Genetics is not the only risk factor for cancer. Indeed, up to 50% of all cancers can be prevented.
In the United States, around 40% of all adults will develop cancer in their lifetime. Genetics plays a role, but so do diet and lifestyle. And external factors can impact whether you will develop cancer. These include ultraviolet rays, ionizing radiation, asbestos in old buildings, tobacco use, environmental pollution, alcohol, and some bacteria and viruses.
Cancer gene mutations may be inevitable in some people, but many cancers can be prevented by controlling the external carcinogenic factors and adopting healthier diet and lifestyle practices. In fact, 30% to 50% of cancers around the world can be prevented by avoiding carcinogens and living a healthy lifestyle. Some cancers can be completely prevented by avoiding exposure to certain external carcinogens. Others are primarily due to genetic factors and are less likely to be caused by external carcinogens.
Avoiding external cancer risk factors
Studies in some western countries have shown the impact of external risk factors on cancer induction. An American Cancer Society study of more than 1.57 million U.S. adults over the age of 30 found that 42% of cancer cases were attributable to these risk factors.
In China, the cancer in 47% of male cancer patients and 28% of female cancer patients were linked to external cancer risk factors. In Brazil, 34% of new cancer cases in men and 35% of new cancer cases in women were linked to external cancer risk factors.
External cancer risk factors also impact the death rates due to cancer. These are smoking, being overweight, alcohol use, radiation, physical inactivity, bacterial and viral infections, poor diet, consumption of processed meats and red meat, and low dietary calcium intake. According to the latest research published in The Lancet in 2022, 44% of cancer deaths worldwide are linked to risk factors.
Moreover, exposure to some toxic chemicals can also cause cancer. For instance, exposure to asbestos can cause lung cancer; and drinking water that contains high levels of arsenic can cause skin cancer, bladder cancer, and lung cancer.
Smoking
Smoking is the number one risk factor for cancer. One out of every three cancer deaths is attributable to smoking. Smoking can cause cancer in almost every part of the body, from the mouth to the bladder.
Harmful chemicals in the smoke that enter the lungs and spread throughout the body through the blood and lymphatic system will interfere with normal cell growth. The chemicals also damage genes that protect the body from cancer. Over time, the accumulation of DNA damage in cells will lead to cancer.
A study of over 220,000 people found that smoking increased the risk of cancer by 42% compared with non-smokers. Smoking greatly increases the risk of lung cancer, laryngeal cancer, liver cancer, esophageal cancer, and bladder cancer. Around 50% of smokers will develop cancer by the time they are 80 years old, and 14% will develop lung cancer.
Being overweight
Being overweight is the second-leading preventable cause of cancer after smoking, and 8% of new cancer cases in the United States are due to patients being overweight.
Excess weight contributes to 13 types of cancer including postmenopausal breast cancer, endometrial cancer, colorectal cancer, pancreatic cancer, and gallbladder cancer. Postmenopausal breast cancer is the most common obesity-related cancer in women, and colorectal cancer is the most common obesity-related cancer in men.
Being overweight can lead to changes in the body, including long-term inflammation and higher-than-normal levels of insulin, insulin-like growth factors, and sex hormones, and this ultimately causes cancer. The more weight a person gains and the longer they stay overweight, the higher their risk of developing cancer.
Alcohol use
Alcohol-related cancers account for 5.6% of new cancer cases in the United States. A Lancet study proves that there is no safe minimum consumption of alcohol for the human body, and it is best not to drink it at all.
Drinking alcohol will increase the risk of developing oropharyngeal cancer, esophageal cancer, stomach cancer, breast cancer, liver cancer, and colorectal cancer.
The decomposition of ethanol in alcoholic beverages in the body is divided into two steps: it is first decomposed into acetaldehyde, and then into acetic acid. Acetaldehyde is a toxic chemical that damages DNA and proteins in cells, which can lead to cancer.
Alcohol can impair the body’s ability to break down and absorb various nutrients, such as vitamin A, folic acid, vitamin C, vitamin D, vitamin E, and carotenoids. Deficiencies in these nutrients can increase the risk of cancer.
Radiation
Radiation can penetrate our bodies and can change the molecules within the cells of our body. The DNA of cells is attacked and damaged, which eventually causes cancer. There are two main types of radiation that cause cancer:
Ultraviolet radiation, especially from the sun, can cause all major types of skin cancer, such as melanoma. Melanoma caused by ultraviolet radiation accounts for 4.7% of all cancer cases in the United States. Tanning beds are also sources of UV radiation.
Ionizing radiation from X-rays, CT scans, fluoroscopy, and nuclear medicine scans can cause many types of cancer, including leukemia, thyroid cancer, breast cancer, myeloma, and others.
The use of CT scans has been increasing. Estimates show that unnecessary repeat CT scans account for one-third of all CT scans in the United States. One study by Columbia University in 2001 found that there were 600,000 abdominal and head CT examinations performed on children under the age of 15 in the United States every year. The researchers estimated that this could result in an additional 500 cancer deaths due to CT radiation.
Physically inactive
Cancers related to the lack of physical activity account for 2.9% of new cancer cases in the United States. Physical inactivity can lead to hormonal imbalances and insulin resistance, which increases inflammation in the body, thereby increasing the risk of cancer. Inactivity can also lead to weight gain.
Cancers that can be attributable to physical inactivity include colon cancer, postmenopausal breast cancer, and prostate, uterine, and lung cancers. Sedentary individuals have a 24% higher risk of colorectal cancer, a 32% higher risk of endometrial cancer, and a 21% higher risk of lung cancer.
Being physically active can help your body regulate hormones such as insulin-like growth factors and estrogen, and affect how quickly food moves through the gut, thereby lowering the body’s exposure to any potential carcinogens.
Poor diet
Low dietary fiber intake also increases the risk of colorectal cancer. Furthermore, a low intake of fruits and non-starchy vegetables increases the risk of oropharyngeal and laryngeal cancers. In addition, insufficient fruit intake also increases the risk of lung cancer. These cancers, caused by a low dietary fiber intake and low fruit and vegetable intake, account for 2.8 percent of new cancer cases in the United States.
A diet high in fat, protein, calories, and red meat increases the risk of colorectal cancer. Eating processed meat also increases the risk of stomach cancer in addition to an increased risk of colorectal cancer. Cancers caused by the consumption of red and processed meat account for 1.3% of new cancer cases in the United States.
Bacterial and viral infections
Some cancers are caused by viral or bacterial infections. These include Human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HPC), Helicobacter pylori, human immunodeficiency virus (HIV), human herpesvirus 8 (HHV8), and Epstein–Barr virus.
HPV can cause cervical, penile, vaginal, anal, oropharyngeal, and vulvar cancers.
Most people infected with HPV do not know that they have an infection. Normally, the body’s immune system will clear the HPV infection naturally within two years. According to statistics, by the age of 50, at least 80% of women will have been infected with HPV at some point in their lives. HPV infection is also common in men, and it is often asymptomatic. When your immune system cannot eliminate this infection, it may eventually develop into cancer. Approximately 10% of women with cervical HPV develop long-term infections, which increases the risk of cervical cancer.
- Helicobacter pylori can cause stomach cancer.
- The hepatitis B virus can cause liver cancer, and the hepatitis C virus can cause liver cancer and non-Hodgkin’s lymphoma.
- Human immunodeficiency virus, also known as HIV, can cause anal cancer, Kaposi’s sarcoma, cervical cancer, Hodgkin’s lymphoma, and non-Hodgkin’s lymphoma
- Human herpesvirus 8, also known as Kaposi’s sarcoma herpesvirus, can cause Kaposi’s sarcoma.
- Epstein–Barr virus can cause Burkitt lymphoma, nasopharyngeal carcinoma, and Hodgkin’s lymphoma.
Which cancers are preventable?
A study published in CA: A Cancer Journal for Clinicians determined the population-attributable factors for certain cancers. They assigned a percentage that can be attributed to external cancer risk factors. The higher the PAF, the more preventable is the cancer. They found the following:
- Cervical cancer and Kaposi’s sarcoma incidence was 100%, meaning it is highly preventable.
- Melanoma skin cancer had a PAF of 95.1%.
- The PAF of lung cancer was 85.8%.
- Lymphoma and ovarian cancers had PAFs of below 10%.
Final thoughts
So many factors in our lives are within our grasp to change. We can’t change our genetics, but we can stop smoking, eat a better diet, and get out to exercise. Doing so today will result in a healthier you and a lower risk of cancer.