Bilirubin is a yellow-orange pigment in blood plasma that is formed when hemoglobin is broken down. Its most important function is to co-create bile that enables the digestion of fats in the digestive tract. What are the norms of bilirubin in the blood? What does elevated bilirubin mean? Are we able to lower its level by taking care of the diet?

Bilirubinoccurs in blood serum in two forms - unbound, also called free, or bound (direct). Too high levels of bilirubin can cause yellowing of the body, the so-called jaundice, especially dangerous for newborns. In adults, elevated bilirubin - the so-called hyperbilirubinemia - often indicates liver problems or biliary obstruction.

Bilirubin - what is it?

The blood of all mammals, including humans, owes its color to a dye - hemoglobin. It is a protein contained in erythrocytes whose main task is to transport oxygen.

A hemoglobin molecule is composed of subunits, each of which contains a non-protein fragment (the so-called prosthetic group) - that is, a heme molecule. The heme molecule, in turn, in its spatial, ring structure has an iron cation (Fe2 +) in the center and it is thanks to this that it can attach oxygen molecules.

During heme degradation, the cyclic ring of the molecule is broken and the iron ion is removed and stored. As a result of the reduction, derivatives are formed - first biliverdin, and then the yellow-orange dye - bilirubin.

It can therefore be said that bilirubin is a product of "utilization" of old erythrocytes and other enzymes containing heme in its structure.

Bilirubin fractions - free, bound and total

Due to its reactivity, bilirubin is one of the most important antioxidants (compounds that inhibit the oxidation of other substances and naturally support the body's defenses) found in blood plasma and cell membranes.

As a large molecule, bilirubin is poorly soluble in water, and therefore in blood plasma it must be transported "in duet" with another protein, albumin.

The fraction of bilirubin unstably bound to albumin is the so-calledfree bilirubinor indirect. This type of bilirubin doesability to penetrate the placenta and blood-brain barrier, but not into urine.

In the liver, free bilirubin is coupled with glucuronic acid and is further transformed into bound bilirubin (also called direct bilirubin). This fraction is soluble in water but cannot penetrate the blood-brain and placenta barriers anymore.

The sum of direct and indirect bilirubin titers is given by the nametotal bilirubin .

Bilirubin in bound formis secreted into bile, stored in the gallbladder, which is essential for proper digestion of fats and ensuring the optimal pH for pancreatic enzymes.

Together with bile, bilirubin goes to the intestines, where it is converted into bile pigments - urobilinogens with the help of enzymes produced by intestinal bacteria. The products of bilirubin metabolism give a brown color to the feces formed in the intestine, while in the kidneys they color the urine yellow.

Bilirubin - norms

Bilirubin is found in a blood test.

In he althy adults, the norms of the individual bilirubin fractions should be :

  • total- from 0.2 to 1.1 mg / dL (3.42-20.6 µmol / L),
  • direct(conjugate) - 0.1 to 0.3 mg / dL (1.7-5.1 µmol / L),
  • intermediate(free) - 0.2 to 0.7 mg / dL (3.42-12 µmol / L).

The above values ​​do not apply to pregnant women in whom a naturally elevated total bilirubin level is possible as a result of hormonal changes.

Separate standards have also been established for newborns. In utero, an excess of erythrocytes accumulates in the baby's body, which break down after birth. The type of hemoglobin also changes: from fetal hemoglobin (which has a greater affinity for oxygen, thanks to which the gas exchange between the mother and the fetus is more efficient) to hemoglobin typical for adults.

So a lot of pigment - bilirubin - is produced in a short time, which the young liver is not able to efficiently excrete. This is why many newborns, especially premature babies, develop physiological jaundice, which usually resolves on its own after a few days.

The norms of total bilirubin in newborns are :

  • in the first day - from 0.4 to 4.0 mg / dl (6.8-68 µmol / l),
  • 3 days postpartum - 0.1 to 10.0 mg / dL (17.1-171 µmol / L),
  • after about 1 month of age - from 0.3 to 1.0 mg / dl (5.2-17.1 µmol / l).

It should be noted, however, that the exact reference values ​​are determined by a specific laboratory depending, among others, on on the method or type of apparatus used

Phototherapy and bilirubin levels in newborns

Bilirubin - as a derivative of the decay of the heme molecule - is also a compound that is extremely sensitive to light (both natural and artificial). This property is used in the treatment of jaundice in newborns during the so-called phototherapy. This method consists in irradiating the largest possible surface of the child's body with white and blue light (most often with a wavelength of 430 to 490 nm).

Intensive phototherapy can reduce bilirubin levels by up to 30-40% within 24 hours of starting treatment. The most intense decrease in the bilirubin level is noted in the first 4-6 hours of exposure.

During the oxidation of the molecule, the formed bilirubin isomers are more efficiently removed from the liver into the bile (skipping the stage of its connection with glucuronide).

The indication to start "light therapy" is, among others :

  • prematurity,
  • low birth weight,
  • perinatal hypoxia,
  • presence of haemolytic disease,
  • free bilirubin concentration between 16-18 mg / dl (273.6 - 307.8 μmol / l),
  • presence of other risk factors for potential bilirubin neurotoxicity.

It should be remembered that strong, persistent and untreated jaundice in a newborn can lead to serious complications, mainly affecting the nervous system. One of the most dangerous is the so-called bilirubin encephalopathy, which results in permanent cerebral palsy, epilepsy and intellectual disability.

Fortunately, regular testing of bilirubin levels and rapidly implemented phototherapy is now the standard of medical care for a newborn in Poland.

Increased bilirubin - causes

An elevated bilirubin is known as hyperbilirubinemia. There are two types of it:

  • hyperbilirubinemia with predominance of indirect (free) bilirubin,
  • and hyperbilirubinemia with predominance of direct (conjugated) bilirubin.

There can be many reasons for the high level of free bilirubin, the most common of which are:

  • haemolytic anemia - congenital or acquired diseases caused by the faster breakdown of red blood cells. The occurrence of hemolysis (breakdown of erythrocytes) then outweighs the natural ability to renew the bone marrow.
  • Gilbert's syndrome - a metabolic disease with genetic conditions, associated with a disturbance of bilirubin-glucuronide conjugation in the liver. Its course is usually asymptomatic (temporary yellowing of the skin may occur periodically), and the disease is diagnosedis accidentally. Interestingly, Napoleon Bonaparte himself suffered from Gilbert's Syndrome.
  • Crigler-Najjar syndrome - type I or II - a genetic disease, similar to Gilbert's syndrome, associated with the deficiency of the enzyme glucuronyl transferase, which allows the excretion of bilirubin from the body. It can manifest in newborns as severe jaundice.
  • liver damage (cirrhosis, viral hepatitis and drug-induced hepatitis).

Hyperbilirubinemia with dominance of the conjugated fraction is diagnosed in patients with, for example:

  • disturbances in bilirubin transport to the bile ducts (e.g. in rare genetic diseases such as Dubin-Johnson syndrome or Rotor syndrome),
  • mechanical blockage of the bile ducts (possible with gallstone disease or in neoplastic diseases oppressing the bile ducts).

It is worth mentioning that the increased level of bilirubin in the blood can sometimes be influenced by physiological factors, such as prolonged starvation (more than 2 days), restrictive diet and stress. Yellow discoloration of the skin and eyes after heavy weight loss may indicate latent Gilbert's syndrome.

Hyperbilirubinemia - symptoms

The main symptom of a persistently high level of bilirubin in the plasma is yellowing of large areas of the skin, mucous membranes and the whites of the eyes - commonly known as jaundice. However, since this condition may be directly related to the occurrence of gallstones and blockage of the bile ducts, it is worth paying attention to non-specific symptoms, such as:

  • occurrence of yellow bruises,
  • skin redness,
  • hemorrhoids,
  • digestive disorders and flatulence, heartburn,
  • nausea after eating fatty foods,
  • swelling of the whole body.

Occurring ailments of this type may indicate many diseases related to the abnormal functioning of the liver, kidneys, and hematopoietic system and require thorough diagnostics.

Bilirubin and diet

Increased bilirubin levels detected during diagnostic blood tests require an individual approach by a specialist doctor. However, it does not always have to be a sign of serious he alth complications or require treatment.

In many cases, hyperbilirubinemia will be one of the indicators of excessive liver load and high risk of gallstones, which requires a rational diet.

Although it is not possible to directly influence the plasma bilirubin level by a certain diet, it is very important to regulate the level of bilirubin.e.g. :

  • eating meals regularly (in people with confirmed Gilbert's Syndrome, long breaks between meals and fasting are not recommended),
  • evenly portioning meals and limiting portions in the evenings (the production of bile juices decreases with the time of day, which is why an incompletely digested meal strains the liver),
  • good hydration of the body (about 2 liters of water a day),
  • restriction of processed and fatty foods (e.g. fast-food),
  • avoiding alcohol
  • thorough washing of fruits and vegetables, avoiding spoiled products with mold (the liver removes all toxins and products of bacterial metabolism from the body, so their excess additionally stresses the organ).

A wise and more rational diet may not only be beneficial for our figure, but above all it will translate into the he alth and proper functioning of internal organs, including liver and bile ducts.

Regular blood tests, including bilirubin level and liver tests will enable early detection of disturbing changes.

  • Liver diseases - symptoms of a diseased liver. Causes and Treatment
  • Cholestasis (cholestasis) - causes, symptoms and treatment
  • Liver Tests: Normal. Blood test to monitor liver function
  • Mechanical jaundice: causes, symptoms, treatment

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