Cancer is cause by a variety of factors, many of which can be prevented. Generally, 53.3% of male cancers and 27.8% of female cancers are thought to have been caused by the lifestyle-related habits and infections listed here. Among them, smoking (male: about 29.7%, female: about 5.0%) and infection (male: about 22.8%, female: about 17.5%) are reported to be the major causes, and the others are relatively small.
Studies have scientifically shown that tobacco causes a variety of cancers, including lung cancer. In addition, smoking causes health hazards not only to the person himself but also to those who do not smoke.
People who are currently smoking can also reduce their risk of developing cancer by quitting smoking.
Drinking has been report to increase the risk of cancer of the oral cavity, pharynx, larynx, esophagus, large intestine, liver and breast. Ethanol taken into the body by drinking is metabolized to acetaldehyde, which has been shown to be carcinogenic in animals, and is thought to cause cancer.
In addition, it has been reported that drinking causes cancer because it suppresses immune function, affects estrogen metabolism, and leads to malnutrition and malnutrition. It is known that when smokers drink alcohol, the risk of developing esophageal cancer and cancer as a whole is particularly high (interaction).
- Food / nutrition:
Various studies have been conduct on food and nutrition, but few foods are definitely at risk of cancer. To be sure, red meat and processed meats such as beef, pork and sheep increase the risk of colorectal cancer. In addition, foods containing dietary fiber reduce the risk of colorectal cancer, and moderate to high-intensity physical activity reduces the risk of colon cancer.
Vegetables and fruits contain various substances such as carotene, folic acid, vitamins, and isothiocyanates, and these components increase the activity of enzymes that detoxify carcinogens, or eliminate active oxygen generated in the body. It is being considered. However, it has not been reported that vegetables and fruits definitely reduce the risk of cancer.
Non-depleted vegetables excluding potatoes are in the oral cavity, pharynx and larynx, and fruits are in the oral cavity, pharynx, larynx and lungs. It has been reported to be “probable” to reduce the risk of cancer. According to the working group of the International Agency for Research on Cancer, the cancer prevention effect of vegetables and fruits is not always an established relationship. However, from the viewpoint of prevention of all diseases including cancer, eat a lot of vegetables and fruits is recommended.
Salted foods have been reported to be “likely” to increase the risk of stomach cancer. High concentrations of salt destroy the mucus that protects the gastric mucosa, causing inflammation of the gastric mucosa due to gastric acid and persistent infection of Helicobacter pylori which causes gastric cancer. It is believed to increase risk. In addition, salted foods contain not only salt but also carcinogens such as nitrite and nitroso compounds, which are thought to increase the risk of stomach cancer.
- Physical activity:
Exercise has been report to definitely reduce the risk of colon cancer and may reduce the risk of postmenopausal breast and endometrial cancer. Reasons for this include elimination of obesity, improvement of the action of insulin, which is a hormone that lowers blood sugar (improvement of insulin resistance), enhancement of immune function, and effect on the metabolism of bile acids that regulate lipid absorption. Is believed to be.
It has been report that the following risks are “certainly” increase due to the influence of physique:
- Obesity: Cancer of the esophagus, pancreas, liver, large intestine, breast (postmenopausal), endometrial cancer, kidney
- Weight gain after adulthood: Cancer of the breast (postmenopausal)
- Tall: Cancer of the large intestine, breast, and ovary
The mechanism by which obesity affects carcinogenesis is thought to be diverse, but the production of estrogen (a type of female hormone) in adipose tissue is thought to increase the risk of endometrial cancer and postmenopausal breast cancer.
In addition, with obesity, insulin does not work sufficiently, causing hyperinsulinemia in which insulin is excessively secreted, and insulin-like growth factors that promote cell proliferation and differentiation are continuously increased. It is thought to increase the risk of colon cancer.
On the other hand, from the results of studies on Asians. it has been observed that being too thin increases the risk of cancer. It is presumed that this is due to a decline in immune function due to malnutrition and a lack of antioxidants.
Infection is estimate to account for about 20% of the causes of cancer in general.
Most of the infections are liver cancer caused by hepatitis B and C virus, cervical cancer caused by human papillomavirus (HPV), and stomach cancer caused by Helicobacter pylori. Others include malignant lymphoma and nasopharyngeal cancer caused by Epstein-Barr virus (EBV) and adult T-cell leukemia / lymphoma caused by human T-cell leukemia virus type I (HTLV-1).
The mechanism of carcinogenesis by infection includes the direct action of carcinogenic proteins produced by infectious agents, such as human papillomavirus, and the indirect action of cell necrosis and regeneration associated with chronic inflammation.
- Chemical substance:
Certain occupations and occupationally exposed chemicals known to increase the risk of carcinogenesis in humans. The International Agency for Research on Cancer lists 120 chemicals and occupations, even those classified as carcinogen. The lungs are the most related organs, but they are also characterized by the skin that comes into direct contact with chemical substances, the nasal cavity, larynx, lungs, and pleura, which are the routes of inhalation, and the urinary tract that is excreted.
In developed countries, the working environment has improved, the use of potentially carcinogenic chemicals has been banned and exposure has been restricted. However, in developing countries, such measures are not sufficient and may continue to be a problem.
- Reproductive factors and hormones:
Sex steroid hormones such as estrogen, progesterone, androgens thought to play an important role in the development of cancer in the breast, endometrial body, ovaries, and prostate. Hormonal and antihormonal agents have also been shown to increase the risk of cancer in some areas while reducing the risk of cancer in other areas.
The following are the main hormones that definitely increase or decrease the risk of cancer.
- Estrogen therapy (postmenopausal: endometrial cancer, ovarian cancer, breast cancer)
- Oral contraceptives with estrogen / progestogen combination (liver cancer, breast cancer, cervical cancer)
- Estrogen / progestogen combination therapy (postmenopausal: breast cancer, endometrial cancer)
- Tamoxifen (endometrial cancer) used to treat breast cancer as an anti-estrogen drug