A patient named Belle, who had just finished months of treatment for breast cancer, asked GP Dr Philippa Kaye a question she hears all the time: "How can I stop the disease from coming back?" Belle's sister, who had come to the appointment with her, had been scrolling social media and asked whether certain supplements could help, whether Belle should cut out sugar completely, and whether some foods could stop the cancer returning.
Dr Kaye writes that more younger people are being diagnosed with cancer than ever before, and that fear of recurrence can be overwhelming for those who have already faced the disease. She says social media is often misleading or false on the topic, and that no single diet, supplement or lifestyle change can guarantee cancer will never return, though certain steps can lower the risk.
Most patients already know the basics, according to Dr Kaye: regular exercise, maintaining a healthy weight and not smoking are backed by strong evidence, and most people are willing to make those changes. She says the subject patients find hardest to hear about is alcohol.
Dr Kaye says the uncomfortable truth is that there is no completely safe level of drinking when it comes to cancer, a fact she believes remains underappreciated. Alcohol raises the risk of at least seven types of cancer, and in heavy drinkers the risk can be up to four times higher, she writes.
She adds that the damage is not necessarily permanent. Research shows cancer risk begins to fall once a person stops drinking, and even people who have drunk regularly for decades can eventually lower their risk to that of someone who has never drunk alcohol. Dr Kaye says this can take around 20 years.
When she explained this to Belle and her sister, they were horrified, she writes. Dr Kaye says alcohol is woven into almost every celebration and social occasion in Britain, and that for roughly one in ten adults, drinking is an everyday habit rather than an occasional treat.
A Group 1 carcinogen
Dr Kaye writes that while many people know excessive drinking can damage the liver, cause weight gain and cause hangovers, far fewer realise it is also one of the world's most well established causes of cancer. The World Health Organization classifies alcohol as a Group 1 carcinogen, the same category as smoking and asbestos, she says.
It is linked to at least seven types of cancer, including breast, bowel, liver, mouth, throat, oesophageal and laryngeal cancer, and the more a person drinks, the greater the risk, according to Dr Kaye. She is a bowel cancer survivor and says she now very rarely drinks alcohol, aside from an occasional cocktail at a wedding or party.
She writes that people often respond to her choice not to drink with disbelief, concern or even horror, which she says reveals how few people appreciate the strength of the link between alcohol and cancer despite decades of evidence. Not everyone who drinks will develop cancer, she notes, but the evidence is clear that drinking less or not at all lowers the risk. In the UK, alcohol is estimated to cause around 17,000 cases of cancer every year, according to Dr Kaye.
Risk rises with every drink
Dr Kaye cites research from the National Cancer Institute showing that one alcoholic drink a day can raise the risk of mouth and throat cancer by up to 17 per cent, oesophageal cancer by 30 per cent and breast cancer by 14 per cent.
Drinking two to three or more alcoholic beverages a day pushes the risk up further, according to the research she cites, by as much as 300 per cent for mouth and throat cancer, 400 per cent for oesophageal cancer and almost 60 per cent for breast cancer. Dr Kaye says the NHS guideline of no more than 14 units of alcohol a week should not be mistaken for a "safe" limit, but is a pragmatic target designed to reduce harm, particularly as around one in five adults regularly exceed it.
How alcohol drives cancer risk
Dr Kaye explains that when alcohol is broken down in the body, it produces a toxic chemical called acetaldehyde, which can damage DNA and increase cancer-causing mutations. Alcohol can also interfere with the body's ability to repair damaged cells, allowing abnormal cells to survive and multiply, and in women it raises levels of the hormone oestrogen, long linked to a higher risk of breast cancer.
Heavy drinking is also linked to obesity, Dr Kaye writes, because alcohol is high in calories and can interfere with the body's ability to burn fat. Obesity in turn raises the risk of at least 13 types of cancer, including cancers of the womb and kidney, according to Dr Kaye.
Alcohol also makes the lining of the mouth and throat more vulnerable to harmful chemicals, particularly those found in tobacco smoke, she says. That is why people who both smoke and drink face a far greater risk of cancers of the mouth, throat and voice box than those who do only one of the two.
Underestimating a drink
Dr Kaye says many people underestimate how much they are actually drinking. A pint of beer contains around two to three units of alcohol, she writes, while a small 125ml glass of wine contains about 1.5 units, but the wine glasses many people use at home are much larger, making it easier to think in terms of a bottle of average strength wine, which contains around ten units.
The encouraging news, according to Dr Kaye, is that the body begins to recover once a person stops drinking, and reducing or stopping intake lowers risk over time. She says it can take years for that risk to return to the level of someone who has never drunk alcohol: head and neck cancer risk falls to that of a never-drinker around 20 years after quitting, while liver cancer risk takes an average of 23 years. That, she writes, is why it is worth making changes sooner rather than later.
