Science Questions

Does alcohol kill brain cells?

Sun, 9th May 2010

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Jennifer Jackson asked:

My friend and I were having a discussion the other night and we wondered if there’s any truth in that common statement that alcohol causes brain cell death what the measurable effect is. Her partner also said that spicy food also kills brain cells, we wonder if there is any truth in that at all. We thought you guys would be the best people to ask!


Chris -   I can deal with the spicy one straight away because in fact, that’s a myth and there’s evidence that people who eat a lot of spicy food have lower rates of Alzheimer's disease than people who don't eat spicy food.  This is because turmeric, the orange stuff which, when you get a bit drunk in the curry house and spill your curry down your shirt (which is always white for some reason when this happens), is the stuff that stains.  Turmeric has actually got anti-inflammatory and anti-oxidant qualities.  It seems to cut down the production in the brain of a chemical called beta amyloid and beta amyloid is the stuff that makes Alzheimer's disease happen.  It builds up and forms plaques in the brain that damage nerve cells.  So if you eat lots of turmeric, it seems to reduce the risk of that happening.  So spicy food is good for your brain. 

That’s that one done.  Booze – booze is more difficult.  The evidence is, if you were to incubate nerve cells in a solution of alcohol, they would die.  So alcohol is a toxin.  Thankfully, the body is really well set up to deal with it metabolically.  The liver handles alcohol extremely well and only a tiny proportion of the alcohol we drink actually gets into circulation because the liver sees all of the blood that comes from the digestive tract before it goes anywhere near the rest of your body, and the liver therefore deals with the booze before it goes systemically around your body and into your brain.  But a small amount of alcohol does go into the brain and when it gets there, the reason it makes us behave the way it does - and we all know what the effects are - at least in modest doses, is that alcohol increases the activity of one of the brain’s inhibitory nerve transmitter chemicals.  This is called GABA.  This damps down the activity of nerve cells.  So unlike certain drugs like ecstasy which can in fact make nerve cells more active and damage them, alcohol damps down the activity of nerve cells and therefore it makes them less vulnerable to damage.

Jennifer -   So they might live longer?

Chris -   Well, they may do.  The evidence is, small doses of alcohol probably don't harm neurons and the body’s pretty well set up to cope with it anyway.  If you look at people who have spent their whole life drinking modest amounts of alcohol, there’s evidence that actually their intellect may be preserved better than teetotalers.  That’s not saying, now, prescribe yourself daily alcohol intake to live a long time and have good brain function into old age.  That’s not what we’re saying.  But what we are saying is that epidemiologically, if you look at populations, the evidence is that it doesn’t do any harm.  There’s no evidence for significant harm in those people.  If you also look at people who are chronic alcoholics, unless they get a condition called Wernicke–Korsakoff's psychosis – which is where they run out of a vitamin called B1 (thiamine) which is very destructive to nerve cells – they don't actually have huge damage to the nervous system unless they are very, very, very heavy drinkers for a very long time.  So therefore, the evidence is that alcohol is probably okay in modest doses and most of the injuries and most of the damage to the brain happens when people get drunk and fall over and hit their head, or get into fights.  That’s actually the reason why head injuries happen with alcohol and why brain damage probably occurs.


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Jennifer Jackson asked the Naked Scientists: Hi Chris and the Naked Scientists I discovered your programme a few weeks ago while searching in desperation for some good scientific media reporting. Your programme is a really excellent example of that, and I've been listening avidly to your back catalogue and recommending your program to friends and colleagues ever since. My good friend Gaby in New Zealand has become a fan too and we were wondering if there is any truth in the common statement that alcohol causes brain cell death, what the measurable effect is, and whether eating spicy food also does this, as we've heard claims along these lines. Very best of luck and success in your work, Jen and Gaby What do you think? Jennifer Jackson , Sat, 8th May 2010

In a sense yes, alcohol can kill brain cells. Being drunk is your brain's reaction to being suffocated. Alcohol replaces oxygen and produces the intoxication. Enough of it can kill you, in essence, killing a lot of brain cells. aaron28, Sat, 8th May 2010

Alcohol doesn't replace oxygen. Bored chemist, Sun, 9th May 2010

Alcohol (ethanol) is a toxic chemical, but the body is metabolically well-equipped to deal with it, with the liver accounting for the majority of this detoxification. This organ is the first port of call for blood draining from the digestive tract before it enters the systemic circulation.

This means the liver has the opportunity to remove, catabolise or metabolise the products of digestion to prevent the tissues of the body being exposed to high concentrations of certain chemicals, like amino and organic acids and sugars, which, if they passed into circulation unchecked, could have deleterious effects.

This is known as "first pass" metabolism and means that the bulk of the alcohol we drink is removed before it gets near the systemic circulation. The small amount that does make it through partitions into the dependent tissues of the body, including the brain. Consequently, the bigger an individual's volume of distribution (i.e. how much body mass they have into which the alcohol can dissolve) the more alcohol they can take in without ill effect.

The brain is quite vulnerable to alcohol intake, however, because it has a high blood flow (i.e. capable of delivering large amounts of alcohol) and it contains a lot of lipid, which dissolves alcohol quite readily. This helps to maintain a good concetration gradient, drawing alcohol into the nervous system. The effect of the alcohol "wears off" through three mechanisms: i) as it is broken down by the liver and the concentration in the body falls, ii) as alcohol redistributes from the brain to other fatty tissues in the body and iii) as the brain adjusts its activity to compensate for the presence of the alcohol.

Alcohol affects the brain by sensitising nerve cells to the main inhibitory nerve transmitter, GABA. This damps down brain activity, which is why alcohol acts as a CNS depressant and, in overdose, causes sleepiness, unconsciousness and even coma or death. Effectively it behaves as an anaesthetic.

At the concentrations encountered normally, alcohol is therefore probably not overly toxic to neurones because it decreases their activity rather than over-exciting them like some drugs (such as ecstasy). The exception to this is in problem drinkers who, if they withdraw suddenly, can experience fits and seizures, which can be fatal - both for brain cells and for the whole patient.

This aside, there is no evidence for declining intellect amongst recreational (safe) drinkers, compared with teatotallers; in fact, the reverse may be true and there are papers showing an association between preserved intellect with age and low-level alcohol intake.

However, there are ways in which chronic sustained alcohol intake can be associated with brain damage. There is a condition called Wernicke-Korsakoff's syndrome, which is characterised by impaired movement and memory problems; sufferers cannot form new memories and also lose their existing memories causing them to "confabulate" - they make up stories to account for things that are happening to them.

This condition is often associated with alcoholism but, despite this association, is not caused by the alcohol directly but by accompanying malnutrition because most problem drinkers fail to eat properly. This causes a deficiency of vitamin B1 - thiamin - which is metabolically critical for the healthy function of cells, including neurones; without it the carboxylic acid cycle cannot function properly and so cells cannot make sufficient energy to sustain their needs and they die.

Therefore, in summary, it's probably not true when someone claims that every hangover costs you a million brain cells, but that's not to say that alcohol isn't toxic - if neurones were incubated in a sufficiently strong solution of alcohol they would die, but such concentrations are not normally encountered in the human body. Instead, alcohol is indirectly linked to brain injury, usually as a consequence of people falling over when drunk, getting into fights or through chronic abuse.

So chin up and let's get another round in; mine's a pint of Carling... chris, Sun, 9th May 2010

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