Whether you drink every day or once a month, any amount of alcohol can increase your breast cancer risk. Here’s what you need to know.

We cling tightly to the studies that say the odd glass of red is healthy, reminding us how it’s packed with polyphenols and brings down your stress levels to boot. But in April, the World Cancer Research Fund ruled that women should be avoiding alcohol just as strenuously as cigarettes as “any amount of alcohol increases breast cancer risk”.

These days we cringe when we see characters in old movies pull out the cigarettes at the first hint of drama. It might have been normal decades ago, but we have come to see smoking as a habit that’s uniquely bad for our health. Now, scientists believe that our favourite pastime could be just as dangerous, for women at least. Here is what we know and how much you can get away with drinking without significantly raising your risk.

Why does alcohol cause cancer, and why is it so risky for women?

It’s not what any of us want to hear, but alcohol is “a known carcinogen,” says Britta Stordal, an associate professor in cancer research at Middlesex University. When you drink alcohol, “your body turns it into acetaldehyde, which is a compound known to cause cancer,” she explains. For this reason, “any amount of alcohol that you drink increases your risk of cancer”.

The World Cancer Research Fund has advised that to reduce our risk of bowel cancer, we should restrict alcohol; however, to reduce breast cancer risk, women should avoid alcohol entirely. The reality is that drinking alcohol is especially likely to lead to breast cancer rather than other cancers. “Alcohol is turned into acetaldehyde primarily in your liver, but this process can also happen inside of breast tissue,” Stordal says. “We also know that drinking alcohol increases your oestrogen levels, which can also increase cancer risk in women.”

There is a “dose response” involved in breast cancer risk, says Dr Harriet Rumgay, an epidemiologist at the World Health Organisation in its international agency for research on cancer. This means that “the more alcohol you drink, the greater your risk,” she says. Though smoking is “still much more harmful to us than alcohol when it comes to all of the consequences for your health, the evidence does say that women should try to limit their alcohol consumption as much as possible to reduce their breast cancer risk, as 8% of all breast cancer cases in women are attributable to drinking [alcohol],” Rumgay says.

More than two bottles of wine a week

Women who drink two bottles of wine a week are at a 27% greater risk of developing breast cancer than women who don’t drink, says Dr Rumgay. Of 100 women who drink two bottles of wine every week, around 14 would develop breast cancer over the course of their lives, not taking into account factors like weight, genetic risk and whether or not they smoke. This compares with the number of non-drinking women who will develop breast cancer at some point in their lives, a figure that’s at 11 in 100.

If you’re keen on wine, you might like to have a large glass most nights with dinner, bringing you up to at least two bottles of wine drunk each week. In units, that’s equivalent to nine pints of beer or cider throughout the week, or nine double-shot cocktails.

According to the World Health Organisation, drinking two bottles of wine a week is in “the middle category of risk, rather than being judged as high risk,” says Dr Rumgay. For a postmenopausal woman, however, drinking in this way could lead to “a 27 per cent higher risk of developing breast cancer,” says Dr Rumgay.

Postmenopausal women are affected differently to premenopausal women when it comes to breast cancer risk. Scientists are still trying to determine why that is. “It might just be a fact of age, because as you age, your cells have more of a chance to divide and mutate, leading to cancer,” says Rumgay. “But postmenopausal women also have different amounts of hormones in their systems. For these women, drinking alcohol could be more likely to cause breast cancer, because the increase in oestrogen that comes with drinking alcohol causes more cell proliferation, where your body’s cells divide to produce more of themselves. Whenever this happens, there is the risk that one of those cells will mutate and become cancerous.”

Fourteen units of alcohol a week

Of 100 women who drink 14 units of alcohol every week, around 14 would develop breast cancer over the course of their lives, not taking into account factors like weight, genetic risk and whether or not they smoke.

One in seven women in Britain drink more than 14 units a week, the “low-risk” guideline set by the UK Government, and they are at a 22% greater risk of developing breast cancer than women who don’t drink.

Drinking 14 units of alcohol every week, equivalent to six medium glasses of wine, would give you a 14.4% chance of developing breast cancer over the course of your life, not including other factors like genetic risk, weight and whether or not you smoke.

But what about the much-quoted government advice that 14 units a week is the safe limit on drinking for women? When it comes to breast cancer risk, “this is quite outdated advice,” says Stordal. “I suspect that the 14-unit guideline doesn’t properly take cancer risk into account. Instead it’s likely based more on issues like liver damage, and is a combination of what the health research suggests is sensible and what people are already doing in a specific country.”

Canada has recently introduced alcohol guidelines that explain the increased risk of cancer with the number of units that you consume. “I’d love to see the UK bring this in instead, just so that people can be aware,” says Stordal. “I certainly didn’t know about the extent of the risk for a long time.”

According to Alcohol Change UK, just one drink per day (1.25 units) can increase your breast cancer risk by 7%. Smoking, either regularly or occasionally, leads to a 7% increased risk of breast cancer, and of 100 women that currently smoke, 12 will develop breast cancer over the course of their lives. “Smoking is worse for your health for a huge number of reasons, however, so I wouldn’t want people to think that it’s safer to smoke than to drink,” says Rumgay.

A small glass of wine with dinner every day

Women who drink a small glass of wine every day, equivalent to around 10 units a week, are at a 15% greater risk of developing breast cancer than women who don’t drink, says Dr Rumgay. Of 100 women who have a small glass of wine every day, around 13 would develop breast cancer over the course of their lives, not taking into account factors like weight, genetic risk and whether or not they smoke.

Much alcohol risk research looks at everyday drinking. The facts are in: having a single drink a day, four times or more each week, can lead to a 20% greater risk of early death. When it comes to breast cancer, the risks escalate further. A report by the American Institute for Cancer Research found in 2017 that one glass of wine a day increased the risk of cancer by 9% in postmenopausal women, and by 5% in premenopausal women.

Studies such as this tend to use the WHO’s definition of a standard drink: a drink containing 10g of pure alcohol, equivalent to a small glass of wine. So having just one tiny glass a day could be having a big impact on your health, and while it may keep you from being too tipsy, “there’s not enough evidence to say whether having food with your wine is any better for your cancer risk, though this is something that research could tell us in the future,” says Rumgay.

Only drinking at the weekend

Women who drink eight double-shot cocktails or eight medium glasses of wine over the course of a weekend are at a 24% greater risk of developing breast cancer than women who don’t drink, says Rumgay. Of 100 women who have eight drinks of this size every weekend, around 14 would develop breast cancer over the course of their lives, not taking into account factors such as weight, genetic risk and whether or not they smoke.

Women who drink four of these drinks over the course of a weekend, meanwhile, are at a 12% greater risk of developing breast cancer than women who don’t drink. Of 100 women who have four drinks of this size every weekend, around 13 would develop breast cancer over the course of their lives.

While having alcohol-free days can improve your health, there are added dangers to drinking large amounts of alcohol in one sitting, says Rumgay. One study she worked on in the past found that “the risk of breast cancer was increased by 40% in women that had had any occasion of heavy episodic drinking in the year leading up to the research,” she says. We might not think of it as such, but the WHO classes “heavy episodic drinking” or binge drinking as consuming 60g of pure alcohol or more in a single drinking session. That’s equivalent to just over two large glasses of wine.

Research into the effects of weekend-only drinking is still ongoing, but “premenopausal women who binge drink seem to be twice as likely to develop breast cancer,” says Stordal. “There is some confidence in the notion that having this carcinogenic compound in your system in high concentrations after a weekend of drinking could be more dangerous compared with having the same quantity over the course of a longer period.”

One drink a few times a week

Women who have one drink three times a week are at a 9% greater risk of developing breast cancer than women who don’t drink, says Rumgay. Of 100 women who have one drink three times a week, around 12 would develop breast cancer over the course of their lives, not including other factors like genetic risk, weight and whether or not they smoke.

Having a break between the days that you visit the pub or have a glass of wine with your dinner is certainly good for your health, says Dr Rumgay. “Drinking frequently can lead to systemic inflammation of the body,” she explains. “If you cut the number of days that you drink, or spread them out, then it’s possible that your body has more time to recover from this inflammatory state, which could potentially avoid increasing your risk of cancer.”

Even this amount of alcohol can increase your cancer risk, however. Another study that Rumgay worked on found that “having just half a standard drink every day increases breast cancer risk by 4%,” she says.

One drink once a week

Women who have one drink once a week are at a 3% greater risk of developing breast cancer than women who don’t drink, says Rumgay. Of 100 women who have one drink a week, around 11 would develop breast cancer at some point in their lives, not taking into account other factors like genetic risk, weight and whether or not they smoke. The same amount of non-drinking women will develop breast cancer at some point in their lives.

More than 40% of women in Britain drink at least once a week. The effects of having one drink each week are hard to study, however, as “most people either drink more than once a week or don’t drink at all,” says Dr Rumgay. The numbers still show that even this much alcohol consumption can increase your risk of breast cancer – though you might see a 3% increased risk as something you’re willing to tolerate.

One drink a few times a month

Women who have one drink every other week are at a 2% greater risk of developing breast cancer than women who don’t drink, says Rumgay. Of 100 women who have one drink a few times a month, around would develop breast cancer at some point in their lives, not taking into account other factors such as genetic risk, weight and whether or not they smoke.

Again, there isn’t a lot of research into this pattern of drinking, though “any amount of alcohol still increases your risk of breast cancer,” says Rumgay. “The simple advice I always give is reduction,” says Stordal. “Whether that’s cutting down to once a week or once every few weeks, whatever you can do will benefit you.”

One drink every few months

Women who have fewer than six drinks over the course of a whole year are 0.3% more likely to develop breast cancer than women who don’t drink. Of 100 women who have one drink fewer than six times a year, 11 would develop breast cancer at some point in their lives, not taking into account other factors like genetic risk, weight and whether or not they smoke.

So while no amount of drinking is completely safe, you may be pleased to know that you can celebrate with a drink a few times a year and only increase your risk of breast cancer marginally, “though the general consensus is that anything more than zero does raise your risk,” says Rumgay.

What about men’s risk?

Men can also get breast cancer, with 390 men in the UK diagnosed every year. However, the overall risk of breast cancer in men is 0.01 per cent over their lifetime, while for women it’s 11 per cent.

One study found that drinking one unit of alcohol (about half a pint of beer) per day increases men’s breast cancer risk by 16 per cent, but given men’s lifetime risk is considerably lower than women’s, this increase is less significant.

That said, the World Health Organisation has found that alcohol plays a causal role in over 200 health conditions, so experts advise that both men and women should reduce or avoid alcohol to improve their health.

How to mitigate the risk of alcohol

Plan how much you want to drink

Set yourself an alcohol limit for the week and stick to it. Having a cap and planning your drinks around it can help you to drink less overall and still enjoy yourself.

Have a few dry days a week

Having a day or two between evenings where you enjoy a drink “gives your body more time to recover”, says Dr Rumgay, which may lessen the risk that comes with drinking.

Don’t smoke and drink

Smoking is still worse for your health overall than drinking. Doing both at the same time “might have compound effects that make both more dangerous than they would be if you just had a glass of wine or a cigarette on their own,” Dr Rumgay says.

Try low-calorie drinks

Keeping within a healthy weight range for your height puts you at a lower risk of breast cancer. Thinking about the kind of drink you have as a go-to could make this easier. (A double gin and slimline tonic contains around 110 calories, while a medium glass of wine contains about 160).

Eat a healthy diet

Eating a range of fruit and vegetables can lower your risk of cancer, as these foods contain antioxidants that can help protect your cells from damage. Dark leafy greens may be particularly powerful when it comes to reducing free radicals, a molecule that can cause cell damage. Red meat and processed meats are both fine in moderation, but diets high in either have been linked to an increased risk of cancer.

Make sure you sleep well

Regularly being sleep deprived over the course of your life can worsen your health and your immune system. Give yourself a sleep “opportunity” of eight hours a night by going to bed eight hours before you need to wake up in the morning. Alcohol consumption can disrupt sleep when consumed shortly before bed, so this might mean having wine with dinner instead of after it.

Get enough exercise

Research suggests that regular exercise (about 150 minutes a week) can lower your risk of breast cancer by as much as 20 per cent.