumption of alcohol can directly damage liver cells and worsen existing liver conditions. Avoid drinking alcohol until your AST levels return to the normal range, even if the cause is not alcohol-related [34].
- If you are overweight, losing weight may improve your liver health and help reduce AST [35].
- Some drugs or supplements can damage the liver, leading to high AST levels. Have a doctor or pharmacist review your medications to see if any of them might be causing harm to your liver [36, 37]. Discuss alternative options with your doctor.
- Research suggests that drinking moderate amounts of coffee on a regular basis may benefit liver health and lower liver enzymes in the blood, such as AST [38, 39, 40, 41, 42, 43]. Discuss your coffee intake with your doctor.
Supplements
There are a number of supplements that may reduce elevated AST levels. But it’s important to stress that these supplements most likely lower AST by improving the underlying condition. It’s always crucial to work with your doctor to treat the underlying cause of elevated AST levels. The supplements in question are as follows:
- Licorice: The effectiveness of licorice in non-alcoholic fatty liver disease (NAFLD) was evaluated in 66 patients. When supplemented with licorice for a period of 2 months, the mean AST levels significantly decreased compared to people who didn’t supplement [44].
- Green Tea: Eighty participants with NAFLD were supplemented with green tea over 12 weeks. At the end of this period, those who took green tea showed significant reductions in AST [45].
- Caffeine: A study involved 177 patients with liver disease who completed a caffeine questionnaire. This allowed researchers to evaluate the relationship between liver disease and caffeine. They found that people with greater caffeine intake had lower AST levels [46].
- Milk thistle: Supplementation with milk thistle in 34 patients with hepatitis C and 51 patients with type 2 diabetes reduced AST levels [47, 48, 49].
- Tudca (tauroursodeoxycholic acids): In a pilot study of 23 patients with liver disease, daily doses of Tudca for 6 months lowered elevated AST levels [50].
Remember, these supplements were given in small-scale trials to people with certain medical conditions (some types of liver disease) and will likely not work in people who have elevated AST due to other medical issues (such as muscle damage or red blood cell destruction). In addition, because most of these studies are low-quality clinical studies, there is insufficient evidence that these supplements would be effective in the general population.
Always consult with your physician before taking any supplements and never use a supplement as a replacement for approved medical therapies!
Animal studies have been looking at turmeric/curcumin, Ganoderma lucidum (mushroom), dill, alpha lipoic acid, N-acetyl cysteine, capsaicin, and vitamins C and E, in terms of lowering AST in liver disease [51, 52, 53, 54, 55, 56, 57, 58]. However, there is no evidence that these would have any effect in humans. We will keep you posted as new studies arise.
