Tolerance to Alcohol

One of the first warning signs of alcoholism

The word tolerance has many meanings. To most people, tolerance denotes a capacity to consume large amounts of alcohol without passing or feeling nauseated. “He has an amazing capacity for the stuff,” an admirer might comment about someone who consistently drinks everyone else under the table and then proceeds to drive home safely.

This interpretation is not entirely accurate, for tolerance is a term that applies to all drinkers. Every drinker has a specific tolerance to alcohol. Below his tolerance level, the drinker can function more or less normally; at levels above their tolerance threshold, they will act intoxicated.

Tolerance is a condition that can only be measured accurately in a laboratory where the drinker’s blood level and behaviour can be carefully monitored.

Nonalcoholics fairly quickly establish a stable level which may be high or low. Alcoholics, however, typically experience a dramatic climb in tolerance in the first stage of alcoholism and can often drink vast amounts of alcohol without showing obvious impairment of the ability to walk, talk, think, and react.

Anyone who observes the early- and middle-stage alcoholic’s drinking behaviour is familiar with the fact that the typical alcoholic can drink as much as a litre of wine, a dozen beers, or even a bottle of whiskey without acting drunk. An average person would probably go into a coma!

Developing tolerance

This ability to tolerate large amounts of alcohol can develop over weeks or years, depending on the individual. Some alcoholics experience a subtle, gradual shift from normal drinking to a drinking pattern of increased frequency and stepped-up amounts over many years.

Most alcoholics, however, experience a more immediate change in their tolerance level and can drink more than their friends and show less impairment soon after they first start drinking.

Regardless of how long it takes to develop increased tolerance, the same adaptational processes underline its development. Physiological adaptations (such as mitochondria) are responsible for increased metabolic tolerance, which is evident in the alcoholic’s ability to metabolize alcohol quickly and efficiently.

Cellular or tissue tolerance results from central nervous system adaptations to alcohol’s toxic effects and is evident in the alcoholic’s ability to drink large amounts of alcohol without becoming intoxicated. 

Misconceptions about tolerance

Two significant misconceptions about the phenomenon of tolerance should be straightened out. The first is the belief that tolerance is a learned response. Many people think that the more the alcoholic drinks, the more he learns how to compensate for the effects of drinking.

But tolerance is not learned, nor is it subject to the alcoholic’s conscious control or willpower. Tolerance is caused by physiological changes which occur primarily in the liver and central nervous system.

These changes cause alterations in the alcoholic’s brain’s electrical impulses, hormone and enzyme levels, and the chemical structure of cell membranes, all of which contribute to tolerance. Learned behaviour cannot possibly account for these physiological and biochemical functions.

The second and very misleading misconception is that tolerance initially develops because the person drinks too much.

Many alcoholism theorists and professionals insist that psychological or emotional problems cause increased drinking; as the person drinks more frequently, they conclude, the person runs the risk of becoming tolerant to alcohol.

Again, the implication is that alcoholics are responsible for contracting their disease – by drinking too much, they make themselves tolerant to alcohol. Yet, the opposite is true. Tolerance is actually responsible for the alcoholic’s continued and increasingly large intake of alcohol. 

When the alcoholic becomes tolerant to alcohol’s effect, he responds to changes occurring inside him. They are not responsible for initiating these changes. The person is not even conscious that these changes are taking place. 

In fact, an increase in the amount and frequency of drinking is the typical symptom of developing tolerance to alcohol and one of the first warning signs of alcoholism.

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