Changes in calcium homeostasis over the first year postpartum: effect of lactation and weaning

Article Abstract:

Women who produce milk after giving birth (lactation) have an increased need for the minerals calcium and phosphorous. Few studies have examined the hormonal regulation of these minerals or the effects pregnancy has on hormonal status during this period. The serum concentrations of calcium and phosphorous and the hormones parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D were assessed in both lactating and nonlactating women for one year after they had given birth. Of the 58 women who participated in the study, 26 fed their babies human milk (lactating group) and 32 fed them formula (nonlactating group). Maternal dietary intakes were monitored, and mineral and hormone levels were measured regularly. Results for the first six months after childbirth showed decreased phosphorous levels in all groups, with the lactating women having significantly higher levels than those who fed their babies formula (4.34 versus 3.44 milligrams per deciliter, or mg/dL). Calcium levels were not different between the two groups and did not change over the first six months. Serum PTH levels decreased over the first six months, but were significantly higher in the lactating group (1.36 versus 1.16 nanograms per milliliter, or ng/mL). The 1,25-dihydroxyvitamin D levels did not change during the first six months and were not significantly different between the two groups. Twelve months following childbirth, women who lactated still had significantly higher serum phosphorous concentrations than those who did not. Calcium concentrations were significantly higher in lactating women who were still breast feeding than in those who had already weaned and those who did not lactate. PTH levels were higher in the women who still breast-fed or who had already weaned than in those who did not lactate (1.46 and 1.68 versus 0.92 ng/mL). The 1, 25-dihydroxyvitamin D levels were also significantly higher in the women who lactated. These results indicate that lactating women have different hormonal responses and mineral needs than women who do not lactate after giving birth. (Consumer Summary produced by Reliance Medical Information, Inc.)

Infants, Metabolism, Lactation, Calcium metabolism, Phosphorus (Chemical element), Weaning, Phosphorus metabolism

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Low serum calcium and high parathyroid hormone levels in neonates fed 'humanized' cow's milk-based formula

Article Abstract:

Most infant formulas have equivalent amounts of calcium and phosphorus, and are thought to have levels of phosphorus and calcium comparable to those in human milk. However, some newborns who are fed infant formulas within the first weeks of life develop convulsions due to hypocalcemia (abnormally low blood levels of calcium) and hyperparathyroidism (increased activity of the parathyroid gland). This gland releases parathyroid hormone, which regulates calcium and phosphorus metabolism. It is thought that hypocalcemia may result from the higher phosphate content of infant formulas as compared with human milk. It has been suggested that decreasing the phosphorus content relative to the calcium content of milk formulas may result in a formula that better resembles the calcium and phosphorus levels of human milk and reduce the incidence of hypocalcemia. The effects of milk formulas with varying proportions of phosphate and calcium on blood calcium levels and parathyroid gland activity were assessed in infants who were fed formulas in the first weeks of life. The findings were compared with results from breast-fed infants. The study involved 69 newborns. Formula-fed infants had higher phosphate levels and lower calcium levels than infants who received human milk. Levels of parathyroid hormone were increased in formula-fed infants and decreased in human milk-fed infants, and were correlated with the intake of phosphorus in the formula-fed infants. Mineral and hormone levels were similar among all formula-fed infants. The findings suggest that the reduction in blood calcium levels in formula-fed infants may contribute to the development of hypocalcemia shortly after birth. (Consumer Summary produced by Reliance Medical Information, Inc.)

Parathyroid hormone, Parathyroid hormones, Calcium in the body, Calcium (Nutrient), Infant formulas, Hypocalcemia

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Bone mineral content in black and white children 1 to 6 years: early appearance of race and sex differences

Article Abstract:

Bone mineral content (BMC) can be used to detect metabolic bone disorders and nutritional diseases such as rickets. Normally, BMC increases with age and is higher in males. However, standard differences in BMC among different races have not been determined. A previous study of the skeletal development of blacks revealed that their larger bone mass was due to the larger body mass. Larger body mass puts a strain on the skeleton, which in turn stimulates the formation of bone. Another study of racial differences in bone structure indicated that bones in black women have more calcium and phosphorus. BMC was measured in 131 children between the ages of one and six to see whether any racial differences exist. Results indicated that black children have a higher BMC than white children regardless of body weight, that females have lower BMC than males, and that BMC increases with age and weight. The differences in diet between the two groups cannot be ruled out as factors affecting the results. The information obtained from this study may be useful in diagnosing bone mineralization disorders in children. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Bones, Children, Anthropometry, Biomineralization, Children, Black

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