The Sugar & Cancer Connection
FDG PET imaging study showing cancer deposits (metastases) throughout the body
Many of my patients ask... What's the connection between sugar and cancer?
A recent study in yeast now contributes to our understanding of the link between cancer cells and sugar (Nature Communications, Oct 13, 2017;8(1):922). Yeast cells, like cancer cells, get most of their energy from fermentation of sugar without needing oxygen. This study shows that fermentation in yeast activates Ras enzymes that increase conversion of normal cells to cancer cells and also increases growth of cancer cells once they are formed.
Difference Between Normal Cells and Cancer Cells
Almost 100 years ago, Nobel Prize winner Otto Warburg showed that cancer cells get most of their energy from sugar without needing oxygen. Normal cells on the other hand are more flexible and able to get their energy from sugar (with oxygen - aerobic glycolysis), fats as well as from protein and they rely much less on converting sugar to energy without oxygen (anaerobic glycolysis). Even though cancer and yeast cells can grow much more rapidly than normal cells, they get most of their energy from the much weaker method of burning sugar without oxygen.
One way that cancer cells try to increase their ability to utilize glucose has to do with glucose transporters. Glucose does not simply passively move from the outside of a cell to the inside of a cell. Glucose needs to be shuttled into the cell via a specialized receptor called a glucose-like uptake transporter, or GLUT. In an attempt to increase their levels of glucose, cancer cells make more GLUT receptors. With more receptors to bring glucose into the cells, the more available glucose there is for the cell to fuel it’s rapid cellular division.
One of the most frequently used tools (and one I use every day in my practice) to detect and monitor the presence of cancer in a person’s body is the positron emission tomography scan, or PET scan. Before the scan is performed, the patient is given a radioactively labeled glucose solution (F18-Fluorodeoxyglucose or FDG). This radioactivity allows glucose to be tracked and seen inside the body when the scan is performed. The places in the body where the radioactivity localizes are areas of increased glucose metabolism and demonstrates areas of cancer - see the image in this article.
Most cancer cells have an increased number of glucose receptors on the their cell surface, and demonstration rapid uptake of glucose by the PET scan, suggesting that sugar/glucose has an important role in cancer development and cancer cell proliferation. Additionally, elevated glucose levels have also been found to influence a person’s prognosis. Having an elevated blood glucose level has been found to be a negative prognostic indicator in many cancer types.
Excess Sugar, Overweight and Cancer
The study published in Nature Communications suggests that taking in excess sugar increases tissue levels of a chemical pathway that promotes the growth of cancer cells. Scientists have not directly shown that eating sugar causes cancer in humans, but recent studies in mice have shown this to be the case. We do know that eating excess sugar increases risk for obesity and diabetes and both obesity and diabetes are associated with increased risk for many different cancers.
Being overweight is associated with the following cancers: colon, rectum, esophagus, kidney, breast (women), endometrium, stomach, liver, gall bladder, pancreas, ovary, thyroid, meningioma, multiple myeloma and B-cell lymphoma as well as the fatal types of prostate cancer and breast cancer in men (N Engl J Med, Aug 25, 2016;375:794-798; Lancet, Aug 30, 2014;384(9945):755-65).
Full fat cells turn on your immunity to cause cancer-provoking inflammation, insulin resistance and oxidative stress, and obese people have higher blood levels of all of these markers (Br J Nutr, Dec 2011;106 Suppl 3:S5-78).
Having excess fat in your belly turns on your immunity to increase inflammation to increase risk for several cancers (Circulation, 2008;117(13):1658–1667, Archives of Physiology and Biochemistry, 2009;115(2):86–96).
Belly fat is associated with increased risk for cancers of the colon, rectum, postmenopausal breast, liver, endometrium, esophagus, kidney, stomach, gall bladder, pancreas, ovary, thyroid and multiple myeloma (Cancer Prev Res, September 1, 2017;10(9):494-506).
People who are not overweight but have big bellies are still at significantly increased risk for diabetes and cancers. Having excess belly fat increases a protein called fibroblast growth factor-2 (FGF2), that converts normal cells into cancerous ones (Oncogene, August 7, 2017).
A high-sugar diet is associated with spread of existing colon cancer (J Nat Can Inst, Nov 21, 2012;104(22):1702–1711).
High blood sugar markedly increases insulin levels which has been shown to increase cancer risk (Med Sci Monit, 2015; 21: 3825–3833).
Researchers have noted that per capita consumption of sugar in the U.S. now exceeds 100 pounds per year, contributing to the worldwide epidemics of obesity, heart disease and cancer. Based on what we know so far, we can’t tell you how much sugar will raise the risk of cancer. But we can tell you that Americans consume way too much, mostly from sweetened beverages and baked goods as well as candy, ready-to-eat cereals and yeast breads.
Too many patients are incorrectly told “eat whatever you want, diet doesn’t matter.” What a person eats, or more importantly- what they don’t eat, rather can have a huge impact on their fight against cancer. To suggest that diet doesn’t have a role in the treatment of cancer is to ignore a treatment that is relatively easy to implement, doesn’t have an excessive cost, and has little potential for adverse effects. There is strong evidence that excess sugar increases risk for heart attacks and strokes, and now we have evidence for a mechanism that can turn normal cells into cancerous ones. Combining a healthy cancer-specific diet along with a personalized integrative treatment plan is the best way to win the war against cancer.
Ways to Reduce Your Risk for Cancer
Reduce your calories, which lowers insulin and insulin-like growth factor-I, and inflammation
Restricting sugar in all drinks and added to foods
Engaging in a regular exercise program
Eating lots of vegetables, fruit and other anti-inflammatory foods