Causes and risk factors
Everyone has a certain risk of developing cancer. A combination of genes, lifestyle and environment can affect this risk. Doctors do not know the exact causes of cancer. But there are risk factors that can increase your chance of developing it.
Having one or more risk factors does not mean you will get cancer. Also, having no risk factors does not mean you will not develop cancer.
Around 1 in 3 cases of the most common cancers (about 33%) could be prevented by eating a healthy diet, keeping to a healthy weight and being more active. There are some things you can do to lower your risk of developing cancer. But you cannot reduce your risk completely through your lifestyle.
Cancer is very common and most of us have relatives who have had cancer. People often worry that a history of cancer in their family greatly increases their risk of developing it. But fewer than 1 in 10 cancers are associated with a strong family history of cancer. If you are worried, you should talk to your GP.
Giving up smoking
In the UK, more than 1 in 4 cancer deaths (over 25%) are caused by smoking.
Breathing in other people’s smoke (passive smoking) also increases your risk of developing cancer.
Keep your home smoke-free to protect you and your family’s health. If you smoke, giving up is one of the most important thing you can do for your health.
If you want to give up smoking, it is never too late to stop. Ask your GP for advice, or contact the stop-smoking service in your area.
Keeping to a healthy weight
Being overweight increases the risk of many types of cancer, including cancers of the bowel, kidney, womb and gullet (oesophagus). Women who are overweight and have been through the menopause also have a higher risk of breast cancer.
Keeping to a healthy body weight reduces your risk of cancer and other health problems, such as heart disease and diabetes.
If you are worried about your weight or need more information, talk to your GP or a dietitian.
Eating a balanced 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 to keep to a healthy weight.
Eating plenty of high-fibre foods helps reduce the risk of bowel cancer. Red and processed meat are linked to a higher risk of bowel and prostate cancer. Try to limit how much you eat. Red meats include beef, pork, lamb and veal. Processed meats include sausages, bacon, salami, tinned meats, and packet meats like sandwich ham.
Being physically active
Many studies have found that regular physical activity can reduce the risk of cancer. You should try to do at least 30 minutes of activity every day.
Your cancer risk is reduced further if you are active for more than 30 minutes a day and if you exercise harder (vigorous activity). The NHS has more information on how to stay active.
Limiting how much alcohol you drink
Drinking alcohol increases your risk of mouth and throat cancers. But it is also linked to other cancers.
In general, the more you drink, the higher your risk. Your risk is even higher if you also smoke.
You should try to stick to the current guidelines on drinking alcohol.
Taking care in the sun
Spending some time outside in the sun helps you stay healthy. Our bodies need sunlight to make vitamin D.
But it is important to protect your skin from burning, as this can increase your risk of skin cancers.
If you are going to be out in the sun for longer than a few minutes, you should protect your skin:
- Keep your arms and legs covered by wearing long-sleeved tops and trousers. Wear a wide-brimmed hat to protect your face and neck.
- Use suncream with a high sun protection factor (SPF) of at least 30. Choose one that protects against UVA and UVB, with four or five stars.
- Make sure you use enough sun cream. Experts say you need at least six to eight teaspoons of lotion for an average-sized adult to give the SPF coverage it says on the bottle.
- Stay out of the sun during the hottest part of the day. This is usually between 11am and 3pm.
Using sun beds or sun lamps also increases your risk of skin cancer. If you want to look tanned, use fake-tanning lotions or sprays.
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.
Viruses and bacteria
Viral infections are very common and usually do not cause cancer to develop. A small number of viruses have been linked to a higher risk of certain types of cancer. These include:
Human papilloma viruses (HPV)
Hepatitus B and C
T-cell leukaemia virus
There is also a common bacterial infection called H. pylori (Helicobacter pylori). Over a long period of time, it can increase the risk of stomach cancer.
Not everyone infected with these viruses or bacteria will develop cancer.
Reducing your risk
You cannot protect yourself against all viruses and bacteria. But there are things you can do to reduce your risk of developing some of these:
Vaccines can be used to protect against HPV infection. The NHS offers the HPV vaccine to:
- girls from the age of 12 or 13
- men who have sex with men.
From 2019, the HPV vaccine will also be offered to boys from the age of 12 or 13.
Other people may also have the HPV vaccine, because they may have an increased risk of cancer caused by HPV infection. Your GP, local sexual health clinic or HIV clinic can give you more information.
Hepatitis B and C and HIV
Using condoms and dental dams during sex can help protect you from these.
If you inject drugs, it is important to never share needles. This is because viruses can pass from person to person in the blood.
The NHS has more information on preventing HIV or reducing your risk that you may find useful.
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