To protect oneself from cancer one needs to know what causes it.

The major causes of cancer can be divided into genetic causes and environmental/external causes. The genetic causes are mostly not in our control, however, the environmental/ external causes which we can control are as follows

1.Tobacco

Tobacco use is the most preventable cause of cancer and accounts for 21 percent of worldwide total cancer deaths and about 30 % of cancer-related deaths in the United States. Adult smokers lose an average of 13 years of life due to this addiction
It is a risk factor for lung cancer, Head and neck cancers, Blood cancer, cancers of larynx, esophagus, pancreas, liver, stomach, cervix, kidney, large bowel, bladder and prostate.

2.Environmental Exposure

Increased exposure to excessive
a) solar radiation or to artificial ultraviolet radiation – causes skin cancer
b) air pollution – increased risk of lung cancer
c) radon gas in enclosed environments -Lung cancer
d) arsenic in drinking water.

3. Physical Inactivity

It is associated with an increased incidence of colon, liver, pancreatic, and stomach

4. Obesity

Obesity has been estimated to cause 20 percent of all cancers
It is associated with esophageal adenocarcinoma, gastric cardia, colorectal, hepatocellular, endometrial, ovarian, gallbladder, pancreatic, renal cell, thyroid, and postmenopausal breast cancers, multiple myeloma, and meningioma.

5. Diet

Specific components of the diet, as well as overall dietary patterns, have been studied in relation to the risk of cancer.
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a) Dietary fat —
a diet high in animal fat may be an important factor in the development of prostate cancer. In particular, the intake of large amounts of alpha-linoleic acid and low amounts of linoleic acid appears to increase risk; this combination is common in red meat and some dairy products

b) Red meat — A high intake of red meat has been associated with an increased risk of colon cancer. The mechanisms for this increased risk have not been determined, but several factors have been suggested including heme content in the meat, animal fat, and carcinogens produced when the meat is cooked at high temperatures. It isn't known if risk varies with different animal raising strategies (eg, grass-fed beef).

c) Fruits and vegetables — Presently no data to suggest the role in the prevention or causing cancer
d) Dairy — The relationship between dairy intake and ovarian cancer is uncertain.
e) Fiber — Fibre intake is associated with a reduction in the risk of heart disease

6.Alcohol

Excess alcohol consumption increases the risk of multiple cancers involving upper gastrointestinal and hepatocellular cancer. 3.6 percent of cancers are associated with chronic alcohol drinking.

7. Infections

17 percent of all new cancers worldwide are due to infections. Various infections associated with Virus infections are as follows

a) Human papillomavirus (HPV) with cervical and other anogenital cancers as well as squamous cell cancers of the head and neck
b) Hepatitis B (HBV) and C (HCV) with hepatocellular
c) Human T-cell lymphotropic virus (HTLV-I) with adult T-cell
d) Human immunodeficiency virus (HIV-I) with Kaposi sarcoma
e) Epstein-Barr virus (EBV) with Burkitt lymphoma
f) Helicobacter pylori with gastrointestinal malignancies including gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphomas
g) Liver flukes with cholangiocarcinoma and hepatocellular carcinoma