The Truth about Alcohol in the Body


Before I get into this article, let me first say that I am not anti-alcohol. I have said that my two favorite treats are dessert and wine and I’ve even provided proof. I am also very aware of the evidence that moderate alcohol consumption is healthy. (By the way, this article provides a really good perspective on why that “evidence” may not be as strong as we think it is.)

At the exact same time, I do not support alcohol consumption by those for whom doing so would be detrimental to their physical, mental and/or emotional well-being. This includes, but is not limited to, people who suffer from alcohol addiction and children. I also generally am not a fan of pregnant women drinking alcohol, since we do not know at what point the unborn child is affected (and we shouldn’t do any research to find out!).

With those two things being said, I know that many people (including myself) are capable of and enjoy drinking in moderation. Because of this, I want to tell you a little bit about what happens when we drink so that you can make an informed choice about whether to drink and, if you choose to do so, what you can do to help your body deal with it as effectively as possible.

One final, critical note before we jump in: The below is what happens for people who drink low or moderate amounts of alcohol. For people who consume large amounts of alcohol on a regular basis, the body invokes other metabolic pathways that have different outcomes and consequences. If you struggle with an addiction to alcohol, please, please, please contact a trained healthcare professional to help you heal your body.

The Absorption of Alcohol

Because alcohol is a small, water-soluble molecule, it is readily absorbed into the body through the stomach (~20%) and small intestine. Once in the body, it immediately distributes throughout all the water containing cells of the body (i.e., everywhere but bones and fat).

Anything that speeds how quickly alcohol gets out of the stomach and into the small intestine will increase the rate of absorption and, therefore, level of intoxication. The things that increase the speed at which alcohol reaches the small intestine include:

  • Drinking small amounts of alcohol speeds up gastric emptying
  • Drinking on an empty stomach (You may hear people say that eating protein helps slow alcohol absorption. This is because protein is the main macronutrient digested in the stomach, so it keeps all the contents in the stomach longer. Not to mention that alcohol “breaks” the enzyme responsible for protein digestion, which I’ll touch on again later.)
  • Mixing alcohol with soda or other bubble containing liquids
  • Higher alcohol by volume of liquid (It doesn’t take a rocket scientist to know you’ll get drunk faster drinking equivalent volumes of liquor versus beer due to the alcohol content.)
  • Drinking alcohol quickly (may be considered “chugging” depending on how quickly you drink it)
  • Stress (causes the contents of the stomach to dump more quickly into the small intestine)
  • Gastric bypass surgery

The Metabolism and Detoxification of Alcohol

Now, let’s look at the specific way the body detoxifies alcohol, rather than relying on the high level view of detoxification I’ve provided before.

Phase 1: There are three pathways that alcohol may go through for the first step in the detoxification process. These are listed in the order in which they are induced by the body, with #1 being by far the primary path of phase 1 detoxification and #3 rarely being induced.

  1. Alcohol dehydrogenase (ADH): an enzyme located in many cells including those lining the stomach and in the liver. Once this pathway is saturated and can’t handle any more alcohol or in the presence of chronic alcohol consumption, the second pathway is invoked…
  2. CYP2E1 (mostly) and CYP4A1: members of the cytochrome P-450 enzymes  located in the microsomes of liver cells, primarily; also called the microsomal ethanol oxidation system (MEOS)
  3. Catalse: an enzyme located in the peroxisomes of a cell

The output of phase 1 is acetaldehyde which is a more toxic substance to the body than alcohol itself!

The cofactors involved with these reactions are:

  1. NAD+, which becomes NADH and H+.
  2. NADPH, H+ and oxygen, which become NADP+ and water.
  3. Hydrogen peroxide, which becomes water.

You don’t need to know what NAD+, NADPH, etc., are, but I want you to vaguely remember that they exist as later I am going to explain why they matter.

Phase 2: Acetaldehyde then travels into the mitochondria where the enzyme aldehyde dehydrogenase (ALDH) transforms the toxin into acetic acid. In this reaction, as in the reaction with alcohol dehydrogenase, NAD+ becomes NADH and H+.

Alcohol metabolism

Elimination: Although some alcohol is eliminated through sweat, urine and the breath unchanged, the majority is converted to acetic acid (or acetate). The acetic acid may be released into the blood stream where it will be taken up by other cells, or it may remain in the mitochondira where it is turned into acetyl-CoA. Acetyl-CoA is then used to create the following:

  • Energy (Alcohol has 7 kcal / gram, but some research suggests these calories are wasted as body heat rather than being useful energy.)
  • Fatty acids
  • Ketone bodies
  • Cholesterol and other steroids

It is worth noting that the body will preferentially use acetate as the precursor to acetyl-CoA. This means that all the other substrates (glucose / carbs, amino acids / protein, and fatty acids… i.e., FOOD) which could become acetyl-CoA will be diverted to other processes, like fat creation and storage. This is why drinking often results in a few (or a lot of) extra pounds.

Now that I’ve explained the metabolism of alcohol, I feel a few other comments are worthwhile…

  1. Genetics plays a role in how effective a person’s ALDH is. For example, about 50% of people of Asian decent have a genetic variation that results in a very slow conversion of acetaldehyde (the really toxic intermediate) to acetic acid. The result is a build-up of acetaldehyde that can lead to flushing, rapid heart beat and hyperventilation.
  2. Women have less ADH and ALDH than men do. In one study, women had between 23 – 59% of the ADH capacity of the men. This is one of the reasons that women, in general, become more intoxicated than men when consuming the same amount of alcohol.
  3. Hormones affect how well detoxification pathways work. For example, one research study found that women tend to detoxify better during the second half of their menstrual cycle, apparently due to the higher progesterone to estrogen ratio.
  4. Other than the amount of ADH in the cells of the GI tract, our ability to detoxify doesn’t generally change how quickly we absorb alcohol or the associated blood alcohol content.

The Problems Caused by Alcohol and its Metabolites

No matter how much we drink, alcohol, acetaldehyde and acetic acid change how our bodies function. Obviously, the more we drink, the more severe the affect. But no matter the amount, our body has to repair any problems that are caused in order to keep us healthy.

And this is where things get interesting! Many of us know the terrible feelings that a hangover bring on – headache, nausea, tiredness, lethargy. But there isn’t a lot of research to explain why most of these things happen! Almost every book and research article that I found said we know that these symptoms occur, but we don’t really know why. The mechanism of action is suggested with words like “likely” and “possibly” included in the sentence. I guess researchers have decided that it’s not a good use of time or money to illicit the root cause of problems that are self-inflicted and unnecessary (unlike the side effects of, say, a life-saving medication).

That being said, there has been quite a lot of research around the cellular changes that occur with alcohol consumption. Here are the problems caused by alcohol for which research has found the cause:

  • Damage to the lining of the stomach and small intestine by depleting sulfhydryl compounds, which protect the tissue. This is especially true for high alcohol containing beverages like distilled liquor. Damage can lead to acute or chronic gastritis (inflammation of the stomach mucosa), peptic ulcers, and/or a leaky gut.
  • Exacerbation of dysbiosis by feeding the bad bacteria and encouraging bacterial overgrowth in the small intestine and stomach
  • Dehydration because alcohol has a diuretic effect that prevents water from being reabsorbed in the kidneys (which is why you urinate more when you are drinking)
  • Creation of free radicals by CYP2E1, CYP4A1 and aldehyde dehydrogenase which deplete the antioxidants (especially glutathione and vitamin E) in the cell and cause tissue damage
  • Diversion of glucose, amino acids and fatty acids away from becoming energy and into their storage form (i.e., fat)
  • Creation of excessive NADH which leads to metabolic disorders including
    • Fatty liver because more fat building blocks are generated, less fat is broken down by the liver, and the liver is triggered to pick-up more fats from the blood
    • Excessive lipids (i.e., fats) in the blood
    • Hypoglycemia (i.e., low blood sugar)
    • Excessive uric acid in the blood (which can lead to gout attacks)
  • Causes acid reflux / GERD / heartburn in some people by relaxing the lower esohageal sphincter, slowing the movements of the esophagus and (from some alcoholic drinks) triggering acid production. This seems to be especially true for low alcohol drinks such as beer and wine.
  • Increased use of nutrients like S-adenosylmethionine (SAMe), which is one of the precursors to glutathione and helps protect against liver injury (which can lead to cirrhosis) by contributing to the production of phosphatidylcholines
  • Depletion of oxygen in the cell by the MEOS which can lead to cell and tissue damage
  • Disruption of sleep and feeling of jet lag due to a disruption to the hormones and body temperature related to the normal sleep / wake cycle, not to mention that your body is working hard while you’re “sleeping” after drinking, so it’s not restful
  • Increase in lactic acid because phase 1 and 2 detoxification of alcohol uses NAD+ and oxygen, which are also needed for the aerobic creation of energy in the citric acid (TCA) cycle. Not only does creating lactic acid not require these cofactors, but it also turns NADH back into NAD+ which can be used for further alcohol detoxification, but also leads to acidosis (too much acid in the body).
  • Creation of adducts or bonds between acetaldehyde and proteins in the body (including hemoglobin in the red blood cells, albumin, gastrointestinal cells, collagen and certain enzymes)  which leads to:
    • Creation of antibodies (trying to clean up the damaged proteins)
    • Enzyme inactivation (because they don’t work when something is attached to them that shouldn’t be)
    • Decreased DNA repair
    • Increased collagen synthesis (i.e., fibrogenesis)
  • Accelerated or decelerated phase 1 detoxification of drugs / medications / chemicals which are also detoxified by the inducible MEOS pathway. These include multiple anesthetics, acetaminophen (i.e., Tylenol), chlorzoxazone (a muscle relaxer) and benzene (an air-based chemical in smoke from coal and air from gasoline). This is bad for several reasons:
    • If accelerated (which happens with heavier drinking so more of the enzyme is being produced to handle a higher volume of alcohol),
      • the person may not get the benefit of the medication.
      • The substances that come out of phase 1 detoxification may be more toxic than the original chemical and the phase 2 detoxification for that substance may not be able to handle the increased workload.
    • If decelerated (which happens with lighter drinking so the enzyme that is present is too busy with the alcohol to deal with anything else), the drug / medication / chemical may build up in the body and not be detoxified in a timely manner.

Here are the problems caused by alcohol which research has not found the exact cause (as far as I can tell):

  • Increased risk of cancer of the mouth, pharynx, larynx, esophagus, lungs, liver, breast, colon and rectum, possibly due to the direct damage caused by alcohol on the gastrointestinal tract, increased free radical production and/or decreased repair of cellular DNA. In fact, 2 – 3 drinks per day increases the risk of cancer in the mouth, pharynx, larynx and esophagus by 200 – 300%!
  • Headaches, may be due to the way alcohol dilates the blood vessels and/or changes the brain’s excitement and relaxation chemicals (i.e., neurotransmitters)
  • Deficiency of nutrients likely due to alcohol’s interference with absorption, transportation and/or use in the body, but may also be due to poorer dietary choices when drinking heavily. Altered levels of the following have been noted in drinkers:
    • Protein / amino acids
    • Folate
    • Thiamin
    • Vitamin B6
    • Vitamin B12
    • Vitamin C
    • Vitamin A (which in turn affects the absorption and use of zinc)
    • Vitamin D
    • Vitamin E
    • Vitamin K
    • Calcium (which may be a particular problem for women given our risk of losing bone density as we age)
    • Magnesium
    • Phosphorus
  • Slowed digestion due to seemingly multiple factors including reducing muscle control and contraction within the digestive system and breaking the enzymes in the stomach responsible for protein digestion. Note that this impact to the digestive system can lead to diarrhea, as the gastrointestinal tract will eventually “give up” on being able to digest and absorb the nutrients.
  • Increased blood pressure which can lead to or exacerbate hypertension, which seems counter-intuitive given that it is also a diuretic, but this is what the science shows. In fact, one study found that excessive alcohol consumption alone (as little as 3 drinks / day) is responsible for 5 – 7% of the population’s hypertension.
  • Inflammation of the pancreas (i.e., pancreatitis) possibly due to the creation of fibrous tissue in the pancreas and/or the activation of digestive enzymes while still housed within the pancreas. Alcohol-induced pancreatitis can lead to nausea, vomiting, abdominal pain, and/or malabsorption, maldigestion and diabetes (because the function of the pancreas is compromised). Note that the first acute attack may not show up for 5 – 10 years of overconsumption.
  • Disrupting the immune system by:
    • Increasing production of immunoglobulins (IgA, IgG and IgM) which leads to increased autoimmune activity,
    • Decreasing barrier (i.e., cilia and lung tissue) effectiveness in the lungs, and
    • Impairing the work of macrophages and neutrophils (two types of white blood cells) which slows recovery time from physical injury and infections.

Important Note about Functional Tolerance

All of the above is happening in our bodies when we choose to drink, whether or not we feel it. Or said another way, just because we can behaviorally “handle our alcohol”, doesn’t mean it’s not doing bad things to us. In fact, this functional tolerance (i.e., when a person doesn’t seem to be intoxicated despite the amount of alcohol consumed) doesn’t change the blood alcohol content and the associated consequences.


Oh goodness! That is a lot of information about all the negative ways that drinking impacts our bodies. In fact, that might feel like a total downer… which was not my intention at all. In fact, my intention was to basically tell you “it does some bad stuff, but here’s how you deal with that”. It wasn’t until I started writing and really researching that I realized everything alcohol does in the body. And, then, I felt like I’d be doing you a disservice to leave any effects out!

Now that that’s all on the table, go on to the next blog post in which I tell you what you can do to help your body handle alcohol better. That is, if you choose to keep drinking after reading the above! 😀


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