Alcohol has been a controversial topic for centuries. Although excessive drinking is clearly linked to risk of disease, accidents, and dependency, less evidence exists for moderate drinking. Indeed, some studies find that drinking small amounts of alcohol may actually provide some health benefits. This article discusses alcohol and explores its negative and positive health effects.
What Is Alcohol?
Alcohol, technically called ethanol, is produced by using yeast to ferment fruit, grain or sugar into a colorless liquid that interacts with your brain and nervous system. It's often consumed when dining out, at parties, or in other social settings because it tends to make people feel less inhibited, more talkative, and relaxed.
For centuries, cultures around the world have consumed alcohol in various forms. The earliest known alcoholic beverages on record were wines made in China from grapes and other fruits, honey, and rice about 9000 years ago (1).
Although today we think of alcohol as a beverage for socializing or celebrating, it was originally considered a health tonic and used in medicine. Hippocrates and other ancient Greek physicians prescribed it for their patients orally as a tranquilizer and pain reliever, as well as topically for disinfection and wound healing (2).
Different Types of Alcoholic Beverages
Alcoholic beverages can be separated into three basic categories: distilled beverages, wines, and beers.
Distilled Beverages (Liquor, Spirits, Hard Alcohol)
After the fermentation process, liquor and spirits are created by evaporating and condensing the liquid, resulting in loss of water and a higher alcohol concentration.
Distilled beverages contain about 40% alcohol by volume (ABV) on average, although they may contain anywhere from 30-90% ABV, depending on type. Because they have a much higher alcohol content than wine or beer, liquor is often referred to as “hard” alcohol.
Some common types of distilled beverages include:
- Brandy: 35-60% ABV
- Gin: 37-50% ABV
- Rum: 35-60% ABV
- Scotch: 40-64% ABV
- Tequila: 32-60% ABV
- Vodka: 35-95% ABV
- Whiskey: 40-68% ABV
- Liqueurs: 15-25% ABV (contain added flavors and sugars that reduce alcohol percentage)
Except for liquors and beverages with added sugar, there are no carbs in distilled beverages.
Wine is produced by fermenting black, red, purple, or green grapes to create a red, white or pink (blush or rosé) alcoholic beverage. Interestingly, white wine can be made from either red or green grapes because the grape skins are removed prior to fermentation, unlike red wine.
Most wine contains between 9-20% ABV:
- Table wine: 9-16% ABV
- Fortified wine (marsala, madeira port, sherry, vermouth): 16-22% ABV
- Sparkling wine (champagne): 8-12% ABV
The best low-carb options are dry red or white wine and sparkling wine (3-4 grams of net carbs per 5 fl oz/ 150 ml serving).
Beer is typically made by fermenting barley with water and hops (flowers of the plant that give beer its characteristic flavor). To create malt liquor, sugar, corn, or other carbohydrate sources are added, thereby increasing the alcohol concentration of the final product.
Beer's ABV content ranges from 3-10%:
- Pilsner: 3-6% ABV
- Ale: 4-7% ABV
- Lager: 4-5% ABV
- Light Beer: 4-5% ABV
- Stout: 5-10% ABV
In the US, labels also list an alcoholic beverage's “proof,” which is twice its alcohol content. For instance, most hard liquors are 40% alcohol, or 80 proof.
Most beer is not suitable for a low-carb diet. Also, apart from a few options, beware that beer contains gluten. The carb count in beer varies significantly between 2 grams of net carbs (ultra light, low-carb beer) and 26 grams of net carbs per (malt beer) per 8 fl oz (250 ml) serving.
How Is Alcohol Processed by the Body?
Alcohol is metabolized in two stages. At first, alcohol is metabolized in the liver. During the second stage, alcohol accumulates in the bloodstream and affects brain functions.
Stage 1 of Alcohol Metabolism
Unlike food, alcohol can be absorbed through the stomach as well as the small intestine. However, only about 20% of its absorption occurs in the stomach.
After alcohol is absorbed into the bloodstream, it goes directly to the liver. There it can be metabolized by a number of pathways. The most common one involves two primary enzymes: alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH).
First, ADH converts alcohol to acetaldehyde, a carcinogenic compound. In order to rid the body of this highly toxic substance, ALDH converts acetaldehyde into a safer compound called acetate, which enters the bloodstream and is used as needed or converted to carbon dioxide and water (3).
Although the pancreas, stomach and other organs also contain ADH and are capable of metabolizing alcohol, your liver is the main organ responsible for this function.
Stage 2 of Alcohol Metabolism
Most alcohol is metabolized by the liver and eliminated from the body during Stage 1. In fact, your liver contains enough ADH to metabolize all the alcohol in one drink within 1-2 hours. However, if you continue to drink, ADH is unable to handle the additional alcohol effectively. Therefore, alcohol begins to accumulate in the bloodstream, increasing your blood alcohol concentration.
Unlike many molecules, alcohol can cross from the blood into the brain very easily. Once inside, alcohol disrupts the function of neurotransmitters, chemical messengers that transmit messages throughout the nervous system. As a result, alcohol can impair alertness, coordination, judgment, memory, and other mental skills.
Factors Affecting Blood Alcohol Concentration (BAC)
Most people's blood alcohol concentration (BAC) reaches a peak within an hour of consuming alcohol, although how much and how quickly this occurs is influenced by a number of factors, including:
- The rate of drinking
- Whether drinking occurs on an empty stomach or with food
- The type of alcohol consumed
- Weight and body composition
What is Moderate Alcohol Consumption?
Although effects vary from person to person, there is some evidence suggesting that consuming alcohol in moderation is safe and may even provide health benefits for many of us.
But What is “Moderate” Drinking?
According to current US Dietary Guidelines, moderate alcohol consumption is a maximum of 1 drink per day for women and 2 drinks per day for men.
For reference, in the US a “standard drink” is defined as 14 grams of pure alcohol, or the amount found in the following serving sizes:
- 1.5 fluid ounces (44 ml) of hard liquor
- 5 fluid ounces (150 ml) of wine
- 12 ounces (350 ml) of regular beer
- 8-9 ounces (240-265 ml) of malt liquor
You may be wondering why men are allowed more alcohol than women are. The same amount of alcohol tends to have a greater effect on women than men, and not just because they generally weigh less. Women process alcohol differently because they have less ADH, the enzyme responsible for alcohol metabolism. In addition, they carry less body water than men, so alcohol becomes more concentrated in their blood.
Benefits of Moderate Alcohol Consumption
Alcohol May Protect Cardiovascular Health
Large observational studies suggest that moderate alcohol intake may reduce risk of heart attack and stroke (2, 4, 5).
In the Health Professionals Follow-Up study of more than 50,000 adult men, relative risk of coronary heart disease (CHD) was reduced significantly in those who consumed 5-30 grams of wine per day (4).
In another study of drinkers vs. nondrinkers from 52 different countries, men and women who drank 1-2 alcoholic drinks per day were 12% less likely to have a heart attack than those who didn't drink at all. However, heavy drinking – defined as consuming 6 or more drinks within a 24-hour period – increased heart attack risk by 60% (5).
Health Effects of Different Types of Alcohol
Red wine seems to provide the most benefits for heart health. This has been attributed to red wine's high content of polyphenols, antioxidants that help neutralize free radicals, unstable molecules that can damage cells and lead to inflammation.
In addition to large studies showing an association between moderate drinking and heart health, some controlled trials have found that wine lowers cholesterol and other CHD risk factors (6, 7). However, here results are mixed. One 12-month study found that although moderate intake of either red or white wine lowered LDL cholesterol equally, neither type reduced any other risk factors (7).
What's more, wine isn't the only type of alcoholic beverage that might be good for your heart when consumed in moderation. Beer contains its own beneficial polyphenols, and alcohol itself may provide some cardioprotective effects.
In one study, 33 men at high risk for heart disease drank 30 grams of alcohol as beer, gin, or a non-alcoholic beverage for 4 weeks each. Both gin and beer led to a reduction in inflammatory markers involved in heart disease, along with an increase in HDL (“good”) cholesterol levels. Additionally, the beer polyphenols were shown to lower other markers of inflammation (8).
Alcohol May Reduce Blood Sugar Levels and Improve Insulin Sensitivity
Once alcohol arrives at your liver, it is given the highest priority for metabolism. Therefore, other liver functions are often affected after drinking, such as its storage and release of glucose.
Although alcohol can raise or lower blood sugar depending on a number of factors, some studies in people with and without diabetes have found that moderate drinking tends to lower blood sugar (9, 10).
Additionally, consuming moderate amounts of alcohol may lead to a reduction in insulin levels and improved insulin sensitivity.
For instance, in a 6-week study, older women found who drank 250 ml of white wine daily experienced lower insulin levels, decreased insulin resistance, and higher levels of adiponectin, a protein that helps regulate body fat (11).
However, a person's response to alcohol is unpredictable. Some may see an increase or no change in blood sugar after drinking.
Most importantly, those who drink alcohol while taking insulin or certain oral diabetes medications are at increased risk for hypoglycemia, a condition in which blood sugar may drop to dangerously low levels. Therefore, if you take insulin or other diabetes medications, be sure to always consume alcohol with food to slow down its absorption, monitor your blood sugar carefully when drinking, and make adjustments to your treatment regimen as needed.
Negative Effects of Alcohol Consumption
Although drinking alcohol may provide some health benefits, it can also lead to health problems, especially when consumed too often or in large amounts.
Alcohol May Cause Liver Damage
As discussed earlier, your liver is responsible for metabolizing alcohol and eliminating its harmful byproducts from the body.
In heavy drinkers, the liver often becomes damaged as a result of processing large amounts of alcohol on a regular basis (12, 13).
Fatty liver is the first stage of alcoholic liver disease (as opposed to non-alcoholic fatty liver disease), in which liver cells accumulate more fat. Continued drinking causes increased inflammation, followed by replacement of healthy liver cells with scar tissue, known as cirrhosis. Eventually, complete liver failure may occur, making a liver transplant the only option for survival.
In a 2015 observational study of more than 55,000 adults, people who consumed alcohol on a daily basis were more than 3 times as likely to develop cirrhosis as those who drank on 4 or fewer days per week. Additionally, people who drank alcohol frequently after age 40 tended to develop cirrhosis more than those whose drinking occurred mostly in their younger years (14).
Although it's clear that chronic excessive alcohol consumption can gradually lead to liver failure, emerging evidence suggests that regularly engaging in “binge drinking”—in which 5 or more drinks are consumed within 3 hours—may also cause severe liver damage within a much shorter period of time (15).
Alcohol May Lead to Weight Gain, Especially Around the Middle
Similar to its other effects, alcohol's impact on weight varies among individuals.
However, some experimental studies have shown that alcohol suppresses fat burning (16). In addition, observational research suggests that excess calories from alcohol seem to be stored mainly as abdominal or visceral fat, the type linked to diabetes, heart disease, and other metabolic conditions (17, 18).
In a study of more than 8,600 Korean adults, those who consumed 3 or more drinks per day were 80% more likely to have excess belly fat than those who drank less alcohol (18).
Overall, research suggests that consuming a lot of alcohol within a 24-hour period is most strongly linked to putting on weight around the middle, even if the drinking only occurs a couple of times a week.
For instance, in another study, those who drank daily but had less than 1 drink per day were likely to have the least abdominal fat, whereas those who drank less frequently but consumed 4 or more drinks on the days they drank tended to have the most belly fat (19).
Pure alcohol provides 7 calories per gram, and depending on the type, a plain drink may contain between 100-150 calories, and many mixed drinks provide considerably more.
Moreover, in addition to providing empty liquid calories, alcohol often looses inhibitions, leading to overeating and making less healthy food choices – both which can ultimately contribute to weight gain.
Alcohol Increases Risk of Certain Cancers
Frequent alcohol consumption has been shown to increase risk of certain cancers, including colon, pancreatic, oral, esophageal, liver, and breast cancer (20, 21, 22, 23, 24). This is especially true for heavy drinkers.
In a 2011 review, researchers concluded that individuals who regularly consume 4 or more alcoholic beverages per day are at 5 times greater risk for developing oral and esophageal cancers than less frequent drinkers. What's more, they found that even a daily drink appeared to raise the risk of these cancers by 20-30% (23).
A more recent 2016 systematic review of 15 large studies exploring the association of alcohol and breast cancer found that even light to moderate alcohol intake seemed to increase breast cancer risk somewhat and that the risk increased significantly in women who drank the most (24).
Although it's good to raise awareness about alcohol's link to some cancers, it's important to understand that a combination of factors play a role in the development of the disease.
For instance, a recent article in The Telegraph entitled “Drinking alcohol raises risk of cancer by snapping DNA, scientists find” went viral. However, although the recent mouse study in question found that alcohol may damage DNA in a way that increases cancer risk (25), a person's genes, ethnicity, and the frequency and amount of alcohol they consume must also be taken into account. For instance, for individuals with genetic mutations in ALDH (the enzyme that converts acetaldehyde into acetate) or other enzymes involved in alcohol metabolism, drinking may significantly increase cancer risk.
It's easy to become confused by media headlines. However, research has consistently shown that the relationship between alcohol and cancer is dose-dependent, meaning the more you drink, the greater your risk of developing the disease. Most people who limit alcohol to a maximum of 1-2 drinks per day do not develop oral, esophageal, breast, or other cancers.
Negative Impact of Alcohol on Gut Health and Inflammation
A somewhat less well-known effect of heavy drinking is altered GI function.
Excessive alcohol consumption may lead to the condition known as "leaky gut.” Normally, the colon walls serve as a barrier that prevents potentially toxic bacteria from entering the general circulation. In leaky gut, the colon can no longer adequately prevent these bacteria from moving out of the colon and into the bloodstream (26).
Alcohol has been shown to increase the amount of lipopolysaccharides (LPS) that enter the general circulation from the colon. LPS makes up part of the outer membrane of certain gut bacteria. It's considered an “endotoxin” because it is released after destruction of the bacterial cell wall.
Although LPS is crucial for helping maintain bacterial balance in the gut, it can cause problems if it enters the general circulation. In healthy people, the body is able to keep LPS at manageable levels. However, in people with compromised liver and gut function related to excessive drinking, higher LPS levels promote widespread inflammation leading to organ damage and disease (27).
Alcohol Consumption May Lead to Dependency
Not everyone who drinks frequently develops alcoholism. However, many people who drink a lot may not realize that they are indeed dependent on alcohol. A 2007 analysis of over 43,000 people in the US found that 12% had experienced alcohol dependence within the past 12 months (28).
Alcohol dependence is another term for alcoholism, which is defined as the physical and/or psychological addiction to alcohol. It involves strong cravings for alcohol and an inability to stop drinking.
Research has shown that genes play a large role in the development of alcohol dependency, and that in susceptible individuals, repeated alcohol exposure may “turn on” the genes involved in addiction (29).
For an alcohol-dependent person, moderate consumption isn't possible; strict abstinence from all types of alcohol is required.
The National Council on Alcoholism and Drug Dependence offers a self-test to explore whether your own drinking habits might suggest alcohol dependency.
Should I Drink Alcohol?
Although experts disagree about the optimal amount of alcohol that healthy people should consume, there are some individuals who should avoid it altogether:
- Women who are pregnant or trying to conceive
- People who have had weight-loss surgery, such as gastric bypass or sleeve gastrectomy
- People with alcoholic liver disease
- Alcoholics and recovering alcoholics
- People taking certain medications that interact with alcohol
Be sure to discuss the topic of alcohol and any health condition or medications you take with your doctor to see whether moderate drinking is safe for you.
Take Home Message
How much or how often to drink alcoholic beverages—if at all—is a personal choice.
There seem to be some benefits to moderate drinking, including protecting heart health and promoting feelings of sociability, relaxation, and well-being. For some people, having a glass or two of wine with dinner or after-dinner drinks with friends seems to improve their overall quality of life.
On the other hand, alcohol affects people differently and may increase the risk of certain diseases, especially when consumed too frequently and in large amounts.
Overall, if you consume alcohol in moderate amounts, practice safe drinking and driving behavior, and don't become dependent on it, drinking can be part of your life.
However, alcohol certainly isn't essential for optimal health. If you don't drink, there isn't any reason to start. You should avoid drinking alcohol if you are trying to lose weight.
In my next article about alcohol, I'll discuss how alcohol affects ketosis and make recommendations for those who want to safely include alcohol in their keto or low-carb lifestyle.
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