Over the last several decades, certain foods have been vilified as being potentially capable of causing cancer. So, which ones are the biggest carcinogenic culprits? And how can you eat to prevent cancer or reduce the chances of a recurrence if you’ve been diagnosed with cancer?
Cancer-Causing Foods
The list of potentially cancer-causing foods includes:
— Red and processed meat.
— Sugar.
— Alcohol.
— Processed and packaged foods.
Red and processed meat
For the carnivores among us, it’s probably tough to hear the news that red meat (beef, veal, pork, lamb and goat) and processed meat (hot dogs, lunch meats, ham and bacon) may be off the table.
“There have been many epidemiological studies that have reported an association with high intakes of processed meat and red meat with an increase in cancer incidence and mortality,” says Jeannette Schenk, senior staff scientist in the cancer prevention program at Fred Hutchinson Cancer Center in Seattle.
According to the American Institute for Cancer Research, a high intake of red meat is defined as more than three servings per week. A single serving of red meat is about 3 to 4 ounces — or one small hamburger, steak or a medium-sized pork chop. Your total weekly consumption, the AICR reports, should be under 350 to 500 grams (about 12 to 18 ounces cooked) each week.
The cancer risk associated with processed meat products is even higher. The International Agency for Research on Cancer, a branch of the World Health Organization, classifies processed meat as a Group 1 carcinogen, meaning that like other Group 1 carcinogens — tobacco, UV radiation and alcohol — research has proven that processed meat can cause cancer in humans. Eating just 50 grams of processed meat each day, the IARC reports, can elevate cancer risk by 18%. Four strips of bacon or one hot dog contains about 50 grams of processed meat.
Why these meats appear to elevate cancer risk, particularly colorectal cancer, is believed to be because red meats and processed meats contain mutagens and carcinogens. Mutagens change genetic information by altering DNA, and carcinogens are cancer-causing agents.
When meat is cooked at high temperatures or grilled, amino acids in the meat interact with the heat to form carcinogenic compounds, called heterocyclic amines and polycyclic aromatic hydrocarbons.
“Those have been linked with cancer risk,” Schenk points out.
With processed meats, the cancer risk appears to be related to the way the meat is preserved and cooked. Specifically, the addition of preservatives called nitrates and nitrites may elevate cancer risk. Similarly, smoking meats can also create carcinogenic compounds.
If you are eating processed meat products, Kailey Proctor, an oncology dietitian at City of Hope in Southern California, recommends moderation, aiming for no more than one serving per week.
[READ: How to Make a Healthy Sandwich]
Sugar
Sugar is also implicated in the development and progression of certain kinds of cancer. In the early 20th century, German biochemist Otto Warburg observed that cancer cells often rely on sugar to fuel their prolific growth. Called the Warburg effect, this process suggests that starving the body of sugar and carbohydrates that can be converted to sugar could theoretically starve cancer cells.
As a result, the ketogenic diet, which reduces carbohydrate intake to 10% or less of calories consumed and increases fat consumption to 70% or more, has been suggested as a way to slow the spread of cancer.
The effectiveness of the keto diet to prevent or slow cancer hasn’t been fully proven, but research suggests there may be an association between sugar and cancer. For this reason, any food with a very high glycemic index, such as sugary beverages, can increase your risk of cancer and should be consumed in moderation, says Dr. Adil Akhtar, an oncologist, palliative care expert and system physician leader of Beaumont Health System’s Oncology Center of Excellence in Michigan. (A food’s glycemic index is the rate at which a food will raise the level of sugar in the blood when it’s digested.)
Some experts say that if you’re concerned about cancer, you should eliminate all refined sugar from your diet because many types of cancer cells use sugar as their primary fuel. In fact, some diagnostic tests for cancer use radioactive glucose to pinpoint tumors on PET scans because most cancer cells have such an affinity for sugar that they absorb glucose molecules faster than noncancerous cells can, thus showing themselves on the scan.
[READ: How Much Sugar Can I Eat If I Have Diabetes?]
Alcohol
Alcohol is a type of sugar and can increase your risk of cancer.
“Alcohol is an established risk factor for mouth, pharynx, esophageal, liver, colorectal, breast and pancreatic cancer,” Schenk says.
Exactly how alcohol increases risk is not clearly understood, but “it’s possibly related to DNA damage” incurred by the cells after exposure to alcohol, Schenk adds.
Alcoholic beverages also contribute a lot of excess calories that offer no nutritional benefits, so it should be consumed in limited quantities .
The federal government’s Dietary Guidelines for Americans 2020-2025 states that if you don’t drink, don’t start. It also recommends that moderating intake is an important way to curb cancer risk in people who do choose to consume alcoholic beverages.
Moderate alcoholic drinking is defined as one drink per day for women and up to two drinks per day for men. A drink is defined as 12 ounces of beer, 8 to 9 ounces of malt liquor, 5 ounces of wine and 1.5 ounces of 80-proof distilled spirits.
“For cancer prevention, it’s best not to drink alcohol,” clarifies Cathy Leman, a registered dietitian and nutrition therapist, certified personal trainer and breast cancer survivor based in Chicago.
[READ Is a Drink Really Just a Drink?]
Processed and packaged foods
Many ultra-processed foods — such as packaged baked goods and snacks, fizzy drinks, sugary cereals, ready meals and reconstituted meat products — have been linked with an increased risk of certain types of cancer, according to a 2018 study in the British Medical Journal.
The study, which included 104,980 healthy French adults, found that a 10% increase in the proportion of ultra-processed foods in the diet was associated with increases of 12% in the risk of overall cancer and 11% in the risk of breast cancer. No significant association was found for prostate and colorectal cancers.
An even larger 2023 study also found a connection between cancer and ultra-processed foods. That study, which was based on data from the European Prospective Investigation into Cancer and Nutrition, involved 266,666 men and women from seven European countries. The researchers noted that increased consumption of ultra-processed foods — in particular animal-based products and artificially sweetened beverages — increased risk of dying from cancer or cardiometabolic disease.
In addition, ultra-processed food products tend to be higher in calories, salt, sugar and saturated fats, all of which may contribute to obesity, a risk factor for cancer, according to a 2023 study in Cancer.
Chemicals in Foods That May Cause Cancer
Certain compounds that may turn up in processed foods can also raise your risk of developing cancer. As mentioned, some to watch out for include:
— Nitrites and nitrates, which are used as preservatives in some processed and ultra-processed meat products.
— Butylated hydroxyanisole, a food preservative.
— Polycyclic aromatic hydrocarbons and heterocyclic amines, compounds that can arise from grilling or smoking meat at high temperatures.
— Potassium bromate, a flour additive.
Many other preservatives, artificial sweeteners and food dyes have also been associated with potential cancer risk.
In addition, some compounds found in food packaging and the environment could also elevate risk. For example, “things like microwaved popcorn have compounds that are linked with cancer,” Akhtar says. The environmental organization Environmental Working Group raised the alarm about a chemical called PFOA that was used to coat the inside of popcorn bags as a likely carcinogen, prompting the Food and Drug Administration to ban its use in food packaging in 2006.
However, a subsequent EWG investigation suggested that the replacement chemicals (needed to prevent oils in the bag from soaking through the paper) are also potentially carcinogenic and likely contain perfluorinated chemicals. The Agency for Toxic Substances and Disease Registry, a division of the Centers for Disease Control and Prevention, reports that these chemicals, known as PFCs, may increase the risk of cancer.
Even seemingly healthy foods, such as farmed salmon, may contain chemicals that might increase cancer risk. The Environmental Protection Agency has classified polychlorinated biphenyls, or PCBs, as probably carcinogenic in humans. This class of chemicals was manufactured from 1929 until they were banned in 1979, but they linger still in the environment. Whether the levels of these chemicals, which enter the food chain from industrial and hazardous waste sites and become concentrated in the feed given to farmed fish, are high enough to cause cancer is still being debated.
If you’re concerned about this risk, Harvard Health suggests removing the skin of the salmon and the fat directly underneath it before cooking, as that’s where the chemicals are most concentrated. Allowing the fat to drain off by grilling, baking or broiling can also reduce risk. Studies have also suggested that lower levels of these chemicals have been identified in fish farmed in Chile and Washington State, so check where your fish is coming from.
Foods That Prevent Cancer and Tips for How to Eat to Avoid Cancer
While some foods have been associated with an increased risk of certain kinds of cancer, anti-cancer foods are believed to help reduce your risk. This is where Yael Vodovotz, a professor in the department of food science and technology at the Ohio State University in Columbus, is focusing her research efforts.
Her lab is investigating the bioactive compounds in food that “potentially can work together for cancer prevention.” (Bioactive means the compound has an effect on cells or a living organism and is used to describe vitamins, minerals, enzymes and other components of food.) In addition, they’re looking to formulate foods or food combinations that can offer a bioactive effect.
Some of these foods include:
— Berries, such as black raspberries, strawberries and blueberries.
— Green tea.
— Tomatoes.
— Grapefruit.
— Cruciferous vegetables, such as broccoli.
“The idea is to incorporate the whole foods,” she says, instead of extracting a single compound. And finding the optimal combination of foods that give the full balance of cancer-fighting phytochemicals and nutrients is still a work in progress.
Vodovotz also notes that eating too much of any food can have negative consequences.
“Foods are all made of chemicals, and if you take in way, way, way too much for a prolonged time, it’s going to be a problem,” she warns.
Eat a Balanced Diet for Cancer Prevention
While she continues determining which compounds can help and which may hurt in the quest to remain cancer-free, Vodovotz says that you can get a jump start by eating a balanced diet.
She recommends the U.S. Department of Agriculture’s MyPlate plan, which advocates incorporating lots of fruits and vegetables, whole grains, fiber and lean and plant-based proteins.
“I do believe there’s an intimate link between cancer prevention and diet,” she says.
Akhtar, who is also chief of clinical operations for the Beaumont Cancer Center and an associate professor at Oakland University William Beaumont School of Medicine, adds that there’s not one specific diet that will solve the cancer question. However, he likes the Mediterranean diet for its balance of nutrients, low levels of sugar and focus on whole foods.
The AICR recommends a mostly plant-based diet for cancer prevention, Proctor adds.
“Their ‘New American Plate’ model suggests having two-thirds of your plate plant-based foods, such as fruits, vegetables, whole grains, beans and legumes,” she explains. “The remaining one-third of the plate should be a lean source of protein, such as chicken, turkey and seafood.”
Seek Individualized Advice and Support
For people who’ve been recently diagnosed with cancer or who are in survivorship, Leman urges you to seek out individualized nutritional guidance to support treatment outcomes and help manage side effects of cancer treatments.
“While undergoing active treatment, people often have special nutritional requirements,” she says. “Working with an oncology dietitian for individualized nutritional care and guidance can help patients manage side effects like nausea, loss of appetite, fatigue and changes in bowel habits.”
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Avoid These Cancer-Causing Foods originally appeared on usnews.com
Update 01/18/24: This story was previously published at an earlier date and has been updated with new information.
