New research from a leading charity, Cancer Research UK, suggests that around 40% of all cancers are avoidable. More than 100,000 cases of cancer diagnosed in the UK each year can be directly attributable to cigarettes, diet, alcohol and obesity, and this figure raises to 134,000 when taking into account over a dozen lifestyle and environmental risk factors, according to a review published as a series of research papers in a supplementary 6 December issue of the British Journal of Cancer.

“Looking at all the evidence, it’s clear that around 40% of all cancers are caused by things we mostly have the power to change,” says Professor Max Parkin, a Cancer Research UK epidemiologist based at Queen Mary, University of London.

This new review of cancer and lifestyle in the UK is the most comprehensive undertaken, according to a statement from the charity.

It shows that smoking is by far the greatest culprit, causing some 23% of cancers in men and 15.6% in women.

Parkin says many people believe cancer is in the genes, and it’s down to fate whether you are going to develop it or not, but this is not what they found. And they came across some unexpected surprises:

“We didn’t expect to find that eating fruit and vegetables would prove to be so important in protecting men against cancer. And among women we didn’t expect being overweight to have a greater effect than alcohol,” says Parkin.

Parkin and colleagues found that of the 158,700 cancers diagnosed in men each year, the top six risk factors impacted as follows (numbers of cases rounded up to the nearest 100):

  • Tobacco use: 23% (36,500 cases).
  • Lack of fruit and vegetables; 6.1% (9,600 cases).
  • Occupation (eg exposure to asbestos): 4.9%. (7,800 cases).
  • Alcohol use: 4.6% (7,300 cases).
  • Overweight and obesity: 4.1% (6,500).
  • Too much exposure to sun/sunbeds: 3.5% (5,500).

Of the 155,600 cancers diagnosed in women each year, the top six risk factors were:

  • Tobacco use 15.6% (24,300 cases).
  • Overweight and obesity 6.9% (10,800 cases).
  • Infections (eg human papillomavirus, HPV) 3.7% (5,800 cases).
  • Too much exposure to sun/sunbeds: 3.6% (5,600).
  • Lack of fruit and vegetables; 3.4% (5,300 cases).
  • Alcohol use: 3.3% (5,100 cases).

Because most cancers have more than one cause (for instance cervical cancer can be linked to smoking and HPV infection), when you add up the percentage of cases that each factor contributes to, you will find it comes to more than 100%.

Parkin and colleagues said when you add up the percentage of cancers that are linked to one or more of the 14 lifestyle and environmental risk factors you get a total of 42.7% (134,000 cases) for men and women, which breaks down to a figure of 45.3% (72,000) for men, and 40.1% (62,000) for women.

Sara Hiom, director of information at Cancer Research UK, tells the press the charity doesn’t want people to feel guilty about indulging a bit more than usual and having a drink at Christmas, and acknowledges it can be hard to limit food and alcohol at this time:

“But it’s very important for people to understand that long term changes to their lifestyles can really reduce their cancer risk,” she urges.

Leading a healthy lifestyle is no guarantee that you won’t get cancer, but this review shows how we can vastly reduce the odds, says Dr Harpal Kumar, the charity’s chief executive.

“Stopping smoking, eating a balanced diet, cutting down on alcohol and maintaining a healthy weight could be New Year’s resolutions that help save more lives in future,” says Kumar.

In a separate science blog on their website, the charity lists the 14 lifestyle and environment factors, together with some information and advice. Here is a summary:

  1. Tobacco use: although rates have fallen dramatically in recent decades, with lung cancer rates plunging too, smoking rates in the UK have stuck at a stubborn 22%. The charity is calling for plain packaging as a key strategy to stop future generations from picking up the habit through brand seduction.
  2. Overweight and obesity: despite being a significant cause of cancer, in a recent survey the charity found only 3% of people are aware that keeping to a healthy weight can reduce their cancer risk.
  3. Fruit and vegetables: too many people in the UK are failing to eat their recommended 5 portions of fruit and vegetables per day, thus leaving themselves short of the essential vitamins, minerals and fibre their bodies need for healthy functioning. Relying on supplements is not the answer and in some cases causes more harm than good.
  4. Alcohol use: you don’t have to cut it out completely, but the less you consume, the lower your risk of cancer. Try tracking your consumption to see what the pattern is, and where you can cut down (eg where it is habitual).
  5. Occupation: some jobs make it more likely that you will be exposed to chemicals or practices that put you at higher risk for cancer. If you have any concerns, then talk to your manager or get in touch with the authorities (eg the Health and Safety Executive in the UK).
  6. Exposure to the sun and sunbeds: too much UV light from either of these sources is the main cause of skin cancers. Rates of melanoma, the deadly form, are rising rapidly. Reduce your risk of sunburn and get SunSmart.
  7. Infections: in the UK, human papillomavirus, or HPV, which causes cervical cancer, is behind the most cancers in the UK, followed by Helicobacter pylori, which causes stomach cancer. Rates of cervical cancer are expected to fall as more girls are vaccinated for HPV.
  8. Red meat (eg fresh or minced or frozen beef, pork, lamb, veal) and processed meat (eg salami, bacon, ham, sausages): eating small amounts should not increase risk of bowel cancer, but it is best to limit intake to no more than twice a week.
  9. Radiation: we are all exposed to this from our environment, and from space, but occasionally we get higher doses from undergoing X-rays, radiotherapy or traveling in aircraft.
  10. Fibre: the benefit of fibre is that it helps speed up the passage of food through the digestive system, thus minimizing the time that cancer-causing chemicals in the food spend in contact with the wall of the gut, which in turn reduces the risk of bowel cancer.
  11. Exercise and physical activity: not only does this help you maintain a healthy weight, it also directly affects cancer risk. You don’t have to be an athlete: 30 minutes of moderate activity on 5 days a week, is enough to make a significant difference. And even if those 30 minutes are from short bursts over the day, it has the same benefit.
  12. Breastfeeding: if you can breastfeed, this will reduce your risk of breast cancer, especially if you can maintain it for 6 months.
  13. Salt: high-salt diets increase the risk of stomach cancer, as does smoking and the common bacterial infection, Helicobacter pylori .
  14. Hormone Replacement Therapy (HRT): may help reduce some of the uncomfortable symptoms of the menopause, such as hot flashes and mood swings, but it can also increase the risk of cancer. Talk to your doctor if you are thinking of starting or stopping HRT.

Written by Catharine Paddock PhD