Diet soda linked to higher leukemia risk

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Jimmy Downs

Monday Oct 29, 2012 (foodconsumer.org) -- Using diet sodas or sugar-sweetened regular sodas may increase risk of leukemia in men, but not in women, according to a new study published on Oct 24, 2012 in American Journal of  Clinical Nutrition.  Diet soda often uses aspartame, an artificial sweetener that has been linked to leukemia in animal studies.

E. S. Schernhammer of Brigham and Women's Hospital and Harvard Medical School  and Harvard School of Public Health in Boston, MA and colleagues conducted the study and  found men who drank one serving or more of diet soda increased risk of non-Hodgkin lymphomas by 31 percent, and risk of multiple myeloma by 102 percent, compared to men who did not use diet soda.

The researchers also found men, but not women who had higher intake of regular sugar sweetened soda were at 66 percent higher risk for non-Hodgekin lymphomas, compared to men who did not use sugar sweetened soda.

The analyses were based on data pooled from two studies, the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS).  During a 22-year follow-up, identified were 1324 cases of non-Hodgkin lymphoma, 285 cases of multiple myeloma, and 339 cases of leukemia.

Additionally, a 41 percent increased risk of leukemia was found in men and women who used one serving of diet soda per day, compared to those who did not use diet soda.

Brigham and Women's Hospital reportedly posted a release on Wednesday to draw the public attention to the study, which unfortunately drew critiques from the media that accused authors of promoting a study that provides weak evidence to suggest that aspartame may increase risk of leukemia.  Dr. Schernhammer was kind of forced to say the study was weak to prove that aspartame causes leukemia.  A report by NBC news indicates that such a study should not be promoted to have the public attention because it has not drawn a final conclusion yet.

According to NBC news, six academic journals refused to publish the study and American Journal of Clinical Nutrition was the seventh that agreed to publish it. It is unknown why so many journals refused to publish the study.   The fact that American Journal of Clinical Nutrition, which is a reputable academic journal, accepted the article suggests that the quality of the study should not be an issue.

Many studies have suggested that aspartame is unlikely to cause blood cancers like leukemia.  But all these studies lasted for a short period.  The current study followed men and women for 22 years and the results provided a different type of evidence to suggest that aspartame may indeed raise risk of leukemia.

The current study kind of confirmed two animal studies published after a 2002  review of more than 500 studies that together suggested aspartame is safe in the dose used in diet sodas.  In these two studies, researchers fed animals aspartame diet for their whole lifespan or until natural death.

M. Soffrutti and colleagues Cesare Maltoni Cancer Research Center, European Ramazzini Foundation of Oncology and Environmental Sciences in Bologna, Italy published their first study in 2006 in Environmental Health Perspectives that found rats with lifetime exposure to aspartame starting at the age of eight weeks were at higher risk of lymphomas and leukemia and other malignant diseases.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392232/

The authors also found such exposure to aspartame increased risk of transitional cell carcinomas of the renal pelvis, ureter and their precursors (dysplasias) in female rats and risk of malignant schwannomas of peripheral nerves in male rats.

The cancer-causing effects were observed at a daily dose of 20 mg/kg body weight, which was much lower than the current acceptable daily intake.  The researchers said the study suggested that the present guidelines on the use and consumption of aspartame should be immediately revised to minimize the potential adverse effect from the food additive.

This study has drawn attention from U.K. authority, which nevertheless refused to take an action saying the 2002 review suggests that aspartame is safe at the levels currently used in foods and beverages.

In 2007, the authors again published in the same journal their second study which is similar to the first one with one exception that rats started being exposed to aspartame through a diet from the 12th day of fetal life until natural death.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1964906/

Again the researchers observed an increase in risk of lymphomas and leukemia in both male and female rats exposed to aspartame and also an increase in risk of mammary cancer in female rats exposed to aspartame.

The researchers concluded "The results of this carcinogenicity bioassay confirm and reinforce the first experimental demonstration of APM (asparatame)'s multipotential carcinogenicity at a dose level close to the acceptable daily intake for humans. Furthermore, the study demonstrates that when life-span exposure to APM begins during fetal life, its carcinogenic effects are increased."

In both studies, the researchers observed a dose response relationship between exposure to aspartame and cancer risk, which led to the question, is there a threshold for the carcinogenic effect of aspartame or any low dose of aspartame may cause a small risk of cancer just as ionizing radiation does?

Aspartame is widely used as an artificial sweetener to replace calories-loaded natural sugars.   In the UK, the acceptable daily intake (ADI) of aspartame is set at 40 milligrams per kg of body weight, while in the US, aspartame ADI is set at 50 milligrams per kg of body weight.

M. Nathaniel Mead published a comment in response to the first study by Soffrutti et al.  It was cited verbatim below to give readers more details about the study so that readers may have a better understanding of the findings from the study.

Sour Finding on Popular Sweetener: Increased Cancer Incidence Associated with Low-Dose Aspartame Intake

M. Nathaniel Mead

Copyright and License information ?
Copyright This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose.

See "First Experimental Demonstration of the Multipotential Carcinogenic Effects of Aspartame Administered in the Feed to Sprague-Dawley Rats" on page 379.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392232/

More than 20 years have elapsed since aspartame was approved by regulatory agencies as an artificial sweetener. But scientists draw conclusions on carcinogenicity based on the evidence available at the time, and new research out of the European Ramazzini Foundation of Oncology and Environmental Sciences bolsters recent calls for reconsideration of regulations governing aspartame’s widespread use in order to better protect public health, particularly that of children [EHP 114:379–385; Soffritti et al.].

The researchers added aspartame to the standard diet of Sprague-Dawley rats, using dosages designed to simulate a wide range of human intakes. Each rat was observed from 8 weeks of age until death. This is in contrast with earlier studies that typically sacrificed animals between 104 and 110 weeks of age, corresponding to about two-thirds of a rat’s lifespan (in humans, approximately 80% of cancer diagnoses are made in the last third of life, after age 55). Deceased animals were examined for microscopic changes in various organs and tissues, enabling a comprehensive assessment of aspartame’s carcinogenic potential. A total of 1,800 rodents were included, far more than in previous studies.

Aspartame-fed females showed significant evidence of lymphomas/leukemias and of carcinomas of the renal pelvis and ureter. The effect on the renal pelvis was much more evident when carcinomas were combined with atypical preneoplastic lesions. The researchers also observed an insignificant increase in incidence of malignant schwannomas of the peripheral nerves in males, as well as hyperplasia of the olfactory epithelium in males and females. Lesions of the kidney and olfactory epithelium are extremely rare in this strain of rats and therefore merit special attention.

The carcinogenic effects were evident at daily doses as low as 400 parts per million, equivalent to an assumed daily human intake of 20 milligrams per kilogram body weight (mg/kg). This dosage is much less than the acceptable daily intake for humans, with current limits set at 50 mg/kg in the United States and 40 mg/kg in Europe. Surveys of aspartame intake in the United States and Europe from 1984 to 1992 showed that consumers typically consumed 2–3 mg/kg daily, with small children and women of child-bearing age consuming slightly more, at 2–5 mg/kg daily.

The public health implications of these findings may be substantial, since aspartame is used in about 6,000 products, and more than 200 million people regularly consume aspartame through foods, beverages, drugs (such as chewable vitamins), and hygiene products (such as toothpaste). Because the study did not take into account in utero and perinatal exposures, the authors point to this as a salient direction for future research, given that children and pregnant and breastfeeding women are among the major consumers of aspartame.



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