Ever wondered what happens when you drink alcohol?

Having a glass of wine is good for your health; alcohol is toxic to the body and is a serious health risk.

We hear these conflicting messages all the time. Which is true? Is the alcohol in wine different from the alcohol that is toxic to the body?

The answer to the latter is ‘no’. The alcohol found in alcoholic beverages is ethyl alcohol. It is different from rubbing alcohol (isopropyl), methanol — an ingredient in many glass cleaners — and ethylene glycol, found in antifreeze used in vehicles, all of which are highly poisonous.

Ethyl alcohol is the result of fermenting food — most commonly grains or grapes. While it is derived from food, you won’t find it on a nutrition food chart because it is not deemed essential for our diet. There is no disease or unhealthy state that results if alcohol is not consumed.

In fact, technically it is a drug. It is a depressant and a diuretic.

So what happens to the body when you have a drink? First of all it’s important to understand how quickly the body absorbs alcohol. Food and other non-alcoholic beverages require time to digest, but alcohol can be absorbed directly across the walls of an empty stomach and reach the brain within one minute.

About 20 percent of it is absorbed into the blood directly from your stomach; a further 80 percent is absorbed from the small intestine. It inhibits a neurotransmitter in the brain, which affects the central nervous system.

Normally the CNS receives sensory information from your body’s organs. It analyses the information and gives an appropriate response. This may be, for example, to contract or relax a muscle. Alcohol interrupts the flow of this information slowing it down and, if sufficient is consumed, a complete breakdown in communication between the brain and some of its organs can take place.

This is what is happening when someone is intoxicated. The CNS cannot properly analyse sensory information. Messages telling the brain information like the distance of an object, how to form a word, the surrounding temperature etcetera are distorted. This results in the hallmark symptoms of drunkenness — blurred vision, slurred speech, loss of balance, heavy sweating and dulling of pain.

Alcohol also stops the production of the hormone that controls fluid loss. This is why you urinate so much when you drink alcohol. But this causes you to become dehydrated.

In fact it’s the dehydration that is the main reason you get a hangover. The dizziness, throbbing headache, excessive thirst, pale pallor and tremors are a result of lack of fluid in the body.

Alcohol also affects the frontal cortex of the brain. This area of the brain is responsible for conscious thought and is the reason those intoxicated with alcohol often lose their inhibitions.

Loss of balance often occurs because alcohol affects the cerebellum. This part of the brain not only controls balance but also coordination and eye movements. For this reason, high alcohol consumption can interfere with the perception of distance and height and cause dizziness.

Only five percent of the alcohol consumed is excreted in urine. Another five percent is lost in the breath (the reason breathalysers work). The vast majority has to be broken down by the liver. But the liver can only break down very small amounts of alcohol at a time. A shot of rum, for example, will take the liver about an hour to metabolise. If you’ve got more than this in your body the excess will circulate in the blood until the liver can process it.

At the same time that the alcohol is having its depressive effect on the CNS, the body also responds to its high sugar content. The pancreas produces more insulin to metabolise the sugar. This process continues until all the sugar is gone, leaving the body glucose-deficient. This is the reason heavy sweating, shakiness, dizziness, blurred vision and tiredness often occur when someone has been drinking alcohol.

It’s also the reason many feel hungry after they’ve been drinking. The body, in an effort to get some energy, often craves carbohydrates.


Many intoxicated by alcohol tend to “crash”, that is they fall into a deep sleep where they snore.

But research has shown that this type of sleep is not as deep and relaxing as it looks. Alcohol interferes with natural sleeping rhythms, so that the person is not getting a good quality sleep. Often the person awakes not feeling rested. Alcohol relaxes muscles in the back of the mouth which causes snoring. This snoring often contributes to a lack of restful sleep.

The Day After

Depending on the amount of alcohol consumed, the liver may still be hard at work the next day — breaking down alcohol that’s still in the system.

Ethyl alcohol, while not as poisonous as antifreeze, glass cleaners and rubbing alcohol, is toxic and can irritate the lining of the stomach causing retching and vomiting.

Alcohol can also irritate the lining of the oesophagus causing inflammation and heartburn.

Alcohol consumption causes more frequent urination and the loss of fluids causes the amount of minerals in the body to become unbalanced. In particular potassium, sodium and calcium move from their norm resulting in thirst, muscle cramps, feeling faint and dizziness.

The dehydration also impacts the liver’s ability to rinse out toxins, forcing it to divert water from other organs including the brain. This is often the reason for the throbbing headaches the day after.

And the situation gets worse. In breaking down alcohol, the liver produces acetaldehyde, a substance toxic to the liver, the brain and stomach lining. Its production often causes severe headache, heartburn, nausea and vomiting.

The good news is that the body does produce enzymes that attack acetaldehyde. The amount of alcohol consumed will impact the speed at which these enzymes can annihilate the toxin, and return the body to feeling okay again. So if you overdo it, expect to feel unwell for a good portion of the day after.

Next month we’ll look at the health benefits of a glass of wine.

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Published Apr 24, 2012 at 8:30 am (Updated Apr 24, 2012 at 8:29 am)

Ever wondered what happens when you drink alcohol?

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