Study Linking Aspartame, Cancer Causes Controversy

A study linking the artificial sweetener aspartame — which is found in lots of diet sodas — to a possible cancer risk in people was set to make a splash earlier this week. But shortly before the paper was published, in a very unusual move, the scientific leaders at the hospital released a statement saying the findings were too weak to promote.

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And I'm Renee Montagne. A scientific study was set to make a splash this week. It linked the artificial sweetener aspartame - found in lots of diet sodas - to a possible risk of cancer. But shortly before the paper was published - in a very unusual move - the teaching hospital behind the study released a statement, saying the findings were too weak to promote to the public in a press release. NPR's Allison Aubrey reports.

ALLISON AUBREY, BYLINE: It was a press release titled "The Truth Isn't Sweet When It Comes To Artificial Sweeteners," that set the tone for how the media team at Brigham and Women's Hospital hyped the findings of a new study, published in the American Journal of Clinical Nutrition. The release described how researchers had documented an increased risk of certain blood cancers in men who consumed more than one diet soda a day.

DR. WALTER WILLETT: I think this grabs people's attention because the question around aspartame is very hotly debated.

AUBREY: That's Walter Willett, of the Harvard School of Public Health. He's a co-author of the paper. But he says the press release failed to fully characterize the findings, and came across as frightening.

WILLETT: This is the kind of thing that probably should never have had a press release, in the first place.

AUBREY: So why weren't the findings ready for prime time? Well, we'll get to that. But Willett says, by way of background, the reason he decided to look into this issue in the first place is because several years back, a big lab study of rats found an increased risk of blood cancers, linked to aspartame. This made them curious. He and his colleagues realized they had the opportunity to look at this in people.

Lead author Eva Schernhammer, of Brigham and Women's Hospital, explains her colleagues had started asking thousands of people about their diet soda consumption way back in the 1980s, just after the FDA had approved the use of aspartame.

DR. EVA SCHERNHAMMER: So we would ask them: How many servings of diet soda did you consume, on average, in the last years?

AUBREY: And they kept asking this question periodically - for 22 years - as part of a wider health and diet survey. So Schernhammer and her colleagues analyzed this data, and they found there did seem to be some associations between aspartame and cancer.

SCHERNHAMMER: This was a surprise to us because we really had not expected an association between aspartame and any of the cancers that we had studied.

AUBREY: Specifically, they found an increased risk of non-Hodgkin's lymphoma in men; but not in women, which was puzzling. And they also saw an increased risk of leukemia that teetered on the edge of clinical significance. Even the authors acknowledge, in the paper, that it's entirely possible that these associations they found were due to chance. These weaknesses were a red flag to the independent experts we asked to review the paper, earlier in the week.

DONALD BERRY: I'm not convinced that this paper shows a relationship between blood-related cancers and drinking diet soda.

AUBREY: That's Donald Berry. He's a professor of biostatistics at MD Anderson Cancer Center. He told us it's likely that the findings are due just to chance. The only other big study of people, found no link between aspartame and cancer. And Amy Subar, of the National Cancer Institute, says what puzzled her about the new findings is that men in the study who drank regular, sugar-sweetened soda also seemed to have an increased risk of cancer. So perhaps something other than aspartame, is at play here.

AMY SUBAR: There might be some other ingredient in soda that might be leading to this, that's common to both diet and non-diet sodas; could be other lifestyle things associated with all soda drinking. And that's interesting, except you'd think you'd find it in women, also. And that's what's puzzling.

AUBREY: These are all interesting questions. And Marji McCullough, of the American Cancer Society, says they are worth further investigation.

MARJI MCCULLOUGH: I think you can bet that there will be other studies, looking at this question.

AUBREY: But until there are more studies, there's no clear message to send to consumers. This is why study author Walter Willett agrees that the findings should never have been promoted to news organizations, in the first place. Science, he says, is messy.

MCCULLOUGH: It's often a back-and-forth process.

AUBREY: And he says for now, the data linking aspartame to possible cancer risks, are still in the gray area.

Allison Aubrey, NPR News.

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