January is usually filled with optimism. But this year, not so much. No, I’m not talking about politics, but I am talking about a new perspective recently published online in PLoS Medicine in which the authors campaign hard against consuming low-calorie sweetened beverages (LCSBs).
According to the authors, LCSBs don’t deliver on their promises, and there are a laundry list of reasons not to consume them. But what evidence do the authors use to support this platform? Let’s take a look.
First, let’s start by calling the PLoS article what it is—it’s a commentary. Even though it was published in a peer-reviewed medical journal, and many media headlines have called this a “study,” it is not a study. No new research was conducted here. Only new opinions.
Now let’s talk about the evidence presented in the commentary. The authors suggest that the numerous studies cited in support of their argument are equal in strength and credibility to the vast amount of peer-reviewed literature with contradictory results. In other words, they foster false balance by positioning two separate bodies of evidence as equal when in fact they are not.
Here are two key points in the article (along with my response) that I hope will add some science-based context to this “commentary”:
1.“There are long-standing concerns that LCSBs may trigger compensatory mechanisms.”
The authors are alluding to an inaccurate argument that seems to be popping up more regularly these days. It’s based on speculation that when you drink LCSBs (instead of a full-calorie beverage or water), you end up consuming more calories that day than you otherwise would have.
I find it particularly interesting that the authors put this concept forward while citing a study that explicitly states, “A critical review of the literature, addressing the mechanisms by which NNS (non-nutritive sweetener) may promote energy intake, reveals that none are substantiated by the available evidence.”
It’s important to understand this—and the authors shine a bright light on it, too—LCSBs are not (and should not be perceived as) magic bullets for health. There is no such thing as a magic bullet in nutrition. However, the highest quality evidence from systematic reviews and meta-analyses (you know, the kinds that underpin official U.S. Dietary Guidelines and other global authoritative statements) illustrate that LCSs are a safe and effective option that can help reduce the number of calories we eat and drink.
While shorter-term trials show efficacy for weight loss and longer-term trials have yielded mixed results, it doesn’t mean that long-term use of LCSBs lead to weight gain. To make these kind of statements, you need evidence, which the PLoS commentary doesn’t provide. Just so we’re crystal clear here, the authors concede that “available evidence does not directly support a role [of ASBs (artificially sweetened beverages)] in inducing weight gain.”
2. “LCSBs may contribute to the development of glucose intolerance by altering the composition and functions of gut microbiota.”
This may be the statement that comes with the least amount of evidence behind it, but it’s made nonetheless. There are issues abound with this study on LCSs and gut microbiota (Suez et al., 2014), and we’ve written about them before. Leaning on this paper for support doesn’t strengthen the argument. In my opinion, it drastically weakens it.
When citing this study, the authors fail to discuss its multiple and severe limitations: short duration, small sample sizes (20 mice, FFQs from 381 people, and a 7-person intervention—where effects were only observed in 4/7), self-reporting, and unadjusted confounding variables, just to name a few. Having just one or two of those limitations can dramatically lower the validity and strength of a particular study.
However, the authors eagerly point to limitations in significantly higher-caliber research studies that lack many of the flaws in Suez, et al. For a more compelling and controlled examination of the impact of LCSBs on body weight, here’s some suggested reading: Peters et al., 2014, de Ruyter, et al., 2012, Miller, Perez 2014.
It’s important to discuss both sides to the research story, and this commentary fails in that regard. Where it doesn’t fail, however, is in using campaign and advocacy rhetoric (not the established totality of science) to justify an opinion about an entire food category—LCSBs, in this case.
I won’t argue that everyone would experience a health benefit from using LCSs or drinking LCSBs—there are numerous alternative strategies for decreasing calorie intake if that’s your goal. I will argue that choice is paramount. And denigrating one’s preferred route of reducing calories in their diet by simple, safe, effective and enjoyable means doesn’t seem like a productive way to advance public health based on scientific consensus.