When I was in high school, I had an eccentric science teacher who, during a lecture on cellular metabolism, wrote on the whiteboard in red capitalized letters, “SUGAR IS DEATH.” At the time I thought he was being a bit dramatic, but I listened with curiosity and wondered if there was any truth to what he was saying about how sugar destroys one’s health. It’s common knowledge that sugar plays a role in diabetes, tooth decay, hyperactivity, and weight gain, but is sugar more dangerous than that? My doughnut-loving self didn’t want to believe it then, but it turns out that yes, sugar consumption does predispose individuals to chronic diseases such as heart disease and cancer, and the powerful influence of the sugar and processed food industries may be why the public has been kept in the dark about its risks. Even the Susan G. Komen Breast Cancer Foundation lists sugar as one of its factors that do not increase breast cancer risk and has partnered with companies like 7-Eleven to sell donuts as a fundraiser and KitchenAid to encourage home cooks to share their cupcake creations to promote breast cancer awareness. What message does this send the public about sugar and cancer?
As early as the 1920s, scientists have observed the deleterious effects of sugar consumption on health. Otto Warburg and his colleagues discovered that cancer cells have an enormous appetite for glucose compared to surrounding healthy tissue because they use it for energy production (glycolysis) in the presence of oxygen. Dr. Warburg stated in a lecture in 1966,
“Cancer, above all other diseases, has countless secondary causes. But, even for cancer, there is only one prime cause. Summarized in a few words, the prime cause of cancer is the replacement of the respiration of oxygen in normal body cells by a fermentation of sugar.”
He went on to study tumor metabolism and when other scientists confirmed his findings, the phenomenon was given the name the Warburg Effect in the early 1970s. The effect of sugar on cancer growth is multifaceted and still not completely understood, but Dr. Warburg’s work did open the door to further investigate sugar’s role in tumor growth. So, if we knew about sugar’s role in cancer growth in the 1920s, why hasn’t more research led to better regulation of the sugar industry?
Just last month, it came to light that research conducted in the 1960s suggested a link between a high-sugar diet and cancer in rats, but the sugar industry put the kibosh on the publication of the study. The study, called Project 259, compared rats fed a high-sugar diet to those fed a high-starch diet and suggested that sucrose (table sugar) consumption might be associated with elevated levels of the enzyme beta-glucuronidase, which is linked to several types of cancer in humans. The study was funded by the Sugar Research Foundation (SRF) and was subsequently terminated without being published, which effectively prevented sugar from being scrutinized as a potential carcinogen. Coincidentally, this occurred during a time when Congress had just passed legislation that prohibited additives in food that were shown to cause cancer in any species of animal, which may have put sugar on the chopping block. The foundation now states that the reason the study ended was because of delays, budget problems, and “organizational restructuring.” The Sugar Association, which is a trade/lobbying association in the United States and the new name of the SRF, has consistently stated that, “no credible link between ingested sugars and cancer has been established.” Well, that’s easy to say when you conceal any evidence to the contrary! This wouldn’t be the first time a trade or lobbying group influenced the public’s perception of the safety of a product (Big Tobacco, anyone?).
The evidence behind sugar’s role in cancer is mounting, with numerous clinical studies showing that cancer patients with the highest carbohydrate intake and blood glucose levels have the poorest outcomes. But how exactly does sugar contribute to cancer development and growth? In addition to the Warburg Effect, here are just a few of the mechanisms by which sugar feeds cancer:
- Sugar increases insulin-like growth factor-1, or IGF-1, which promotes rapid cell replication while reducing normal programmed cell death (apoptosis)
- Sugar boosts leptin, which is a hormone that stimulates cell proliferation, migration, and invasion, giving rise to more aggressive and metastatic tumor cells
- Sugar promotes angiogenesis, which is the development of new blood vessels that allows cancer cells to grow and spread
- It compromises the immune system by blocking uptake of vitamin C into white blood cells, which weakens their ability to perform phagocytosis (engulfing of pathogens and cell debris).
Knowing that sugar consumption promotes cancer metastasis and weakens the body’s ability to protect itself from developing cancer in the first place, consumers need practical ways to reduce sugar intake and find safer alternatives. Nutrition therapy practitioners can help educate clients on how to minimize sugar cravings, choose products that are naturally lower in sugar, and how to cook and bake delicious foods without adding a lot of sugar. Sugar is ubiquitous in the American diet and can be difficult to avoid, especially in processed foods, but there is a positive change in the works that may make it easier to avoid overconsumption. You may have noticed that there has never been a % Daily Value listed for sugar on the nutrition facts label, which seems to imply that there is no recommended limit. Since the FDA now recognizes that no more than 10% of your total daily calories should come from added sugar, they announced last year that the label will be required to have a separate line item for “added sugars.” This will enable consumers to determine which foods have naturally occurring sugars (like those derived from milk or fruit) versus those that have added sweeteners and will provide much-needed context to the number of grams of sugar per serving. Some manufacturers have started using the new labeling guidelines already, but they have until Jan. 1, 2020 to comply (this is an extension to the previous July 26, 2018 compliance date). This is sweet news indeed for nutrition therapy practitioners and consumers alike.
Cadie Berrian, BA, MNT