The headline, Infant formula could change gut bacteria, contribute to childhood obesity, is alarming.
The findings are worrisome:
[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]If they had used a growth chart of how all infants grow, not merely breastfed infants, the title might easily be ‘Exclusive Breastfeeding and the Risk of Underweight in the First Year of Life.’[/pullquote]
A new study shows that babies who were breastfed had different bacteria environments, or microbiomes, in their guts –- and lower obesity levels as they grew -– than babies who were primarily fed formula…
For the study, published in the Journal of Pediatrics [sic], researchers in Canada looked at data from the Canadian Healthy Infant Longitudinal Development, or CHILD, focusing on the first year of life for more than 1,000 infants from four different sites.
Researchers in this study wanted to know if only breastfeeding, breastfeeding plus some early foods, or formula feeding alone affected the type of bacteria found in the infants’ guts at two ages: 3 to 4 months and 12 months.
What did they find?
Of the formula-fed babies, 33 percent were overweight or at risk of being overweight, while 19 percent of exclusively breastfed babies were overweight or at risk.
There’s a serious problem with the study, however. It uses a flawed and arbitrary measure of infant obesity.
The authors report:
There were 1087 infants in the study (507 girls and 580 boys); at 3 months, 579 of 1077 (53.8%) were exclusively breastfed according to maternal report. Infants who were exclusively formula fed at 3 months had an increased risk of overweight in covariate-adjusted models (53 of 159 [33.3%] vs 74 of 386 [19.2%]; adjusted odds ratio, 2.04; 95% CI, 1.25-3.32). This association was attenuated (adjusted odds ratio, 1.33; 95% CI, 0.79-2.24) after further adjustment for microbiota features characteristic of formula feeding at 3 to 4 months …
Here is a chart of the results.
How did they determine which babies were “obese”?
At 12 months of age (mean [SD] age, 12.4 [1.3] months), infants were weighed and measured by CHILD Study staff. Age- and sex-specific weight for length z (WFLz) scores were calculated according to World Health Organization standards. A WFLz score greater than the 97th percentile was considered overweight, and a WFLz score greater than the 85th percentile was considered at risk for overweight …
But breastfed babies and formula fed babies grow differently. The CDC acknowledges:
The WHO growth charts reflect growth patterns among children who were predominantly breastfed for at least 4 months and still breastfeeding at 12 months. These charts describe the growth of healthy children living in well-supported environments in sites in six countries throughout the world including the United States. The WHO growth charts show how infants and children should grow rather than simply how they do grow …
The WHO growth charts establish the growth of the breastfed infant as the norm for growth. Healthy breastfed infants typically put on weight more slowly than formula fed infants in the first year of life. Formula fed infants gain weight more rapidly after about 3 months of age. Differences in weight patterns continue even after complementary foods are introduced
Wait, what? Formula fed infants are being evaluated on a scale designed for breastfed infants?
To understand why that’s a serious problem it’s instructive to consider the genesis of the current WHO standards. Previous standards evaluated growth based predominantly on formula fed infants since most infants were formula fed at the time they were developed. Many breastfed infants were diagnosed as underweight using these charts. Breastfeeding advocates claimed that it was wrong to evaluate breastfed infants using formula fed infants as the standard.
They had a point, but it’s not clear that it was a valid one. It’s based on the assumption that every breastfed infant is fully fed when the reality is that breastfeeding has a significant failure rate and some breastfed babies are actually underfed. Far fewer babies receiving formula are underfed since they can eat until satiety instead of merely until the milk runs out.
The WHO charts purportedly show “how infants and children should grow rather than simply how they do grow.” But they don’t measure how infants “should” grow, they measure how breastfed infants, including underfed infants, grow. It’s a classic example of the naturalistic fallacy: if something is a certain way in nature, that’s how it ought to be. But that’s makes as much sense as constructing a child growth chart including those with rickets to evaluate contemporary children who have easy access to calcium and vitamin D.
It’s not clear at all that any of the purportedly obese infants in this study would be considered obese if the authors used a growth chart of how all infants grow, not merely breastfed infants. In that case, the title of the study might be ‘Exclusive Breastfeeding and the Risk of Underweight in the First Year of Life.’
This paper is yet another example of white hat bias.
‘White hat bias’ (WHB) [is] bias leading to distortion of information in the service of what may be perceived to be righteous ends… WHB bias may be conjectured to be fuelled by feelings of righteous zeal, indignation toward certain aspects of industry, or other factors. Readers should beware of WHB and … should seek methods to minimize it.
Breastfeeding researchers are so sure that breastfeeding is beneficial, and are so hostile to the infant formula industry that they arrange their data in ways that promote breastfeeding and demonize formula. Creating and employing infant growth charts that assume that breastfeeding is always best for every baby is bias in the service of what are perceived to be righteous ends. But it’s bias nonetheless and it’s wrong.
And that makes the conclusion of this study entirely arbitrary.
