Imagine a person living in ancient Greece gets cancer. They visit a doctor, who tells them they have too much “black bile.” This was a fluid they thought was in the body that affected health and how people looked and acted. The doctor would say that the fluid, made by the pancreas, was clogged somewhere and made a tumor. The doctor could prescribe a drug or surgery, much like today. But, back then, those “treatments” for black bile wouldn’t work. Later research did not find any black bile, and newer ideas came around.

After the microscope was invented, scientists could actually see the cancer cells in tumors. With a better understanding of cancer, they were able to figure out some real causes and treatments.

When someone gets cancer, they often wonder why. What happened to cause this? Will it happen to someone in their family? Was there some way to prevent this? Here are some things we know about what causes cancer.

Common causes of cancer

Inheritance/family history

One of the most obvious causes of certain types of cancer is having it in your family. This is because some types of mutations that cause cancers can be passed on from parents to children. They are genetic. But, this can only happen if the mutations are in egg or sperm cells. More often, mutations happen to other cells during a lifetime, like skin cells. These mutations are not passed down. Inheriting a mutation is not a guarantee that a person will get cancer. One well known example of a mutation that is passed down is in the BRCA gene that can cause breast and ovarian cancer.

Tobacco

You have probably heard that smoking causes cancer. In fact, cigarette smoke has over 70 substances that damage the mouth, throat, and lungs. This damage can very often lead to cancer. Before we knew this, smoking was much more common. People could smoke almost anywhere - on planes, in restaurants, in bowling alleys, and more. Eventually laws were passed to ban smoking in many public places due to the harm of breathing in second-hand smoke. Chewing tobacco also damages the cells in the throat and mouth. However, not all people that get lung cancer are or have been smokers.

Vaping - this info will be a caption

Vaping is a relatively new and popular way to smoke. It is known that vaping introduces harmful chemicals into the body. However, vaping has not been around long enough to study if it causes cancer. The vapor is not all water, so second-hand vapor is also dangerous.

Sun exposure

Sunlight (and tanning beds) contain UV (ultraviolet) light. UV light mutates the DNA in skin cells by locking together base pairs of DNA that are next to each other. When the DNA is copied for cell division, the mutations are misread, so the wrong base is copied from the mutated strand.

The fact that UV light can cause mutations is why it can be used to sterilize equipment. UV light causes mutations in the DNA of bacteria. Remember that compared to the 20,000 - 30,000 genes in humans, many bacteria only have 1,500 - 7,500 genes. This makes it much easier to cause mutations in bacteria that can kill them.

Age

Cancer is a disease of aging. The longer cells are alive and dividing, the more time there is for mutations to happen and add up. More people are dying from cancer than in the past, and this is for many reasons. One reason is that some common diseases like heart disease are better treated than they were in the past. Now that people are living longer, there are more chances for cancer to develop as we age.

Another reason more people seem to be dying from cancer is that we have become better at detecting it. The more we look, the more we find. It’s just like looking for birds around you. If you are not looking, you might not notice any when you are out and about. But if you start to look for them, you will find more than if you weren’t looking. With newer technology, cancer is more easily found.

Some viruses and bacteria

Some viruses and bacteria can cause cancer. Have you ever had a wart on your foot, or seen a wart? That wart was caused by HPV. HPV (human papillomavirus) infects skin cells. There are over 100 different kinds of HPV that affect all different types of skin cells on the body.

Ulcers are another issue caused by bacteria. Helicobacter pylori (or H. pylori for short) is bacteria found in the stomach of some people. This bacteria can cause stomach cancer, but most often it does not. It is possible that half of the population of the United States has an H. pylori infection. H. pylori can cause ulcers in the stomach and intestines, and can be treated with antibiotics.

The Western diet

What we put in our bodies affects so many aspects of our health. This is especially true when it comes to what we eat. Some substances in food can react with cells and cause damage. A common diet that is linked to cancer is a “western diet.” It consists of processed foods, red meat, dairy products, eggs, high sugar foods, and pre-packaged foods. Think: crackers, steak, hamburgers, hot dogs, cheese, soda, cookies, and more. This diet is strongly linked to colon and rectal cancers, and possibly other types of cancer.

Carcinogens

Carcinogens are substances that can directly cause cancer. They do this by causing mutations in DNA. These can be found in things like soot (black stuff in chimneys), in asbestos in old insulation in buildings, and in pesticides. Pesticides are designed to kill insects, so oftentimes they can also hurt humans. This is one reason it is important to wash fruits and vegetables before you eat them.

The unknown causes of cancer

Cancer research is very important to help us understand how to find, prevent, and treat cancers.  While cancer science is always improving, there are still many issues to address. For example, cancer screening often looks for certain proteins or chemicals in the blood. However, not all of them are only related to cancer. This makes it tough to use those proteins or chemicals to accurately diagnose cancer.

Treatments can be hard on the body and cause many side effects such as hair loss, extreme weakness, and weak immune function. Surgery is also hard on the body, and can remove important organs and tissues. For example, sometimes the ovaries, fallopian tubes or the uterus are removed because they have tumors. This can alter a woman’s hormones and affect how her body works.

Some cancers are very difficult to diagnose. One such cancer is pancreatic cancer. The pancreas is hard to examine because of its location in the body. Also, little is known about pancreatic cancer, so doctors don’t really know what to look for.

These questions continue to be studied all over the world. As time goes on, more research pushes our understanding and technology forward. Hopefully, continued research will help us address these issues and gaps in our knowledge.