Warning! Understatement of the year to follow: Many fascinating changes take place in a mother’s body during and after pregnancy. One of the most interesting changes for many new moms, myself included, is breastfeeding. Often called “nature’s perfect baby food,” breast milk seems to contain an almost magical mix of essential elements—proteins, fats, carbohydrates, water, vitamins, minerals and immune-boosting substances—that babies need to grow and thrive.
An extensive review article recently published in Physiological Reviews looks at calcium, which is an important nutrient for fetal and newborn development, and how mothers supply calcium to their babies during pregnancy and breastfeeding. The author, Christopher Kovacs of Memorial University of Newfoundland, sifted through more than 1,000 research articles on how humans and other animals transfer calcium to their offspring.
He found that during pregnancy, hormones signal a mother’s intestines to double the amount of calcium they absorb from food to provide the growing baby with enough to build and strengthen its bones. But the process changes during lactation. Studies showed that eating more or less calcium did not have an effect on the amount of calcium in a mother’s milk. According to Kovacs, the calcium in breast milk comes mainly from mom’s bones.
Our bones are constantly being built up and broken down. Normally, cells within the bone called osteoclasts break down old bone by secreting acid and enzymes, which makes minerals such as calcium available for the body to use. At the same time, cells called osteoblasts help develop new bone by secreting other enzymes and proteins that harden collagen into bone and help to store calcium. During breastfeeding, mothers secrete hormones that speed up bone breakdown to provide babies with roughly 200 milligrams of calcium—about the amount contained in a one-ounce serving of cheddar cheese—each day for about the first six months of life.
After weaning, mom’s body sends signals to ramp up the rebuilding of lost bone. “The maternal skeleton rapidly restores itself such that by six to 12 months after lactation (breastfeeding), the bone density has usually returned to baseline or better, even in women who suffered fragility fractures,” Kovacs wrote. Additionally, most of the studies showed that pregnancy and breastfeeding do not increase the chances of osteoporosis or broken bones and may even be protective for the bones.
There’s much more about breastfeeding that researchers are still trying to understand. But if you were breastfed, consider including a block of cheese as part of your Mother’s Day present. It’s not a full payback for all the calcium she’s given you, but it’s a start!