Sugar, for as much pleasure as it gives us, has become a source of uncertainty and fear for many people battling cancer. And that’s because of the commonly cited evidence that sugar feeds cancer.
While conventional medicine will tell you sugar causes “no problem” when you’re fighting cancer, the research shows otherwise. In these pages I’ve often called sugar “cancer’s favorite food.”
How sugar causes cancer
Eating anything with too much sugar on a regular basis will make you gain weight, which leads to the risk of obesity and diabetes.
Those conditions absolutely do increase a person’s risk of cancer, and plenty of research shows that being overweight or obese can raise your chances of developing at least 11 different types of cancer. That includes pancreatic, ovarian, breast, colorectal, and uterine cancer.
Sugar also causes cancer more directly.
Just like all your other cells, cancer cells need sugar to survive. Cancer cells also tend to grow quickly and multiply at an exponential rate, which requires a lot of energy, which is obtained through glucose.
One leading medical pioneer in the research into sugar and cancer development is Dr. Lewis Cantley, Director of the Sandra and Edward Meyer Cancer Center and Weill Cornell Medicine.
In the 80’s, Dr. Cantley was a professor at Tufts University School of Medicine when he identified a new enzyme called PI3K, phosphoinositide-3-kinase, which is a master growth switch for cancer. When working normally PI3K alerts cells to the presence of insulin, signaling them to pump in glucose for fuel. In cancer, PI3K shifts into high gear and feeds tumors with large amounts of glucose, driving their growth.
PI3K-related gene linked to 80 percent
Since Dr. Cantley’s original research, mutations in the gene that triggers PI3K have been linked to 80 percent of cancers.
Today, Dr. Cantley is researching how to use PI3K to treat cancer, including PI3K inhibiting drugs. In a study in mice Dr. Cantley’s team found spikes of insulin reactivated the PI3K pathway in tumors, countering the anti-cancer effects of the inhibiting drug.
“Our preclinical research suggests that if somewhere in your body you have one of these PI3K mutations and you eat a lot of rapid-release carbohydrates, every time your insulin goes up, it will drive the growth of a tumor,” explains Dr. Cantley. “The evidence really suggests that if you have cancer, the sugar you’re eating may be making it grow faster.”
Not surprisingly, Dr. Cantleyhasn’t eaten sugar in 40 years. And Dr. Cantley’s research is just the tip of the iceberg on sugar and the development of cancer.
- Increases Colon Cancer: A study by Harvard Medical School of 40,000 American women found those who ate the most foods with the highest glycemic index—a number that dictates how quickly sugar levels in the blood rise after eating it—had a three times higher risk of getting colon cancer than women who ate lesser amounts of these foods. Another study in 50,000 men found similar results.
- Increases Pancreatic Cancer: A study in Sweden found that consuming added sugar increased the risk of pancreatic cancer by 69 percent over people who ate the least sugar.
- Increases Prostate Cancer: An Italian study found that men whose diets were more likely to trigger an increase in blood sugar levels had a 57 percent higher risk of getting prostate cancer.
- Increases Endometrial and Breast Cancer: The Iowa Women’s Health Study examined 23,000 post-menopausal women. Researchers found that those who consumed a diet most likely to raise blood sugar levels experienced a 46 percent higher risk of getting endometrial cancer. For breast cancer the increase in cancer risk was a remarkable 135 percent.
- Increase in ALL Cancers: After studying 1.3 million men and women in Korea for ten years, researchers found that those with the highest fasting glucose levels were more likely to die from ALL types of cancer combined. In addition to more cancer deaths, those with the highest fasting glucose were also more likely to develop cancer.
Sugar takes on many forms
I hope by now I’ve scared the dickens out of you when it comes to eating sugar. But you need to know something else: sugar takes a lot of different forms. You need to know what you’re eating.
The simplest form is the single molecule of glucose. Glucose is a primary fuel for all cells, cancer cells included. Your body converts any carbohydrates you eat — fruits, vegetables, whole grains, and dairy — into glucose, which is what “blood sugar” consists of.
Refined carbohydrates like table sugar, soda, pasta, white rice, potatoes white breads, and candy are very rapidly converted into glucose or blood sugar in the body and do enormous damage when you eat them in large quantities – as nearly all of us do.
These foods contain sucrose (e.g. cane or beet sugar) or fructose (typically found in fruit but also in other types of food) and some glucose as well. These are called “simple sugars” because they consist of one molecule. But high-carb foods also contain various forms of starch that are converted quickly to blood sugar.
When molecules of simple sugars stick together in different chain forms, those combinations are classified as carbohydrates, which is your body’s main source of energy.
These longer chains of sugar are called polysaccharides. As they get longer, they’re less sweet and no longer dissolve in water the way a simple sugar like table sugar can. Polysaccharide chains are found in a lot of the starchy foods I mentioned earlier like rice, bread, and pasta.
You can see that broadly speaking, “sugar” consists of a lot more than the white crystals of table sugar most of us think of when we hear the word. Table sugar is made up of sucrose, and is a combination of the glucose and fructose molecules. But table sugar is refined, which means it’s been processed and extracted from another source – typically the sugar beet.
Some foods we like to think of as healthy – fruits or honey – also contain a lot of sugar and should be eaten in moderation. Honey, like table sugar, is nearly pure sucrose.
These different sugars act differently in the body.
If you consume something high in simple sugars, like soda, your blood glucose levels immediately soar. If you eat a starchy food like bread, your digestive juices break down those carbohydrates to isolate and use the glucose. And if you attempt to go completely without sugar or carbohydrates, your body will target fat and protein cells, breaking them down to their basic components in order to extract some glucose, simply because your cells need glucose to survive.
What to do?
I’m going to give you the advice that I’ve heard from countless alternative cancer doctors over the years: Cut refined sugar from your diet completely. You can eat fruit, but stay away from all refined sugar and the processed foods that contain them. This is especially important if you’ve ever been diagnosed with cancer.
Not only does excess sugar stimulate your pancreas to produce more insulin to feed cancer cells that might be in your body, but what’s more, high levels of insulin are also inflammatory. And as we know, inflammation is also a precursor for cancer.
You’ll be better off, and healthier in the long run, if you eat whole-grain carbohydrates, fruits, vegetables, legumes and lean meats.
The keto diet
Some alternative doctors advocate a keto diet, which is a very low carbohydrate diet. Dr. Cantley and his team are currently investigating the effects of a keto diet that’s a bit different from the high protein keto diets that so many celebrities praise.
In the Cantley keto diet, 85 percent of the calories are from fat, ten percent from protein and five percent from carbohydrates. This is a big change from the common Western diet where a whopping 65 percent of calories come from carbohydrates. While results of the dietary study aren’t in, Dr. Cantley and his team hope to show that cancer patients can reduce insulin levels and starve their tumors.
Of course, that doesn’t mean that lowering insulin levels will cure all cancers. Some cancers actually feed on protein.
“You need to know the logic of the cancer in order to understand what would be the best dietary intervention for a given patient,” Dr. Cantley says. “Some cancers are addicted to sugar, but others depend on very high levels of the amino acids glutamine or serine, for example.”
Even still, eating less sugar is clearly beneficial.
“It’ll help you in so many different ways, with so many different diseases,” says Dr. Cantley.
I couldn’t agree more.
- “Cancer causes: Popular myths about the causes of cancer.” Mayo Clinic Staff, 21 March 2020.
- “Does sugar feed cancer?” Retrieved 8 November 2020.
- “Sugar and cancer – what you need to know.” By Emma Smith, 20 October 2020.
- “Does sugar cause cancer?” BY Adelina Espat for MD Anderson.
- “Q&A: Does sugar feed cancer?” By Colleen Gill, MS, RD, CSO on behalf of the ON DPG.
- “Increasing evidence of a strong connection between sugar and cancer.” By Amy Crawford,
Weill Cornell Medical College. https://medicalxpress.com/news/2019-03-evidence