In a cabinet in London’s British Museum nestles a 5,300 year-old wedged-shaped tablet called a cuneiform. On its surface is scrawled one of the earliest forms of written language in the world.
And it’s a tape of Mesopotamian workers’ beer rations.
Clearly, humanity’s partnership along with alcohol stretches spine thousands of years, yet a long partnership doesn’t necessarily mean a healthy and balanced one.
We know that alcohol is damaging to our health in a number of ways. And the one we’re most concerned concerning here at Cancer Research UK is its impact on cancer risk.
We’ve written concerning the link between alcohol and cancer numerous times prior to – from discussing the evidence that it induces cancer to talking concerning how drinking much less reduces your risk of creating the disease.
But we haven’t yet explored the science behind how alcohol affects and loss our cells, and how this Can easily cause the cells in our bodies to make in to cancer.
Which cancers?
There are seven types of cancer linked to alcohol – bowel, oesophageal (meals pipe), larynx (voice box), mouth, pharynx (upper throat), breast (in women), and liver. There’s additionally mounting evidence that heavy drinking may be linked to pancreatic cancer. yet how, and why?
According to Dr Ketan Patel, a Cancer Research UK expert on how alcohol induces cancer: “We don’t really know. We don’t fully understand why alcohol induces some cancers and not others.”
There are some theories, however, even though some are stronger compared to others.
The finest evidence we have actually is for mouth and throat cancers where alcoholic drinks directly damage cells in these tissues.
And, because alcohol additionally raises a person’s chances of creating a scarring of the liver known as cirrhosis, it’s believed that this raises their chances of creating liver cancer.
There’s additionally some evidence that certain bacteria in your mouth and throat – and maybe even in the bowel – could be involved in alcohol causing cancer. yet the link isn’t clear and we don’t know for sure, so we should wait for much more data.
And, as we will certainly briefly discuss below, there’s good reason to believe that alcohol’s effects on hormone levels may be behind its link to breast cancer.
While there might be a perception that the health risks of alcohol only apply to heavy drinkers, research is revealing that it’s not merely drinking large amounts of alcohol that raises your chances of creating cancer – drinking small amounts Can easily be harmful too.
Although there’s a lot we still don’t know concerning how alcohol is linked to different types of cancer, researchers are starting to figure out at least one of the ways that it induces harm.
A nervous breakdown
Like most points you consume or drink, alcohol – be it in a pint, shot or cocktail – gets broken down by your cells.
In the case of ethanol – the chemical name for the alcohol we drink – it ultimately gets broken down to make energy.
First an enzyme called alcohol dehydrogenase (ADH) converts ethanol to one more molecule – acetaldehyde. This then gets broken down by a second enzyme, acetaldehyde dehydrogenase (ALDH), in to acetate, which our cells Can easily use as a source of energy.
This is a relatively straightforward process, and one that evolution has actually equipped our bodies to handle along with ease. So where’s the harm in having a drink or two?
Dr Ketan Patel Image via Wikimedia Commons CC-BY-3.0
The risk lies along with the middle man – acetaldehyde.
“Ethanol itself is relatively non-toxic others compared to the consequences of drunkenness,” says Ketan Patel. “It doesn’t directly damage DNA. yet as the physique breaks it down, it goes through a step where it is converted to a highly reactive, toxic chemical called acetaldehyde.”
“And it’s a build-up of this which most likely induces changes that lead to cancer.”
To steer clear of acetaldehyde building up and damaging DNA, human cells contain three ALDH enzymes – ALDH1A1, ALDH2 and ALDH1B1, which rapidly break down acetaldehyde in to acetate. This means that acetaldehyde doesn’t usually have actually time to build up or hang around for long enough to cause considerable DNA damage.
But this protection mechanism Can easily be overwhelmed once alcohol is in the bloodstream, meaning it doesn’t job properly.
What’s more, it isn’t available to everyone. Some people have actually mistakes or changes in the genetic code of their ALDH enzymes which cause them to malfunction, so acetaldehyde Can easily build up. In turn, this leads to DNA damage.
“It’s known as the flushing mutation” says Patel. “It’s particularly common among Southeast Asian populations – for example, up to 70% of the Taiwanese population have actually it.”
“people along with mutated ALDH enzymes become flushed in the face and pretty often feel pretty sick after drinking alcohol.”
Thankfully, our cells contain a further layer of protection, in the form of a variety of ‘toolkits’ that Can easily repair damaged DNA (which we’ve discussed at length in this post).
But both of these units have actually their limits, so damage Can easily still happen.
“Most organisms – from bacteria to humans – have actually these two protection systems. yet if you overwhelm them they won’t work,” says Patel. “That’s as soon as you grab acetaldehyde causing DNA damage and changes that lead to cancer.”
Mutations and rearrangements and clumps….
This is an necessary portion of the chain of evidence linking alcohol to cancer risk.
“The evidence that mistakes in DNA Can easily lead to cancer is overwhelming,” says Patel.
So how exactly does acetaldehyde affect our cells’ DNA? Over the years, scientists have actually identified several forms of damage.
- DNA ‘spelling mistakes’
Acetaldehyde Can easily cause errors in DNA called point mutations. These are a type of mistake where one base – or ‘letter’ – in a gene is swapped for another. And because DNA is the instruction manual that tells our cells Exactly what to do, mistakes in it Can easily lead to cancer.
- Rearranging the furniture
Acetaldehyde Can easily additionally trigger larger-scale changes to our DNA, by messing up entire chromosomes (the technical name for the long strings of DNA in our cells). It Can easily cause bits of chromosomes to break off and to swap around, meaning genes end up in the wrong place and don’t job properly – these are additionally phenomena that Can easily trigger cancer.
Acetaldehyde has actually additionally been shown to bind to DNA, forming clumps called adducts. These play havoc along with how DNA works, folds, replicates and repairs itself. Essentially, adducts are one more type of mutation, and they too Can easily cause cells to become cancerous.
The mug runneth over
So far we’ve seen that alcohol Can easily be broken down in to a harmful chemical – acetaldehyde. We’ve looked at the units in place to steer clear of it damaging our DNA. And we’ve looked at the sorts of damage it Can easily cause.
Now let’s take a closer check out what’s going on as soon as we have actually a drink or two. To visualise how alcohol overwhelms our cellular defences, imagine you’re pouring alcohol – say red wine – in to a glass through a funnel.
If you only pour a small quantity in to the funnel, the wine will certainly flow right through.
But if you continuously pour the alcohol in to the funnel, devoid of taking time to stop or pause, the funnel will certainly overflow.
Similarly, too much alcohol stops the ALDH enzymes and DNA repair pathways from working properly, so the units become overwhelmed, resulting in a build-up of acetaldehyde, and damage that Can easily lead to cancer.
While this neatly explains why certain cancers – such as bowel and liver tumours – are linked to heavy drinking, what’s much more of a mystery is why others forms are linked to much lower levels of consumption.
For example, we know that light drinking raises a person’s risk of creating cancers of the upper aero-digestive tract, namely mouth, upper throat and oesophageal cancers.
One theory that might explain this is the bacteria we mentioned earlier. It’s believed that the bacteria in our mouth are pretty good at converting ethanol in to acetaldehyde, resulting in a pretty higher level of acetaldehyde, even if only a small bit of booze is drunk.
Clearly there’s a lot much more job to be done to really understand how the ‘funnel’ suggestion plays out in different tissues of our bodies, and merely how much (or little) alcohol Can easily cause it to ‘overflow’. As well as why some forms of cancer are much more strongly linked to alcohol compared to others.
But as well as acetaldehyde causing DNA damage, there are others ways alcohol Can easily lead to cancer too.
Other potential mechanisms
Smoking is the number one preventable cause of cancer. So it’s not surprising that if a person drinks and smokes, they’re increasing their chances of creating cancer even further. yet for some cancers, it appears that these two effects in combination are much worse compared to either by itself. Why?
The interaction between alcohol and smoking is complex. Acetaldehyde is additionally a by-product of burning tobacco, as is a second, similar chemical: formaldehyde.
But to go spine to our funnel, if you drink and smoke there’s much more possibility of developing an overflow because the body’s units can’t job fast enough to handle the damage caused by both of them at the same time.
“If you smoke and drink, you’re going to have actually a greater build-up of acetaldehyde and others toxins, which will certainly increase the damage to your DNA and, in turn, your chances of creating cancer.”
As well as this, there’s additionally evidence that alcohol Can easily make it much easier for the cancer-causing tobacco chemicals found in cigarettes to grab in to tissue and cells.
Alcohol raises a woman’s chances of creating breast cancer – yet how and why this happens still isn’t fully understood.
One theory is that drinking alcohol affects women’s hormone levels, increasing the quantity of oestrogen in the body, which is then used by breast cancer cells as fuel for growth.
But it’s not necessarily straightforward to unravel. Several others points affect oestrogen levels, including whether the woman is pre- or post-menopausal, the stage of her menstrual cycle and whether she’s taking hormonal contraceptives or hormone replacement therapy (HRT).
Patel is cautious. “We know alcohol raises women’s risk of creating breast cancer. yet so far, the exact mechanism that induces this increased risk hasn’t been pinned down,” he says. “At the moment, the evidence is too weak to say for definite how alcohol induces breast cancer.”
“We need much more research to figure out this complex cause-and-effect relationship.”
More or less?
Research is slowly revealing much more concerning how alcohol induces cancer, and the theories we’ve discussed in this guide are the ones along with the strongest supporting evidence.
But there are others ideas that haven’t yet been fully explored or resolved. These include changes in folate metabolism, increased production of reactive oxygen species and reactive nitrogen species and the role of bacteria in how alcohol is metabolised.
At Cancer Research UK, we’re committed to finding out much more concerning the mechanisms by which alcohol induces cancer.
We’re continuing to fund Dr Patel’s research, which is focusing on how alcohol is broken down in to different chemicals in the physique and how this Can easily damage cells and trigger cancers – particularly liver cancer. He is additionally studying both the long and short-term effects of exposure to alcohol.
And one of the big questions raised by our Grand Challenge funding scheme is asking if the mutational fingerprints left behind by lifestyle factors like drinking alcohol Can easily insight us much better understand the link between environmental factors and cancer.
But no matter how alcohol induces cancer, one thing is clear.
The finest means to reduce the risk of cancer from alcohol is to drink much less of it – whether that’s by having much more alcohol-free days every week, swapping out some glasses of booze for soft drinks during a night out, or picking lower strength drinks or smaller sized servings.
The partnership between humans and alcohol goes spine millennia and it’s an integral portion of numerous societies’ social lives. Of course, adults have actually the right to decide how much they want to drink, yet alcohol’s health impacts are undeniable. By working along with the Government, policy-makers and healthcare professionals, we’re aiming to raise awareness of the risks of alcohol and insight people make selections that Can easily reduce their cancer risk.
–Aine
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