I wasn’t sure how many non native-English speakers would get that joke, and jokes are rarely improved by explaining them, so if you don’t get it, just keep on reading.
Terrin G, Berni Canani R, Passariello A, Messina F, Conti MG, Caoci S, Smaldore A, Bertino E, De Curtis M: Zinc supplementation reduces morbidity and mortality in very-low-birth-weight preterm neonates: A hospital-based randomized, placebo-controlled trial in an industrialized country. The American journal of clinical nutrition 2013, 98(6):1468-1474. A multi-center RCT enrolled nearly 200 VLBW infants at 7 days of age to receive a zinc supplement (intravenous and oral) or placebo. The zinc supplement gave much more than the current recommendations, around 10 mg per day, while the controls received around 1.3 mg/day, which is consistent with some guidelines, but a bit less than some newer guidelines (which recommend about 2-2.2 mg/kg/d). The authors were interested in clinical outcomes, as zinc has multiple actions, being incorporated into several enzymes, and having effects on immune function and maybe cerebral development. The zinc supplemented group had no cases of NEC (compared to 6% in the controls), but a few more cases of late-onset sepsis; they had less PVL, slightly less BPD and no RoP >stage 2 (compared to 3% in controls). The primary outcome of the study was a composite including the development of at least one of those complications, which was significantly reduced by zinc supplementation, 27% vs 42%. There were quite a few deaths in the study after enrollment, and I think the authors should have included mortality in their composite outcome. There were, however, more deaths in the controls, 17/96 vs 5/97, which was also significant, and I assume that a combined outcome of death or morbidity would have been significant.
An editorial accompanying the article gives some interesting background, and notes that zinc reduces copper absorption, and when high doses of zinc are given, also inhibits iron absorption. It is appropriately cautious, and states that we should be ensuring that babies receive zinc according to current recommendations, and that further research on higher, ‘pharmacologic’ doses of zinc will be important.
As far as I can work out, current human milk fortifiers added to human milk don’t seem to give enough zinc, they add about 0.72 to 1.2 mg of zinc per 100 mL of milk, depending on which you use, it appears that we should probably be giving more, just based on balance studies.
Check out “Galvanised by a rash diagnosis” in Archives circa 2003. Some nice pics and a neat story even if I do say do myself!!
In human milk, lactoferrin may be involved in the uptake of zinc (1), as well as of calcium and iron. Zinc, calcium and iron may be more efficiently absorbed when bound to a biological carrier protein than in their inorganic state. Perhaps that could explain why babies fed human milk developed higher whole body bone mass than formula fed babies, despite the lower calcium content of human milk. (2) Could such factors as these impact on appropriate recommended daily intakes of all three metals?
(1) Blakeborough P, Salter DN, Gurr MI. Zinc binding in cow’s milk and human milk. Biochem J. 1983 Feb 1;209(2):505-12.
(2) Fewtrell MS1, Williams JE, Singhal A, Murgatroyd PR, Fuller N, Lucas A. Early diet and peak bone mass: 20 year follow-up of a randomized trial of early diet in infants born preterm. Bone. 2009 Jul;45(1):142-9. doi: 10.1016/j.bone.2009.03.657. Epub 2009 Mar 21.