For a long time, bilirubin was considered a waste product generated from dead red blood cells. As such, low levels of bilirubin were not considered dangerous or a risk factor for other life-threatening conditions. But recent research has revealed that bilirubin functions as a metabolic hormone and an antioxidant. Here we discuss the effects of low levels of bilirubin.
As a part of annual physical check-ups, doctors often advise lab work including liver function tests. Liver function tests include testing for bilirubin levels in the blood. Many people are aware of increased bilirubin levels and how it may lead to jaundice. The effects of low levels of bilirubin are not commonly known. Let’s talk about what bilirubin is, its normal levels, and the effects of low levels of bilirubin.
What is bilirubin?
Red blood cells have an iron-containing compound called heme and a lifecycle of 120 days. When red blood cells die, heme is broken down to form a green-colored bile pigment called biliverdin. Biliverdin is then converted to a red-orange compound called unconjugated bilirubin. This unconjugated bilirubin helps in controlling adiposity. In the liver unconjugated bilirubin is converted to conjugated bilirubin.
The conjugated bilirubin is temporarily stored in the gallbladder, then it enters the small intestine. The bacteria in the small intestine act on it to convert it into stercobilin. Some portion of conjugated bilirubin is processed by the kidneys into urobilin. Eventually, stercobilin and urobilin are excreted through urine and feces.
Given that it is excreted out of the body, bilirubin was considered a waste product from blood. However, recent research has proven that bilirubin performs several important functions in the human body. Researchers are beginning to understand the role of bilirubin as a hormone and an antioxidant.
Normal range of bilirubin
Typically, the normal level of bilirubin in adult males is:
| Type | Normal range |
| Conjugated bilirubin | Less than 0.3 mg/dL (less than 5.1 µmol/L) |
| Total bilirubin | From 0.1 to 1.2 mg/dL (1.71 to 20.5 µmo) |
These ranges may vary from lab to lab depending on the method of testing. Also, bilirubin levels for neonates, children, and women vary. High levels of bilirubin are common in newborns. Consult your doctor to discuss your bilirubin levels after your annual physical exam.
Why is a low bilirubin level risky?
Bilirubin helps in protecting several body tissues:
Heart muscles
In the heart muscles, bilirubin increases a chemical called nitric oxide. This nitric oxide helps in relaxing the walls of the blood vessels, improving the blood flow, and thereby reducing the formation of free radicals harmful to the body. Bilirubin has a protective effect on blood vessels. Low bilirubin levels can lead to various heart diseases and metabolic disorders. When in its normal range bilirubin helps in preventing stroke due to pathologies of blood vessels.
Liver
In the liver, bilirubin works with other enzymes to reduce the chances of a fatty liver. The early stages of the fatty liver do not have any major symptoms, but later people may experience pain in the liver area (right side of their abdomen), fatigue, weight loss, and weakness. Non-alcoholic fatty liver disease can lead to liver cancer or liver failure. When bilirubin levels are low it increases the risk of non-alcoholic fatty liver disease.
Bilirubin also has an effect on fat cells in the
body or the adipose tissue. Low bilirubin levels are usually associated with
obesity, increased blood sugar, and an increase in triglyceride levels. Bilirubin
prevents inflammation and improves the glucose sensitivity of the cells.
The brain and nerves
The brain and nerves are also affected by low bilirubin levels. The nerves have an outer protecting covering called the myelin sheath. Bilirubin has a protective effect on these myelin sheaths. In patients with multiple sclerosis, low levels of bilirubin were found. Low levels of bilirubin are associated with white matter lesions in the brain.
Kidney
Low bilirubin levels may be associated with diseases such as ulcerative colitis or kidney diseases. To improve bilirubin levels, treatment of underlying diseases is necessary. Although no specific treatment is recommended for low bilirubin levels, your doctor may recommend lifestyle changes such as adding more flavonoid-rich fruits and vegetables such as blackberries, oranges, and kale.
In a nutshell, bilirubin is not just a waste product formed by dead red blood cells but is an important hormone and antioxidant. High levels of bilirubin in the blood can lead to jaundice. Low levels of bilirubin increase the risk of obesity, non-alcoholic fatty liver disease, and stroke. Generally, lower bilirubin levels do not need any aggressive treatment. Talk to your doctor to discuss lifestyle changes that would help in elevating bilirubin levels.
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Bilirubin is a by-product generated from the breakdown of dead red blood cells.
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Low levels of bilirubin can be an indicator of various diseases such as obesity, nonalcoholic fatty liver disease, lung cancer, and stroke.
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The nervous system (brain and nerves) is also affected by low bilirubin levels.
2 resources
- Frontier Cellular Neuroscience. Effects of bilirubin on the development and electrical activity of neural circuits.
- American Journal of Physiology. Bilirubin as a metabolic hormone: the physiological relevance of low levels.
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