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.

Updated Guidelines for Alcohol Use are based on Scientific Research and Canadians’ Right to Know

According to a comprehensive 2023 report from the Canadian Centre for Substance Use and Addiction, research on the effects of alcohol reveals several trends since 2011 when Canada’s now-outdated guidelines for low-risk drinking were published:

  • a significant proportion of Canadians who had been following the 2011 alcohol guidelines experienced deaths attributable to alcohol
  • research shows that alcohol use is increasingly associated with elevated risk of more diseases
  • all recent alcohol recommendations from other countries fell below Canada’s 2011 guidelines

The resulting review of research and evidence revealed greater than anticipated risks to health and well-being linked to even very small amounts of alcohol. These facts and recommendations are described in Canada’s Guidance on Alcohol and Health, a January 2023 full report of scientific findings and their relevance to various groups within the Canadian population. Some key topics include more steeply increasing health risks for females compared to males; far more injuries, violence, and deaths related to men’s alcohol use; greater adverse outcomes from alcohol use by youth compared to adults; how intersections of sex, gender, social and other factors affect alcohol use and harms; stakeholders’ perceptions about effective communication of health recommendations related to updated research.

The purpose of the 2023 CCSA report is to provide evidence that accurately informs the decision-making of Canadians about their own choices regarding alcohol use. Alcohol is a leading preventable cause of death, disability, and social problems, including certain cancers, cardiovascular disease, liver disease, unintentional injuries, and violence. Public health guidance is intended to promote awareness and autonomy in harm reduction and is aimed at the unique concerns of people with diverse backgrounds and personal experiences. Improving alcohol literacy can affect Canada’s drinking culture and better manage the normalization of harmful alcohol use in society.

Health Canada’s Centre for Substance Use and Addiction offers an infographic to summarize recommendations for Alcohol Use and several updated resources.


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.

All alcohol intake increases health risk, and depending on how much you drink there can be chronic or acute consequences. Chronic conditions include liver disease, cancer, diabetes, etc. whereas examples of acute consequences include alcohol poisoning, assaults, and accidents.

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.

Increasing blood alcohol content (BAC) comes with increases in physical and mental impairments such as:.

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.

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

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. Considering 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 return to physiological sobriety.

Ethanol Consumption

Distilled spirits have exceptionally few nutrients while beer and wine provide minimal 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. Urination increases with the amount of alcohol consumed leading to dehydration that affects all cells in your body including your brain cells. This is the cause of the so-called “morning hangover”. Do not take acetaminophen (Tylenol) for hangover symptoms. 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, manage uncomfortable symptoms by drinking 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 breath. Breathalyzer tests measure the exhaled alcohol levels in the lungs to determine the state of inebriation.

Some Health Effects of Alcohol Use

Metabolic Effects 

Alcoholic drinks in excess can contribute to weight gain by substantially increasing caloric intake. Excessive alcohol intake reduces the secretion of pancreatic juices 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 gaunt appearance and multiple associated micronutrient deficiencies that include thiamine, pyridoxine, folate, vitamin A, magnesium, calcium, zinc, and more. In addition, alcoholics typically replace calories from nutritious foods with alcohol, sometimes receiving 50 percent or more of their daily caloric intake from alcoholic beverages.

Effects of Dehydration 

The most common macronutrient deficiency among alcoholics is water, which is excreted in excess. Alcohol is a diuretic that results in dehydration by suppressing the release of antidiuretic hormone causing less water to be reabsorbed and more water to be 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 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. In extreme cases death may follow.

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 by-products destroy brain cells.

Alcohol can damage Liver Function

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 with cirrhosis due to excessive consumption of alcohol. Source: “Cirrosi Micronodular” by Amanda Alvarez [<- Click link if image does not appear]/ 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: Initially a benign disorder that develops after excessive alcohol consumption but can progress to more serious and fatal disease. 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, fever, abdominal pain, nausea, jaundice, and vomiting. Although linked to alcohol use, not all alcohol abusers develop this condition yet people who drink moderately sometimes do. If a person stops drinking alcohol liver damage can be reversed but cirrhosis may develop if drinking continues; 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. Cirrhosis cannot be cured but can be stopped with medical treatment that manages complications and improve survival if the individual stops drinking. 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 liver cells release VLDL particles into the circulation, levels of VLDL particles in blood increase and their accumulation in the blood causes a condition called hyperlipidemia. In their journey through circulation, VLDL particles are eventually degraded to low density lipoproteins (LDL) particles 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 (a type of heart disease called 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, the heart cells cannot work causing 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 heart is more susceptible to a second heart attack.

Alcohol increases Cancer Risk

Cancer is the leading cause of death in Canada and alcohol is a carcinogen that can cause at least seven types of cancer with most cases being breast or colon cancer, followed by cancers of the rectum, mouth and throat, liver, esophagus, and larynx. According to the Canadian Cancer Society, drinking less alcohol is among the top 10 behaviours to reduce cancer risk.

Alcohol increases Risk of Heart Disease

After cancer, heart disease is the second leading cause of death in Canada. For many years, the idea that drinking in moderation offered some protection against coronary artery disease was widely publicized but is no longer supported by scientific research.

Newer research and the highest quality systematic reviews show that drinking a little alcohol neither decreases nor increases the risk of artery-narrowing ischemic heart disease, but proves that alcohol is a risk factor for most other types of cardiovascular disease, including, hypertension, heart failure, high blood pressure, atrial fibrillation, and hemorrhagic stroke.

Alcohol increases Exposure to Violence

Alcohol is frequently associated with violent and aggressive behaviour, including intimate partner violence, male-to-female sexual violence, and aggression and violence between adults. Alcohol can also increase the severity of violent incidents. Consistent evidence indicates that avoiding drinking to intoxication will reduce individuals’ risk of perpetrating alcohol-related violence.

Alcohol causes Fetal Damage and Pregnancy Risks

There is no safe amount or type of alcohol that can be consumed during pregnancy. Any alcohol intake causes risk of damage to the unborn baby and the more alcohol consumed during a pregnancy the greater that risk including increases in miscarriage, hypertensive disorders of pregnancy, and placental abnormalities.

Alcohol consumption can also negatively impact breastfeeding by decreasing milk production, causing early cessation of breastfeeding, and negatively affecting infant sleep patterns.

The safest choice is not to drink alcohol when you are pregnant or planning on becoming pregnant.

Alcohol use during pregnancy can cause lifelong disabilities to the baby. The various negative effects of alcohol are classified according to a spectrum of fetal alcohol disorders and can result from alcohol consumption on a single occasion. Fetal alcohol syndrome is a term that describes a specific range of health and behavioural problems that affect babies whose mothers drank during pregnancy [1] These debilitating 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

Alcohol Offers No Health Benefits

In contrast to previous assumptions based on outdated studies, Canada’s Guidance on Alcohol and Health 2023 provides more recent research about increased health risk associated with the effects of alcohol and confirms that consuming alcohol provides no health benefits to any group within the Canadian population.

  1. 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.


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