Explainer: why, exactly, is alcohol bad for us long-term?

What, exactly, makes alcohol unhealthy?

After a big night, the answer to this might seem obvious – or perhaps more disturbingly, not obvious at all. But even in moderation, alcohol carries longer-term health risks too.

So what are they, and why do they happen? Cosmos investigates.

Why is alcohol bad for you long-term?

The biggest culprit is a substance called acetaldehyde.

Alcohol – or strictly speaking, ethanol – doesn’t stay that way in the body for long. The body metabolises it and turns it into a few different compounds, mostly acetaldehyde.

As well as causing a lot of the symptoms you’d experience during a hangover, like headaches, nausea, and facial flushing, acetaldehyde is a carcinogen.

“Acetaldehyde is highly reactive and extremely toxic,” says Dr Leon Booth, a research fellow at the George Institute for Global Health in Sydney.

“It binds to different proteins, or to DNA, and it can impair enzyme and cell functions.

“Essentially, because it’s so reactive, it increases the risk of cell mutations and therefore increases the risk of a cancer developing.”

Globally, around 4% of cancers can be attributed to alcohol. The Lancet estimates that in 2020, there were 741,300 new cancers around the world that came from alcohol consumption.

“A lot of them are in the digestive tract, which kind of intuitively makes sense, because that’s where the alcohol is coming into contact with the body,” says Booth.

“So there’s an increased risk of cancer in the throat, mouth, oesophagus, liver, in the colon and for females, quite an increased risk for breast cancer.”

One study estimates that a bottle of wine per week is roughly the equivalent of smoking 10 cigarettes per week for women, or five cigarettes per week for men.

Acetaldehyde doesn’t stay in your body forever: an enzyme called acetaldehyde dehydrogenase, or ALDH, turns it into largely harmless acetic acid, and then eventually on to carbon dioxide and water.

But here’s where genetics can play a role in your susceptibility too: some people have a genetic mutation that makes their ALDH enzymes less effective.

This gene is particularly common among people of East Asian descent, which is why some East Asian people flush red after only a small drink. Unfortunately, there’s evidence that people with this gene are also more susceptible to cancer.

“In studies of Asian populations, they seem to have a much greater risk of getting cancer from alcohol,” says Booth.

While cancer and acetaldehyde draw the most attention, alcohol can have other long-term effects too – like high blood pressure and increased risk of strokes.

“If you drink heavily and consistently, you get scarring in the liver – cirrhosis, which is also linked to an increased risk of cancers in the liver,” says Booth.

Alcohol can also interfere with hormones, causing poorer sleep or – once again – a higher risk of cancer.

It’s also linked to mental health issues, like anxiety and depression, but Booth says this can be a “chicken-and-egg situation”.

“There’s a lot of literature to suggest that people with mental health issues drink to help cope. But unfortunately, it tends to make things worse.”

All in all, not a great wrap. Is there any good news?

Isn’t low or moderate drinking a little bit good for you?

We’ve all seen – and Cosmos has published – headlines about low and moderate drinkers (around 10 or fewer standard drinks per week) doing better in some health metrics, particularly heart disease.

Does this really mean that regular low-moderate drinking might be better than not drinking at all?

“Long story short, I think the jury’s probably still out on that one,” says Booth.

The trick is that a lot of non-drinkers avoid alcohol for health reasons. This is called the “sick quitter” effect.

If you develop a health condition, or discover you’re at an increased risk of something like heart disease, often one of the first things a doctor will recommend is that you stop drinking.

“What that means is, sometimes when you do these big population studies, the people who don’t drink alcohol can look less healthy than the people who do drink alcohol,” says Booth.

While many of these studies have tried to control for the sick quitter effect, and still produced some compelling evidence that low or moderate drinking helps, other studies have found the opposite.

“My overall opinion would be that it’s just a bit too early to know, and to really understand that relationship,” says Booth.

“And even in those studies, once you get beyond that moderate consumption, alcohol does seem to be really detrimental to cardiovascular health.”

So, for now – other than the benefit you get from spending a night at the pub in good company – you probably can’t claim alcohol’s improving your health. We’re as sorry about this as you are.