Absorption Of Alcohol

Alcohol is absorbed into the bloodstream mainly from the upper small intestine. Although it enters the stomach, there is only a limited exit into the blood from that organ.

Emptying of the stomach's contents is controlled by the pyloric sphincter muscle at the base of the stomach. It opens when the pH of the contents falls below 3. The presence of proteins, which act as buffers, or fats, which delay access of the stomach's enzymes and acid to their substrates, delay the fall in pH and thus also the exit of food or drink from the stomach.

All the blood that nourishes the entire digestive tract, and that in turn carries all the digested foodstuffs from the tract, first enters the liver via the portal vein. Thus alcohol absorbed from the stomach or the small intestine goes first to the liver. This probably accounts for the old and incorrect belief that alcohol is oxidized to acetaldehyde only in the liver.

Alcohol consumed at high concentrations is absorbed more rapidly than when consumed in diluted forms. The presence of carbon dioxide also accelerates the absorption. Fatigue and exercise delay the absorption.

It has been recently found that a considerable amount of alcohol is metabolized in the stomach to acetaldehyde, and that the quantity oxidized is higher in men than in women and lower in alcoholic men and women (1). The blood alcohol curves for alcohol administered by mouth or intravenously for nonalcoholic and alcoholic men and women are shown in Figure 2. Of course, the alcohol metabolized in the stomach can have no effect elsewhere. This so-called first-pass metabolism accounts for the more ready effect that alcohol has on women than on men.

A comparison among whiskey, wine, and beer showing the maximum blood alcohol concentrations for the three beverages is shown in Table 1 (2). Wine and whiskey reach about the same maximum concentration, but whiskey is faster. Beer achieves a lower maximum, and it takes longer to get there.

At a lower alcohol level, the same relative relations are maintained, but the maximum concentrations attained are lower (Fig. 3) (3).

Table 2 shows the relationship between body weight, amount of beer and whiskey to reach certain blood alcohol levels, and the time at which the maximum concentration is reached. For example, an average person weighing 175 lb (79.5 kg) who consumes four 12-oz bottles of beer will have a maximum blood alcohol level of 0.08% in about 95 min (4).

Another set of experiments compared the sequential blood alcohol levels in a group of 50 men weighing between 145 and 175 lb who consumed 44 g of alcohol (four bottles of beer or four shots of whiskey) at once. The results in

2q Alcoholic women

10 Alcoholic women

100 200 300 100 200 300

Minutes after ethanol administered

Figure 2. Effects of gender and chronic alcohol abuse on blood ethanol concentrations. Ethanol was administered orally (solid lines) or intravenously (dashed lines) in a dose of 0.3 g/body weight. The shaded area represents the difference between the curves for the two routes of administration (the first-pass metabolism).

Table 1. Effects of Alcoholic Beverages on the Maximum Blood Alcohol Levels and the Time at Which These Levels Are Reached
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