Lead levels in breast milk invariably low

By Michelle Rizzo

NEW YORK (Reuters Health) – Findings from a new study
should provide some reassurance to breastfeeding mothers that
even if they’ve been exposed to high amounts of lead, very
little of this toxin is excreted in their breast milk. In
addition, the use of calcium pills may help bring down lead
levels even further.

Dr. Adrienne S. Ettinger, of Harvard School of Public
Health, Boston, and colleagues examined the contribution of
cumulative lead exposure, breastfeeding practices, and calcium
intake to levels of lead in breast milk among 367 women in
Mexico City.

The investigators measured levels of lead in the blood and
breast milk of the mothers at 1, 4, and 7 months postpartum,
and obtained bone lead measurements at 1 month postpartum.
Results of the study are published in the American Journal of
Epidemiology.

The average levels of lead in breast milk at 1, 4 and 7
months were 1.4, 1.2, and 0.9 micrograms per liter,
respectively — a significant decreasing trend over the course
of lactation.

“Even among this population of women who had relatively
high cumulative lifetime exposures to lead, the concentrations
of lead in breast milk were quite low,” Ettinger pointed out to
Reuters Health. “This provides additional reassurance that
breastfeeding should be encouraged, because human milk is the
best and most complete nutritional source for young infants.”

Breastfeeding practice modified the relationship between
lead levels in the bone and lead levels in breast milk. Women
with high levels of lead in the knee bone who were exclusively
breastfeeding had the highest levels of lead in the breast
milk.

Calcium intake also had an effect on breast milk levels of
lead. “Lactating women who were (randomly assigned) to receive
1200 mg of calcium had lower breast milk lead levels at seven
months postpartum than women who were assigned to the placebo
group,” Ettinger said.

“Dietary calcium supplementation may constitute an
important intervention strategy,” she commented, “albeit with a
modest effect, for reducing lead in breast milk and thus the
potential for infant exposures, particularly among women with
low dietary calcium intakes.”

SOURCE: American Journal of Epidemiology, January 2006.