Contents
- Issue 45 September 2009
- Anti-Discrimination
- Puffing
- A Borneo Connection
- More Hepatitis Nurses
- eBox
- The Liver Protection Scheme
- 10 Tips for Good Liver Health
- Monarto!
- Peer Support Program
- HCV Antibody Research
- Shared Care
- Providing Treatment
- Warinilla Clinic
The Liver Protection Scheme
How the liver works, and how to look after it
The liver is situated on the upper right side of the abdomen, just below the diaphragm. The liver receives 30% of the circulating blood each minute, and it acts as a giant chemical processing plant in the body. The liver cells, called hepatocytes, perform vital chemical reactions called ‘metabolism’, which are central to normal body maintenance.
Metabolism of nutrients
Once digested, nutrients enter the blood; they are then taken straight to the liver to be processed. How the hepatocytes deal with the nutrients depends on whether each nutrient is in abundance, or whether levels are low in the body.
The liver processes carbohydrates in many ways. Carbohydrates are broken down into glucose in the gastrointestinal tract, which enters the blood and is taken to the liver. Glucose is a vital energy source for cells, and levels in the blood stream must remain constant. When the blood glucose level is within the right range, the liver converts the excess glucose into glycogen for storage. The glucose that is not stored is used to produce energy. In between meals, during starvation, or during exercise, blood glucose levels fall. The hepatocytes detect this change, and restore glucose levels by either converting glycogen back to glucose, or by converting non-sugars such as amino-acids into glucose.
The liver is involved in breaking down fat and creating compounds that include fat, such as lipoproteins, cholesterol and phospholipids. If fat is in excess, the liver joins fatty acids and glycerol together to form a storage molecule for storage in subcutaneous tissue (tissue just under the skin) and other storage depots. If energy and glucose levels are low, as one would find between meals, or as a result of exercise, stored fat is converted back into glycerol and fatty acids which are then transported to the liver for use as an alternative energy supply.
Proteins are broken down to amino acids in the intestines and are transported to the liver via the blood. If proteins are in excess, amino acids can be converted into fat and stored in fat depots, or if required, made into glucose for energy. However, before amino acids can be utilised in these ways, the nitrogen component must be removed from the compound. In the hepatocytes, nitrogen quickly changes into ammonia, which is highly toxic to the body. The liver acts fast to convert ammonia into urea which can then be excreted in the urine and eliminated from the body.
A cross-section from a liver biopsy, showing damage from alcohol consumption (image © Euthman)
Processing of toxins
The liver is vital for the detoxification and destruction of substances that are harmful to the body. These substances may be by-products of normal metabolism, or ingested/inhaled substances such as drugs and alcohol. The liver filters the blood, removing cellular debris and any invading bacteria; amino acids are broken down, and the nitrogen dealt with; some hormones are inactivated; and excess cholesterol is metabolised. Toxins and unwanted substances are released into the intestinal tract or sent to the kidneys for excretion from the body. Once alcohol is broken down, its components are used to create fat, which is subsequently stored if not burnt.
Production of bile
The liver creates bile, which is needed for the absorption of fat and fat-soluble vitamins, and to provide a route for excretion of unwanted substances from the body. Bile is stored in the gall bladder, which empties the bile into the intestines when needed. Metabolic wastes and drug products may form part of the bile which can then be excreted from the body via the digestive tract in faeces.
Storage of nutrients
The liver plays an important role as a storage facility. The hepatocytes take up many types of vitamins and minerals from the blood and store them, such as vitamins A, B12, D, E, K and minerals like iron and copper. Glycogen, which is the storage form of glucose, is also stored in the liver, although muscle tissue can also store glycogen.
The role of exercise and diet in a healthy liver
Many liver problems are a result of contracted diseases (such as hepatitis C), genetic defects or substance abuse. Once damage has occurred, nutrition becomes instrumental in managing the liver damage. However, there is one important disease, known as non-alcoholic fatty liver disease, which is associated with a poor diet and inadequate physical activity. Fatty liver disease affects around 1 in 10 Australians, and is one of the most common causes of liver problems. It is a condition where fat builds up in the liver cells, causing abnormal liver function tests and, in some people, inflammation which can lead to liver scarring (cirrhosis).
Fatty liver disease is associated with being overweight. Exercising regularly and eating a healthy, low fat diet can help to achieve and/or maintain a healthy weight. A high fat diet by itself does not cause fatty liver. If something goes wrong in the processes of breaking down, building, or storing fat, fat can build up in the liver instead of being transported to other parts of the body for storage. However, it makes sense to eat a diet low in fat to reduce the processing work that the liver has to do.
There is evidence that exercise itself (with or without weight loss) can prevent and reverse fatty liver disease. In a 2008 study, researchers gave obese rats access to voluntary running wheels for 16 weeks. Scientists then transitioned the rats to a sedentary lifestyle. After a week, the rats began showing signs of fatty liver disease. In the animals tested immediately at the end of 16 weeks of voluntary running, there were no signs of the disease.
Fatty liver disease is also associated with diabetes and heart disease. Therefore, it is important to eat a healthy diet that reduces your risk of developing these conditions, and/or help you to manage them. The dietary recommendations for these conditions are to consume only small amounts of fat, and to have the right types of fat to keep cholesterol levels under control. The healthy fats are known as unsaturated fats. Eating small, frequent meals and snacks that are high in fibre will help to reduce the workload on the pancreas and therefore help to prevent/manage diabetes.
"Detox" diets
Some people believe that it is possible to “detox” the liver, to make it function better. Unfortunately there is no scientific evidence to prove this. The liver is a detoxifying organ which rids the body of unwanted substances by breaking them down into non-harmful components and/or adding them to bile for excretion from the body. Toxins do not build up in liver cells, and hence there is no plausible rationale of a “detox diet”. In fact, many herbal remedies thought to cleanse the liver are actually harmful, as the liver goes into overload to metabolise them and rid them from the body.
