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Harvard hospital retracts statement about data on aspartame and cancer

This is a story about clinical research, misinterpreting said clinical research, an overaggressive Public Relations department, honest scientists, and good scientific journalism. Let’s start at the beginning.

This week, an article was published in the American Journal of Clinical Nutrition by Schernhammer et al., scientists from Brigham and Women’s Hospital, a teaching affiliate of Harvard University Medical School, that examined potential risks of certain cancers in groups that consumed diet drinks. The study identified, over 22 years, 1324 non-Hodgkin lymphomas (NHLs), 285 multiple myelomas, and 339 leukemias. They then determined their intake of diet sodas (or pop, depending on your location in the United States).

They determined that:

  • Men who had greater than 1 daily serving of diet soda had increased risks of NHLs and multiple myeloma. Women had no observed increased risks.
  • They also observed an unexpected elevated risk of NHL with a higher consumption of regular, sugar-sweetened soda in men but not in women. 
  • Neither regular nor diet soda increased risk of leukemia but were associated with increased leukemia risk when data for men and women were combined.

Based on these results, you might think that diet sodas are dangerous, at least for men. Or maybe just sodas (or pop), whether sweetened with sugar or artificial sweeteners, are dangerous. Or maybe not. The authors themselves conclude:

Although our findings preserve the possibility of a detrimental effect of a constituent of diet soda, such as aspartame, on select cancers, the inconsistent sex effects and occurrence of an apparent cancer risk in individuals who consume regular soda do not permit the ruling out of chance as an explanation.

In other words, there’s really not much there. And that’s not bad in science. They tried to look for something, and they didn’t find anything. Maybe those men who drank sodas heavily had other confounding risk factors like obesity, diet, or other environmental factors. Or it may just be random.

At this point in the story, it’s just one of those published articles that really isn’t much of anything. No one would make much of it, because it really doesn’t provide much evidence that aspartame or sodas are that dangerous. 

Then Brigham and Women’s Hospital puts out a press release with an attention grabbing headline of “The truth isn’t sweet when it comes to artificial sweeteners.” Now, if you saw that headline, you would have assumed that the article provided a solid conclusion that there was a direct causal link between artificial sweeteners and certain cancers. But the article said no such thing, it showed a very weak link, if one at all.

I guess the real scientists at Harvard saw the press release and decided their reputations mattered more than marketing the hospital in an unethical way. But whatever the real story, the hospital issued an “apology”:

It has come to our attention that the scientific leaders at Brigham and Women’s Hospital did not have an opportunity, prior to today, to review the findings of the paper entitled Consumption of Artificial Sweetener and Sugar Containing Soda and the Risk of Lymphoma and Leukemia in Men and Women”, to be published in today’s Journal of Clinical Nutrition (sic). Upon review of the findings, the consensus of our scientific leaders is that the data is weak, and that BWH Media Relations was premature in the promotion of this work. We apologize for the time you have invested in this story.

Uh,  it’s actually the American Journal of Clinical Nutrition, shocking they can’t get that right. Maybe I’m just being picky, but Public Relations should represent the organization better than that. 

Robert Bazell, NBC News reported that “the situation is a great example of why the public often finds science confusing and frustrating. After being asked some hard questions – and just before the report was to be released —  the hospital changed its tune.”

Bazell further reports that “the conclusion was so weak that the researchers had to submit it to six journals before they found a seventh, the American Journal of Clinical Nutrition, that would publish it. Few reporters read that journal. If it was not for the frightening headline no one would have known about this study.”

This study was a well-intended one that could have found a causal link if there was one, because of the way it sought out information. But it did not find the link, and that is how research is done. Sometimes, you find evidence of the null hypothesis, that artificial sweeteners don’t do anything.

And just in case there’s any confusion, Bazell reported that the lead author Schernhammer, when asked whether the published “research proves that aspartame is dangerous, she answered emphatically, ‘No, it does not.'”

The vast weight of evidence shows aspartame is safe. This doesn’t add to that weight, it just doesn’t support that it causes cancer. And it proves one more thing. Do NOT use press releases as your scientific proof source. They aren’t worth anything, because they aren’t written by scientists, and they are used to promote the facility. 

Drink your diet soda. Or pop. Your choice.

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