A recent flurry of news articles have reported on a recent study that showed that treatment of pancreatic cancer cells with fructose increased cell proliferation - uncontrolled proliferation is a hallmark of cancer. This follows on the heels of another study that linked fructose consumption from added sugars to elevated blood pressure. The bad press on fructose is making people question the safety of the ubiquitous commercial sweetener, high fructose corn syrup (HFCS).
Due to the introduction of HFCS, fructose intake has increased dramatically in the U.S. since the 1970s. Between 1970 and 2000, HFCS intake increased by 100-fold, and total fructose intake increased by 30%.1
Fructose makes up half of the sucrose molecule (with glucose), but may also be present in "free" form. Abosrption of fructose and glucose, and the differences between fructose in natural foods and fructose in HFCS are explained here.
These authors investigated whether cancer cells could use fructose for energy, because they are known to use glucose - cancer cells are known to have a greater number of glucose transporters and metabolize glucose more rapidly than normal cells because their rapid proliferation requires greater amounts of energy.2
Although different transport mechanisms are used to get fructose and glucose into cells, their metabolism is thought to be similar once they enter cells. However, these scientists found that in human pancreatic tumor cells, metabolism of fructose and glucose occurs via different pathways, both leading to cell proliferation. Keep in mind that both sugars led to increased cell proliferation at similar rates - that is, this study did not show that fructose is "worse" than glucose, just that they stimulate proliferation by different mechanisms. Glucose was used by the cancer cells for energy production, whereas fructose was used to generate nucleic acids (DNA and RNA). This study was the first to show that cancer cells could differentiate between fructose and glucose, and that they could use fructose as efficiently as glucose to fuel cell growth.3,4
Sucrose intake, fructose intake, and high glycemic load have all been associated with pancreatic cancer in epidemiological studies, and diabetes also increases risk.5,6
The message of this study and others on the negative effects of fructose is that added sugars, abundant in the Western diet, are detrimental to health and should be minimized, but sadly this is not the message that is getting through to the public.
With the recent media frenzy around HFCS, the conventional wisdom seems to have become that sugar is superior to HFCS because it is more 'natural' - prompting many companies to switch from HFCS to sugar for sweetening their products. Meanwhile, the high fructose, low glycemic index sweetener agave nectar, once elevated to health food status, is now being doubted because of the negative press on fructose.
Comparing sweetener to sweetener is missing the point. All sweeteners have negative health effects, regardless of their relative quantities of fructose, glucose, and sucrose.
Some sweeteners spike blood glucose, others raise triglycerides and form advanced glycation end products (AGEs), and all provide excess calories and are devoid of nutrients. This is not a question of which sweeteners are healthy and which are unhealthy. None are healthy. All are merely concentrated sugars - contributing to obesity and all its consequences - and therefore should all be minimized or completely avoided in a health-promoting diet.
1. Bray GA, Nielsen SJ, Popkin BM. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Am J Clin Nutr. 2004 Apr;79(4):537-43.
2. Medina RA, Owen GI. Glucose transporters: expression, regulation and cancer. Biol Res. 2002;35(1):9-26.
3. Liu H, Huang D, McArthur DL, et al. Fructose induces transketolase flux to promote pancreatic cancer growth. Cancer Res. 2010 Aug 1;70(15):6368-76.
4. EurekAlert! Pancreatic cancers use fructose, common in the Western diet, to fuel their growth. August 2, 2010
American Institute for Cancer Research Blog. Glucose, Fructose, and the Alarming Pancreatic Cancer News. August 4, 2010. http://www.aicrblog.org/2010/08/04/glucose-fructose-and-the-alarming-pancreatic-cancer-news/
5. Nöthlings U, Murphy SP, Wilkens LR, et al. Dietary glycemic load, added sugars, and carbohydrates as risk factors for pancreatic cancer: the Multiethnic Cohort Study. Am J Clin Nutr. 2007 Nov;86(5):1495-501.
6. Michaud DS, Liu S, Giovannucci E, et al. Dietary sugar, glycemic load, and pancreatic cancer risk in a prospective study. J Natl Cancer Inst. 2002 Sep 4;94(17):1293-300.