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Liver Phase I and Phase II Detoxification Pathways


A major function of the liver is to filter blood, neutralizing and removing toxins and other harmful substances. Blood moves from the intestines through the portal vein to the liver. Poisons from the intestines, including heavy metals, are typically deactivated in the liver.

Some of what is filtered is chemically neutralized and expelled from the body through bile or through the kidneys. Many of the toxins, however, are chemically changed into a more active form and “tagged” for recognition so they can later be neutralized and eliminated from the body.

As long as our filter, the liver, stays clean, it can quickly break down toxins such as coffee, alcohol, nicotine, drugs, pesticides and food additives. A properly functioning liver is able to clear 99% of toxins from the blood before they enter the general circulation of the body. Approximately 2 quarts of blood pass through the liver every minute for detoxification.

Because of the liver’s central role in detoxification, the major difference between a person who experiences symptoms when exposed to toxins and one who does not is in the ability of his/her liver to detox the blood adequately.

The Detoxification Process

The body eliminates toxins by either:

excreting them directly via the kidneys, colon, skin and lungs


chemically converting them into substances that can be excreted by the liver into the bile or, if necessary, stored in the body

There are basically two types of toxins. Toxins that enter from the environment are called exotoxins. Some examples are prescription drugs, alcohol, pesticides, heavy metals and food additives. Anything that enters the body and is not food for cells probably needs to be filtered and eliminated.

Toxins are also created inside the body which are called endotoxins. Endotoxins often originate in the intestinal tract. Many are created from undigested food or as a by-product of the overgrowth of bacteria or fungi. Undigested food putrefies which produces ammonia or alcohol. Bacteria and fungi can produce many toxins like ammonia, indo or skatole.

Regardless of the origin of toxins, it is the function of the liver to process and filter them to be excreted from the body.

Phase I and Phase II Detoxification

The liver transforms fat-soluble chemicals into water-soluble compounds so they can be released through the kidneys and bowels. This is carried out by a complex system of enzymes that are made in liver cells.

Phase I of detox involves activation of a series of enzymes called cytochrome P450. This system consists of 50-100 enzymes, each specializing in detoxification of chemicals. They metabolize or chemically break down toxins absorbed from the intestines, hormones, alcohol, drugs and chemicals from food and water. When the body is deficient in some of these enzymes, its Phase I capability is limited.

Cytochrome P450 enzymes begin the transformation of toxins into non-toxic substances. Fat-soluble toxins are converted into active intermediaries which is even more toxic than the original substance and therefore can do significant damage if not properly eliminated.

To function properly cytochrome p450 requires copper, magnesium, zinc and vitamin C. A sufficient intake of cabbage, broccoli and brussel sprouts, as well as foods rich in B vitamins (whole grains) and vitamin C (peppers, tomatoes, citrus) will ensure that this enzyme system is working well. Phase I detox slows down as we age so it’s important to eat a healthy diet and supplement as needed.

If Phase I is inhibited, many drugs, caffeine, histamine, hormones, dyes, insecticides and other substances will not be detoxed adequately and will be stored in the liver.

In Phase II, the substances must be broken down a second time, combining with minerals, amino acids or other chemicals that are water-soluble. This process is called conjugation. There are at least eleven of these conjugation processes in Phase II. Each process requires special nutrients and enzymes. If these processes are not functioning in the liver, then there is a delay in the breakdown of toxins, and they can build up in the body.

Causes of Phase II liver dysfunction are:

  • illness that causes our livers to not function well
  • toxic load is more than the liver can handle
  • nutrients aren’t available for detoxification process
  • digestive tract is overburdened with endotoxins which causes leaky gut or constipation

People most prone to chronic illness, such as Lyme disease for myself, usually have rapid Phase I systems but depressed Phase II systems. This is because a build up of bio-transformed substances from Phase I increase overall toxicity. This forces other organs apart from the liver to store these toxins for later elimination. If these “backup” organs fail to neutralize and eliminate them, toxins get stored in fatty tissues leading to degenerative disease.

The liver has an amazing ability to heal itself as long as we give it the nutrition it needs. Diet, exercise and regular detoxing will help keep your liver in tip top shape!


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