Previous studies with diet and cancer focused on the influence of dietary fat primarily on breast and pancreatic cancers. From personal experience, my own graduate research involved the effects of omega-6 and omega-3 dietary fats on breast cancer in rats. (By the way, our results showed that there was not much difference in number of tumors between the two groups – and the study was repeated with the same results.)
Not much research has been done with carbohydrates (primarily sugars) and cancer. It has been known for decades that cancer cells thrive on glucose. Moreover, foods that cause a sharp rise in blood glucose trigger the secretion of insulin and insulin growth factor (IGF-1), two hormones that also promote cancer growth.
A study published in Cancer Research has investigated the effects of a high or low carbohydrate diet on the growth of various cancers. The researchers implanted various strains of mice with human or mouse tumor cells and assigned them one of two diets. The first diet, a typical Western-type diet, contained about 55% carbohydrate, 23% protein and 22% fat. The second diet contained 15% carbohydrate, 58% protein, and 26% fat. They found that the tumor cells grew consistently slower on the second diet.
Even more dramatic was the result that mice genetically predisposed to breast cancer given the Western diet developed breast cancer within their first year of life while none on the low carbohydrate, high-protein diet did. Only one on the Western diet reached a normal life span (about 2 years), with 70% of them dying from cancer while only 30% of those on the low-carbohydrate diet developed cancer and more than half these mice reached or exceeded their normal life span.
The lead author, Gerald Krystal, PhD, a distinguished scientist at the British Columbia Cancer Research Centre stated, “tumor cells, unlike normal cells, need significantly more glucose to grow and thrive. Restricting carbohydrate intake can significantly limit blood glucose and insulin, a hormone that has been shown in many independent studies to promote tumor growth in both humans and mice.”
According to the American Institute for Cancer Research (AICR), commenting on the study “the findings are interesting, but more research is needed before it can be used to make recommendations on public health”. It is also important to realize that this was just one study and it was a cell study. The findings may not necessarily be the same using animals including humans.
What kind of fuel are cancer cells particularly fond of? It appears to be the sugar, fructose based on previous study in Cancer Research. Fructose is found primarily in sucrose or table sugar (half of which chemically is fructose) in addition to high fructose corn syrup. U.S. consumption of high fructose corn syrup went up 1,000 percent between 1970 and 1990, researchers reported in 2004 in the American Journal of Clinical Nutrition.
The study administered glucose or fructose to two separate sets of pancreatic cancer cells. It was discovered that both sugars increased cancer cell growth at similar rates but the way these two types of sugars were metabolized affected cell proliferation.
According to the authors:
” Importantly, fructose and glucose metabolism are quite different… These findings show that cancer cells can readily metabolize fructose to increase proliferation.” The study supports the old adage that sugar feeds cancer because they found that tumor cells do thrive on sugar (glucose). However, the cells used fructose for cell division, speeding up the growth and spread of the cancer.
In a nutshell, ALL forms of sugar are detrimental to health in general and may play a role in cancer promotion, but in slightly different ways, and to a different extent. Overall, fructose, however, clearly seems to be the most harmful.
The AICR additionally comments that these studies do not “prove” that adding sugar to your diet raises cancer risks. Most dietary factors act in the promotional stage of cancer, not in the initiation stage, so their effects are not causative, but add to cancer cell growth or proliferation, once a cancer is established. “A healthy diet will always include some sugar, as it naturally occurs in nutritious foods like fruits and milk. The key is to limit added sugars of all types, rather than focusing on glucose versus fructose or sucrose”.
American Association for Cancer Research (2011, June 15). Low-carbohydrate, high-protein diets may reduce both tumor growth rates and cancer risk. ScienceDaily. Retrieved June 25, 2011, from http://www.sciencedaily.com /releases/2011/06/110614115037.htm
