Cancer prevention is the holy grail of medical research. Students in medical school dream of finding a cure, scientists hope their work will provide the foundation for the one true end of this disease, and patients and family members pray for a future without cancer. Until that grand discovery, we will have to count on the wisdom of our bodies.
Healthy immune systems work hard to spot and eliminate cancerous cellular mutations before the disease can begin its wild, uncontrolled growth. Prevention, then, is all about keeping ourselves as healthy as possible and eating the kinds of foods that have been shown to help protect us — right down to our cells.
What Affects Cancer?
Cancer doesn’t surface overnight. It is the end point of a process that spans years or even decades. The process starts when normal body cells are damaged by a virus, radiation, toxic chemicals, inflammation, or randomly occurring errors in cells’ DNA that accumulate as we age. Every time a cell is damaged, there is the possibility that its genetic structure may mutate. Cells can handle a certain number of mutations without serious consequences, but after a certain point, the mutations change their essential nature, turning them from normal body cells into precancerous cells. This first stage of cancer development is called initiation. Precancerous cells can reside harmlessly in the body without ever progressing to full-fledged cancer, but sometimes they become activated. In this stage, called promotion, the cells begin to grow and multiply. The third stage of cancer development is called progression, when the cells multiply out of control and begin spreading.
The first step toward cancer prevention is avoiding the kinds of damage that cause mutations. Although scientists don’t have all the answers regarding what turns a precancerous cell into a cancer cell, it is widely believed that the forces behind mutations also allow the promotion and progression of cancer. The primary cancer culprits are detailed below.
Smoking has been estimated to cause about 30 percent of all cancers in the United States. You probably know that smoking is linked to the risk of lung cancer, but it also increases the risk of cancers of the mouth, throat, esophagus, stomach, pancreas, kidney, bladder, and cervix. Furthermore, secondhand smoke increases the risk of cancer among people who live with smokers.
Tobacco smoke contains dozens of toxins capable of damaging cells. The delicate lining of the lungs is directly exposed to the smoke, but toxins move from the lungs to the bloodstream to cells throughout the body.
Moderate drinking is defined as no more than two servings of alcohol per day for men and one serving per day for women. Excessive alcohol intake has been linked to an increased risk of cancer of the breast, mouth, throat, esophagus, colon, rectum, and liver. The association is especially strong for breast cancer — even one drink or less per day has been shown to increase a woman’s risk.
No one is really sure what makes alcohol so dangerous, but there are theories: Alcohol itself is toxic to cells, and so are some of the by-products created when it is metabolized. Alcohol also increases hormone levels, thus heightening the risk of hormone-related cancers like breast cancer. And because alcohol makes cells more vulnerable to other cancerous compounds, smokers who drink have a tremendously increased risk of mouth and throat cancers. And the more you drink and smoke, the greater the risk. Heavy drinkers who don’t smoke have a risk of head and neck cancers that is ten times higher than the risk for people who neither drink nor smoke. But if heavy drinkers also smoke, their risk jumps to about 150 times higher.
It has been known for decades that radiation from excessive exposure to X-rays can cause cancer. The amount of radiation we get from medical X-rays is very small and is thought to contribute to only about 1 percent of cancer risk worldwide. Sunlight contains a form of radiation called ultraviolet rays, which penetrate skin cells and may cause mutations that can turn into skin cancer. Long-term, cumulative exposure to sunlight causes mainly basal cell and squamous cell carcinomas, which are types of cancer that can be disfiguring but are rarely lethal. Severe sunburns, usually in childhood, increase the risk of developing the more dangerous cancer, malignant melanoma, later in life.
Viruses and Bacteria
Infection with some strains of the human papillomavirus (HPV) can lead to cervical cancer. Hepatitis B and C bacteria can lead to liver cancer, and the H. pylori bacterium, which causes stomach ulcers, increases the risk of developing stomach cancer. Some scientists believe that these infections represent just the tip of the cancer iceberg and that many more links between cancer, viruses, and bacteria are likely to surface.
Researchers don’t fully understand why some infections lead to cancer. We do know, though, that viruses can insert copies of their own DNA into normal body cells, altering the genetic structure of the cell, and that bacteria can produce toxins that may damage body cells enough to promote cancer.
After smoking, obesity is the largest risk factor for cancer. According to the National Cancer Institute, obesity contributes to the development of cancers of the colon, endometrium, kidney, esophagus, and breast (in postmenopausal women only). Gallbladder, ovarian, and pancreatic cancers, as well as certain types of prostate cancer, may also be related, but the links are less consistent.
Since fat tissue produces and stores estrogen, postmenopausal women who are overweight can have up to twice the estrogen levels as lean women, potentially leading to the growth of estrogen-sensitive breast tumors. Other cancers may be due to the effects of high levels of insulin common among overweight people, the irritation of reflux disease, or inflammation caused by cytokines and related hormones produced in fat tissue.
The longer women are exposed to high levels of estrogen, the greater their risk of developing breast cancer. Estrogen levels climb at puberty and remain generally high until menopause, so the risk is higher for women who begin menstruating early (before age 12) or who go into menopause later in life (older than age 55). In addition, anything that increases levels of estrogen is thought to also increase the risk of breast cancer — and that includes carrying excess body fat, drinking alcohol, and taking hormone replacement therapy after menopause. High estrogen exposure is also linked to endometrial and ovarian cancers.