alcohol
Meaning of alcohol: A whole family of compounds in chemistry, though outside the laboratory the word means exactly one of them.
Definition of alcohol
Alcohol is a class of chemical compounds carrying a hydroxyl group, an oxygen bonded to a hydrogen, attached to a carbon framework. In everyday use the word means ethanol specifically, the alcohol in beer, wine and spirits, which is also present in some medicines, mouthwashes and household products. Other alcohols include methanol and isopropyl alcohol.
What does ethanol do in the body?
Ethanol is a depressant of the nervous system, not a stimulant, despite the loosening of inhibition that comes early and can look like one. It reaches the brain within minutes and dampens signaling there, producing in sequence relaxation and talkativeness, then slowed reactions, unsteadiness and impaired judgment, then drowsiness, and at high enough concentrations suppression of breathing and loss of consciousness. It also acts as a diuretic and irritates the stomach lining. Effects depend on the amount, how quickly it is drunk, body size, whether food is present and individual differences in how it is broken down.
How is it broken down?
| Step | What happens |
|---|---|
| Ethanol to acetaldehyde | Carried out mainly in the liver by the enzyme alcohol dehydrogenase |
| Acetaldehyde to acetate | By a second enzyme; acetaldehyde is toxic and causes flushing, nausea and headache |
| Acetate onward | Broken down to carbon dioxide and water |
The liver processes ethanol at a roughly fixed rate, so the level in the blood falls at a steady pace that nothing speeds up. Coffee, cold air and food do not accelerate it. Inherited differences in the second enzyme are common in East Asian populations and cause acetaldehyde to build up, producing marked flushing after small amounts.
What does long-term heavy use affect?
The liver bears the most familiar damage, progressing through fat accumulation to inflammation and eventually to scarring. Heavy use also affects the heart muscle, the pancreas, the nerves of the limbs and the brain, and it interferes with nutrition, particularly the absorption of thiamine. Alcohol is classified as a cause of cancer, with the clearest links to cancers of the mouth, throat, esophagus, liver, colon and breast. Regular heavy use produces tolerance and physical dependence, and alcohol dependence involves a withdrawal state on stopping that can be medically serious. Alcohols other than ethanol are not interchangeable with it: methanol and ethylene glycol are metabolized into substances that damage the optic nerve and kidneys, and isopropyl alcohol is intended for use on surfaces and skin.
Also known as
Used in a sentence
The patient's history included daily alcohol use, which was noted as part of the intake evaluation.
Good to know
In everyday use alcohol means ethanol, while the chemical term also covers compounds such as methanol and isopropyl alcohol that are not intended for consumption and are broken down into substances that damage the eyes, nerves or kidneys.
Word origin
Where “alcohol” comes from
From Arabic al-kuhl, originally a fine powder used as eye cosmetic, applied later to any substance refined by distillation and eventually to the spirit obtained that way.