The internet is full of recommendations on what to add or remove from your diet to prevent cancer. Eat broccoli. Drink green tea. Cut the sugar. Don’t overcook your food. But how often do these claims hold up? Are there really any superfoods that can prevent cancer or bad foods that can cause or worsen disease?
Nutrition plays an important role in our overall health, and a poor diet can influence our chances of developing cancer. According to the American Cancer Society, about 1 in 5 cancers in the United States and about 1 in 6 cancer deaths can be linked to a poor diet, being overweight, not exercising, or drinking alcohol. The American Cancer Society recommends healthy eating habits, which include lots of vegetables, fruits, and whole grains, as well as limiting red meats, sugary drinks, highly processed foods, and refined grains.
But how does a specific food or type of food affect our risk for cancer? Here’s the evidence – or the lack of evidence – behind some of the most popular cancer-related diet claims.
The Claim: Sugar Fuels Tumor Growth
All cells in our body, including cancer cells, use sugar molecules, also called carbohydrates, as their main source of energy. But this is not the only source of fuel for our cells. Cells can use other nutrients, such as protein and fat, to grow.
We have no evidence that simply cutting out sugar from your diet will stop cancer cells from spreading. “Yes [cancer cells] don’t get sugar, they’ll start breaking down other components of other energy stores in the body, ”said Carrie Daniel-MacDougall, PhD, MPH, nutritional epidemiologist at the MD Anderson Cancer Center in Houston and director of MD Anderson’s Bionutrition Research Core.
Scientists are, however, investigating whether certain diets can help slow tumor growth. For example, some preliminary evidence from rodent and human trials shows that the ketogenic diet, which is low in carbohydrates and high in fat, may help slow the growth of certain types of tumors, such as those in the rectum, when is associated with cancer treatments such as radiation therapy and chemotherapy.
While they don’t understand exactly how this might work, the experts have a few assumptions.
Ketogenic diets are effective at lowering levels of insulin, a hormone that helps our cells absorb sugar, and research in mice shows that high levels of insulin may weaken the ability of some therapies to slow tumor growth. , according to Neil Iyengar, MD, physician oncologist at Memorial Sloan Kettering Cancer Center in New York City. “We and others are studying ketogenic diets for these types of tumors in clinical trials,” Iyengar said. “But a ketogenic diet is probably one of those types of diets that doesn’t apply to overall cancer risk reduction. I think it’s one of those diets that needs to be tailored to your biology. the tumor.
But what about cancer prevention? Christine Zoumas, a registered dietitian and director of the Healthy Eating Program at the University of California, San Diego Moores Cancer Center, noted an indirect link between consuming large amounts of sugar and cancer risk. “Anything with a lot of added sugars is a source of a lot of calories,” Zoumas said. “When you look at the things that increase cancer risk the most, especially for women, it’s excess body fat.”
The verdict: Cutting out the sugar won’t stop cancer from growing, but early evidence suggests that a low-carb diet may improve the effectiveness of some cancer treatments.
The Claim: Eating Overcooked Or Burnt Food Causes Cancer
When cooked at a high temperature, certain foods – especially carbohydrates like bread or potatoes – release a chemical called acrylamide.
“Some studies have suggested that [overcooking or burning food], you create carcinogens in food that can potentially harm the body, ”said Iyengar. “I would say that’s a guess at the moment. I am not convinced that this is really the case.
Scientists have found that in rodents, high levels of acrylamide – many times what is found in food – can cause tumors to form. Human studies, however, have found little evidence that acrylamide in foods increases cancer risk. When researchers looked at large groups of people to see if there was a link between acrylamide and cancers in various parts of the body, including the gut, kidneys, bladder, and prostate, the majority didn’t have failed to find a clear link.
In some cases, even when a potential link appears, such as between acrylamide and ovarian cancer, this link disappears after using more robust measurement tools, such as examining acrylamide levels. in the blood.
Some methods of cooking meat, such as frying, grilling, or smoking, can release other chemicals, substances called heterocyclic amines and polycyclic aromatic hydrocarbons. As is the case with acrylamide, rodents exposed to high levels of these chemicals develop tumors in various organs. In humans, however, the evidence is much less clear. While some studies suggest that consuming chemicals from cooked meats may increase the risk of certain cancers, such as colorectal or pancreatic cancer, others have reported no association.
The verdict: The evidence that eating overcooked or burnt food causes cancer in humans is neither conclusive nor convincing.
The Claim: Eating Processed Foods Causes Cancer
The evidence linking processed meats, such as salami, beef jerky and deli meats, to the risk of certain cancers, namely colorectal cancer, is strong.
In 2015, the International Agency for Research on Cancer (IARC), part of the World Health Organization, classified processed meats as a Group 1 carcinogen, a designation reserved for carcinogens. In a statement on the decision, made after 22 experts from 10 countries reviewed hundreds of studies, the agency noted that the decision was based on “sufficient evidence in humans that consumption of processed meat causes the colorectal cancer”.
At the same time, IARC also looked into the association between red meat and cancer. After reviewing hundreds of studies, the group concluded that although there were links to colorectal, pancreatic and prostate cancer, the evidence was limited and classified red meat as a “probable carcinogen.”
Some studies that follow people over time suggest that other “ultra-processed” foods, such as sodas, canned soups, and instant noodles, may increase the risk of developing cancer. These foods can contain potentially harmful chemicals, such as acrylamide, nitrates, heterocyclic amines, and polycyclic aromatic hydrocarbons, but they are also often high in added sugar, salt, and saturated fat.
It is the nutritional composition of these foods that is of most concern, Zoumas says, as they are high in calories, which means that eating too much can lead to increased body fat. Zoumas also noted that it is important to distinguish between “processed” and “ultra-processed” foods. Cutting up fruit, bagging lettuce, or fortifying foods with iron or calcium are ways of processing foods that don’t compromise nutritional value or add potentially carcinogenic compounds.
The verdict: There is a strong link between processed meat and cancer risk. Red meat and ultra-processed foods may also increase cancer risk, but the evidence isn’t as strong.
The Claim: Certain Superfoods May Prevent Cancer
While experts say a diet high in plant-based foods, such as vegetables, fruits, and whole grains, may reduce cancer risk, they warn of claims of any superfood that ward off cancer.
“So far, there has not been strong enough data to suggest that a particular food or food product can by itself reduce the risk of cancer or cancer progression,” Iyengar said. “Nutrition is very complex and is highly dependent on the synergy within the total diet you consume, as well as in the context of your general metabolic health, level of physical activity and genetic predisposition. “
Another consideration when it comes to dieting is whether you start a diet before or after you are diagnosed with cancer. While a plant-based diet may help prevent cancer in healthy people, when it comes to cancer patients, other considerations must be taken into account. Daniel-MacDougall noted, for example, that she would not recommend that cancer patients start a vegetarian or vegan diet without speaking with a cancer dietician. “Cancer patients really need to think about supporting their immune system, so I don’t want to see a cancer patient start a [new] diet and become deficient in protein or vitamin B, ”she said.
Also, not all cancers – or all people – are the same, so a dietary change that is good or bad for one person may not have the same effect on everyone. “The type of dietary intervention that is optimal for an individual will vary from person to person depending on that person’s biology, but also on their type of cancer and their stage or environment,” said said Iyengar. “While there are general recommendations we can make to reduce an individual’s risk of developing cancer, I envision a future where we have the data to support much more personalized recommendations. “
Remember, diet is just one of many things to consider when it comes to preventing cancer, and even people who eat healthy can develop cancer, Zoumas noted. “If you have cancer and you live a healthy lifestyle, it will be easier to undergo treatment and recover more easily – and you don’t know how much worse it could have been,” she said. declared. “For those who choose a healthy lifestyle, it’s never a waste – and for those who haven’t yet had a healthy lifestyle, it’s never too late.”
The verdict: Adding just one superfood to your daily food won’t stop you from getting cancer. But eating a diet rich in plant-based foods such as vegetables and whole grains can help prevent disease.
Diana Kwon is a Berlin-based freelance journalist. She covers health and life sciences, and her work has been published in publications such as American scientist, The scientist, and Nature. Find her on Twitter @DianaMKwon.