Metabolism is the set of chemical reactions or processes in the body that leads to the breakdown of foods and other nutrients, the generation of energy from the products of the breakdown and then the growth and repair of cells and tissue for optimal function of the body system.
These chemical processes are modulated by biological catalysts called enzymes which are proteinous in nature. The enzymatic activity can either be increased or decreased by the presence of some substances like drugs and alcohol. An increase in the amount of enzyme by the activities of these external agents is called induction. A decrease in the amount of these enzyme proteins by the presence of these agents is called repression. Other terms like enzyme activation and inhibition are used when there is an increase in enzyme-specific activity and a decrease in enzyme-specific activity respectively.1
Most of the enzymes of metabolism are produced by the liver cells, kidney cells, skin, stomach and so on. Of all these sources of enzymes, only a few dozen 1, 2, and 3 CYP450 enzyme families are responsible for the metabolism of the majority of the drugs and other xenobiotics.2
The activities of these enzymes can either be enhanced or reduced by the presence of other substances like alcohol in the body.
Alcohol is the only psychoactive agent that is also a source of energy. The energy provided by alcohol is about 7.1Kcal/g which lies between that of carbohydrate which provides 4 Kcal/g of energy and lipids which provide 9.2Kcal/g of energy.3
Alcohol is an enzyme inducer. This means that it increases the number of metabolizing enzymes and hence increases the metabolism of both drugs and food. Therefore, when alcohols are ingested concurrently with drugs or food, the rate of metabolism of such drug or food is greatly increased which results in enhanced absorption of the drug and food. Invariably, the drugs and food or other xenobiotics are easily cleared from the system as a result of these enhanced enzymatic activities which results in more water-soluble products that are easily removed from the body
Alcohol consumption can affect many parts of the body. The effect of consumed alcohol on the body depends on the age, gender, type of beverage, presence of food in the stomach and so on.
How is it processed by the body
The effect of alcohol on the different body parts depends on the blood alcohol concentration(BAC) over time.4
When alcohol is consumed, it is first converted to acetaldehyde by the enzyme Alcohol dehydrogenase (ADH).acetaldehyde is responsible for most of the tissue-damaging effects of alcohol and also its addictive behaviour. Other enzymes involved in alcohol metabolism are; aldehyde dehydrogenase, Cytochrome P450 (CYP2E1) and catalase. The variations in the genes that code for these enzymes have been linked to being the major influence on alcohol consumption, alcohol-related tissue damage and alcohol dependence.4
The blood alcohol concentration is determined by the absorption, distribution, metabolism and excretion rate from the body. Alcohol is absorbed from the small intestine into the veins that transport blood from the stomach to the small intestine. The alcohol is transported to the liver through the hepatic portal vein. At the liver, it is acted upon by the enzymes and hence broken down into excretable by-products. Some find their way into the lungs and skin where they are exhaled and removed through sweat respectively.
How does alcohol impact weight loss
Alcohol increases the rate of food metabolism. When this happens, the amount of food absorbed by the body decreases, hence resulting in weight loss. The dehydrating effect of alcohol consumption also results in a considerable loss in weight. However, alcohol consumption has been associated with an increase in appetite stimulation through the suppression of leptin, enhancing the effects of glucagon-like peptides, serotonin, and gamma amino butyric acid. hence, greater consumption of alcohol with an absence of dependency and binge drinking can result in obesity.3
Even though alcohol is said to have a high-calorie content of up to 7 Kcal/g, the calorie is described as ‘’empty’’ because it is lacking in basic vitamins and minerals that support basic cell growth and functions.2
Body prioritises metabolizing alcohol instead of food
Impact on organs
When alcohol is consumed, it finds its way to the bloodstream through the small intestine. It is then transported to the other parts of the body through the blood. Alcohol gets to the brain, liver, kidney, liver, skin and other organs and they affect them differently. In the brain, alcohol affects the cerebral system and hence affects cognitive ability. It affects the limbic system and messes with emotions and memory. Its effect on the cerebellum brings uncoordinated movement because of the effects on muscle movement.
The effect of alcohol on the heart can be seen in the increased heart rate. As a vasodilator, it increases blood flow through the blood vessels and hence decreases the pressure with which blood is pumped to the other parts of the body by the heart. To compensate for this decrease in pressure, the heart rate is increased.
In the kidney and bladder, alcohol represses the antidiuretic hormone called vasopressin, leading to a decrease in water reabsorption by the kidney cells and hence, results in excessive passage of water which leads to dehydration, dry mouth, blurry vision and general fatigue.
Alcohol can be exhaled through the lungs and perceived in the breath when they get to the air sacs called the alveoli. The skin reacts to alcohol ingestion by increasing the production of sweat.
The alcohol that gets to the liver is highly metabolized there. Up to 90% of the total alcohol consumed is metabolized by the liver. The liver breaks down the alcohol to water-soluble acetaldehyde which the body perceives as very toxic and hence gets rid of it from the body as soon as possible.
There is no considerable increase in weight by alcohol consumers indicating that alcohol is not a risk factor for obesity.3 However, due to the appetite-stimulating effect of alcohol, some consumers tend to increase their body weight because of an increase in food consumption that results from taking alcohol.
Alcohol inhibits proper digestion and nutrient uptake
Alcohol increases the risk of gastroesophageal reflux disease (GERD) by increasing the pressure of the oesophageal sphincter and gastric motility.5
The major way that alcohol affects proper digestion and decreases nutrient uptake is by causing malabsorption and diarrhea. Alcohol causes ulceration and necrosis of the jejunal mucosa thereby reducing its absorptive power. Small doses of alcohol increase gastric emptying time, thereby increasing the motility time, while high doses of alcohol decrease gastric emptying time and affect bowel movement.5
All these put together lead to a decrease in nutrient uptake.
Alcohol influenced behaviors
Alcohol influences behaviours to range from social, physical and psychological effects. Aggression, self-disclosure and sexual adventurousness have been associated with the social behaviour induced by alcohol consumption.6
Alcohol affects the limbic system, thereby affecting muscle movement which results in an uncoordinated movement, posture and girt. This is seen in the staggering movement of drunk persons.
Alcohol also affects memory and cognitive behaviours.
Poor food choices
Those who take alcohol make more poor choices for diet than those who do not. That is to say, food choices change in an unhealthier direction on the days people drink. Men consumed more than 400 calories while women consumed more than 300 calories on the days they are drunk.6
A hangover occurs when one consumes excess alcohol. It is associated with different body reactions like fatigue, dizziness, headache, nausea and vomiting. While the exact mechanisms behind hangovers may be difficult to unravel, there are a number of foods that have been found to improve the condition. They include; banana, egg, water, watermelon, honey, milk and cheese.
Impacts of long term alcohol consumption on the body
The impact of long-term alcohol consumption is related to the different organs that are affected. Liver cirrhosis has been linked to excessive consumption of alcohol since the majority of the alcohol consumed is metabolized by the liver cells. Over time, the liver cells weaken as a result of heavy labour giving rise to scarring and liver damage. Long-term use of alcohol also affects brain function, leading to loss of memory and cognitive disorders.
Alcohol consumption generally affects the metabolism of both foods and drugs in the body. The dose of the alcohol and the frequency of consumption plays a vital role in determining the extent of the effects of the alcohol. Alcohol facilitates the metabolism of food and drugs leading to its fast removal from the body, thereby affecting nutrient absorption. This results in malnutrition, impaired cell function and general health of the individual. Long-term consumption of alcohol also causes long-term damage to the vital organs of the body like the bladder, liver, heart, kidney and so on.
- Steele CM, Southwick L. Alcohol and social behavior I: The psychology of drunken excess. J Pers Soc Psychol. 1985 Jan;48(1):18–34.
- Toffolo MCF, Aguiar-Nemer AS de, Silva-Fonseca VA da. Alcohol: Effects on Nutritional Status, Lipid Profile and Blood Pressure. Journal of Endocrinology and Metabolism. 2012;2(6):205–11.
- Zanger UM, Schwab M. Cytochrome P450 enzymes in drug metabolism: Regulation of gene expression, enzyme activities, and impact of genetic variation. Pharmacology & Therapeutics. 2013 Apr 1;138(1):103–41.
- Drug Metabolizing Enzyme - an overview | ScienceDirect Topics [Internet]. [cited 2022 Aug 14]. Available from: https://www.sciencedirect.com/topics/neuroscience/drug-metabolizing-enzyme
- Zakhari S. Overview: How Is Alcohol Metabolized by the Body? Alcohol Res Health. 2006;29(4):245–54.
- Bujanda L. The Effects of Alcohol Consumption Upon The Gastrointestinal Tract. The American journal of gastroenterology. 2001 Jan 1;95:3374–82.