Irish oncologists share eight things they do to lower their risk of cancer

With the WHO pointing out that between 30–50% of all cancer cases are preventable, we ask four oncologists about the lifestyle habits they embrace to mitigate their cancer risk.

Exercise

As a schoolboy, Dr Michael McCarthy, consultant medical oncologist at Galway University Hospital, played a lot of hurling and football. “Then I fell out of the habit — I lost my way with exercise in my 20s,” McCarthy says. “I’m grateful I went back to it about 14 years ago. I run quite a bit. I aim for 50km a week, five out of seven days, generally around Salthill.”

McCarthy says a lot of studies have been done or are in progress that clearly suggest — for a range of cancers — that physical exercise reduces the risk of relapse in patients who have had cancer and who have had curative treatment.

“It’s harder to quantify how much exercise reduces risk of a first cancer but it seems in epidemiological studies, there’s evidence exercise reduces the risk of most cancers by about 10-20%,” he says.

Prof Janice Walshe, consultant medical oncologist at St Vincent’s University Hospital, says exercise is one of three lifestyle habits she practises to reduce cancer-risk: “I believe exercise is very important. I do two types: cardio classes — I enjoy being in a group as opposed to running on my own — and two strength classes a week involving weights. I enjoy it — again, it’s a class, and I feel motivated. And I know it’s good for keeping my bones strong, so I’m reducing my osteoporosis risk too.”

Cut out processed food

A multinational study involving researchers from the International Agency for Research on Cancer found that higher consumption of ultra-processed foods is associated with an increased risk of cancer and cardiometabolic multi-morbidity. The study investigated data from over 266,000 people from seven European countries, where consumption of ultra-processed foods was estimated at more than half of a person’s daily food intake.

Dr Ciara O’Hanlon Brown, oncologist at St James’s Hospital, says what we put into our bodies is critical: “It has been proven that the Western diet, featuring so much highly processed food, is behind the development of a lot of cancers, particularly gastro-intestinal, endometrial and breast cancers.

“Unfortunately our food environment has changed. There’s so much availability of over-processed food that isn’t good for us. It can be easy to eat the wrong things.”

O’Hanlon Brown admits she doesn’t eat fresh food every day: “I’m running around, working, and I’ll just grab what’s there, but I’m very conscious not to eat processed food too often. I’m married to someone who feels like that too, and we cook in the evening.

McCarthy agrees eating fresher, less processed food is very important: “If somebody’s diet isn’t right, it’s hard to compensate for that with exercise. I don’t have a big sweet tooth. Anything I drink is sugar-free. I steer clear of crisps, chocolate and sweets."

Keep weight in check

The Irish Cancer Society says being overweight or obese clearly increases the risk of the following cancers: breast, pancreatic, bowel, oesophageal, gallbladder, kidney and womb. It points to growing evidence that being overweight could increase the risk of many other cancers, including thyroid, brain, leukaemia, liver, multiple myeloma and non-Hodgkin lymphoma.

Yet nearly two-thirds of all adults in Ireland are overweight or obese.

Consultant gynaecological oncologist Ms Claire Thompson says it is thought approximately 40% of endometrial cancers are linked to obesity: “A major part of my work is ovarian cancer, but we also do a lot of work in endometrial and womb cancer. These are the most common gynaecological cancers we’re seeing now, and it’s because of obesity.

“If a lady is carrying a lot of weight — as well as her ovaries producing oestrogen, so is the fat tissue, and oestrogen can thicken the lining of the womb. If that happens for a long time, the cells can start to become abnormal, raising the risk of endometrial cancer.”

While it used to be thought that endometrial cancer affected post-menopausal women, Thompson says as many as 15% of these cancers today are in women who haven’t yet undergone menopause: “And that’s because of obesity.”

She takes it as a lesson to stay in shape: “Not that I’m carrying weight but I know it’s very easy to put it on. Because I work long hours, I might come home at 10.30pm and eat whatever’s in the cupboard. I know I should stay away from the takeaway at night when I’m tired. I empathise with women who are busy — but because I can see what happens, I know it’s worth the effort.”

Walshe is a believer in keeping her weight under control: “It can be a challenge, particularly when I come to the perimenopause. I try to eat healthily. I practise intermittent fasting — not because it’s indicated as reducing cancer risk but because it allows me to manage the amount of calories I eat daily.”

Quit smoking

According to Cancer Research UK, smoking causes at least 16 different types of cancer, including two of the most common: lung and bowel cancer.

The cancer charity points out that cigarette smoke contains over 5,000 chemicals, many of which are harmful — at least 70 can cause cancer. “These chemicals damage DNA, including parts of DNA that protect us against cancer. Chemicals in cigarette smoke also make it harder for cells to repair DNA damage [so] the damage can build up,” the charity says.

McCarthy says quitting smoking is one of the biggest things you can do to limit cancer risk over a lifetime. He was never tempted to smoke: “Two family members who smoked did develop cancer, they died in their 40s.”

Thompson says smoking is very much associated with lung cancer risk but points out that it also increases the risk of cancers of the vagina, vulva and cervix: “I never smoked. I never liked it. As a medical student, I started to see what it could do. I automatically said no.”

She worries about the many younger women who come to her clinic who are vaping: “We don’t know what risk that poses yet.”

O’Hanlon Brown agrees that not smoking is “probably the number one thing you can do to reduce cancer”. Recalling how she dabbled in smoking as a teen and in her early 20s, she says: “I’d have had the odd cigarette on nights out. Everybody else would be smoking and someone would give you a cigarette and you’d smoke a bit.”

She “very quickly” became determined she would not be a smoker: “I made a clear decision I wasn’t going to do it on health grounds. I could see the effect it had on people long-term. I didn’t want to do that to myself.”

Get more than seven hours of sleep

Getting less sleep is associated with an increased risk of cancer, according to a study published in the journal Cancer .

Researchers, analysing data from almost 15,000 people, found evidence to suggest those who slept less than six hours each night, those who did not nap during the day, and those who got less than seven hours of sleep in total had an increased risk of cancer.

“Cancer develops as a result of wear and tear on the genome — the cells don’t repair properly. Repair happens in the sleep cycle,” says McCarthy.

People vary around how much sleep they need to feel at their best, he says, adding that sleep is a factor he tries to get right: “I aim to get eight hours. That’s how much I need so I’m ready to go again the next day. I don’t have any caffeinated drinks from 6pm onwards and I try to get to bed between 10 and 11pm.”

Limit alcohol intake

According to the HSE, 1,000 people are diagnosed with alcohol-related cancers in Ireland each year.

Alcohol, it says, causes almost 400 bowel cancers annually and at least 260 female breast cancers — and it causes at least five other cancers: liver, mouth, upper throat, larynx and oesophagus.

Walshe keeps her alcohol intake as low as possible: “I like a drink as much as anyone else. I have a glass or two of wine at the weekend to unwind. I tend to leave it at that. If I’m at a wedding or some other celebratory event, these are times I might have a bit more but it’s the exception more than the rule.”

Use sunscreen daily

According to Worldwide Cancer Research, over 80% of skin cancers are caused by overexposure to UV radiation. This includes UV rays from the sun but also from sunbeds and tanning lamps.

The cancer research charity explains that UV radiation damages DNA in skin cells, which can accumulate over time and increase the risk of cancer-causing genetic mutations.

“The more often you get burnt, the more damage is done and the higher the risk of skin cancer. It’s important to know that you don’t necessarily need to get a sunburn for UV rays to damage your cells,” its website notes.

O’Hanlon Brown, who works in the areas of breast and skin cancers, puts sunscreen on every day: “I put it on my face and on the back of my hands. With our Irish glow-in-the-dark white skin, which I certainly have, we shouldn’t be exposing ourselves to too much UV radiation. The highest incidence of skin cancer is in Australia, which has a large population of Irish and English origin.”

She uses sunscreen not just for its cancer-reducing effect: “Part of it is vanity. As a woman of a certain age, I know if I want to develop less wrinkles I need to use sunscreen — and not smoke.”

She believes sunscreen should be made cheaper: “The cost can be prohibitive.”

Take up screening offers

In 2022, the National Cancer Registry Ireland report showed that screening programmes are contributing to better patient outcomes for breast, cervical and colorectal cancer — all of which have population-based screening programmes in place.

Speaking about cervical screening, Thompson says the rule for her is take up the offer when you’re called: “It’s important when you get the letter or call to go. It’s very easy to ignore it when you’re busy, and no woman likes it, but it’s important to grin and get on with it.

“And if it’s fine, it’s fine — if it isn’t you can be treated early to prevent cancer.”