Causes and risk factors

Most of the time, we do not know why one person gets cancer while someone else does not.

Some things can increase a person’s risk of getting cancer. These are called risk factors. There are some general risk factors for developing cancer. And there are some that increase the risk of developing a specific type of cancer.

Having 1 or more risk factors does not mean you will definitely get cancer. Some factors only increase your risk a small amount. Others are much more likely to cause cancer, such as smoking. You can still develop cancer even if you do not have any known risk factors.

About 4 in 10 cancers (40%) could be prevented. Living a healthier lifestyle can help reduce your risk (see below). But you cannot reduce your risk of cancer completely.

There are many factors involved in developing cancer. Having a healthy lifestyle does not guarantee that you will not get cancer. But it reduces your risk and improves your general health. It also reduces your risk of other illnesses such as heart disease.

Smoking is the biggest cause of cancer in the UK. It causes 15 in every 100 cancers (15%). Over 70 in 100 lung cancers (72%) are caused by smoking. Giving up smoking is the single most important thing you can do for your health.

Chewing or sucking tobacco is not a safe alternative to smoking cigarettes. If you chew or suck tobacco, you have a higher risk of mouth and oral cancers.

Breathing in other people’s tobacco smoke (passive smoking) also increases your risk of cancer. Keeping your home smoke-free will protect you and your family’s health.

Many people now use e-cigarettes. The long-term effects of e-cigarettes are not yet fully known. E-cigarettes are thought to be a lot safer than tobacco cigarettes. But it is still much better to not smoke at all.

If you want to give up smoking, it is never too late to stop. Ask your GP for advice, or contact a stop-smoking service in your area.

After smoking, being overweight is the second biggest cause of cancer. It increases the risk of many cancer types, including cancers of the bowel, kidney, womb, and gullet (oesophagus). Women who are overweight and have had the menopause also have a higher risk of breast cancer.

Keeping to a healthy weight reduces your risk of cancer and other health problems, such as heart disease and diabetes.

Here are some tips to help you keep to a healthy weight:

• Eat a healthy diet with lots of fruit and vegetables and less fat and sugar.
• Only eat as much food as you need depending on how active you are.
• Be more physically active.

If you are worried about your weight or need more information, talk to your GP or a dietitian.

There is no single food that causes or prevents cancer. Eating a balanced diet is good for your overall health and helps reduce your risk of some cancers. It can also help you keep to a healthy weight.

Try to limit how much red and processed meat you eat. These are linked to a higher risk of bowel and prostate cancer. Red meat is beef, pork, lamb and veal. Processed meats include sausages, bacon, salami, tinned meats, and packet meats such as the ham you have in sandwiches. We have more information about eating a balanced diet.

You can find more detailed information about diet and cancer risk on the World Cancer Research Fund website.

Regular physical activity can help reduce the risk of some cancers. Physical activity is also good for your general health and well-being. Each week, you should try to do at least 150 minutes of moderate activity or 75 minutes of vigorous activity.

Moderate activity raises your heartbeat and makes your breathing faster. It includes things like brisk walking, riding a bike and dancing.

Vigorous activity makes you breathe hard and not be able to say much without taking a breath. It includes running, swimming and walking up the stairs.

If you are not used to doing exercise, ask your GP for advice about getting started. You can find more information about keeping active on the following websites:

• England – nhs.uk/live-well/exercise
• Scotland – nhsinform.scot/healthy-living/keeping-active
• Wales – gov.wales/physical-activity-health
• Northern Ireland – nidirect.gov.uk/articles/physical-activity

Drinking alcohol increases your risk of mouth and throat cancers. It is also linked to cancers of the gullet (oesophagus), bowel, liver and breast.

In general, the more you drink, the higher your risk. Your risk is higher if you also smoke.

Current guidelines say:

• do not drink more than 14 units of alcohol in a week
• spread the amount you drink in 1 week over 3 or more days
• try to have several alcohol-free days every week.

There is no safe level of drinking alcohol. But sticking to these guidelines reduces your risk of damaging your health.

You can find more information about alcohol and drinking guidelines at drinkaware.co.uk

Spending some time outside helps you stay healthy. Our bodies need sunlight to make vitamin D. This is important for bone health and reduces the risk of some illnesses.

But it is important to protect your skin from too much sun. This is because too much sun can increase your risk of skin cancer. If you have white or pale skin or do not tan easily, you should avoid letting your skin go pink or red in the sun. If you have black or brown skin, the signs of sun damage may not be as obvious, but you should still protect your skin in the sun.

Here are some tips to help you stay safe in the sun:

• Wear clothes made of fabric that does not let sunlight through. Make sure they cover your body, arms and legs.
• Wear a wide-brimmed hat that protects your face, ears and neck.
• Wear sunglasses with wide wraparound lenses or wide arms with the CE Mark and British Standard Mark 12312-1:2013 E.
• Stay in the shade when you can, especially between 11am and 3pm.
• Use a suncream with a sun protection factor (SPF) of at least 30. Choose one that protects against UVA and UVB, with four or five stars.

Using sunbeds or sunlamps also increases your risk of skin cancer. If you want to look tanned, use fake tan lotions or sprays.

Exposure to harmful substances in the environment or workplace can cause cancer. Substances that cause cancer are called carcinogens. Some of these carcinogens can cause cancer years after you have been exposed to them.

If you have a cancer caused by your workplace, you may be able to claim Industrial Injuries Disablement Benefit.

If you have low immunity, your immune system does not work as well. This means you are more likely to get infections.

People with a lower immunity may have:

• had a transplant and take drugs to suppress the immune system – these drugs stop the body rejecting the transplant
• HIV (human immunodeficiency virus)
• a medical condition that lowers their immunity.

If you have low immunity, you may be more likely to develop some cancers. These cancers include lymphoma, non-melanoma skin cancer and Kaposi’s sarcoma, or cancers caused by a virus or bacteria.

Having a pre-cancerous condition does not mean that you have cancer, or that you will definitely develop cancer. But pre-cancerous conditions are diseases or syndromes that might develop into a cancer, so it’s important to monitor your health.