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. Do not overcook your food. But how often do these claims hold water? Are there really superfoods that can prevent cancer or bad foods that can cause or worsen the disease?
Nutrition plays an important role in our overall health and poor diet can affect 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 related to poor diet, overweight, lack of exercise or alcohol. The American Cancer Society recommends healthy eating habits that include lots of vegetables, fruits, and whole grains, as well as restricting red meats, sugary drinks, highly processed foods, and refined grains.
But how does a particular food or type of food affect the risk of cancer? Here’s the evidence — or lack of evidence — behind some of the most popular cancer-related diet claims.
The statement: Growth of tumors on sugar fuels
All cells in our body, including cancer cells, use sugar molecules, also known as 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 proteins and fats, to grow.
We have no evidence that simply cutting sugar from your diet will stop the spread of cancer cells. “If [cancer cells] do not get sugar, they will begin to break down other components of other energy stores in the body, “says Dr. Carrie Daniel-McDougall, MD, food epidemiologist at the MD Anderson Cancer Center in Houston and director of MD Anderson’s Bionutrition Research core.
However, researchers are investigating whether certain diets can help slow the growth of tumors. For example, some preliminary evidence from rodent and human experiments suggests that a low-carbohydrate, high-fat ketogenic diet may help slow the growth of certain types of tumors, such as those in the rectum, when combined with standard cancer treatments such as radiation and chemotherapy.
Although they do not understand exactly how this can work, experts have some hypotheses.
Ketogenic diets are good for lowering insulin levels, a hormone that helps our cells absorb sugar, and studies in mice have shown that high insulin levels may weaken the ability of some therapies to slow tumor growth, according to Neil Iyengar. a doctor of medicine oncologist at the Memorial Sloan Kettering Cancer Center in New York. “We and others are studying ketogenic diets for these types of tumors in clinical trials,” Iyengar said. “But the ketogenic diet is probably one of those types of diets that are not applicable to the overall reduction of cancer risk. I think this is one of those diets that needs to be in line with the biology of the tumor. “
But what about cancer prevention? Christine Zumas, a registered nutritionist and director of the Healthy Eating Program at the University of California, San Diego Moores Cancer Center, noted an indirect link between high sugar intake and cancer risk. “Anything that has a lot of added sugar is a source of a lot of calories,” Zumas said. “When you look at the things that increase the risk of cancer the most, especially in women, it’s excess body fat.”
The verdict: Reducing sugar will not stop the growth of cancer, but early evidence suggests that a low-carbohydrate diet may increase the effectiveness of some cancer treatments.
The statement: Eating boiled or burnt food causes cancer
When cooked at high temperatures, some foods – especially carbohydrates such as bread or potatoes – release a chemical known as acrylamide.
“Some studies suggest that up to [overcooking or burning food]”You create carcinogens in food that can potentially harm the body,” Iyengar said. “I would call it a hypothesis right now. I’m 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. However, human studies have found little evidence that acrylamide in food increases the risk of cancer. When researchers examined large groups of people to see if there was a link between acrylamide and cancer in different parts of the body, including the gut, kidneys, bladder and prostate, most failed to find a clear link.
In some cases, even when a potential link occurs, for example between acrylamide and ovarian cancer, this link disappears after using more stable measuring instruments, such as looking at acrylamide levels in the blood.
Some methods of cooking meat, such as grilling, grilling or smoking, can release other chemicals – substances called heterocyclic amines and polycyclic aromatic hydrocarbons. As 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 show that consuming chemicals from cooked meats may increase the risk of some cancers, such as colorectal or pancreatic, others do not report a link.
Sentence: Evidence that eating cooked or burnt food causes cancer in humans is unconvincing and unconvincing.
The statement: Eating processed foods causes cancer
The evidence linking processed meats, such as salami, beef and sausages, 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 meat as a group 1 carcinogen, a designation reserved for cancer-causing substances. 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 the consumption of processed meat causes colorectal cancer”.
At the same time, the IARC also looked at the link between red meat and cancer. After studying hundreds of studies, the group concluded that although it had links to colorectal, pancreatic and prostate cancer, the evidence was limited and it classified red meat as a “likely 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. Such foods may contain potentially harmful chemicals such as acrylamide, nitrates, heterocyclic amines and polycyclic aromatic hydrocarbons, but are also often high in added sugar, salt and saturated fats.
According to Zumas, the nutritional composition of these foods is the most likely cause for concern, as they come with a lot of calories, which means that eating too much can lead to an increase in body fat. Zumas also noted the importance of distinguishing between “processed” and “ultra-processed” foods. Slicing fruit, packing lettuce or enriching foods with iron or calcium are ways to process foods that do not compromise nutritional value or add potentially carcinogenic compounds.
Sentence: There is a strong link between processed meat and the risk of cancer. Red meat and ultra-processed foods can also increase the risk of cancer, but the evidence is not as strong.
The statement: Some superfoods can prevent cancer
While experts say a diet rich in plant-based foods, such as vegetables, fruits and whole grains, can reduce the risk of cancer, they warn of claims about each individual superfood that protects against cancer.
“So far, there is not enough reliable data to suggest that a particular food or food product alone can reduce the risk of cancer or cancer progression,” Iyengar said. “Eating is very complex and relies heavily on synergies in the overall diet you consume, as well as in the context of your overall metabolic health, levels of physical activity and genetic predisposition.”
Another consideration when it comes to diets is whether you start a diet before or after a cancer diagnosis. While a plant-based diet can help prevent cancer in healthy people, other considerations need to be considered when it comes to cancer patients. For example, Daniel-McDougall noted that he would not recommend cancer patients to start a vegetarian or vegan diet without talking to a cancer nutritionist. “Cancer patients really need to think about supporting their immune system, so I don’t want to see a cancer patient start [new] diet and get deficient in protein or vitamin B, ”she said.
In addition, not all cancers – or people – are the same, so a change in diet that is good or bad for one person may not have the same effect on everyone else. “The type of nutritional intervention that is optimal for an individual will vary from person to person based on that person’s biology, but also the type of cancer and what stage or situation it is in,” Iyengar said. “While there are general recommendations we can make to reduce an individual’s risk of developing cancer, I envision a future in which we will have data to support much more personalized recommendations.”
Remember that diet is just one of several things to keep in mind when it comes to cancer prevention, and even people who eat healthily can develop cancer, Zumas said. “If you get cancer and have a healthy lifestyle, it will be easier to switch to treatment and easier to recover – and you don’t know how much worse it could be,” she said. “For those who choose a healthy lifestyle, it’s never a loss – and for people who haven’t had a healthy lifestyle yet, it’s never too late.”
The verdict: Adding a superfood to your daily diet will not protect you from cancer. But eating a diet rich in plant foods, such as vegetables and whole grains, can help prevent the disease.
Diana Kuon is a freelance journalist based in Berlin. She covers health and life sciences, and her work appears in publications such as Scientific American, The Scientist, and Nature. Find her on Twitter @DianaMKwon.