A colourless liquid produced from the fermentation of carbohydrates by yeast. Also known as ethanol, alcohol is the active constituent of drinks such as beer and wine. In medicine, it is used as an antiseptic and solvent. Methanol is a related, highly toxic substance. Alcohol is a drug and produces a wide range of mental and physical effects. The effect of alcohol on the central nervous system is as a depressant, decreasing its activity and thereby reducing anxiety, tension, and inhibitions. In moderate amounts, alcohol produces a feeling of relaxation, confidence, and sociability. However, alcohol slows reactions, and the more that is drunk, the greater is the impairment of concentration and judgement. Excessive consumption of alcohol results in poisoning or acute alcohol intoxication, with effects ranging from euphoria to unconsciousness. Short-term physical effects of alcohol include peripheral vasodilation (widening of the small blood vessels), which causes the face to flush, and increased flow of gastric juices, which stimulates the appetite. Alcohol increases sexual confidence, but high levels can cause impotence. Alcohol also acts as a diuretic, increasing urine output. In the long term, regular excessive alcohol consumption can cause gastritis (inflammation and ulceration of the stomach lining), and lead to alcohol-related disorders. Heavy drinking in the long term may also lead to alcohol dependence. However, people who drink regular, small amounts of alcohol (an average of 1–2 units a day) seem to have lower rates of coronary heart disease and stroke than total abstainers.


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