Physiology: Alcohol and The Body

Alcohol: What is it?
Alcohol is a substance produced by the process of fermentation that consists of a number of organic chemical elements. During fermentation, alcohol is produced by yeast acting upon liquids that contain starches, or sugars. There are many types of alcohol, but the only one present in drinks intended for human consumption is called ethyl alcohol, also known as ethanol, a colourless, tasteless substance.

Alcohol in the Body
Once consumed, the alcohol present in drinks becomes rapidly absorbed. A small amount is metabolized (broken down) by enzymes inside the gut, and the remainder is absorbed directly into the blood stream via the small intestine and the stomach. The absorption rate can vary between individuals, and it can also vary for one person from time to time. The speed of the process is affected by the concentration of ethyl alcohol in the drink itself, the temperature of the drink, and also the amount of food present in the gut at the time of drinking. Once inside the bloodstream, the alcohol is then distributed throughout the body into the water soluble body fluids, about two percent of which is excreted in the form of urine, sweat, and of course, breath. It is this excretion of unchanged alcohol ions contained in breath particles that enables "breath testing" to be performed. Breath testing is used to estimate a person's "Blood Alcohol Concentration" (or BAC), which provides an index of the level of alcohol concentration that is present throughout the body fluids.

As the liver slowly breaks down the alcohol in the bloodstream, the levels of alcohol present gradually begin to fall (one "standard drink" usually takes about one hour). Acetaldehyde is then formed, broken down into a combination of acetic acid and water, and then later converted into carbon dioxide. This breakdown process usually occurs almost instantaneously, but in around 10 percent of people of Caucasian extraction, and a higher percentage of people of Oriental extraction, the process is interrupted. The acetaldehyde quickly builds up after only a small amount of alcohol, causing obvious flushing, and symptoms related to illness, such as vomiting and nausea.

Short-Term Effects
Alcohol almost immediately affects the brain by dampening the arousal centres, resulting in an initial reduction of physical tension. Inhibitions also tend to be reduced, resulting in feelings of intense relaxation or excitement. As the level of alcohol consumed rises, the motor and sensory centres of the brain also become dampened, resulting in slower reactions to external stimuli, such as in the case of slower reactions whilst operating a motor vehicle.

As the Blood Alcohol Concentration rises, coordination becomes impaired, and movement becomes more difficult, along with the ability to reason cognitively, and articulate verbally. At this stage, some people may vomit due to the effects that excessive alcohol and acetaldehyde have on the centre of the brain that controls vomiting.

When alcohol in the bloodstream is at levels that are far beyond the recommended limit, all bodily systems slow down to the point of eventually causing unconsciousness, and resulting in inhibited breathing, a potentially fatal occurrence. The pituitary gland is also affected, resulting in the suppression of the normal release of a hormone that balances the body's fluid reserves, insufficient amounts of water are reabsorbed from the urine by the kidneys, and too much water is excreted, hence the occurrence of headaches, and feelings of excessive dehydration.

Long-Term Effects
The long-term effects of consuming alcohol can be classified into two major categories: longer-term health benefits associated with consumption of low levels of alcohol over an extended period of time, and longer-term health consequences associated with consuming excessive amounts, resulting in disease. The level at which the benefits outweigh the risks, and vice versa is known as the "Threshold Effect", since each person, and even different population groups, tend to have a differing threshold of tolerance that tends to determine the balance between health benefits and risks associated with long term alcohol consumption.

Regarding the long-term benefits, there has been evidence to suggest that, at low levels, alcohol can assist with the prevention of certain diseases, such as heart disease, stroke, hypertension, cognitive decline, Type 2 diabetes, and gall stones. However, when alcohol is used unwisely over an extended period of time, it is one of the major causes of ill health in our society. The risks associated with consumption of alcohol at levels and rates that are not recommended include cirrhosis of the liver, dementia, cancer, and alcohol dependence.