There are several factors that influence how easily someone gets drunk including body size, biological sex, age, ethnicity, medications, health conditions, and genetics. Some people seem to get drunk very quickly after just one or two drinks, while others can consume far more alcohol before feeling impaired. Understanding what causes these differences can help explain why intoxication levels vary so much between individuals.
Body Size
One of the most important factors is body size. Someone who is larger and has more body mass will not feel the effects of alcohol as quickly as someone smaller. This is because alcohol is diluted in the body’s total water volume. For example, if a 150 pound woman drank the same amount as a 200 pound man, the alcohol would be more concentrated in the smaller woman. The man’s body size helped dilute the alcohol.
Larger people have more fluid in their bodies to help dilute the alcohol. Men also tend to have less body fat and more muscle mass than women of the same weight, which also helps reduce the effects. Muscle tissue has a high water content that dilutes the alcohol. Meanwhile, body fat cannot absorb alcohol so it remains at higher concentrations in the bloodstream of someone with higher body fat.
| Body Size | Impact on Alcohol Absorption |
|---|---|
| Smaller | More affected by alcohol |
| Larger | Less affected by alcohol |
Biological Sex
Biological sex differences also help explain why women tend to feel impaired faster than men of the same weight after drinking equivalent amounts of alcohol. Women’s bodies generally contain less water than men. Females also metabolize alcohol differently because they have lower levels of enzymes in the stomach and liver that break down alcohol before it enters the bloodstream.
Women produce smaller quantities of the enzyme alcohol dehydrogenase (ADH) in the stomach, allowing more alcohol to reach the bloodstream rather than being eliminated. The smaller quantities of ADH, as well as lower levels of the enzyme aldehyde dehydrogenase (ALDH) in the liver, cause higher blood alcohol concentrations in females compared to males after consuming the same number of drinks.
| Sex | Impact on Alcohol Absorption |
|---|---|
| Female | More affected by alcohol |
| Male | Less affected by alcohol |
Age
Younger individuals are generally more affected by alcohol than older people. Someone in their 20s likely has less tolerance than someone in their 40s or 50s. As we age, our bodies change in many ways that allow us to absorb alcohol more efficiently.
Older individuals tend to have more body water to help dilute alcohol with less going to fatty tissues. The activities of alcohol metabolizing enzymes also increase with age, allowing more rapid elimination before alcohol reaches the bloodstream.
Another factor is that young people tend to binge drink at faster rates, spiking blood alcohol concentrations to higher levels that take longer to be eliminated. Older adults tend to drink more slowly, allowing more time for alcohol metabolism and excretion.
| Age | Impact on Alcohol Absorption |
|---|---|
| Younger | More affected by alcohol |
| Older | Less affected by alcohol |
Ethnicity
Genetic differences between ethnic groups also seem to affect alcohol tolerance levels. Research shows that people of East Asian heritage tend to feel the effects of alcohol more quickly.
Up to half of individuals of East Asian descent have an inherited mutation in their aldehyde dehydrogenase 2 (ALDH2) gene that makes this enzyme almost inactive. With very low ALDH2 activity, acetaldehyde builds up in the body after drinking instead of being converted into acetate. This causes a flushed face along with heart palpitations, nausea, and other unpleasant reactions.
Higher acetaldehyde levels contribute to what is known as “alcohol flush reaction” or “Asian glow” in these individuals, serving as an indicator they cannot metabolize alcohol normally. The inactive ALDH2 enzyme greatly reduces alcohol tolerance.
Medications
Many prescription and over-the-counter medications can interfere with the body’s ability to metabolize alcohol efficiently. As a result, standard amounts of alcohol hit the bloodstream faster and effects are felt sooner.
Some examples of medications that may reduce tolerance include:
- Antibiotics – erythromycin, metronidazole, tinidazole
- Antidepressants – paroxetine, fluoxetine
- Blood pressure medications – propranolol
- Pain relievers – aspirin, ibuprofen
- Sedatives – diazepam, lorazepam
The sedative effects of these medications get compounded by alcohol, causing increased drowsiness, dizziness, and loss of coordination. Antihistamines like diphenhydramine also have similar interactions with alcohol.
Health Conditions
Certain medical conditions affect alcohol absorption and increase sensitivity to its effects. For example, liver diseases like hepatitis and cirrhosis impair the liver’s ability to metabolize alcohol, leading to higher blood alcohol concentrations.
Individuals with diabetes also have low tolerance because alcohol further disrupts glucose metabolism on top of insulin problems. Alcohol spikes blood sugar initially by releasing stored glucose from the liver followed by a plunge in blood sugar later as the liver becomes occupied metabolizing alcohol.
People with hyperthyroidism have increased metabolism that speeds up alcohol breakdown into acetaldehyde, quickly producing unpleasant symptoms like rapid heart rate and facial flushing.
Genetic Factors
Underlying genetic differences help explain why some people seem to get drunk much faster than others despite similar alcohol intake, weight, age, and sex characteristics. Researchers have identified multiple genes involved in alcohol metabolism that occur in variant forms in different people.
For example, variation in ADH and ALDH genes that regulate key enzymes for alcohol metabolism has a major effect on rates of alcohol breakdown and clearance from the body. Someone with gene types causing low ADH/ALDH activity will show greater impairment from alcohol.
Body water content is also influenced by genetics, contributing to either lower or higher dilutional effects. In addition, genetics around brain receptors that bind alcohol and transmit its effects can differ between individuals. All of these gene-based factors can predispose someone towards lower alcohol tolerance.
Food Effects
Consuming alcohol after eating a meal slows down absorption compared to drinking on an empty stomach. Food helps close pyloric sphincter to delay alcohol passing from the stomach into intestines. High protein foods like meats are especially effective.
Fatty foods can also help slow absorption of alcohol, while carbohydrates have little effect in this regard. People drinking on an empty stomach are likely to have less tolerance and feel effects sooner as absorption into the bloodstream occurs more rapidly.
| Stomach Contents | Impact on Alcohol Absorption |
|---|---|
| Empty | Faster absorption, lower tolerance |
| After meal, especially high protein | Slower absorption, higher tolerance |
Habitual Drinking
Regular heavy drinking leads to physiological changes that increase alcohol tolerance. The liver boosts production of metabolizing enzymes like ADH, allowing faster breakdown before alcohol reaches the bloodstream. Transporter proteins also increase that move alcohol into liver cells at higher rates for detoxification.
Chronic alcohol exposure causes liver cells to proliferate more rapidly, increasing the liver’s mass and ability to filter alcohol. Brain cells may also change by reducing reception of chemical signals from alcohol.
Due to these adaptations, habitual heavy drinkers can consume what seem like very high amounts of alcohol compared to occasional drinkers before showing signs of intoxication. However, this increased tolerance does not always indicate less damage is occurring in the body.
Pace of Drinking
Drinking alcohol quickly produces higher blood concentrations than sipping drinks slowly over time. Downing multiple shots or cocktails back-to-back is riskier than gradual consumption. Rapid binge drinking often outpaces the liver’s capacity to break down alcohol as it enters the system.
When alcohol builds up faster than it can be metabolized, impairment occurs more quickly. Even someone genetically predisposed towards high alcohol tolerance will feel effects sooner if they drink at a fast pace without breaks.
| Drinking Pace | Impact on Alcohol Absorption |
|---|---|
| Fast guzzling | Faster absorption, lower tolerance |
| Slow sipping | Slower absorption, higher tolerance |
Conclusion
Many complex factors interact to determine alcohol tolerance between individuals and drinking episodes. However, some key influences include body weight, sex, age, ethnicity, genetics, health status, medications, food intake, drinking habits over time, and pace of alcohol consumption.
Understanding causes of variation can help guide safer drinking practices. Those predisposed towards low tolerance can reduce their intake accordingly and avoid risky behaviors like rapid drinking on an empty stomach. However, there are no guaranteed safe levels, and alcohol always carries health risks that increase with the amount consumed.