2.11.3. Alcohol

Alcohol is an adaptation of the chapter “Alcohol” from Human Nutrition, by the University of Hawai‘i at Mānoa Food Science and Human Nutrition Program, which is licensed under a CC BY 4.0 license. New material has been incorporated that includes the following: Canadian statistics and Canadian drinking guidelines and information on risks of alcohol consumption during pregnancy. Additionally, information that is not relevant to this course has been removed.


Alcohol is a psychoactive drug. A psychoactive drug is any substance that crosses the blood-brain barrier primarily affecting the functioning of the brain, be it altering mood, thinking, memory, motor control, or behaviour. Alcohols in chemistry refer to a group of similar organic compounds, but in beverages the only alcohol consumed is ethanol.

It is estimated that 4 to 5 million Canadians engage in high risk drinking.[1] Depending on how much you drink there can be chronic or acute consequences. Chronic conditions include liver disease and cancer whereas acute consequences include alcohol poisoning, fights and accidents.

Alcohol in excess is detrimental to health; however since its beginnings it has been suspected and promoted as a benefit to the body and mind when consumed in moderation. Canadian Low Risk Drinking guidelines define moderate alcohol intake as no more than two drinks per day for women and no more than three drinks per day for men.[2] Drinking above these recommendations increases health risks associated with cancer, etc. Although drunkenness has pervaded many cultures, drinking in moderation has long been a mantra of multiple cultures with access to alcohol. More than 90 percent of ingested alcohol is metabolized in the liver. The remaining amount stays in the blood and is eventually excreted through exhaled breath, urine, saliva, and sweat. The blood alcohol concentration (BAC) is measured in milligrams percent, comparing units of alcohol to units of blood. BAC is a measurement used legally to assess intoxication and the impairment and ability to perform certain activities, as in driving a car. As a general rule, the liver can metabolize one standard drink (defined as 12 ounces of beer, 5 ounces of wine, or 1 ½ ounces of hard liquor) per hour. Drinking more than this, or more quickly, will cause BAC to rise to potentially unsafe levels. Table “Mental and Physical Effects of Different BAC Levels” summarizes the mental and physical effects associated with different BAC levels.

Table Mental and Physical Effects of Different BAC Levels

BAC percent Typical effects
0.02 Some loss of judgment, altered mood, relaxation, increased body warmth
0.05 Exaggerated behaviour, impaired judgment, may have some loss of muscle control (focusing eyes), usually good feeling, lowered alertness, release of inhibition
0.08 Poor muscle coordination (balance, speech, vision, reaction time), difficulty detecting danger, and impaired judgment, self-control, reasoning, and memory
0.10 Clear deterioration of muscle control and reaction time, slurred speech, poor coordination, slowed thinking
0.15 Far less muscle control than normal, major loss of balance, vomiting

Source: Blood Alcohol Level & Effects on the Body. https://www.alcohol.org/effects/blood-alcohol-concentration/. Sourced: Dec 22, 2020.

Increasing blood alcohol content (BAC) comes with increases in physical and metal impairments.

In addition to the one drink per hour guideline, the rate at which an individual’s BAC rises is affected by the following factors:

  • sex (a woman’s BAC will rise more quickly than a man’s.)
  • weight (BAC will rise more slowly for heavier people.)
  • genetics
  • length of time as a heavy drinker
  • type of alcohol consumed
  • amount of alcohol consumed
  • consumption rate
  • consumption before or after a meal (food in the stomach slows absorption)
  • mixture (carbonated mixers speed absorption)
  • medications may increase the bioavailability of alcohol

Alcohol Metabolism

Image by Serge Esteve on unsplash.com / CC0 

Giving the liver enough time to fully metabolize the ingested alcohol is the only effective way to avoid alcohol toxicity. Drinking coffee or taking a shower will not help. The legal limit for intoxication is a BAC of 0.08. Taking into account the rate at which the liver metabolizes alcohol after drinking stops, and the alcohol excretion rate, it takes at least five hours for a legally intoxicated person to achieve sobriety.

Ethanol Consumption

Distilled spirits have exceptionally few nutrients, but beer and wine do provide some nutrients, vitamins, minerals, and beneficial plant chemicals along with calories. A typical beer is 150 kilocalories, a glass of wine contains approximately 80 kilocalories, and an ounce of hard liquor (without mixer) is around 65 kilocalories.

As a person starts drinking alcohol, up to 5% of the ingested ethanol is directly absorbed and metabolized by some of cells of the gastrointestinal tract (the mouth, tongue, esophagus and stomach). Up to 100% of the remaining ethanol travels in circulation. This is one reason why blood tests are more accurate in measuring alcohol levels.

The lungs and kidneys will excrete about 2% to 10% of this circulatory ethanol. The more you drink the more quick trips to the restroom. The human body dehydrates as a result of these frequent trips to the restroom. This dehydration affects every single cell in your body, including your brain cells. This is the cause of the so-called “morning hangover”. Do not take Tylenol (acetaminophen). Alcohol metabolism activates an enzyme that transforms acetaminophen into a toxic metabolite that causes liver inflammation and damage. The resulting liver damage may not be reversible. Instead, drink water with electrolytes or sport drinks to rehydrate the body’s cells.

Alcohol is a volatile (flammable) organic substance and can be converted to a gas. The lungs exhale alcohol as a gas. The more alcohol consumed, the stronger the smell of alcohol in a person’s breathe. Breathalyzer tests measure the exhaled alcohol levels in the lungs to determine the state of inebriation.

Health Consequences of Alcohol Abuse

Alcoholic drinks in excess can contribute to weight gain by substantially increasing caloric intake. When alcohol is drunk in excess, it reduces the secretion of pancreatic juice and damages the lining of the gastrointestinal system, impairing nutrient digestion and absorption. The impaired digestion and absorption of nutrients in alcoholics contributes to their characteristic “skinniness” and multiple associated micronutrient deficiencies. The most common macronutrient deficiency among alcoholics is water, as it is excreted in excess. Commonly associated micronutrient deficiencies include thiamine, pyridoxine, folate, vitamin A, magnesium, calcium, and zinc. Furthermore, alcoholics typically replace calories from nutritious foods with alcohol, sometimes getting 50 percent or more of their daily caloric intake from alcoholic beverages.

Alcohol is a diuretic that results in dehydration. It suppresses the release of antidiuretic hormone and less water is reabsorbed and more is excreted. Drinking alcohol in excess can lead to a “hangover,” of which the majority of symptoms are the direct result of dehydration.

Effects of Alcohol Abuse on the Brain

A small amount (up to 10%) of the liver acetaldehyde may accumulate inside the liver cells and diffuse into the blood circulation. In circulation, high levels of acetaldehyde cause nausea and vomiting. Vomiting causes more body dehydration and loss of electrolytes. If the dehydration becomes severe enough, this can impair brain function and a person may lose consciousness.

Alcohol can adversely affect nearly every area of the brain. When BAC rises, the central nervous system is depressed. Alcohol disrupts the way nerve cells communicate with each other by interfering with receptors on certain cells. The immediate impact of alcohol on the brain can be seen in the awkwardly displayed symptoms of confusion, blurred vision, slurred speech, and other signs of intoxication. These symptoms will go away once drinking stops, but abusive alcohol consumption over time can lead to long-lasting damage to the brain and nervous system. This is because alcohol and its metabolic byproducts kill brain cells.

Effects of Excessive Alcohol on the Liver

The increased accumulation of both stored triglycerides and very low density lipoprotein (VLDL). particles inside the liver cells causes a condition called fatty liver or hepatic steatosis. This can impair normal liver function. The more alcohol consumed, the more lipids produced and stored inside the liver cells. These effects are cumulative over time.

Although not every alcoholic or heavy drinker will die from liver problems, the liver is one of the body’s main filtering organs and is severely stressed by alcohol abuse. The term alcoholic liver disease (ALD) is used to describe liver problems linked to excessive alcohol intake. ALD can be progressive, with individuals first suffering from a fatty liver and going on to develop cirrhosis. It is also possible to have different forms of ALD at the same time.

Figure Liver Cirrhosis

A liver that has cirrhosis due to the excessive consumption of alcohol. Source: “Cirrosi Micronodular” by Amanda Alvarez/ CC BY SY 4.0

Excessive alcohol consumption causes the destruction of liver cells. In an attempt to repair itself, the liver initiates an inflammatory and reparation process causing scar tissue to form. In the liver’s attempt to replace the dead cells, surviving liver cells multiply. The result is clusters of newly formed liver cells, also called regenerative nodules, within the scar tissue. This state is called cirrhosis of the liver.

There are three common forms of ALD:

  • fatty liver: A rather benign disorder that develops after excessive alcohol consumption; however it can progress to more fatal diseases. Fatty liver is reversible if alcohol use is brought under control.
  • alcoholic hepatitis: The symptoms of this alcohol-induced liver inflammation are a swollen liver, abdominal pain, nausea, fever, jaundice, and vomiting. Although linked to alcohol use, even people who drink moderately can sometimes develop this condition, and not all alcohol abusers do. If a person stops drinking alcohol, the liver damage can be reversed. But if they continue, cirrhosis may develop and death can result.
  • cirrhosis: This serious and sometimes fatal form of ALD develops when liver cells die and form scar tissue, which blocks blood flow and causes wastes and toxins to build up in the system. Strictly speaking, cirrhosis cannot be cured. It can, however, be stopped with medical treatment and complications can be managed if the individual stops drinking, and many do survive. Not all cases of cirrhosis are strictly due to alcoholism, and not all alcoholics develop the disease. Symptoms of cirrhosis include the buildup of abdominal fluid (ascites), abdominal pain, fever, thirst, confusion, and fatigue.

Figure The Progression of ALD

Source: “Stages of Liver Damage” by National Digestive Diseases Information Clearinghouse/ Public Domain

As the liver cells release VLDL particles into circulation, this increases the levels of VLDL particles in blood. As VLDL particles continue to accumulate in blood, this cause a condition called hyperlipidemia. In their journey through circulation, VLDL particles are eventually degraded to low density lipoproteins (LDL) particles. LDL particles are also known as “bad cholesterol”. Higher levels of LDL particles in circulation lead to the build-up of cholesterol deposition plaques inside the walls of the blood vessels (known as atherosclerosis). These plaques can impair or stop blood flow to the cells. If an artery is blocked, the cells cannot make enough energy and eventually stop working. If the artery remains blocked for more than a few minutes, the cells may die. When a cardiac artery is blocked, this causes a heart attack (acute myocardial infarction). Depending on the length and severity of the blockage, damage to the cardiac cells may be permanent and irreversible. Once the heart structure and function is compromised, the more susceptible a patient would be to suffer a second heart attack.

Effects of Alcohol in Pregnancy

The more alcohol that is consumed during a pregnancy the greater risk there will be damage to the baby. There is no safe amount of alcohol that can be drank during pregnancy. There is also no safe type of alcohol that can be drank during pregnancy. The safest thing to do is not drink alcohol when you are pregnant or planning on becoming pregnant. Alcohol use during pregnancy can cause life long disabilities to the baby. Fetal alcohol syndrome is a term that describes a range of health and behavioural problems that affect babies whose mothers drank during pregnancy.[3] These problems include but are not limited to the following traits:

  • abnormal facial features
  • small head size
  • shorter than average height
  • low body weight
  • poor coordination
  • hyperactive behaviour
  • difficulty with attention
  • poor memory
  • learning disabilities
  • speech and language delays
  • poor reasoning and judgement
  • vision or hearing problems
  • problems with the heart, kidney or bones

Health Benefits of Moderate Alcohol Intake

In contrast to excessive alcohol intake, moderate alcohol intake has been shown to provide health benefits to some segments of the population. The data is most convincing for preventing heart disease in middle-aged and older people. A review of twenty-nine studies concluded that moderate alcohol intake reduces the risk of coronary heart disease by about 30 percent in comparison to those who do not consume alcohol.[4] Health Canada notes that alcohol raises cancer risk for many people, particularly those with elevated cancer risk (previous occurrence, family history, related conditions, etc).

Several studies demonstrate that moderate alcohol consumption reduces the incidences of stroke and heart attack, and also death caused by cardiovascular and heart disease. The drop in risk for these adverse events ranges between percent. Moreover, there is some scientific evidence that moderate alcohol intake reduces the risk for metabolic syndrome, Type 2 diabetes, and gallstones. In addition to providing some health benefits, moderate alcohol intake also serves as a digestive aid, a source of comfort and relaxation, and inducing social interactions, thereby benefiting all aspects of the health triangle. It has not been clearly demonstrated that moderate alcohol consumption benefits younger populations, and the risks of any alcohol consumption do not outweigh the benefits for pregnant women, those who are taking medications that interact with alcohol, and those who are unable to drink in moderation.

  1. Alcohol. Government of Canada. https://www.canada.ca/en/health-canada/services/health-concerns/alcohol-health-concerns.html. Accessed on Jun 17, 2014. Accessed on January 27, 2020.
  2. Canada's Low Risk Guidelines. CAMH.https://www.canada.ca/en/health-canada/services/health-concerns/alcohol-health-concerns.html. Updated in 2013. Accessed on January 27, 2020.
  3. Pregnancy and Alcohol Use. Health Link BC. https://tophat.com/marketplace/social-science/psychology/textbooks/oer-openstax-psychology-openstax-content/85/4057/. Updated December 2017. Accessed on February 3, 2020.
  4. Ronksley PE, et al. Association of Alcohol Consumption with Selected Cardiovascular Disease Outcomes: A Systematic Review and Meta-Analysis. BMJ. 2011; 342, d671. http://www.bmj.com/content/342/bmj.d671. Accessed October 5, 2017.


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Fundamentals of Health and Physical Activity by Kerri Z. Delaney and Leslie Barker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.