Beautiful study, ugly reporting

A new study from The American Journal of Medicine strengthens the link between breastfeeding and diabetes prevention. In looking at 2,233 Californian women, ages 40-78, from a single health plan (Kaiser), the researchers discovered a signficantly higher rate in the women who had children but never breastfed (405 of the women), compared to those who either hadn’t given birth (703 of the women) or who had nursed or pumped exclusively for at least a month (1,125 of the women).

The breakdown of those who developed Type 2 diabetes later in life was as follows (copied from WebMD):

  • 17.5% of the women who hadn’t given birth.
  • 17% of the women who breastfed all their children for a month or longer.
  • 20.3% of those who breastfed, but not all children for a month or longer.
  • 26.7% of moms who didn’t breastfeed.

Of those, 405 were not mothers, 1,125 were mothers who breastfed for at least a month, and 703 were mothers who had never breastfed.

You might expect that I’m going to pick apart this study, explaining that it was impossible to control for all confounding factors, lamenting the fact that the results relied on the (personal, and therefore likely flawed) recollections of women who’d been in their childbearing stages up to 50 years prior…. but I’m not. It’s a beautiful study, mostly because the authors are judicious in their analysis, and don’t hide behind “breast is best” rhetoric to disguise shaky results. I can’t copy and paste from the PDF of the entire paper here, but I did link to it, and I’d highly suggest reading the “Discussion” section, which outlines the advantages and flaws of a study such as this. The authors are also responsible enough to point out that the mechanisms behind their findings are completely unknown – in other words, while breastfeeding for even a short duration seems to have some protective effect against later development of Type 2 diabetes, they aren’t sure how this protective effect is conferred. Some have hypothesized that the type of fat lost more easily by lactating women may be the reason, or the apparent ability of lactation to alter insulin resistance. But the really important thing to acknowledge here is that once again, this could be a simple case of chicken and egg. Some of the same factors that may increase the risk of diabetes later in life – insulin resistance and obesity – are also significantly linked to shorter breastfeeding duration and lactation complications. So the same women who developed diabetes in this study could have refrained from breastfeeding for the same reasons that contributed to their later development of the disease… make sense?

Regardless, it’s an interesting finding, and I have no problem with it. I’m happy to see a study that examines the benefit of breastfeeding to mothers, rather than just focusing on what it can do for babies. It takes two to tango, after all. Plus, a month of breastfeeding, for those who physically/emotionally can handle it, doesn’t sound so daunting. Considering most U.S. maternity leaves are approximately 6 weeks, this could indeed be possible for women without having to deal with pumping, engorgement, etc, at work.

But I wouldn’t be the FFF if I didn’t find something to get all hot and bothered about with this news byte, would I? This time, it’s the media that I want to skewer. Because let’s face it – most folks are not going to read the entire study, cover to cover, and draw their own conclusions; they’re not going to see the sensitive discussion and thorough analysis the researchers did. They will probably just read about it in, oh, say, the Los Angeles Times, where reporter Shari Roan treats us to this little nugget of wisdom:

Breastfeeding a newborn for even one month will lower a woman’s lifetime risk of developing Type 2 diabetes, according to a study published Friday. Other research has also linked breastfeeding to a reduced risk of diabetes among women, but the new study establishes the strength of the association to a much greater degree…The question now is, why wouldn’t every new mother breastfeed for at least one month? 

Oh, Shari. Shari, Shari, Shari. If you’ve got 10 minutes, I’d be more than happy to answer that burning question for you. And while we’re at it, a little basic math might be useful, considering you write:

Researchers found that 27% of the mothers who did not breastfeed developed Type 2 diabetes. These women were almost twice as likely to develop the disease compared with women who had breastfed or who had never given birth. Among the women who breastfed for one to six months, 19% developed Type 2 diabetes compared with 16% among women who breastfed for six months or more.

Um, where did you get these numbers? I’m craptastic at math, so if any FFFs feel like picking through the actual study and figuring out why her numbers are off from the ones cited by Web MD, I’d be grateful. Either way though, unless I am even worse at number crunching than I thought (not bloody likely, as I believe I’m borderline LD on math stuff), last I checked 19% (the percentage of diabetes cases in those who had ever breastfed, which I’m assuming this writer is referring to by “compared to women who had breastfed”)x2= 38%. That’s significantly more than 27%, isn’t it? Not exactly “doubling”. Even if we use WebMD’s numbers (and I honestly can’t tell you who is right, although I’m assuming WebMD has a review board which is more familiar with accurate assessment of studies, so I’m leaning towards them), 17%x2= 34%, and again, the statistic for parous (meaning “having given birth”) women who never breastfed was 26.7%. Closer, but still no cigar.

Another strange piece of journalism comes out of the UK’s Daily Mail, which either misquotes lead study author Eleanor Bimla Schwarz, or Dr. Schwarz has changed her tune since writing the original paper:

“We have seen dramatic increases in the prevalence of type 2 diabetes over the last century,” said Eleanor Bimla Schwarz, M.D., M.S., assistant professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh. “Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breastfeeding also reduces mothers’ risk of developing the disease later in life by decreasing maternal belly fat.”

Huh. That’s interesting, considering in the actual study, the authors discuss the possibility that belly fat might be the reason for this breastfeeding advantage, but are also quick to add that “further studies are needed to identify the pathways and mechanisms through which lactation reduces subsequent risk of diabetes.” Again, not a huge deal, but these little soundbytes have a way of spreading like swine flu through society – and even more dangerously, through science and medicine – and before you know it, you’ll be seeing every breastfeeding study citing this study as definitive proof that breastfeeding lowers diabetes risk by reducing belly fat. This is sadly how these things work (For a great breakdown on this phenomenon, I highly recommend reading Jules Law’s definitive paper, The Politics of Breastfeeding.)

Anyway, this quote is also used in CBS’s report on the study, which, like the LA Times, has to throw in its own clever digs to bottle feeders. First, the headline:

Breast-Feeding Protects Moms from Diabetes, Study Shows: Why Use a Bottle?

And then, the classic snappy ending:

“Our study provides another good reason to encourage women to breastfeed their infants, at least for the infant’s first month of life,” said Dr. Schwarz.
As if moms needed another reason.

Thanks, David W. Freedman. There’s a free seat in my lecture about why moms might choose a bottle, right next to your colleague from the LA Times. I’ll even throw in some free coffee and donuts.

Suzanne Barston is a blogger and author of BOTTLED UP. Fearless Formula Feeder is a blog – and community – dedicated to infant feeding choice, and committed to providing non-judgmental support for all new parents. It exists to protect women from misleading or misrepresented “facts”; essentialist ideals about what mothers should think, feel, or do; government and health authorities who form policy statements based on ambivalent research; and the insidious beast known as Internetus Trolliamus, Mommy Blog Varietal.

Suzanne Barston – who has written posts on Fearless Formula Feeder.

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