The effects of moderate, regular drinking on a person’s health vary from one individual to the next.

Different people respond very differently to alcohol, which means it is impossible to make recommendations that apply across the board to an entire population. Genetic history, age, weight, sex (differences in biology cause men and women to metabolize alcohol differently) and circumstances are all important factors that every one of us must take into account.

Genetics[1]

Some genes – located in specific areas of the chromosomes – play an important role in determining how much alcohol it takes for a person to feel the effects. Recent studies show that as much as 50% of the risk of alcohol dependence is determined by genetic factors.

Slow response to alcohol. People who need a large quantity of alcohol in order to feel the effects are at greater risk of developing dependence. Men and women who tend not to feel drunk should therefore pay closer attention and refrain from unlimited drinking.

Quick response to alcohol. Some people have to be careful for the opposite reason. These are the drinkers who feel drunk and lose control over their bodies sooner than the average person.

It is not uncommon for such people to have a family member with a serious drinking problem.

Like those who are slow to respond to alcohol, people who are quick to respond must be more careful than the average drinker. They should drink less than the amount recommended by Health Canada in order to avoid social gaffes and accidents.

Weight

The recommendations proposed by Health Canada are for men and women of average weight and height. But we know that blood alcohol level is basically the amount of alcohol you absorb divided by the amount of water present in your body. Thus, the less water you have in your body, the higher your blood alcohol level will be.

Low body weight. A warning for those whose weight is below average, as their bodies will also have lower-than-average water content. For equal amounts of alcohol consumed, people of below average weight will have a higher concentration of alcohol in their blood stream. As a result, they should be vigilant and observe low-risk drinking guidelines that are more restrictive than those issued by Health Canada.

High body fat. The same warning applies if you have a higher-than-average body fat percentage. Given two people who weigh the same, where one is well muscled and the other is overweight with a high body fat percentage, the one with the high body fat will feel the effects of alcohol more than the one with all the muscle. That’s because fatty tissue does not contain much water.

Age[2]

Young adults. Teenagers can’t handle alcohol as well as adults. They often weigh less and have less water in their bodies to dilute the alcohol. Also, compared to adults, young people have fewer of the enzymes that help the liver eliminate alcohol.

Furthermore, the adolescent brain is more vulnerable to damage by alcohol. Recent studies in neuroscience and child psychiatry show that the brain is not really fully developed until the age of 25. Teens are therefore at greater risk when they drink because alcohol inhibits the development of some parts of the brain.

Older people. As people age, their kidneys, liver, cardiovascular system and brain undergo changes. Some of these changes make the elimination of alcohol less efficient, while others make people more sensitive to the effects of alcohol.

Older people tend to have a higher body fat percentage than younger adults and less water in their bodies. An older person will therefore have a higher blood alcohol level than a younger person who drinks the same amount.

Also, because of their increased physiological vulnerability and the fact that many of them take prescription drugs, some older people should drink less than the low-risk guidelines proposed by Health Canada for the general adult population.

You should not drink if: 

  • you are taking medication that interacts with alcohol;
  • you are taking legal or illegal drugs;
  • you have mental or physical health problems;
  • you have an alcohol dependence problem;
  • you are engaged in dangerous physical activity;
  • you are pregnant or trying to get pregnant.

Drinking is not recommended if: 

  • you are stressed, tired or hungry (alcohol is absorbed more quickly by the blood when you drink on an empty stomach);
  • you have important decisions to make;
  • you are operating a motor vehicle, or any kind of mechanical or electrical machinery or equipment;
  • you are responsible for the safety of others.

[1] Verhulst, B., Neale, M. C., & Kendler, K. S. (2015). The heritability of alcohol use disorders : A meta-analysis of twin and adoption studies. Psychological Medicine45(5), 1061‑1072. https://doi.org/10.1017/S0033291714002165

[2] https://www.educalcool.qc.ca/wp-content/uploads/2022/09/THE_EFFECTS_OF_EARLY_ALCOHOL_USE_2023.pdf