What the Body Was Going to Throw Away Had a Use
The short answer
The colour you see when a bruise turns yellow is bilirubin. It was long taken for nothing but the residue left over from clearing old red cells, and now it is read as an antioxidant the body makes for itself. The road out and the work being done lie along one line, which is why the flow of bile is not a matter of digestion alone.
Contents
Watch a bruise over a few days and the colour changes. What was dark red turns bluish, and then yellow, and then it goes.
That yellow has a name. It is bilirubin. It is a substance produced in the course of clearing away red cells that have reached the end of their life, and the body sends it to the liver to be carried out in the bile.
For a long time this substance was taken for nothing but residue. Since it turns the eyes and skin yellow when it builds up, it was seen only as something to be cleared away. But it is read a little differently now.
What was to be thrown away was doing work
Bilirubin has a force that holds off oxidation.
While the body uses energy, highly reactive fragments keep being produced. These damage the lipids and proteins of cell membranes, and bilirubin acts on the side of catching those fragments and breaking that chain. It has been confirmed that it does in fact relieve oxidative stress in human vascular endothelial cells.
More striking is the concentration. In that study, the range at which the effect appeared was the amount that actually circulates in human blood. It does not have to be present in great quantity; it works at about the level that circulates ordinarily.
It was doing work even while being carried out along the road for discarding.
That said, this is not to say the more the better
A misunderstanding arises easily here, so let me note it.
If bilirubin rises greatly, that is a problem in its own right. Jaundice, in which the eyes and skin turn yellow, can be a sign that something is blocked in the liver or the bile ducts, and in newborns a high level is itself dangerous. Saying it has a use and saying more is better are two different things.
Most things in the body are like that. They do their work when present in the right place in the right amount, and become harmful outside that range.
Which is why the flow becomes the issue
Use or no use, bilirubin has in the end to be carried out in the bile.
Bile is made in the liver, gathers in the gallbladder, and comes out into the intestine when food arrives. It is well known for the work of breaking fat into fine particles to aid absorption, but that is not all it does. It is also the passage by which the body sends out substances that do not dissolve well in water.
So when this flow slows, it is not only digestion that becomes uncomfortable. The time that substances needing to go out remain grows longer. The account of things arising where the flow catches comes up here too. (Vessels Do Not Narrow Just Anywhere)
An herb has long aimed at opening this flow
In Korean medicine, rhubarb — daehwang — is widely known as a medicine that sends things downward. But I take it that explaining this herb by bowel movement alone misses half of it.
The place daehwang aims at is closer to somewhere that has narrowed and blocked so that stagnation has set in. Sending out in one go what has lingered long in the intestine, and thereby changing the environment inside it, is like that; and so is its acting on the side of how bile circulates. As we saw above, bile is the road along which bilirubin is carried out, so opening that road hangs on both the sending out and the putting to use.
Those who used this herb could not have known about bilirubin. They worked out by observation what it loosened and set it down, and chemistry is now putting a name to that road. Whenever I meet a place like this I feel there is much to learn.
What I ask in the consulting room
When I hear about digestion, I ask separately how things are after a fatty meal. When the flow of bile catches, it shows at that spot.
I look as well at what colour the stool is, how many days apart it comes, when the fullness in the belly arrives. And I look at the whites of the eyes. It is the place where a yellow cast shows first in the body, so it has long been used in examination. (Why I Look at Your Eyes in the Consultation Room)
When to be seen first
If the whites of the eyes or the skin look yellow, examination comes first. The same holds if the stool becomes noticeably paler, if the urine turns dark brown, or if pain in the upper right belly comes with a fever. Signs like these can mean something is caught in the road by which bile goes out, so they need to be checked.
In the few days a bruise takes to turn yellow, this is what passes through the body.
Korean medicine has long treated the work of sending out as important. It asked what was staying put, where things were blocked, and it kept a separate set of herbs for loosening and bringing down. It was not a question about clearing residue away but a question about turning the flow back.
Now a name can be put to that road. Colour comes from the place where red cells were cleared, that colour does the work of holding off oxidation, and it goes down into the intestine carried in the bile.
The road out and the work being done lay along one line. There is less in the body that is simply thrown away than one might think, and I study places like that and set them out for my patients.
Sources
- A study confirming that bilirubin relieves oxidative stress in human vascular endothelial cells, and that the effect appears within the range of concentrations that actually circulate in the blood — Frontiers in Pharmacology, 2012
- A systematic review gathering several studies on the relationship between blood bilirubin levels and carotid atherosclerosis — Systematic Review and Meta-Analysis, 2025
Written by Dr. Heo Ji-young (Ph.D. in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)
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