Physiological Actions Of Alcohol

Alcohol Free Forever

Quit Drinking Help

Get Instant Access

Alcohol is one of only two substances to which human cells have never found a need to bar entrance. The only other freely moving substance is water. Because there is no barrier to entrance, there are no known cellular receptors to alcohol. This free movement indicates that the body does

Figure 4. Blood alcohol curve after ingestion of 44 g alcohol in form of whiskey and of beer by 50 subjects, weighing between 65 and 79 kg.

Figure 5. Blood alcohol maximum after ingestion of 0.5 g alcohol per kg body weight in form of several alcoholic beverages with different dilutions.

Figure 4. Blood alcohol curve after ingestion of 44 g alcohol in form of whiskey and of beer by 50 subjects, weighing between 65 and 79 kg.

Alcoholic solution (12.5%A)

Aperitif, undiluted (17%A) Aperitif, diluted (12.5%A)

Champagne (14%A) Champagne, dry (12.5%A) Champagne, semidry (13.5%A)

Whiskey, undiluted (45%A) Whiskey, diluted (22.5%A) Whiskey, diluted (11.2%A)

Figure 5. Blood alcohol maximum after ingestion of 0.5 g alcohol per kg body weight in form of several alcoholic beverages with different dilutions.

not consider alcohol toxic or in any way foreign. It is this facile movement that permits alcohol to be excreted in the urine and in breath and also permits it to be found and measured in the breath.

There is many-faceted evidence that alcohol is a product of normal metabolism in humans; it has even been found in teetotalers. The amount is low, about 0.001%.

Effect of Alcohol on Fluid Balance

The initial effect of alcohol is to produce a slight retention of water, followed by a more marked diuresis of water and sodium. This latter effect is due to an inhibition by alcohol of the pituitary antidiuretic hormone (vasopressin). This diuresis occurs only when the concentration of blood alcohol content is rising. The concerted drinking of wine or whiskey, but not beer, requires the imbibition of other fluids to maintain homeostasis (7).

Effect of Alcohol on Nutrition

Alcohol is readily metabolized and yields 6.9 kcal/g. The rate of metabolism varies from person to person and ranges from 50 to 100 mg/kg of body weight per hour. Alcohol does not affect the use of dietary protein and is as effective as carbohydrates in protecting the body from loss of protein.

Alcohol does not raise heat production or C02 production, so it has no thermogenic effect. There is no increase in alcohol metabolism with exercise, nor a decrease with rest.

Alcohol has only a minor effect on appetite. Distilled spirits consumed in concentrated form decrease gastric motility, whereas dilute alcohol increases gastric motion. These will appear to affect appetite.

In addition, during a meal, the palate-cleansing action of wine and beer will promote eating and lessen the feeling of satiety. It is probably the tannin in wine and the hops in beer that are responsible for this action. Yet heavy drinkers are far less likely to be obese than nondrinkers. Among a large group of low-income women in their 30s, 41% of nondrinkers were obese, whereas only 22% of heavy drinkers were so rated. Among men, the ratio is 31% obese for nondrinkers and 16% for drinkers.

Effects of Alcohol on the Central Nervous System

The primary effect of alcohol in the body is a sequential depressant action on the central nervous system. From the spinal cord rises the medulla oblongata, the pons, and the midbrain, the control centers for the autonomic nervous system, which regulates reflexes and those functions beyond control of the will. Above the midbrain lies the thalamus and hypothalamus, whose dominion includes functions not willfully regulated, such as body temperature, metabolism of fats, and blood sugar level.

Above all this, and more recent in the evolution of the species, lie the cerebellum and the cerebral cortex. The former has sway over voluntary muscular movements and manual skills, as well as balance and speech. The cerebral cortex, the corolla of the mind, is master of all that distinguishes humans and makes them distinguished.

Alcohol, which has ready access to all cells and crosses the almost impenetrable blood-brain barrier as if it were a sieve, exerts its earliest action on the cerebral cortex. Its action is not as a stimulant but as a tranquilizer or depressant. It lessens inhibitions and increases confidence. It replaces discontent with discovery, bashfulness with bravado, and cowardice with courage. Alcohol negates a no and affirms a yes.

These effects, which people had sought long before the tensions of modern life were imposed on them, occur at blood levels between 0.02 and 0.05%. Whatever pressures and problems were mankind's lot in Biblical days, they were surely different in scope and pervasiveness than those we confront today. But alcohol was used then and was considered of priestly stature. In many cultures, its production was limited to the clergy.

Apparently, the evolution of the cerebral cortex, with its awesome powers of the mind, brings with it a need to lessen its potent sway over our actions. This alcohol does with speed and thoroughness.

At blood alcohol levels between 0.05 and 0.10%, the sphere of its influence expands to the cerebellum. Balance and speech become less than normal. The gait becomes unsteady and speech uncertain. It is at the higher of these levels that ability to operate machinery is impaired.

At 0.2%, balance is more seriously affected and speech nearly incoherent. Neurotransmission in the cerebellum is disturbed. At increasing blood alcohol concentrations, the effects become deeper and parts of the brain developed earlier in evolution are also effected.

At 0.3-0.4%, most of the behavior that we call human is sharply curtailed if not lost. Anesthesia sets in. In fact, alcohol was the earliest anesthetic, before ether was discovered.

At 0.5-0.6% a remarkable shut-off valve operates and wakefulness is not maintained. This normally prevents any further action, because even the autonomic nervous system, controlling basic functions of respiration and heart beat, are denervated at a level above 0.6% and death ensues. But sleep normally prevents further inhibition, so fatal levels are not attained except with rapid drinking of strong whiskey. Fatal levels cannot be achieved with wine or beer.

Interaction of Alcohol and Other Nutrients

Alcohol and its primary metabolite, acetate, serve as excellent sources of energy. Alcohol and acetate penetrate the blood-brain barrier almost as efficiently as glucose. Everywhere, alcohol is used in preference to all other energy sources. Acetyl CoA, the entry point of all energy sources into the citric acid cycle, is most easily produced from alcohol.

Also, while all other energy sources—fatty acids, glucose, and amino acids—can be stored in polymolecular forms, alcohol and acetate cannot be stored. Neither do they act as substrates for conversion to glucose, amino acids, or lipids. Alcohol must thus be metabolized as it becomes available (8).

Effect on the Digestive Tract

Alcohol slightly increases gastric and intestinal mobility. It also has a slight positive but very transient effect on appetite. It has no effect on the absorption of fats or cholesterol from the intestinal tract. Some of the very slight appetite stimulation may not even be due to alcohol, but to other factors present in some alcoholic beverages— juniper in gin, bitters in some aperitifs, hops in beer.

Effect on Cardiovascular System

Alcohol slightly dilates peripheral capillaries, leading to blushing and a feeling of warmth. The effects are transitory and meager.

Moderate alcohol consumption reduces the risk of coronary heart disease. It also reduces the risk of cardiac mortality. Its action is probably mainly due to its effect on raising the HDL levels in the blood, as well as lowering the triglyceride levels. Physical activity has the same effect, and the effects are additive.

Moderate drinking is taken to be between 25 and 80 g of alcohol a day (two to six 12-oz. bottles of beer, 5% alcohol by volume; 250-750 ml of table wine [12% alcohol]; or 70250 ml of whiskey [80 proof]).

The LDL in the blood (the "bad" cholesterol) is now believed to have its malign effect on atherosclerosis after it is oxidized. And so antioxidants have been shown to have a protective effect. This is the so-called French Paradox: the French consume diets high in cholesterol and saturated fats and yet have very low coronary artery disease. The explanation is their relatively high consumption of alcohol, mainly in the form of red wine. Many of the poly-phenals, gallic acid, rutin, epicatechin, and quercitin present in red wine are potent antioxidants (9). Such phenolics are also present in oak-aged whiskey and in full-bodied and darker beers.

Alcoholic beverages therefore have a two-pronged effect on reducing coronary heart disease, raising the "good" HDL and keeping the LDL from becoming "bad."

Effect of Alcohol on Men versus Women

Alcohol per se has the same effects on either sex. However, a given amount of alcohol has a greater effect on women than on men for several reasons.

First, women are usually smaller than men, so a given volume of an alcoholic beverage will have a greater effect on the smaller person.

Second, women have a lower water content in their bodies than do men. Thus the alcohol, which is only soluble in water and not in fat, will reach a higher concentration in women. This difference in water content, on an equal weight basis, is about 12%.

And last, and probably most important, women have a lower gastric activity of alcohol dehydrogenase than do men. They therefore do not destroy as much alcohol in their stomach as do men, allowing more of it to be absorbed into the blood. This phenomenon, only recently discovered (1), is known as first-pass metabolism. It may differ by 2030% between men and women. Thus the bioavailability of alcohol is considerably greater in women than in men. However, men over 50 years of age begin to lose the high alcohol dehydrogenase activity in their stomachs and become equal to women in their first-pass metabolism (10).

Alcohol as Medicine

Before the advent of the modern pharmacopoeia, alcohol was prescribed for many human ills. It dulls pain, summons sleep, soothes the spirit, and tames the teeming mind. Each of these functions can now be accomplished by a coterie of drugs, so alcohol is rarely recommended for these ills. But no one substance does all of what alcohol does, and people in all cultures have found alcohol to be the preferred, and possibly less noxious, means to tran quility. Furthermore, as a controlled way to peace and pleasure, alcohol has no peer.

Regulations in the United States prohibit any declaration of therapeutic value for any alcoholic beverage, so each generation must rediscover the value of alcohol. Many countries permit some therapeutic claim for alcohol, such as a bedtime relaxer or tension reducer.

As medicine, alcohol differs from drugs. All drugs are detoxified in the liver, ie, the liver so chemically modifies the drug as to render it inactive and able to be excreted, usually by the kidneys. This detoxification usually involves oxidation, hydrolysis, or sulfation. But alcohol is not detoxified, it is metabolized, just as is any foodstuff. No drug supplies energy; alcohol does. It may be more valid to consider alcohol as a food that has effects on the body rather than as a drug. As was pointed out earlier, alcohol has free entrance to every cell in the body; no drug has. All drugs operate by attaching themselves to a specific cellular receptor; alcohol needs none and has none.

Alcohol has at least one clinically proven and prescribed medicinal function. It is the only antidote to poisoning with ethylene glycol (antifreeze). Quick administration of alcohol, usually intravenously, makes all alcohol dehydrogenase sites act on the alcohol, harmlessly, instead of acting on the glycol, which produces very toxic oxalic acid. The glycol, not oxidized, is slowly excreted by the kidneys. The preferential reaction of alcohol dehydrogenase with alcohol permits this therapeutic action.

There are foods other than alcohol that affect the brain and human behavior. The amino acid tryptophane is a soporific and has been used as such. Meals high in carbohydrates produce high tryptophane blood levels. This they do by producing an influx of insulin into the blood, which in turn mobilizes some amino acids from plasma to muscle, leaving a higher concentration of tryptophane in the plasma. Histidine, threonine, tyrosine, and choline also are neuroactive, but their action is compromised by complex factors.

There are no confirmed allergies to alcohol per se. Its free entrance to all cells and ubiquitous presence mitigate against any allergic reaction.

Alcohol the Day After

The day after a serious session of drinking is often one of mental and physical fatigue and headache. In the United States, these symptoms are lumped together and called a hangover. In other languages the term is more descriptive, a wooden mouth in French, for example. The symptoms relate to the known constituents of alcoholic beverages and the known physiology of alcohol.

Alcohol masks fatigue, so a night of drinking will lead to excessive activity, which will be revealed by fatigue and malaise the next day. Rest always allows return to the normal state. The dry mouth or excessive thirst is the result of the diuretic effect of alcohol (and possibly the very salty nibbles that often accompany drinking). Drinking water or fruit juice, and a little time, alleviate this condition.

The headache may result from the fatigue and the dehydration but may also result from the congeners of distilled spirits and of wine. The congeners are simple com pounds produced by yeast concomitant with alcohol. They range from ethyl acetate to amyl alcohol. Also, particularly in some wines, and in brandy, there may be measurable amounts of methyl alcohol. These levels of methyl alcohol are not toxic per se, but when metabolized to formaldehyde may produce headaches. The drinking of a small amount of some alcoholic beverage the next day, possibly beer or vodka, will induce the liver to return to oxidizing alcohol and allow the methanol to be eliminated by the kidneys.

Alcohol and Alcoholism

Alcohol, although it effects many organs and systems, is singularly responsible for only one disease, alcoholism. Those who have this disease are called alcoholics.

An alcoholic has been defined as a person who has a compulsion to drink and cannot stop drinking once begun, to the point where that person's social and economic life are adversely affected. There is no certain cause of this disease, although a genetic factor may well be involved. An alcoholic is a heavy drinker, but not all heavy drinkers are alcoholics. Drinking because they want to characterizes drinkers, heavy or light, but drinking because they have to is the hallmark of alcoholics. In an alcoholic drinking sets up a chain reaction, which terminates only with sleep. There is no clear evidence that an alcoholic metabolizes alcohol any differently than others, but there appears to be, in alcoholics, a strong predilection toward alcohol metabolism, rather than carbohydrate or fat metabolism, as the major energy source.

Alcoholism may lead to several other pathological conditions. It is important to understand that alcoholics may derive up to or even above 50% of their daily caloric requirements in the form of alcohol. The human system can only tolerate such univalent load with carbohydrates. Either fat or protein in such excess will lead to problems of a different nature, but none the less severe.

The major problem facing alcoholics is a series of metabolic and structural changes in the liver. The initial change is the accumulation of fats in the liver, resulting in a fatty liver. This is easily reversible. It occurs because, in the presence of alcohol, the liver uses it as a preferential source of energy and the fatty acids, which it would otherwise use, accumulate. This change is followed, after some years, by structural changes in the liver, including scarring or necrosis of the liver tissue, the mark of cirrhosis. About 20% of long-term alcoholics develop cirrhosis.

Alcohol consumption equivalent to about 50% of the daily caloric intake, for from 5 to 20 yr, is necessary to induce cirrhosis in susceptible persons. Cessation of drinking often leads to reversal of the cirrhotic condition.

The male to female ratio of alcoholics in the United States is now 4:1. Although alcohol is a necessary component in alcoholism, it is no more correct to say that alcohol is the cause of alcoholism than it would be to say that marriage is the cause of divorce. The roots of alcoholism are social, metabolic, and genetic. No medical treatment exists. The use of drugs that produce unpleasant symptoms if alcohol is consumed is not widespread because of toxic effects. Societal treatment, in groups of peers such as Alcoholics Anonymous, has proved most beneficial.

Prenatal alcohol abuse can lead to birth defects known as fetal alcohol syndrome. The most benign symptom is low birth weight, and the most serious is impaired brain development and mental retardation. The most severe effects are known to occur in chronic alcoholics, but because it is neither known what the safe lower limit of alcohol intake is nor when during the pregnancy alcohol is most likely to harm the fetus, it is generally recommended to avoid alcohol during pregnancy (11,12).

The Salubrity of Alcohol

The vast majority of consumers of alcohol—as beer, wine, or distilled spirits—do so because it makes them feel better. It relieves stress and smooths the way from work to winding down. Not for naught has the time in a tavern after work and before the trip home come to be called the happy hour.

In addition to general relief from stress and care, moderate drinkers have been found to show genuine improvement in health. Recall that the ill effects of alcohol are confined to those who consume, regularly and for many years, alcohol in excess of 80 g a day. This amounts to almost two cases (twenty-four 12 oz packages) of beer a week, or more than a 750 mL bottle of wine a day, or six 1-1/2 oz shots of whiskey a day.

The consumption of moderate amounts of alcohol has been found to decrease stepwise the risk of coronary heart disease. The lowest level of consumption produces the least salutary effect, and the highest levels, more than 31 g but less than 80 g a day, reduce the risk to only 20-75% of that in nondrinkers. These results have been found in many studies, in many lands, among men and women, and among various socioeconomic strata. The Framingham Study, the longest and largest research of its kind, has always found this correlation between alcohol consumption and coronary heart disease—moderate alcohol use lowers the risk of coronary heart disease.

The recent (1989) Physicians Health Study, in which 22,000 physicians were studied prospectively, to determine the effect of aspirin on cardiovascular mortality showed incidentally that daily alcohol consumption significantly reduced the overall mortality rate over that produced by aspirin alone.

Physicians using alcohol daily and taking aspirin had a myocardial infarction rate of 1% whereas those taking aspirin alone had a 1.4% rate. This 40% improvement was among the best of any other risk factor studied. The synergistic effect of moderate alcohol consumption was not expected.

Alcohol and Drugs

Alcohol has a potentiating effect on some drugs, particularly sedatives. This may be drug specific, but also in many cases is due to the fact that the liver, where all drugs are detoxified, may prefer to metabolize alcohol and the drugs may persist in the bloodstream longer than they would normally. Repeating the drug dosage, in, say, 4 or 6 h, may lead to an overdosage if the drug has not been removed by the liver.

Those taking drugs for any chronic ailments should find out if alcohol interferes with the action or metabolism of those drugs.

Was this article helpful?

0 0
101 Power Tips For Preventing and Treating Headaches

101 Power Tips For Preventing and Treating Headaches

Are you fed up with your frequent headache pain? 101 Simple Ways to Attack Your Headache BEFORE the Pain Starts Guaranteed No Pain, No Fear, Full Control Normal Life Again Headaches can stop you from doing all the things you love. Seeing friends, playing with the kids... even trying to watch your favorite television shows.

Get My Free Ebook

Post a comment