The internet is chock full of recommendations of what to add or remove from your diet to stave off cancer. Eat broccoli. Drink green tea. Cut sugar. Don’t overcook your food. But how often do these claims hold water? Are there really that can prevent cancer or bad foods that can cause or worsen the disease?
Nutrition does play 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 whole grains, as well as limiting red meats, sugary beverages, highly processed foods, and refined grains.
But how does a specific food, or type of food, affect our risk of cancer? Here is the evidence — or lack of evidence — behind some of the most popular cancer-related diet claims.
The Claim: Sugar Fuels Tumor Growth
All cells in our bodies, including cancerous ones, use sugar molecules, also known as carbohydrates, as their primary source of energy. But that’s 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 cancer cells from spreading. “If [cancer cells] are not getting sugar, they’ll start to break down other components from other energy stores within the body,” said Carrie Daniel-MacDougall, PhD, MPH, a 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 the growth of tumors. For instance, at Memorial Sloan Kettering Cancer Center in New York City. “We and others are studying ketogenic diets for those types of tumors in clinical trials,” Iyengar said. “But a ketogenic diet is probably one of those types of diets that is not applicable to general cancer risk reduction. I think it’s one of those diets that needs to be matched to the tumor biology.”
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 eating high amounts of sugar and cancer risk. “Anything that has 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 sugar won’t stop cancer from growing, but early evidence suggests that a low-carb diet could enhance the effectiveness of certain cancer treatments.
The Claim: Eating Overcooked or Burnt Food Causes Cancer
When cooked at high temperatures, some foods — particularly carbohydrates such as bread or potatoes — release a chemical known as acrylamide.
“Some studies have suggested that by [overcooking or burning food], you create carcinogens in the food that can potentially harm the body,” Iyengar said. “I would call it a hypothesis right now. I’m not convinced this is truly 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 turned up little evidence that the acrylamide in foods raises the risk of cancer. When researchers have examined large groups of people to see if there is a link between acrylamide and cancers in , the evidence was limited, and it classified red meat as a “probable carcinogen.”
Some studies that vegan diets without talking with a cancer dietitian. “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 protein or B vitamin deficient,” she said.
In addition, not all cancers — or people — are the same, so a dietary change that is good or bad for one person may not have the same effect on everyone else. “The type of dietary intervention that is optimal for an individual is going to vary from person to person based on that person’s biology, but also their type of cancer and what stage or setting they’re in,” Iyengar said. “While there are general recommendations we can make to lower an individual’s risk of developing cancer, I envision a future where we will have the data to support much more personalized recommendations.”
Remember that diet is only one of several things to consider when it comes to cancer prevention, and even people who eat healthy can develop cancer, Zoumas noted. “If you get cancer and you have a healthy lifestyle, it’s going to be easier to go into a treatment and easier to recover — and you don’t know how much worse it could have been,” she said. “For those who choose a healthy lifestyle, it’s never a waste — and for people who haven’t had a healthy lifestyle yet, it’s never too late.”
The Verdict: Adding a single superfood to your daily foods won’t keep you from getting cancer. But eating a diet rich in plant-based foods such as vegetables and whole grains can help prevent the disease.
Diana Kwon is a freelance journalist based in Berlin. She covers health and the life sciences, and her work has appeared in publications such as Scientific American, The Scientist, and Nature. Find her on Twitter @DianaMKwon.