In the year 2013, it is forecasted that there will be more than 1.6 million new cases of cancer diagnosed, and more than a half million deaths attributed to it.

We all fear cancer, but why– what actually makes it such a formidable foe? And what can we do to reduce our chances of succumbing to it?

Normal human cells follow certain rules, which are coded for in our genes, or DNA. They replicate at a controlled rate and stop replicating when signaled to do so. They have a set lifespan. They do not invade other tissues. They produce organized/functional offspring.

But cancer cells break all these rules! Their DNA is altered, so they do not perform their usual function, rather they divide and multiply out of control. They ignore the host’s chemical signals to stop their madcap replication and invade neighboring tissues and/or spread (metastasize) to distant areas. It is this uncontrolled/invasive growth of non-functioning tissue that produces the devastating diagnosis we call cancer.

What makes a normal cell become cancerous?  Much is still being researched, but generally, scientists agree that of the 100-plus known malignancies, approximately 90 to 95% of them are environmentally-provoked.

One way this occurs is by exposure to chemicals that damage DNA. These substances are called  carcinogens, and tobacco is the leading carcinogen recognized. Exposure to tobacco is currently held responsible for 25 to 30% of all cancer diagnoses, and almost 90% of all lung cancer cases. It also is a potent factor in developing oral, esophageal, stomach, pancreatic, and bladder cancer. In addition to tobacco, other environmental exposures that increase cancer risk are asbestos and chemical solvents.

Infections are another way our environment can trigger cancerous cell transformations. The human papilloma virus (HPV) is known to be a major cause of cervical cancer. The Epstein-Barr virus, responsible for infectious mono in the United States, is responsible for lymphoma development in other parts of the world. Liver cancer is frequently due to viral infections with either hepatitis B or hepatitis C. And it is now understood that not only stomach ulcers, but also stomach cancer is often caused by the bacterial infection Helicobacter pylori.

Diet and exercise, too, are important environmental factors that may increase our cancer risk. For example, a potent chemical found in the molds that commonly invade grain and nut crops is called aflatoxin. It is a potent carcinogenic substance that, if ingested in large enough amounts, can cause liver cancer. Additionally, red meats and processed food have also been implicated in an increased cancer risk; conversely, diets rich in fruits, vegetables, and whole grains are linked to a reduced malignancy rate.   And regardless of the type of food intake, obesity is a separate and significant risk factor for developing cancer. People with a body mass index of >30 are at increased risk for many malignancies, including breast, colon, uterine, kidney, and esophageal.

Another environmental issue that can spur the development of cancer is radiation exposure. Survivors of nuclear accidents or attacks have a dramatically increased rate of thyroid cancer. Radiation from the sun in the form of UV light is responsible for a majority of skin cancer diagnoses. And radiation from medical testing remains an alarmingly frequent cause of cancer; one study estimates that more than 29,000 new cases of cancer will arise due to the 70 million CATscans performed in the United States in the year 2007 alone.

While the vast majority of cancers are due to environmental causes, there is a substantial portion attributed to genetic problems. In these scenarios, there is no outside damaging force such as radiation or tobacco smoke that damages the cells; rather the cell malfunction is caused by a “programming error”, so to speak, in the host’s own DNA. The most famous example of this are alterations of the BRCA genes, which when normal, function to suppress cancerous growth. People with mutations of the BRCA genes are known to be at increased risk of breast and ovarian cancer. Another abnormal gene, called CDH1, is so strongly associated with stomach cancer that if found in a healthy person, they may be advised to have their stomachs removed!

Yes, cancer is a scary thing. Yet we can take comfort in the fact that there are many things we can do to minimize our risk. Stopping exposure to tobacco is essential to reducing the likelihood  of receiving a cancer diagnosis. Getting vaccinated against hepatitis B and HPV will also improve our cancer odds. A healthy diet rich in fruits, vegetables and fresh whole grains while low in red meat and processed foods will make cancer less likely to develop, too. And it is important to avoid or reverse obesity.

Doctors and patients alike must work to avoid unnecessary medical radiation exposure; and everyone should get in the habit of using sunscreen!  If there is a suspicion you make be at risk for the genetic types of cancer, get tested so preventive strategies can be implicated.

Lastly, work with your doctor to assure the proven-effective screening for cervical, breast, and colorectal cancers is implemented as advised.