John E. Searcy

Bone mineral content and serum 25-hydroxyvitamin D concentrations in breast-fed infants with and without supplemental vitamin D: One-year follow-up

in association with hypothyroidism. We did not obtain parietal cell or intrinsic factor antibodies. There was no evidence of other au to immune diseases or deficiencies in the mother (or int2ant) on the basis of routine clinical and laboratory tests. Breast-fed infants are at risk for nutr i t ional deficiencies if the mother is malnourished, a vegan, or if she has an abnormali ty in nut r ien t metabolism. Physicians should be aware tha t even with a well-balanced mate rna l diet, an occasional breast-fed infant can develop a serious nutritional deficiency.

Bone mineral content and serum 25-hydroxyvitamin D concentration in breast-fed infants with and without supplemental vitamin D

Eighteen term, healthy, appropriate for gestational age, breast-fed infants were studied in a double-blind prospective study to determine whether or not supplemental vitamin D affected bone mineralization. All patients were from a single, private pediatric practice. Nine infants were randomly assigned to a vitamin D supplement of 400 IU/day and nine infants to a placebo. By 12 weeks of age, infants receiving placebo had a significant decrease in bone mineralization and in serum 25-hydroxyvitamin D concentrations compared to the vitamin D-supplemented group. It is not known whether or not the increased BMC at 12 weeks of age in vitamin D-supplemented breast-fed infants is of ultimate value. Supplemental vitamin D may be necessary for optimal bone mineralization in term breast-fed infants. A longer follow-up study and additional analyses are required to make conclusive statements.

Increasing serum calcium and magnesium concentrations in breast-fed infants: Longitudinal studies of minerals in human milk and in sera of nursing mothers and their infants

Longitudinal calcium, magnesium, and phosphorus concentrations were measured in human milk and in the sera of 18 nursing mothers and their infants over a six-month period. During this time, progressive increases in serum calcium and magnesium concentrations were observed in breast-fed infants, in association with a decreasing phosphorus content of breast milk. Maternal serum calcium and magnesium concentrations also increased during this period. It is speculated that the physiologic rise in serum calcium and magnesium concentrations in exclusively breast-fed infants may be partly accounted for by a decrease in dietary phosphorus intake.

EFFECT OF RACE & NORMAL MATERNAL DIET ON BREAST MILK VITAMIN D CONCENTRATIONS

Differences in breast milk (BM) vitamin D by race and the influence of maternal vitamin D intake, in ranges normally consumed, on BM D have not been reported. We hypothesized that BM D or 25-hydroxyvitamin D (25OHD) concentrations were decreased in blacks, because of decreased skin production of D vs whites, and correlated with maternal D intake; and infant serum 25OHD is related to BM D content. All infants were less than 6 mos. and exclusively breastfed. BM and serum samples, and 3-d diet diaries, were obtained from 25 mother-infant pairs. D was purified by organic extraction and chromatography; metabolites were quantitated by ligand binding assay and HPLC . Mean total bioactivity from BM D and 25OHD was 51 IU/1 with 25OHD contributing 77% (D 25 pg/ml = 1 IU/1, 25OHD 5 pg/ml = 1 IU/1). Mean (95% confidence) BM D concentrations for white and black mothers were 662 (400-1094) and 112 (61-206) pg/ml resp (t-test p<.001); BM 25OHD concentrations were 212 (171-263) and 156 (140-175) pg/ml (p=.03). BM D2, D3, and 25OHD3 metabolites differed by race (p=.002, p<.001, and p=.03 resp); 25OHD2 did not differ by race. BM D (r=.57, p=.005), but not 25OHD (p=.24) correlated with vitamin D intake ([xmacr ;[equals;457, range 0-706 IU/d). BM D2 was correlated with D intake (r=.55, p=.006) even after control for race by multiple regression; BM D3 was not correlated with D intake with race controlled. Infant serum 25OHD did not correlate with BM D or 25OHD (p=.11 & p=.33). Thus, black mothers have lower breast milk D2, D3, and 25OHD3 than white mothers; breast milk D, in particular D2, correlated with D intake in ranges normally consumed; infant serum 25OHD was not correlated with breast milk D or 25OHD.

557 DECREASED BONE MINERAL CONTENT (BMC) IN BREAST-FED INFANTS WITHOUT SUPPLEMENTAL VITAMIN D (D): “CATCH UP” MINERALIZATION AT 6 MONTHS AND ONE YEAR; POSSIBLE.EFFECTS ON LENGTH

We previously reported a double blind randomized prospective study of 9 exclusively breast-fed infants without supplemental D (placebo, plac) and 9 exclusively breast-fed infants on supplement of 400 IU D/d (suppl.); 12 infants were fed exclusively Similac 20 cal/oz (form). As reported, at 3 mos plac had significantly lower BMC (modified photon absorptiometry) and serum 25-OH D. By 6 mos, serum 25-OHD had decreased and was still lower in plac vs suppl. (12.9±4.0 SE vs 32.7±4.1ng/ml. p<.01). BMC at 6 mos was 70±6, 75±5, and 94±7mg/cm for plac suppl. and form; plac and suppl. did not differ; plac was less than form (p<.05). After 6 mos, the study was unblinded, infants received solids and breast-fed infants received 400 IU D/d. 10 form and 13 breast-fed infants were seen at 12 mos, when serum 25-OHD, parathyroid hormone, calcitonin, Ca, P, Mg and alkaline phosphatase did not differ between plac and suppl. BMC at 12 mos was 120±19, 108±20, and 132±8mg/cm for plac, suppl. and form and did not differ; grps did not differ in wt, but plac was shorter (73.3±.38cm) than suppl. (75.8± .89cm, p<.1) or form (75.8±0.32cm, p<.02); one way analysis of variance for 3 grps, p<.05. Thus, vitamin D supplements may be necessary for optimal bone mineralization in breast-fed infants but “catchup” mineralization may occur in infants not given D initially. We speculate that D supplements may also be necessary for optimal body length in breast-fed infants.

594 LINEAR INCREASE IN BONE MINERAL CONTENT IN CHILDREN 1 TO 7 YEARS OF AGE WITH LOWER CONTENT IN FEMALES AFTER 4 YEARS

We reported that bone mineral content (BMC) in the first 6 mos of life was decreased in breast-fed infants without vitamin D, vs breast with D or formula-fed infants. No data have been reported on BMC and bone width (BW) in healthy children from 1 to 7 yrs. We hypothesized that BMC increases with age and is lower in females, with no difference by previous breast vs formula intake, or sun exposure. BMC and BW were determined on 96 children 1-7 yrs using direct photon absorptiometry at 1/3 distal radius. BMC (gm/cm) was highly correlated with age (r=.81, p<.001). Mean (±sd) BMC values for l-, 2-, 3-, 4-, 5-, and 6-year olds were .140 (±.020), .174 (±.031), .215 (±.046), .254 (±.047), .272 (±.041) and .363 (±.058) gms/cm. BW also increased with age (r=.23, p=.03) with means of 7.8 (±.9), 8.5 (±1.4), 9.2 (±1.3), 9.0 (±1.4), 8.8 (±1.1), and 9.6 (±.9) mm resp. Females had lower BMC vs males: .219 (±.063) vs .259 (±.080) resp (p<.01): there was no sex difference at 12-47 mo; 48-83 mo females had lower BMC than males (.262 ±.053 vs .301 ±.066 resp, p=.03). BMC was not related to previous breast or formula feeding, even after adjusting for time since discontinuation (p=.9). BMC correlated with hrs of sun exposure per week (r=.31): but not (p=0.9) when age was controlled (multiple regression). Thus, bone mineral content increases significantly and linearly with age from 1 to 7 yrs; females have lower BMC than males after 4 years. Age and probably sex specific comparisons should be made in childhood BMC studies.

1264 CYCLICAL SERUM 25-HYDROXYVITAMIN D PARALLELLING SUNSHINE EXPOSURE IN EXCLUSIVELY BREAST-FED INFANTS: MIRROR IMAGE IN SUMMER VS WINTER BORN

Previously we reported low serum 25-hydroxyvitamin D (25OHD) in breast fed infants without vitamin D supplements. However prospective serum 25-OHD vs sun exposure studies have not been done in relation to season of birth. We hypothesized that breast-fed infants <1 yr of age have serum 25-OHD varying directly with sun exposure & that opposite patterns occur in summer vs winter-born infants. 25 term infants exclusively breast-fed without vitamins were followed longitudinally from birth for > 6 mos: 13 born in summer and 12 winter. Sun exposure was monitored for 1 wk of every mo until 12 mos. A sun exposure score, previously verified, quantified time & surface area exposed (e.g., 0=no exposure, 5=13hrs/wk, diaper only). 25-OHD was determined by protein-binding assay (N 11-68ng/ml; CV 11%). Mean (±sem) values by age were:Monthly exposure scores peaked in summer, were low in winter (p< .01), & intermediate in fall & spring. 25-OHD paralleled sun exposure, irrespective of age; 25-OHD was correlated with exposure (r=.54, p<.001). Thus, summer vs winter-born infants had mirror image patterns of both sun exposure and 25-OHD; large seasonal differences in both sun exposure and 25-OHD were observed.