The liver is a vascular, secretory and metabolic organ that resides in the upper abdomen.  It receives a dual blood supply from the hepatic artery and the portal vein, and is by far our most important metabolic and detoxification organ.

The liver metabolizes (burns) all three macronutrients (fats, carbohydrates and proteins), providing energy, vitamins, minerals and other nutrients.  Composed of thousands of tiny functional units called lobules, this organ filters over 1,500 ml of blood per minute.  If not functioning well, toxins spill into the bloodstream or out into the bile causing inflammation and oxidative stress.  The liver is also a major storage organ. Nutrients are extracted, converted and stored. For example, excess sugars are converted into glycogen and stored for later release. The same is done for fat-soluble vitamins, other essential nutrients (proteins and fats etc.) and even blood. Moreover, the liver can also store toxins, hopefully for later elimination.  The liver is responsible for the creation and secretion of bile, necessary to emulsify and digest fats and carry away wastes. It also synthesizes various immune and blood proteins necessary for life processes.

Complex chemical substances that enter the liver are neutralized in one of three major ways:
• They are eaten by Kupffer cells.
• They are captured and dissolved into the bile, produced in the gall bladder from components supplied by the liver, and excreted to the intestine
• They are chemically dismantled, tagged and sent off by the enzyme systems for elimination.

Kupffer cells are large specialized macrophages (white blood cells) which phagocytize (eat) bacteria, endotoxins, antigen-antibody complexes and other liver poisons. This makes the liver an important immune system organ. These cells chew up most of the larger particles that enter the liver.  However, they produce dangerous oxidative free radicals as a by-product of this process, and the liver requires a sufficient supply of protective antioxidants to neutralize them. 

The liver's cytochrome P450 system works on complex chemicals.  As substances such as hormones, drugs, alcohol, carcinogens, pesticides and inflammatory chemicals like histamine enter the system, enzymes oxidize and break down the intruders (a process called phase I detoxification).  After that, the liver chemically tags and changes the breakdown products so that they can be excreted (called phase II detoxification).  This process also results in the release of free radical poisons, so it is important to supply the body with the protective anti-oxidant herbs mentioned above.

The liver synthesizes more than a liter of thick, viscous, heavily pigmented and bitter bile each day to capture, neutralize and carry away poisons, acids, dying red blood cells, drugs, mucus, cholesterol, lecithin, mucin, chemicals, pigments, salts, and minerals.  Once released by the gall bladder into the intestine, the bile helps emulsify and digest fats.  The condition in which the liver is congested or sluggish is known as cholestasis.  This often occurs because the bile has become too thick and loaded down with mucus and inflammatory toxins.  Of course, evaluation and regulation of dietary habits--especially fat intake--should be the initial and continuing treatment method for permanent resolution of this condition.

By the way, a lot of mystery concerning how your body reacts to things is eliminated if your realize that sometimes herbs or drugs (and even common foods) help activate individual cytochrome P450 enzymes, which speeds removal of molecules. They can also inhibit the action of these enzymes, which can be useful for keeping certain chemical substances in the general circulation for a longer period of time.  The importance of this varies.  If we have a "bad guy" chemical in our blood, speeding removal is good.  However, if we have a necessary or "good guy" chemical in our blood, speeding removal would be bad.  In the same way, if we have a "bad guy," slowing removal would be bad and if we have a "good guy, " slowing removal would be good. 

For example, drinking grapefruit juice will keep the expensive pharmaceutical drug Viagra in circulation longer, which means you could probably use half as much and save money.  Drinking grapefruit juice when taking cardiac glycosides could raise our blood levels and be dangerous.  Individual variations in our cytochrome P40 enzymes help to demystify why there are so many variations in how we respond to drugs and herbs.  This is why one man's herbal meat is another mans herbal poison.  A well-trained medical practitioner can exploit these facts to your advantage.  For more information on this process with common drugs, and a few herbs, look for Dave Flockhart's Drug Tables.