The One Downside to Breastfeeding

Could Breastfeeding be Bad for Your Bones?

Study finds a link between decline of bone density to length of time spent breastfeeding.

Breastfeeding is categorically and relatively undisputedly known to hold countless benefits for baby as well as mom – however they may be a downside. A recent study (Vitamin D status and skeletal changes during reproduction- A longitudinal study from late pregnancy through lactation) has concluded that there was a correlating decrease in bone density in nursing women, compared to the length of time they breastfed.

You’re not about to stop breastfeeding of course, so what does this mean for you?

“Researchers at the University of Gothenburg in Sweden studied the bone density of 95 women from late pregnancy to 18 months after birth and compared them to a group of women who weren’t pregnant or nursing.” //

Petra Brembreck, who is a researcher at the University of Gothenburg in Sweden, observed a decrease in bone density as much as four percent.

“We found that during the first four months postpartum, bone mineral density decreased in the hip, lumbar spine and shin bone, but only in women lactating at least four months. Still at 18 months after delivery, bone mineral density in the shin bone was lower than shortly after delivery, but only in women lactating at least nine months. This was a new finding.” // Petra Brembreck

Vitamin D

Originally, Brembeck hypothesised that there would be a reduction in vitamin D levels, which is critical for the absorption of calcium, with the length of time spent breastfeeding. Now a days, breastmilk has been shown to be lacking in vitamin D as most women get less vitamin D than their ancestors, and thus it is not passed on into the milk. However, when the vitamin D levels of breast milk were measured, there was no indication of a decrease.

“We found no changes in vitamin D status during the first year postpartum, and no association between duration of lactation and changes in [vitamin] D during the first year postpartum,” she says. “This has not been studied before.”

So if it’s not vitamin D, what is causing a general weakening in the bone density of breastfeeding mothers?

“The major determinants for changes in bone minerals postpartum was body weight—a higher body weight was related to smaller decreases in bone minerals postpartum—and duration of lactation—a longer duration of lactation was associated with larger decreases in bone minerals postpartum,” Brembeck says. “It appears that the longer women breastfeed, the more time it takes for the bone mineral density to return to values shortly after delivery or pre-pregnancy values.” This could have something to do with the reduction in estrogen, which also helps protect bones, that occurs during breastfeeding.

However, don’t stop breastfeeding early! It does not indicate that there is an increased fracture risk for the affected women later in life, as bone minerals recover themselves. A protective factor is to simply have a higher total calcium intake via your diet as well as through supplementation. This will help to protect your bones. So we’re talking plenty of dairy and vegetables, but of course speak to your doctor before changing your diet.

Breastfeeding Mother

Finally, of course, we come to another conclusion that seems to be a very positive factor in countless health related issues: EXERCISE.

Exercise can also help strengthen your bones generally, and whilst breastfeeding.

“Generally, a higher mechanical load on the skeleton, such as exercise, strengthens the skeleton,” Brembeck says, although her study didn’t find an association between physical activity and changes in bone density.”

Brembeck concludes however, that a longer term follow up period is required to evaluate if long term breastfeeding women will fully recover all their bone minerals, or if the changes in bone density are indeed long term and increasing the long term risk of bone fractures and related problems.




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