Despite decades of research, the origins of cancer remain a mystery.
Advancements in treatments have increased the survival rates for many forms of cancer, but what causes cancer in the first place is still unclear.
The link between smoking and many cancers has been well known for some time now, and family history is considered a key factor. Countless studies have been devoted to discovering how cancers develop from just about every angle, including the effects of living near power lines, getting too much sun and exposure to household cleaning products.
With this onslaught of information, it is understandable when people become overwhelmed and conclude that there's not much that can be done to prevent cancer besides saying no to smoking. However, the choices we make, especially regarding diet and exercise, can either help us or haunt us.
"A lot of people think they don't have much control over their risk, but they really do," says Colleen Doyle, director of nutrition and physical activity at the American Cancer Society. "They have more than they think."
Diet plays a crucial role in almost every health-related issue, and cancer is no exception. Though there is no direct link between a particular food and its ability to prevent or cause cancer, the evidence continues to mount that what we eat can reduce or increase our risk of developing cancer. The foods that most studies have found to help prevent cancer are the same nutrient-packed fruits and vegetables that are staples of a well-balanced diet.
*Broccoli, cauliflower, kale and other cruciferous vegetables may reduce the risk of breast, stomach and skin cancers.
*Berries contain antioxidants, which counteract, reduce and repair damage to cells.
*Orange fruits and vegetables -- such as carrots, sweet potatoes, cantaloupes and mangoes -- contain Beta Carotene, an antioxidant thought to protect cell membranes from damage.
*Beans are good sources of protein, making them good alternatives to red meat, which is associated with colon cancer. They're also low in calories and loaded with fiber.
*Others include whole-grain bread, rice and pasta, fish, tomatoes, watermelon and garlic.
However, it's probably not practical for most people to keep up with every new study that touts the latest cancer-fighting food. Doyle recommends a reasonable approach.
"When you look at all the evidence, what it really points to is that it's the overall diet that we eat, not an individual food, that reduces our risk from cancer," Doyle says. "It really is the combination of plant food, whole grains and not eating a lot of red or processed meats."
Because research continues to find that obesity can lead to several cancers, maintaining a healthy diet is especially important. Obese people tend to have poor diets and exercise habits -- which can lead to several chronic conditions -- but it is the higher levels of hormones that concern cancer experts.
"We know there are certain hormones -- insulin, estrogen -- that tend to be associated with cell and tumor growth, and we know people who are overweight have higher levels of those circulating hormones," Doyle says.
Soy products contain weak estrogen-like compounds, and some researchers have considered that if you eat more soy, your body will produce less estrogen. We know that estrogen has an effect on cell and tumor growth, so when your body produces lower levels, it may lessen your risk of developing hormone-related cancers, primarily breast and testicular cancers. However, there have been limited studies on how soy affects the body, and some researchers have found risk factors associated with soy that outweigh any positives.
"The jury is still out on that," Doyle says.
Even though beef and pork are on the list of foods to avoid, how you cook them can make a difference. Grilling meats at high temperatures can create carcinogens, but cooking meat in the oven at a lower temperature and then putting it on the grill for a short time lessens the risk and may result in more tenderness.
Studies continue to find associations between alcohol and numerous cancers, including liver, breast, esophageal and oral cancers. The American Cancer Society, along with many other health organizations, recommends that women have no more than one drink per day and that men have no more than two.
"Some of that evidence is getting stronger and stronger," Doyle says.