Alcohol, and in particular excessive alcohol consumption, causes the signs and symptoms of a hangover, and has many adverse effects on various organs in the body.
The adverse effects of alcohol on the body occur because:
Ã¢â‚¬Â¢ During alcohol metabolism, one molecule of ethanol (the primary active ingredient in alcoholic beverages) produces 2 molecules of NADH in a reaction that uses Vitamin B12 as a coenzyme. Excessive consumption of ethanol can cause Vitamin B12 deficiency.
Ã¢â‚¬Â¢ Ethanol causes dehydration because it has a diuretic effect on the body, which means that it increases urine production. Such dehydration can cause symptoms such as headaches, dry mouth, and lethargy. Dehydration also causes the brain to shrink away from the skull slightly. The dehydrating effects of alcohol can be reduced by drinking water before, during, and after the consumption of alcohol.
Ã¢â‚¬Â¢ Ethanol is broken down (metabolized) in the liver and converted to acetaldehyde (also known as ethanal) by the enzyme alcohol dehydrogenase, and then from acetaldehyde to acetic acid by the enzyme acetaldehyde dehydrogenase. Acetaldehyde is a compound that is mildly toxic to the body and contributes to the ill effects of a hangover.
Ã¢â‚¬Â¢ These two metabolic reactions in the liver also require the conversion of NAD+ to NADH. During times of excessive alcohol consumption, excess NADH can build up. When this occurs, the lactate dehydrogenase reaction is forced to derive lactate from pyruvate (the end product of glycolysis) in order to regenerate NAD+ and maintain life. This reaction diverts pyruvate from other pathways such as gluconeogenesis, thereby impairing the ability of the liver to supply glucose to tissues and organs of the body, especially the brain. Because glucose is the primary energy source of the brain, this lack of glucose contributes to various hangover symptoms, including fatigue, weakness, mood disturbances, and reduced concentration and attention span.
Ã¢â‚¬Â¢ As alcohol is broken down by the body and the levels decline, there is a corresponding decline of the depressive effects of alcohol on the brain, and this is believed to cause the light and noise sensitivity.
Ã¢â‚¬Â¢ During the fermentation process of alcohol, various by-product alcohol compounds are formed, called congeners. The amount of these congeners in the beverage also seem to influence the type and severity of the hangover symptoms. For example, red wines have more congeners than white wines, and many people report that they suffer from quite severe hangover symptoms even when they drink a relatively small amount of red wine.
Ã¢â‚¬Â¢ Alcohol’s effects on the stomach lining causes symptoms such as nausea.