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Zinc binding in cow's milk and human milk.

ABSTRACT: In both cow's milk and human milk, zinc was associated with proteins of high molecular weight (greater than 100 000), as judged by analysis with Sephadex G-75. Precipitation of the casein at pH 4.6 and filtration of the resultant acid whey on Sephadex G-25 led, however, to the recovery of about 90% of the zinc as a compound of low molecular weight, which was tentatively identified as zinc citrate. Over 95% of the zinc of cow's milk was sedimented with the casein micelles on ultracentrifugation. Filtration of these micellar caseins on Sephadex G-150 gave two peaks containing zinc, which corresponded to aggregates of alpha-casein-kappa-casein and of alpha-casein-beta-casein. Ultracentrifugation of human milk sedimented only approx. 40% of total zinc. Analysis of sediment and supernatant on Sephadex G-150, however, indicated that about 85% of the zinc was associated with a protein complex of molecular weight greater than 150 000. The major protein of this complex was identified as lactoferrin. A minor zinc-binding component of average molecular weight 30 000 was also observed in the supernatant. The results indicated that zinc is bound to different macromolecules in cow's and human milk. This may be a factor affecting the bioavailability to the human infant of zinc from the two milks, and it is suggested that in human milk lactoferrin may be involved in the uptake of zinc.

SUBMITTER: Blakeborough P

PROVIDER: S-EPMC1154118 | biostudies-other | 1983 Feb

REPOSITORIES: biostudies-other

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Project description:BackgroundCurrent guidelines emphasize early introduction to potentially allergenic foods, but the optimal timing, amount, and exposure routes for foods other than peanut are not well-established. Cow's milk is often the first allergenic food introduced through infant formulas.ObjectiveTo examine timing of cow's milk protein introduction (CMPI), including interaction with formula supplementation after delivery, in relation to reported cow's milk adverse reactions throughout childhood.MethodsAmong children in the Boston, Mass-area Project Viva cohort, we assessed timing of CMPI (<2 weeks, 2 weeks-<6 months, ≥6 months) with questionnaires administered in infancy. Outcomes were (1) parent-reported cow's milk adverse reactions via annual questionnaires from age 2 to 13 years (n = 1298) and (2) milk sensitization (n = 505) and IgE-mediated milk allergy (n = 491) at age approximately 8 years. We used multivariable logistic regression models adjusted for parental atopy history, delivery mode, gestational age at delivery, child race, and census tract median household income, and investigated effect modification by ever/never breast-fed status and formula supplementation in the delivery hospital.ResultsA total of 32% were introduced to cow's milk protein at age less than 2 weeks, 38% at age 2 weeks to less than 6 months, and 30% at age 6 months or more. Compared with children with CMPI at age less than 2 weeks, children with CMPI at age 6 months or more had a higher risk of cow's milk adverse reaction at age 2 to 5 years (odds ratio, 2.4 [1.2-4.7]). Children given formula after delivery + CMPI at age less than 2 weeks had the lowest risk overall. Among children not given formula after delivery, CMPI at age 2 weeks to 6 months appeared most protective. Results were similar among ever-breast-fed children. Timing of CMPI was not associated with milk sensitization or IgE-mediated milk allergy in mid-childhood.ConclusionsEarly, consistent cow's milk exposure appears protective against adverse reactions to cow's milk.

Project description:BackgroundCow's milk protein allergy (CMPA) is one of the most common food allergies in infancy. Most infants with CMPA tolerate baked milk from diagnosis and gradually acquire increased tolerance. Nevertheless, parents often display significant anxiety about this condition and a corresponding reluctance to progress with home introduction of dairy due to concerns about possible allergic reactions.ObjectiveTo evaluate the impact on gradual home introduction of foods containing cows' milk after a supervised, single low-dose exposure to whole milk at time of diagnosis.MethodsInfants less than 12 months old referred with suspected IgE-mediated cow's milk allergy were recruited to an open-label randomized, controlled trial of intervention-a single dose of fresh cow's milk, using the validated dose of milk that would elicit reactions in 5% of CMPA subjects-the ED05 - vs routine care. Both groups implemented graded exposure to CM (using the 12 step MAP Milk Tolerance Induction Ladder), at home. Parents completed food allergy quality of life questionnaires and State and Trait Anxiety Inventories (STAI). Main outcome measures were milk ladder position at 6 months and 12 months post-randomization.ResultsSixty patients were recruited, 57 (95%) were followed to 6 months. By 6 months, 27/37 (73%) intervention subjects had reached step 6 or above on the milk ladder compared to 10/20 (50%) control subjects (p = .048). By 6 months, 11/37 (30%) intervention subjects had reached step 12 (i.e. drinking unheated cow's milk) compared to 2/20 (10%) of the controls (p = .049). Twelve months post-randomization, 31/36(86%) of the intervention group and 15/19(79%) of the control group were on step 6 or above. However, 24/37 (65%) of the intervention group were at step 12 compared to 7/20 (35%) of the control group (p = .03). Maternal STAIs were significantly associated with their infants' progress on the milk ladder and with changes in skin prick test and spIgE levels at 6 and 12 months.ConclusionThis study demonstrates the safety and effectiveness of introduction of baked milk implemented immediately after diagnosis of cows' milk allergy in a very young cohort. A supervised single dose of milk at the ED05 significantly accelerates this further, probably by giving parents the confidence to proceed. Maternal anxiety generally reflects infants' progress towards completion of the milk ladder, but pre-existing high levels of maternal anxiety are associated with poorer progress.

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Zinc binding in cow's milk and human milk.

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