Only approximately 10 to 15% of alcohol dependent drinkers develop liver cirrhosis and, of those, only 10% develop liver cancer (Hall 1995). Similarly, not all heavy drinkers develop cancer and some light-to-moderate drinkers develop cancer. This suggests that an individual’s genetic predisposition influences their risk of developing cancer and it has also been suggested for colorectal cancers; such that there is a stronger relationship between alcohol consumption and colorectal cancers among individuals with a family history of colorectal cancer (Cao et al. 2015).

Alcohol is absorbed into the blood from the gastrointestinal tract by passive diffusion. On consumption, a small amount of alcohol is absorbed in the mouth and stomach, but most of the absorption takes place in the small intestine. Usually, 30–45 minutes after consumption, the absorption of alcohol is at its maximum. The blood alcohol concentration (BAC) reached depends on several factors:

• the amount consumed,
• the rate at which the amount is consumed,
• gender,
• body mass,
• recent food intake and
• type of alcoholic beverage consumed.

The BAC reaches higher levels when both larger volumes of alcoholic beverages or higher alcohol percentage (ABV) are consumed. Alcohol is distributed from the blood into all tissues and fluids throughout the body in proportion to their relative content of water.

When drinking the same quantity of alcohol, women usually reach a higher BAC level than men, mostly because of their overall lower percentage of body water and higher percentage of body fat, and average lower body weight compared to men. Similarly, lean body mass and total body water is reduced in elderly individuals compared to younger individuals, leading to a relatively higher BAC[1].

Another important factor in predicting a person’s BAC level is recent food intake. The same amount of alcohol can produce a BAC as much as 50% lower in a person who has recently eaten compared with a person who is drinking on an empty stomach.  The balance between the absorption and breakdown of alcohol determines how the BAC changes over time. Most of the alcohol is metabolised for elimination by the liver. As described earlier, alcohol elimination is typically driven by specific alcohol-metabolising enzymes: alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH).  This enzyme system, however, becomes saturated at relatively low concentrations of alcohol.

Therefore, during periods of heavy and binge drinking, the liver’s microsomal ethanol oxidizing system (MEOS), an alternative pathway of alcohol metabolism, gets involved and breaks down the excess ingested ethanol to help clear the ethanol faster from the body. During this process, however, free radicals (very reactive oxygen molecules) are created which can damage the cells of the liver (Cederbaum 2012). 

[1] BAC = Blood alcohol concentration

Alzheimer’s disease (AD) is a form of dementia. AD and other types of dementia are most common in the elderly. 

Another meta-analysis was carried out in an attempt to quantify the effect of moderate consumption of alcoholic beverages on overall cancer incidence in the Western world (Hendriks 2018). The authors wanted to estimate the overall cancer risk of the most common cancer types among men and women at light and moderate levels of alcohol consumption. The following was found:

• At light to moderate levels (up to 14.5 g alcohol/day), the overall effect of alcohol consumption on the risk of acquiring cancer was slightly lower in both men and women compared to non-drinkers (abstainers).
• At higher drinking categories (up to 60 g alcohol/day), the relative risk was slightly higher (5% for men and 10% for women) compared to non-drinking.
• The overall cancer risk only increased substantially when drinking 60 g or more alcohol/day.
• A gender difference in cancer risk was observed for a given amount of alcohol such that an increase in risk was observed at 22 g/day for women but at 46 g/day for men.
• Overall, the authors found that the light to moderate consumption of alcoholic beverages was not associated with a higher incidence of the 20 most common cancer types in the Western world in contrast to higher consumption.

Based on their results, Hendriks et al (2018) concluded that moderate drinking had no substantial impact on overall cancer risk. Moderate consumption of alcoholic beverages as such may therefore be considered as a less important lifestyle factor for affecting the overall cancer risk compared to other lifestyle factors, such as smoking and obesity. In contrast, heavy consumption, both regular and binge drinking of more than 60 g alcohol/day, is associated with an increased incidence for most types of cancer investigated in this present meta-analysis.

Proteins that bind lipids, such as cholesterol and fat, to form lipoproteins and transport lipids through blood and lymph.

a type of cell death in which a series of molecular steps in a cell lead to its death. This is one method the body uses to get rid of unneeded or abnormal cells. Apoptosis plays a crucial role in developing and maintaining the health of the body by eliminating old cells, unnecessary cells, and unhealthy cells. The human body replaces perhaps one million cells per second. Too little or too much apoptosis can play a role in many diseases. The process of apoptosis may be blocked in cancer cells. When apoptosis does not work correctly, cells that should be eliminated may persist and become immortal, for example, in cancer. When apoptosis works too well, it kills too many cells and inflicts severe tissue damage. This is the case in strokes and neurodegenerative disorders such as Alzheimer's, Huntington's, and Parkinson's diseases. Also known as programmed cell death.

cause weight loss by restricting the amount of food the stomach can hold, causing malabsorption of nutrients, or by a combination of both gastric restriction and malabsorption.

is defined as consuming 5 drinks or more in a row for men (> 4 drinks for women) per occasion within the past 2 weeks or 30 days

Binge drinking (consuming rapidly four or more alcoholic drinks over a short period of time) has been found to have a particularly negative impact on health (Roerecke et al 2014, Chen et al 2011). This pattern of consumption results in a rapid and relatively sustained increase in the alcohol concentration circulating throughout the body and brain (Wechsler et al 1998). Such a high blood alcohol concentration (BAC) can impact on metabolic processes in response to alcohol drinking such as the development of free radicals implicated in certain cancers (Brooks et al 2017). In these circumstances, the elimination of alcohol from the body via the enzymes ADH and ALDH may not be sufficiently effective (Seitz et al 2007) and a high BAC continues to circulate until it triggers the MEOS system to switch on, thereby increasing the capacity of the liver to eliminate the alcohol from the body.

Thus, there is no doubt that binge drinkers have a high risk to develop cancer.

The CASCADE study (CArdiovaSCulAr Diabetes & Ethanol) is the first randomized wine study with a focus on diabetes. 224 abstainers with type 2 diabetes were randomly assigned to consume 1 glass (150 ml) of red wine, white wine or water for 2 years, on top of a Mediterranean diet that was not restricted in terms of calories.

a study comparing two groups: one with and the other without a certain disease, however with similar characteristics. The aim is to try identifying the factors leading to the disease.

is a global independent network of health practitioners, researchers, patient advocates and others, responding to the challenge of making the vast amounts of evidence generated through research useful for informing decisions about health. It is a not-for-profit organisation with collaborators from over 120 countries working together to produce credible, accessible health information that is free from commercial sponsorship and other conflicts of interest.

A comprehensive review of more than 7,000 peer-reviewed papers on the association of lifestyle factors and cancer undertaken by the World Cancer Research Fund in cooperation with the American Institute for Cancer Research (2007), reported that there are also alcohol threshold effects for colorectal cancer (CRC), the third most commonly diagnosed cancer worldwide (Bray et al 2018). Indeed, an increased risk for colorectal cancer is only apparent above a threshold of 30 g alcohol/day for both men and women (Cai et al 2014). In addition, a large meta-analysis of 16 studies observed a J-shaped dose-response relationship such that moderate alcohol consumption (1-2 alcoholic beverages/day) was associated with a reduced CRC risk compared to abstinence; consistent with other studies, risk of CRC increased with consumption of three or more drinks per day (McNabb et al 2020).

Confounding factors is a possible source of bias interfering with the variable that you would like to examine, i.e. age, what people eat, if they smoke, etc.

the defining feature of a cross-sectional study is that it can compare different population groups at a single point in time (see also longitudinal study).