Are you wondering if that burger you had for lunch increases your cancer risk? While the answer isn't clear-cut, what you eat on a regular basis can increase or decrease your disease odds.
According to research published in JNCI Cancer Spectrum in May 2019, a poor diet is the driving factor behind a high number of preventable cancer diagnoses; in 2015, that number totaled more than 80,000.
"Diet can play a significant role in cancer risk, especially when you're looking at overall lifestyle," says Stacy Kennedy, RD, a senior clinical nutritionist and board-certified specialist in oncology nutrition at the Dana-Farber Cancer Institute.
While cancer doesn't discriminate, eating a variety of fresh foods in moderation is one factor you can control. "It's about your habits over time, not just one meal or food," says Kennedy. To strike a healthy balance in your diet, aim for each meal to be made up of half veggies or fruit, a quarter lean protein and a quarter whole grains. And if you are at increased risk for cancer (or want to reduce your risk), it might be a good idea to reduce or eliminate these 10 foods that have been linked to the disease.
1. Foods With Low Nutritional Quality
A massive 2018 study of 471,495 people from the French National Institute for Health and Medical Research in Paris found that those who typically ate foods with low nutritional quality were at a higher risk for developing cancer. Specifically, men with poor diets were more susceptible to colorectal cancer, cancer of the upper aerodigestive tract and stomach, and lung cancer. And eating foods that were low in nutrients increased women's risk of liver cancer as well as postmenopausal breast cancer.
But which foods are considered to have low nutritional quality? They're the foods you typically think of as "unhealthy," because they provide tons of calories without many nutrients. Examples include "highly processed snack foods, sugar-sweetened beverages, refined (white) grains, refined sugar, fried foods, foods high in saturated and trans fats, and high-glycemic foods such as potatoes," according to the Harvard T.H. Chan School of Public Health. Instead, reach for nutrient-dense, minimally processed foods such as fruits, vegetables, whole grains, heart-healthy fats and lean protein.
2. Processed Meat
After reviewing more than 800 animal and human studies, in 2015 the World Health Organization (WHO) announced that processed meats like hot dogs, ham, bacon, sausage, prosciutto and salami are carcinogenic. "Processed and red meat is clearly linked to cancer," says Elizabeth Platz, M.P.H., Sc.D., a cancer epidemiologist and researcher with the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University. While the exact reasons aren't understood, it's believed to be because sodium used for preservation combines with amines in meat to form carcinogenic compounds and encourages the growth of gut bacteria known to cause cancer.
Both the American Cancer Society (ACS) and the American Institutes for Cancer Research (AICR) recommend limiting your processed meat intake, and Kennedy points out that just 1 to 2 ounces a day may increase the risk of breast and colorectal cancer. For a better alternative, Kennedy recommends roasted or baked poultry because you can control ingredients like sodium.
3. Red Meat
The same 2015 recommendation from the WHO also found that red meat like beef, pork and lamb is "likely" to cause cancer, although the exact reasons aren't well understood. What types of cancer, exactly? According to studies cited by the WHO: "The strongest, but still limited, evidence for an association with eating red meat is for colorectal cancer. There is also evidence of links with pancreatic cancer and prostate cancer." Still, in moderation, lean red meat can be a good source of protein, B vitamins and iron. The ACS recommends eating less than 18 ounces per week, while the WHO suggests just 11 ounces.
4. Charred Meat
Many chefs take pride in those chargrilled marks on burgers and steaks, but it turns out that they aren't so good for your health. When all types of meat (including poultry, beef and pork) are cooked at very high temperatures, they release chemicals that have been linked to cancer in animals, explains Platz.
According to the ACS, charred meat has two concerning components: Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), both chemicals that have been found to be mutagenic — that is, they cause changes in DNA that may increase the risk of cancer. HCAs form when sugar and substances in meat muscle react to the high heat, and PAHs form when fat and juices drip onto the surface and cause smoke. That smoke then rises and sticks to the meat. When you're grilling, Kennedy recommends, "Flip the meat often, and avoid sugar-based marinades or add them after cooking."
Heavy drinking increases the risk of cancer developing in your throat, voice box, esophagus, liver, colon and rectum, according to the National Institutes of Health (NIH) — especially if you smoke. That may be because alcohol kills cells that have to replace themselves, "and in that process, mutations can occur," notes Platz. The AICR notes that just one drink a day for women has also been linked to breast cancer. "The research is consistent, even if it's not clear why," says Platz.
One question Kennedy regularly gets asked: "Is it better to choose red wine over other alcohols?" She says, "While it's better in terms of heart disease, for cancer risk it's about the amount of alcohol, not the type." Guidelines from the ACS and other organizations limit women to one and men to two drinks daily.
6. Processed Foods
A recent study by BMJ linked "ultra-processed foods" like cakes, chicken nuggets and mass-produced bread to cancer. The likely cause? According to the ACS, people who eat the most processed foods are more likely to be overweight — a factor that accounts for about 8 percent of all cancers in the United States. And obesity commonly causes GERD, which physically damages the esophagus. Then, mutations sometimes happen as cells replicate, Platz notes. Fat also produces estrogen, and high levels of the hormone may cause breast and endometrial cancers. What's more, obesity increases the odds of being insulin-resistant, and hyperglycemia has been associated with a higher risk of many cancers.
7. Canned Foods
Low-sodium canned foods can be a healthy, convenient way to fit in veggies. However, according to the NIH, the BPA in some packaging not only interferes with human hormone production, but high exposure to BPA has been linked to breast, prostate and ovarian cancers. A study by the Journal of Environmental Research found people who ate the most canned foods had higher BPA levels in their urine. Even though the experts say the link between the two is weak, "a lot of companies have decided they don't want BPA in their products anyway," says Platz. If you're concerned, Kennedy says, "Use fresh or frozen veggies. It's healthier since it retains more nutrients." And look for BPA-free cans, or choose foods packaged in glass, boxes and Tetra Paks.
8. Scalding-Hot Tea and Coffee
If it burns, cool it: A number of studies, including those by BMJ and a recent report by the Annals of Internal Medicine, have linked scalding-hot drinks like tea or coffee to esophageal cancer, especially when combined with smoking. This theory isn't new, however, and has been clinically observed as early as the 1930s, when New York physician W.L. Watson wrote, "Thermal irritation is probably the most constant factor predisposing to the cancer of the esophagus." The reason? High heat kills off cells that can mutate as they're replaced, promoting cancer. "It's recognized as a risk factor for cancer, but not at the heat level Americans tend to drink," says Platz. The link is more of a concern outside the U.S. in countries where people tend to drink their tea over the WHO's maximum of 65 degrees Celsius (149 degrees Fahrenheit).
9. Farmed Salmon
Everyone knows salmon is loaded with good-for-you benefits. It's heart-healthy and has inflammation-taming omega-3 fatty acids and essential vitamins like D and B. However, some of the farmed stuff also has polychlorinated biphenyls (PCBs), which have been linked to cancer in animal and human studies, according to the EPA.
A 2003 report by the Environmental Working Group found farmed salmon had 16 times the PCBs as the wild stuff and four times as much as beef. The numbers may sound scary, but there really isn't any evidence that PCB levels in farmed salmon are high enough to increase cancer risk, cautions Platz. Still, Kennedy suggests choosing wild fish — or sustainably farmed fish — when possible, because levels of some nutrients like omega-3s may be higher in these products. To reap the benefits of fish, Kennedy recommends eating two to three servings a week. And don't forget to check the frozen section of your supermarket if fresh fish isn't available.
10. Full-Fat Milk
According to the American Journal of Clinical Nutrition, dairy products have been linked to prostate cancer. Excessive intake of whole milk, in particular, has been shown to raise risk of mortality from prostate cancer, adds Kennedy. The likely connection is because high levels of calcium can block the body's ability to produce vitamin D, which is known to protect against all types of cancers, explains Platz. "But it's hard to achieve high levels of calcium through diet alone. You generally need to take a supplement to reach 1,500 milligrams or higher per day," says Platz.
That said, dairy serves up loads of calcium, protein, iodine and vitamin D, and the Annals of Oncology found that dairy products had a protective effect against colorectal cancer risk in men and women. So instead of swearing off dairy, opt for lower-fat versions instead, and get some calcium from plant-based sources like spinach, Swiss chard, kale and tofu.
- Annals of Internal Medicine: "Hot Tea and Esophageal Cancer"
- JNCI Cancer Spectrum: "Preventable Cancer Burden Associated with Poor Diet in the United States"
- PLOS Medicine: "Nutritional quality of food as represented by the FSAm-NPS nutrient profiling system underlying the Nutri-Score label and cancer risk in Europe: Results from the EPIC prospective cohort study"
- Harvard T.H. Chan School of Public Health: "The Best Diet: Quality Counts"
- World Health Organization: "Q&A on the carcinogenicity of the consumption of red meat and processed meat"
- American Cancer Society: "ACS Guidelines for Nutrition and Physical Activity"
- American Institute for Cancer Research: "Red and Processed Meats"
- National Cancer Institute at the National Institutes of Health: "Diet"
- American Institute for Cancer Research: "New Report: Just one alcoholic drink a day increases breast cancer risk, exercise lowers risk"
- American Cancer Society: "Alcohol Use and Cancer"
- BMJ: "Consumption of ultra-processed foods and cancer risk: results from NutriNet-Santé prospective cohort"
- American Cancer Society: "Does body weight affect cancer risk?"
- The American Journal of Clinical Nutrition: "Ultraprocessed food consumption and risk of overweight and obesity: the University of Navarra Follow-Up (SUN) cohort study"
- American Cancer Society: "Endometrial Cancer Risk Factors"
- National Institutes of Health: "Health risk of exposure to Bisphenol A (BPA)"
- BMJ: "Drinking very hot tea linked to oesophageal cancer"
- Annals of Internal Medicine: Hot Tea and Esophageal Cancer
- American Cancer Society: "World Health Organization Says Very Hot Drinks May Cause Cancer"
- EWG: "PCBs in Farmed Salmon"
- United States Environmental Protection Agency: "Learn about Polychlorinated Biphenyls (PCBs)"
- The American Journal of Clinical Nutrition: "Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies"
- Annals of Oncology: "Dairy products and colorectal cancer risk: a systematic review and meta-analysis of cohort studies"