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.
General risk factors for cancer include the following:
- Age – the risk of developing cancer increases as you get older.
- Lifestyle factors – these include smoking, your weight, your diet, how active you are, sun exposure and sunbed use, and how much alcohol you drink. You can read more about how to reduce your risk below.
- Family history – some cancers are more common in some families. We have more information for people with a family history of cancer.
Giving up smoking
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.
Keep to a healthy weight
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.
Eat a healthy diet
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.
Be physically active
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:
Limit how much alcohol you drink
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
Take care in the sun
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.
A small number of viruses have been linked to a higher risk of certain types of cancer. These viruses include:
- Human papilloma virus (HPV), which increases the risk of cervical cancer and is linked to cancers of the head and neck, anus, vulva, vagina and penis
- hepatitis B and C, which are linked to liver cancer
- HIV, which can increase the risk of cancers including lymphoma and sarcoma.
There is a vaccine to protect against HPV. This is given to children aged 12 to 13 as part of the NHS vaccination programme.
If you have an increased risk of cancer caused by HPV, you may be able to have an HPV vaccine. Your GP, local sexual health clinic or HIV clinic can give you more information.
Using condoms and dental dams during sex can help protect you from some viruses.
If you inject drugs, it is important to never share needles. This is because viruses can pass from person to person in the blood.
Workplace and environmental factors
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.
Asbestos is a natural mineral that is now banned in the UK. It can damage the lungs and cause mesothelioma. The people most likely to have been exposed to asbestos at work include people who work in construction, ship and boiler makers. People who have not worked with asbestos may also be at risk. This can happen if they have been exposed to asbestos factories, buildings that contain asbestos or if they live with someone working with asbestos.
Some chemicals have been linked to bladder cancer. The chemicals were previously used in dye factories and other industries. Many of these chemicals are now banned. But bladder cancer can take more than 25 years to develop after you are exposed to the chemicals. Some chemicals can also slightly increase the risk of skin cancer. Many of these chemicals are also banned.
One of the main environmental causes of cancer is ultraviolet (UV) radiation from the sun. We know that many skin cancers, including melanoma, are caused by spending too much time in the sun. The people most at risk are those who work outside, and those who are fair-skinned. There are things you can do to reduce your risk (see above).
Radon is another possible source of radiation that may be linked to cancer. Radon is a natural gas that is found in rock in parts of the UK. Radon has been linked to lung cancer. But the risk is very small.
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.
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