How Alcohol Travels Through the Body
Alcohol is metabolized extremely quickly by the body. Unlike foods, which require time for digestion, alcohol needs no digestion and is quickly absorbed. Alcohol gets ?VIP? treatment in the body ? absorbing and metabolizing before most other nutrients. About 20 percent is absorbed directly across the walls of an empty stomach and can reach the brain within one minute.
Once alcohol reaches the stomach, it begins to break down with the alcohol dehydrogenase enzyme. This process reduces the amount of alcohol entering the blood by approximately 20%. (Women produce less of this enzyme, which may help to partially explain why women become more intoxicated on less alcohol than men.). In addition, about 10% of the alcohol is expelled in the breath and urine.
Alcohol is rapidly absorbed in the upper portion of the small intestine. The alcohol-laden blood then travels to the liver via the veins and capillaries of the digestive tract, which affects nearly every liver cell. The liver cells are the only cells in our body that can produce enough of the enzyme alcohol dehydrogenase to oxidize alcohol at an appreciable rate.
Though alcohol affects every organ of the body, it?s most dramatic impact is upon the liver. The liver cells normally prefer fatty acids as fuel, and package excess fatty acids as triglycerides, which they then route to other tissues of the body. However, when alcohol is present, the liver cells are forced to first metabolize the alcohol, letting the fatty acids accumulate, sometimes in huge amounts. Alcohol metabolism permanently changes liver cell structure, which impairs the liver?s ability to metabolize fats. This explains why heavy drinkers tend to develop fatty livers.
The liver is able to metabolize about ½ ounce of ethanol per hour (approximately one drink, depending on a person?s body size, food intake, etc.). If more alcohol arrives in the liver than the enzymes can handle, the excess alcohol travels to all parts of the body, circulating until the liver enzymes are finally able to process it. (Which is another good reason not to consume more than one drink per hour.).
How the Liver Breaks Down Alcohol
The alcohol dehydrogenase enzyme breaks down alcohol by removing hydrogen in two steps:
1. Alcohol dehydrogenase oxidizes alcohol to acetaldehyde
2. Acetaldehyde dehydrogenase oxidizes the acetaldehyde to acetyl CoA. These reactions produce hydrogen ions (acid). The B vitamin niacin (in its role as the coenzyme NAD) picks up these hydrogen ions (becoming NADH). Thus when alcohol is metabolized, NAD diminishes and NADH increases.
- During alcohol metabolism, NAD becomes unavailable for the many other vital body processes for which it is needed, including glycolysis, the TCA cycle and the electron transport chain. Without NAD, the energy pathway is blocked, and alternative routes are taken, with serious physical consequences:
- The accumulation of hydrogen atoms shifts the body?s balance toward acid.
- The accumulation of NADH slows the TCA cycle, resulting in a build up of pyruvate and acetyl CoA. Excess acetyl CoA results in fatty acid synthesis and fat begins to clog the liver. (An accumulation of fat in the liver can be observed after only a single night of heavy drinking).
Fatty Liver and Liver Disease
With moderate drinking, the liver can process alcohol fairly safely. However, heavy drinking overtaxes the liver resulting in serious consequences. A liver clogged with fat causes liver cells to become less efficient at performing their necessary tasks, resulting in impairment of a person?s nutritional health. Fatty liver is the first stage of liver deterioration in heavy drinkers, and interferes with the distribution of oxygen and nutrients to the liver?s cells. If the condition persists long enough, the liver cells will die, forming fibrous scar tissue (the second stage of liver deterioration, or fibrosis). Some liver cells can regenerate with good nutrition and abstinence, however in the last stage of deterioration, or cirrhosis, the damage to the liver cells is the least reversible.
Alcohol and Malnutrition
For moderate drinkers, alcohol does not suppress food intake, and may actually increase appetite. Chronic alcohol consumption appears to have the opposite effect. Alcohol causes euphoria, which depresses appetite, so that heavy drinkers tend to eat poorly and become malnourished.
Alcohol is very rich in energy, packing 7 calories per gram. But like pure sugar or fat, the calories are void of nutrients. The more calories an individual consumes in alcohol, the less likely it is that they will eat enough food to obtain adequate nutrients. To make matters worse, chronic alcohol abuse not only displaces calories from needed nutrients, but also interferes with the body?s metabolism of nutrients, leading to damage of the liver, digestive system, and nearly every bodily organ.
