While there are many factors you cannot change that increase your cancer risk, such as genetics and environment, there are others you can control. In fact, estimates suggest that less than 30% of a person’s lifetime risk of getting cancer results from uncontrollable factors. The rest you have the power to change, including your diet.
Keep in mind that most research only points to associations between diet and cancer, and not necessarily a cause-and-effect relationship. "It not 100% certain that consuming more or less of certain foods or nutrients will guarantee cancer protection, but science has found that certain dietary habits tend to have a greater influence " says Dr Edward Giovannucci of Harvard’s T.H. Chan School of Public Health. Here is a look at four areas that stand out.
Processed and red meat
Processed meat is any meat that has been smoked or fermented or includes added salt and nitrites to enhance flavor. The connection between processed meat and cancer is consistent. For instance, about 30 prospective studies of colorectal cancer — the third most diagnosed cancer in men — found that eating around 50 grams a day of processed meat is associated with about a 20% increase in colorectal cancer risk.
Antioxidants no doubt are important for cancer prevention, as they help neutralize free radicals that can damage cells. But the larger question is whether taking more through your diet or supplements further reduces your risk.
So far the research to support the more-is-better approach has not been impressive. We do not yet know how long you would need to take extra antioxidants for a benefit to be seen. Some cancers develop over many decades, and you may need to increase dietary antioxidants in your early years to see a benefit.
Do not target individual antioxidants, but instead aim for a diet that includes a variety of high-antioxidant foods. Focus on bright colors, such as dark green, orange, purple, and red fruits and vegetables — for instance, spinach, carrots, and tomatoes.
Glycemic index (GI), a measure of how fast carbohydrates turn into sugar in the blood.
A study of 3100 people, presented at the 2016 Experimental Biology forum, found that consuming foods with a high GI (70 or higher on the 100-point GI scale) was associated with an 88% greater risk for prostate cancer. High-GI items include sugar-sweetened soft drinks, fruit juices, and processed foods.
Eating lower-GI foods like legumes (beans, lentils, and peas) was linked with a 32% lower risk of both prostate and colorectal cancers.
Some evidence suggests higher calcium intake can lower the risk for cancer, especially colorectal cancer. Researchers believe calcium binds to bile acids and fatty acids in the gastrointestinal tract. This acts as a shield to protect cells from the damaging stomach acids.
However, other research has shown that extra calcium — 2,000 milligrams (mg) or more per day — may be linked to a higher risk of prostate cancer.
Your best approach is to keep your daily calcium intake to 500 mg to 1,000 mg per day, either from food like dairy products or supplements.
Weight gain and cancer
Another way to look at diet’s role in cancer prevention is in terms of weight management. Modifying your diet can keep your weight under control, which offers even more protection.
A 2014 study in The Lancet found that a higher body mass index increases the risk of developing some of the most common cancers. Scientists discovered that among five million people studied, gain of 34 pounds was linked with a 10% or higher risk for colon, gallbladder, kidney, and liver cancers. Experts say body fat produces hormones and inflammatory proteins that can promote tumor cell growth.
While diet and weight loss are central for cancer prevention, combining a good diet with other healthy habits can further lower your risk, according to a study in the May 2016 issue of JAMA Oncology.
Harvard researchers examined four main lifestyle areas that are associated with health status: smoking, drinking, weight, and exercise. They looked at 46 000 men over 26 years and classified about 12 000 as a low-risk group because they they did not smoke, drank moderate amounts of alcohol (no more than two servings per day), had a body mass index of 18.5 to 27.5, and engaged in 150 minutes of moderate-intensity exercise per week.
When they compared these men with others who did not meet these standards, the researchers discovered that men could avert or delay 67% of cancer deaths and prevent 63% of new malignancies each year. In terms of specific cancers, men could reduce incidence of bladder cancer by 62%, prostate cancer by 40%, and kidney cancer by 36%.