Can toxins accumulate in the liver?

Question

There are many articles and products that claim that toxins (pollutants from the environment, chemicals from pesticides, heavy metals from drinking water, etc.) can accumulate in the liver and cause adverse health effects. Many times, a "liver detox" is recommended to help the liver clear out these toxins.

Some examples:

If you inhale or ingest something toxic then the toxins enter your circulation and head directly to your liver. [...] If your liver cannot do its job well or has been inundated with too much work (toxic exposure, illness, etc), then toxic levels rise in your blood and this is considered a significant stress by your body as these toxins can irritate vital organs like your heart, brain, and kidneys as they remain in the circulation too long.

(from article Liver Detox: Get Rid of Toxins)

If “the norm” for you is constant misery and dis-ease, it may be an indication that your body and liver are overloaded with function-impeding toxins. In such instances, the best course of action is to take inventory of your lifestyle to remove the sources of toxins and complement that lifestyle change with a liver cleanse using all-natural, organic methods.

(from blog post Symptoms of Liver Toxicity)

There seems to be some vagueness here. In at least in these two examples, the "toxins" aren't specified. My question is: Is there any validity to these claims? Can harmful compounds bioaccumulate in the liver?

Answer 1

Detoxification is one of the primary functions of the liver. When you ingest something, if it is absorbed, it enters the portal vein which delivers the blood directly to the liver. There, the liver metabolizes, "detoxifies", excretes, synthesizes, and stores.

What needs to be stored

The liver stores excess glucose in the form of glycogen, fat-soluable vitamins A, D, K, iron used for the synthesis of red blood cells, copper (used as an integral part of enzymes), fat, B12, and some other substances. (This is why eating polar bear liver results in hypervitaminosis A.) It does not store toxins.

How the liver "detoxifies"

The liver has a staggering number of metabolic pathways involving a series of enzymatic reactions that neutralize and solubilize toxins for excretion by the liver or kidney. It should be noted that some of the same enzymes are used to render "pro-drugs" into active drugs, and that delivery of absorbed molecules directly to the liver (where they may be converted or removed, called "first pass" metabolism) is the reason that some drugs simply are less effective or ineffective if taken by mouth. (The gut also is responsible for some metabolism.) This is so much a feature of the liver that first-pass metabolism of medications must be taken into consideration to determine the right dose of a drug.

Generally lipid soluble toxins are first made water soluble by any of a group of enzymes called the CYPs, e.g. cytochrome P450. Each of these enzymes has the potential to alter very many different toxins. Liver enzymes then add another water soluble molecule (called conjugation) to the toxin which renders it less toxic and water-soluable enough to be transported for excretion by the liver (with bile, which is excreted into the intestines and carried out of the GI Tract) or the kidneys (in urine).

Toxins can kill the host, injure a specific tissue (for example, an overdose of acetaminophen can cause enough liver damage to shut down detoxification leading to death), act as carcinogens altering DNA, be metabolized and excreted, sometimes be stored in adipose tissue (fat), or take other routes through the body. I personally know of no toxin (nor could I find one) that can bypass these things and be stored in the liver.

There are toxins that damage the liver: alcohol for example. Yet that doesn't get stored in even a damaged liver.

Clearly there are toxins everywhere that we don't even know about, but if drugs and toxins* studied are metabolized and excreted by the liver (or follow other routes), it stands to reason that the ones we don't know about are probably being handled similarly.

*Disclaimer: Heavy metals are handled differently. Also, this answer doesn't deal with concentration of toxins in other tissues, e.g. fat. (Some toxins are stored in fat cells, and become mobilized again on weight loss.)

_{Metabolic Detoxification
FUNCTIONS OF THE LIVER
The Physiology of the Liver
Effects of yo-yo diet, caloric restriction, and olestra on tissue distribution of hexachlorobenzene}

Answer 2

No, these claims do not hold any validity. As you have said, the claims are vague, often saying that these "toxins" (not specified) are the cause of a catch-all list of symptoms. Unsurprisingly, they are usually associated with some sort of "detox" product or program. After all, the premise of "toxins accumulate" goes hand-in-hand with "therefore we need to detox."

There is no medical standard for this type of "detox." There is no consistency in the ingredients of these products. There is no scientific evidence that these things help your health. There are "success stories." Some people may feel better after treatment. But those that feel worse are often told that this is part of the process, that they will feel worse before they feel better. (In other words, there is no chance of not being a success.)

Certainly, there are specific substances with specific effects that have specific treatments, all scientifically validated. It is true, for example, that arsenic in drinking water over time at high enough levels can cause chronic toxicity. This is a poisoning. It has characteristic symptoms and standards for treatment. There are methods to confirm or to rule out the diagnosis. The claims you cited aren't talking about poisonings, though; they are much too nebulous.

I recommend this article on Science-Based Medicine, which goes into more detail about this type of claim: https://www.sciencebasedmedicine.org/detox-what-they-dont-want-you-to-know/