How Your Diet Affects Your Risk for Cancer

How Your Diet Affects Your Risk for Cancer

The foods you avoid are just important as the ones you eat.

Cancer is a leading cause of death worldwide—and while survival rates are on the rise, many cases of the disease are preventable. In fact, in the United States, roughly 42 percent of all cancers and 45 percent of deaths due to the disease are tied to risk factors that can be controlled, according to research from the American Cancer Society (ACS).

Unlike certain risk factors that influence your cancer risk that you can’t change, like your age and your DNA, there are plenty of things you can influence. You may already know that you shouldn’t smoke and that you should wear sunscreen. But obesity and drinking alcohol can also increase your risk for the disease. Another risk factor for cancer that you can control is your diet.

A May 2019 study published in Journal of the National Cancer Institute Cancer Spectrum estimates that diet-related factors may account for 80,110—or 5.2 percent—of new invasive cancer diagnoses in adults in 2015. These numbers are comparable to the link between alcohol consumption and cancer risk.

So, which foods should you avoid and include in a cancer-prevention diet?

Foods associated with cancer risk
“One specific food is not going to cause cancer, but as part of an overall pattern, what you eat can increase your risk,” says Kelly K. Rashid, RD, CSO, a clinical dietitian and certified specialist in oncology nutrition at Holy Cross Hospital in Fort Lauderdale, Florida.

Certain foods, in particular, have been associated with an increased risk of cancer, so it’s best to take steps to limit or avoid them. Some of the biggest concerns include:

Processed meats: Studies have shown that excess intake of processed meats is one of the main dietary culprits that could increase the risk for cancer. “Processed meats are one of the foods we have the most research on when it comes to colon and rectal cancer,” Rashid says. These cured, smoked, or salted meats are associated with about 8 percent of all colon cancers, according to ACS researchers. The preservation methods used to make these products may be what increases the risk of cancer. Processed meats are often red meats, which may be another factor (more on that later).

“Even a small amount increases your risk,” Rashid adds. So it’s best to limit your intake of preserved meats as well as bacon, bologna, hot dogs and deli meats—or avoid them entirely. The same rules apply for other processed foods, like packaged snacks and frozen meals. These products have also been tied to an increased risk for cancer.

Red meat: “Red meats are also tied to colon and rectal cancer,” Rashid says. In fact, ACS researchers suggest they are associated with 5.4 percent of all cases of the disease. Although experts aren’t exactly sure why, the connection may be related to the amount of animal fat or heme iron red meat contains, or carcinogens that form when the meat is cooked at high temperatures or charred on the grill.

You don’t have to cut red meats, such as beef, lamb, and pork, out of your diet completely, but moderation is key. For the purposes of cancer prevention, it’s a good idea to limit your intake to no more than about three portions per week, or about 12 to 18 ounces cooked, according to the American Institute for Cancer Research. It’s also wise to opt for lean cuts of beef, including eye round, top round, round tip, bottom round and sirloin, and bake or broil your meats rather than frying or charbroiling them, according to the ACS.

Alcohol: Alcohol—especially heavy drinking—is linked to an increased risk for several different types of cancer. A comprehensive August 2018 review published in The Lancet showed that even one alcoholic drink per day could increase the risk for breast, colorectal, esophageal, pharyngeal, and oral cancers. Essentially, any amount of alcohol increases your risk for the disease. And the more you drink, the higher your risk.

Multiple explanations for this connection exist. It’s believed that the ethanol in alcohol is a carcinogen that contributes to cancer, and that alcohol may also increase the ability of carcinogens to enter your body’s cells and increase cell production. It may also raise estrogen levels and influence your body’s ability to absorb folate, a key nutrient that actually helps protect against colon cancer. Your DNA, medical history, weight and lifestyle will also come into play but when it comes to cancer prevention, avoidance is your best measure. If you do drink alcohol, don’t exceed current guidelines for light or moderate drinking. If you’re a man, that means you shouldn’t have more than two drinks daily. If you’re a woman, limit yourself to one drink per day.

Sugar: Sugar has not actually been found to directly increase cancer risk, but there is an indirect link.

“Sugar in general does not provide any nutritional value, and it causes obesity—and obesity is linked to at least 12 different types of cancer,” explains Rashid. So, it’s important to limit your sugar consumption. “If you drink a sugary beverage on a special occasion, is it going to cause you cancer? No,” she adds. “But the risk increases if you consume excess calories and sugar, and it causes obesity. There are also a number of other health concerns associated with sugar-sweetened beverages.”

When it comes to added sugar, stick to the 2015-2020 Dietary Guidelines and limit your total intake to less than 10 percent of your daily calories.                                                       

What’s included in a cancer-prevention diet
“The recommendations for a healthy, cancer-prevention diet are not really different at all from your standard dietary recommendations,” Rashid points out. You should start by basing your meals around plant-based food sources, according to the ACS. This includes things like:

Fruits and vegetables: One reason to load your plate up with fruits and veggies? A diet that’s lacking these essential food groups has been shown to increase cancer risk. Diets low in fruits and vegetables are linked to roughly 17 percent of oral and throat cancers as well as about 9 percent of lung cancers, ACS researchers report.

What’s more, fruits and vegetables contain cancer-fighting nutrients called phytochemicals. “Different color groups have different types of phytochemicals, and they work in different ways to fight off cancer,” says Rashid. So be sure to include a variety in your diet.

Whole grains: Not eating enough whole grains can also increase your cancer risk. On the other hand, including whole grains such as brown rice, whole wheat bread, and barley in your diet can help prevent certain types of cancer. They’re essential sources of dietary fiber, which could provide colon cancer-protective benefits. A low-fiber diet is associated with roughly 10 percent of all colon cancer cases, according to ACS researchers. Heart-healthy whole grains also contain a variety of other compounds that could help ward off cancer.

Legumes: Like whole grains, legumes are another plant source that’s rich in cancer-fighting fiber. They’re also good sources of folate. Be sure to include foods like kidney beans or black beans, lentils and peas in your diet, as well.

Dairy: “There’s a lot of mixed research with dairy, though with some cancers, it’s now looking like dairy may have a protective effect,” says Rashid, especially when it comes to preventing colon cancer. A low-calcium diet is tied to nearly 5 percent of all cases of the disease, the ACS points out.

Keep in mind that it’s best to choose low-fat or fat-free options. A study presented at the 2019 American Society of Clinical Oncology meeting also found that after a long-term follow up, postmenopausal women who followed a low-fat diet that focused on fruits, vegetables, and grains reduced their risk of death from breast cancer by 21 percent.

Low-fat dairy products often also contain probiotics, which some preliminary research suggests may have cancer-fighting properties, Rashid says. Good sources of probiotics include: yogurt with live, active cultures; kefir, a drink made from fermented cow's milk; and other fermented foods.

The bottom line
It all comes down to variety, and making healthy choices when you can.

“I would never tell someone they can’t ever have certain foods or never use their grill again; just try to save them for special occasions,” says Rashid. “Instead, we want more of a plant-based diet. It doesn’t have to be plant-only, but you should focus on more plant foods and less on processed or animal products.”

Medically reviewed in July 2019.

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