One of the studies is a longitudinal (ALSPAC) study of 11K infants in the UK. The executive summary:
Exposure to antibiotics during the first 6 months of life is associated with consistent increases in body mass from 10 to 38 months. Exposures later in infancy (6-14 months, 15-23 months) are not consistently associated with increased body mass.
In their discussion they describe other factors: maternal weight, smoking, and other things that can correlate with infection rates. They found "remarkably weak" correlations with those variables (when you have such a large population you can segment by maternal weight if you want to).
The other (Blaser's) study was on mice:
Blaser’s team treated young mice with low doses of antibiotics and found that while the treated mice did not become larger overall, they were, in fact, more obese
Treated and untreated mice had different populations of gut bacteria.
The scientists then did a genetic analysis of the bacteria’s metabolism and found that some genes responsible for fat synthesis showed a higher activity in the treated mice. Overall, the scientists concluded that the treated mice had bacteria that were more efficient in digestion.
It is notorious that antibiotics mess up your gut bacteria, and there've been some reports suggesting that gut bacteria change the blood chemistry slightly (with things that mimic hormones, perhaps?). I'm not sure how much of fat synthesis happens in the gut, but if any does then a change to a different and more efficient population could change the input ratios of sugar and fat in the blood. I assume the body compensates, but long term that might make a difference.
You are what you eat, I suppose, but also what meds you take/were given. Notice that for the kids the major factor was whether they got antibiotics in the first six months; later didn't matter so much. That's a little odd, unless these sorts of bacteria have a gut habitat that tends to keep antibiotics out.
They didn't have good information on the types of antibiotics used (this was with parental questionnaire), and so that detail isn't included.
It should be straightforward to check those farm animal growth rates and see how much of that is increase in fat (well-marbled steak, anyone?). I should ask somebody over in Ag.
2 comments:
"Grow" is such an interesting word. We'd generally want our children to be taller, but not fatter. The influence on the digestion of sugars might be interesting as well
Every time I turn around there's a new and interesting article about gut bacteria. I've even read that people who keep their appendixes do better at warding off serious gut infections like c. diff. -- something about the ability to recolonize from the appendix reservoir after we wipe out the gut with a course of antibiotics. A messed-up gut is a melancholy condition.
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