Cancer is not a single disease, but is instead a collection of related diseases that arise from different kinds of cells in the body.  Cancer occurs when cells that normally grow in a controlled fashion begin out-of-control growth and continue to divide without stopping. On a molecular level, scientists know that mutations in certain genes contribute to the development of cancer but it is impossible to predict when and where cancer will occur. Genes, lifestyle, and protective/risk factors all play a role in the development of cancer. 
Cancer prevention is the set of actions a person takes to reduce their risk of developing cancer. 
Reducing Risk Factors
1Quit using tobacco products. Smoking is the biggest risk factor for developing lung cancer. The use of tobacco products in general is a risk factor for cancers of the mouth, pharynx, esophagus, stomach, pancreas, bladder, cervix, colon, and ovaries. Quitting smoking or quitting using tobacco products can be difficult, but with a good plan, support group, and perseverance, it can be accomplished. The National Institute of Dental and Craniofacial Research provides some helpful guidelines to help people quit using tobacco products. 
- Decide to quit and make a plan. Many people find it helpful to write down reasons why they want to quit.
- Choose a date about one week in the future that you will quit using tobacco. Prepare yourself for quitting, and stick to the date you picked.
- Begin to taper your tobacco use prior to your quit date.
- Gather support. Tell your family and friends about your decision to quit using tobacco products. Warn them that you may not be quite yourself for the next few weeks, but let them know you are determined!
- Keep busy by exercising and participating in activities not associated with using tobacco products.
2Avoid exposure to intense sunlight. Sunburns cause lasting damage to the skin. Children who have had at least one blistering sunburn are at twice the risk of developing melanoma (a type of skin cancer) compared to children who never suffered blistering sunburns.  Exposure to intense sunlight can be limited by covering up with long sleeves, pants, and hats and by wearing sunscreen. The Skin Cancer Foundation provides guidelines for minimizing exposure. 
- Seek out shady areas and minimize your time in the sun when it is most intense – typically between 10AM and 4PM.
- Cover yourself with loose-fitting clothing, preferably made from fabric with Ultraviolet Protection Factor (UPF) rating.
- Wear a wide-brimmed hat and sunglasses that block ultraviolet (UV) light.
- Apply sunscreen that is at least Sun Protection Factor (SPF) 30 when you will be out for an extended period of time. It is best to apply the sunscreen about 30 minutes before heading outside, and then to reapply sunscreen every 2 hours.
- Do not use tanning beds.
3Consume alcohol in moderation. Alcohol is broken down in the body to acetaldehyde, which is a probable carcinogen (cancer-causing agent) that can damage DNA.  The use of alcohol together with smoking increases the risk for cancer more than the use of either substance by itself  The American Cancer Society suggests that people who do drink alcohol should have no more than 2 standard drinks per day for men, and 1 standard drink per day for women. 
- One standard drink is 12 fluid ounces of beer, 5 fluid ounces of wine, or 1.5 fluid ounces of 80-proof liquor.
4Avoid exposure to known carcinogens. If you work in a laboratory environment, a factory, or even in an office, you likely come into contact with known or probable carcinogens from time to time. Three agencies maintain lists of carcinogens. They are The National Toxicology Program  the International Agency for Research on Cancer  and the Environmental Protection Agency.  A non-exhaustive list of human carcinogens can be found at The American Cancer Society. 
- Adhere to all workplace rules regarding personal protective equipment such as masks, respirators, gloves, goggles, and gowns.
- Read the labels of household cleaners, herbicides, and pesticides. Wear appropriate protective equipment and follow all safety guidelines.
5Avoid risky behaviors such as unprotected sex. Some viruses can be transmitted by sexual contact between individuals. Infection with certain kinds of these viruses can put people at increased risk for cancer. For example, the viruses that cause hepatitis B and hepatitis C increase the risk for liver cancer.  Human Immunodeficiency Virus (HIV) attacks immune system cells and kills them. A weakened immune system increases the risk of many types of cancer, including a type of skin cancer called Kaposi’s sarcoma.
Enhancing Protective Factors
1Eat a healthy diet. Experts believe that eating a healthy diet could prevent up to 10% of all cancer cases in the United Kingdom.  Eating more fruits and vegetables has been linked to reduced risk of cancers of the mouth, esophagus, stomach, lung, and larynx. Eating too much red meat (beef, pork, lamb) and processes meat (salami, bacon, hot dogs) has been linked to increased risk of cancer.  People who eat more fiber have reduced risk of bowel cancers. 
- Include chicken and fish in your diet. Replace some of the red or processed meat you eat with chicken or fish 1-2 times per week. Try replacing some of the meat in meals with beans or tofu.
- Eat at least 5 servings of fruits and vegetables each day. 
- To boost fiber content in your meals, adhere to the 5 servings of fruits and vegetables per day. Include whole grain foods in your meals daily.
- Diets high in saturated fats may increase breast cancer risk. Avoid saturated fats by reading food labels and choosing alternatives with less saturated fat. 
2Exercise regularly. Studies have shown that women who exercise 30 minutes per day 5 times per week have a 15-20% reduction in breast cancer risk.  Other studies have consistently demonstrated a 30-40% reduction in colon cancer risk when individuals increase their physical activity.  Physical activity has also been shown to reduce the risk of lung and endometrial cancer.
- Exercise at a moderate to vigorous intensity for 30-60 minutes per day. Examples of moderate intensity exercises include walking briskly, water aerobics, and bicycling at less than 10 miles per hour.  Examples of vigorous intensity exercises include jogging, hiking uphill, swimming laps, and jumping rope. 
3Maintain a healthy weight. Being obese is defined as having a Body Mass Index (BMI) greater than 30, if you are over 20 years old.  Obesity puts people at an increased risk of many types of cancer, including cancers of the pancreas, kidney, thyroid, gallbladder.  Tips to maintain a healthy weight include: 
- Get regular exercise.
- Eat healthy foods.
- Avoid foods that you tend to overeat.
- Weigh yourself regularly to track your progress.
- Consult a dietician or nutrition professional for additional advice and help with planning.
4Get vaccinated. Infection with certain types of viruses increases the risk for certain kinds of cancer. For example, the virus that causes hepatitis B (HBV) increases the risk for liver cancer.  Infection with certain strains of the human papillomavirus (HPV) increases the risk for cervical, anal, vaginal, and vulvar cancers.  Vaccines are available that are effective in preventing infection with these viruses. It is important to note that the HPV and HBV vaccines are not the same as a “cancer vaccine”. Cancer vaccines are designed to stimulate the body to attack cancer cells once cancer has developed. Researchers are currently working on cancer vaccines, and many are in clinical trials as of this writing. 
- Ask your healthcare provider which vaccines are suitable for you and your children.
5Get adequate sleep. There is some evidence that disrupted circadian rhythms increases cancer risk.  One study found that women who worked irregular schedules had a 30% higher risk of developing breast cancer than those who worked a more regular schedule. Shift work is also a risk factor for prostate cancer.  Inadequate sleep is also a risk factor for obesity, which is itself a risk factor for cancer.  Experts suggest trying the following in order to sleep more soundly at night: 
- Create a sleep schedule. Go to bed the same time every night.
- Have a sleep routine. Wind down the same way every night.
- Create a comfortable sleeping atmosphere. For most people, this means cool temperatures, low noise, and a dark room.
- Avoid certain foods and drinks in the hours before bedtime. Caffeine can keep you up for hours after you consume it. Alcohol may seem to put you to sleep initially, but it can disrupt sleep later in the night. Going to sleep overfull can create discomfort and a need to visit the restroom in the middle of the night.
- Take power naps during the day, but keep them under 30 minutes. Too much sleep during the day can interfere with your ability to fall asleep and stay asleep.
- Get daily exercise, but avoid exercise too close to bedtime.
- Maintain a stress-free life. Worries about finances, relationships, and work can keep you up at night.
Detecting and Treating Pre-Cancerous Conditions
1Get regular check-ups with your healthcare provider. This includes regular dental exams, during which oral cancers are often found. Regular check-ups allow you to ask questions about your cancer risk, get information about cancer screening tests, and to get any symptoms checked out. Catching cancer early or catching pre-cancerous conditions offer the best possibility of successful treatment. A regular physical should also include exams for cancers of the mouth, reproductive system, skin, thyroid, and other organs. 
2Discuss your family history with your healthcare provider. Sometimes, certain kinds of cancers run in families.  This can be because of common lifestyle choices (smoking), environmental exposures, or because of an abnormal gene that is passed down from generation to generation. If people in your family have had cancer, there is a possibility that you are at increased risk for cancer. Your healthcare provider can advise you about your specific risk and recommend additional tests.
3Get the recommended cancer screening tests. The American Cancer Society has published guidelines for cancer screening tests  which include*:
- Yearly mammograms for women, beginning at age 40
- Tests that either detect colon polyps and/or colon cancer, beginning at age 50 for men and women
- Cervical cancer screening for women, beginning at age 21
- Discuss prostate cancer screening with your physician, beginning at age 50 (men only)
- Listed here are general guidelines. Read the entire American Cancer Society guidelines for the most complete information. 
4Monitor yourself and recognize early warning signs. Men and women can monitor themselves for skin cancer by doing skin checks and paying close attention to odd-looking moles or growths.  Other cancers can sometimes present with skin abnormalities as well.  Women should perform monthly self-breast exams. Men can perform self-testicular exams. Sudden, unplanned weight gain or weight loss can be a sign of cancer. Consider weighing yourself on a regular basis so you are aware of weight changes.