A dietitian’s guide to calcium when pregnant and breastfeeding
Calcium is a mineral hard to find missing from any pregnancy or breastfeeding supplement. Not surprising when considering the high demand for this nutrient by little growing bones: the average baby has 30g calcium in their body at birth and another 30g will be accumulated by 9 months of age! A huge amount of calcium all to be provided by the mother who is nurturing her baby inside the womb and producing breastmilk after birth.
But when you look at the science the amount of calcium needed from the diet does not go up during pregnancy or during breastfeeding. This is due to the amazing female body undergoing several biological adaptations:
Gut absorption of calcium doubles by the 12th week of pregnancy!
When breastfeeding calcium is absorbed from the mothers’ bones to make milk
If dietary calcium intake is very low during pregnancy a mother can take additional calcium from her bones to supply the placenta
What about bone health?
You may have worry about your bones if you are pregnant and/or breastfeeding. I certainly did after being told we ‘leech calcium from our bones’ to provide milk for our babies! But what does the science actually say? Well yes it is true that studies have shown temporary decreases in bone density during pregnancy and lactation but this bone mass is typically restored after pregnancy and after weaning from breast milk.
In rare cases some women do experience a bone disease called osteoporosis (weak and brittle bones prone to fractures) during pregnancy and breastfeeding but many of these women will have additional risk factors for bone fragility such as vitamin D deficiency, or another comorbidity that affects bone health. A diet very low in calcium may weaken bones during pregnancy and increase risk of bone disease during pregnancy, although more research is needed here.
What about future risk of poor bone health?
The research tells us that pregnancy and breastfeeding are not associated with increased risk of osteoporosis (weak bones) or fractures later in life which supports the idea that bone mass is restored after pregnancy and after weaning from breastfeeding. Instead, the research shows the opposite, that having breastfed an infant at some point in your life may even have a small protective effect on bones- and reduce your future fracture risk!
What should I do with calcium in my diet whilst pregnant?
The gut increases absorption of calcium so that it can meet the needs of a growing foetus. Ideally normal calcium intake from a healthy balanced diet should continue. If dietary calcium is very low despite gut absorption doubling, then some calcium may be taken from a mother’s bones and this may place the mother more at risk of weakened bones. Significantly low calcium levels can impair the delivery of calcium to the foetus and is also a risk factor for maternal pre-eclampsia. Having a condition which affects calcium absorption (such as undiagnosed coeliac disease or another malabsorptive disorder) could also lead to low calcium levels.
Should I supplement my diet with calcium during pregnancy?
Studies have shown excessively high calcium intakes from supplementation during pregnancy could be harmful to the fetus and cause an imbalance in calcium metabolism (for example in studies with 3-6g daily calcium supplementation). Meeting the normal daily calcium requirement from diet and avoiding low intakes is key. Supplementation during pregnancy may be needed to meet normal requirements if calcium intakes from the mother’s diet are very low. Discuss individual calcium needs with a dietitian or healthcare professional first.
What should I do with calcium in my diet whilst breastfeeding?
Studies have shown that low calcium intake from the diet (e.g. <300mg/day) does not reduce the amount of calcium in breast milk nor does it increase the amount of calcium taken from a breastfeeding mums bones. This may be because the body is hormonally programmed to supply the calcium needed for breastmilk from bones and this does not change if mum follows a high or a low calcium diet.
Should I supplement my diet with calcium when breastfeeding?
The science tells us that when breastfeeding getting extra calcium in the form of supplements on top of our normal diet does not prevent the loss of calcium from bones. However, there may be a benefit when calcium supplements are taken after weaning a breastfeeding infant. One study showed a small but statistically significant benefit on bone mass when a 1g calcium supplementation was taken daily during the post-weaning phase versus placebo supplement, despite no benefit during the breastfeeding period itself! It appears that dietary calcium may be more important during the post-weaning phase when the skeleton is rebuilding its mass!
How much calcium do I need?
0-1 year: 525mg
1-3 years: 350mg
4-6 years: 450mg
7-10 years: 550mg
11-18 years: 800mg girls, 1000mg boys
Adults aged 19 and over need 700mg of calcium a day
What happens if I take too much calcium?
It is recommended not to take more than 1,500mg of calcium per day
Conclusions
A doubling of intestinal calcium absorption occurs during pregnancy
When breastfeeding calcium is taken from a mother’s bones
Fractures do occur rarely during pregnancy and during lactation whilst bone mass and strength are temporarily reduced but many will have poor bone health or other risk factors for bone disease when entering pregnancy
Normal calcium intake from a healthy balanced diet should continue throughout pregnancy, breastfeeding and beyond
There may be a benefit of taking calcium supplements after weaning a breastfeeding infant when the skeleton is rebuilding its mass!
Women with very low calcium in their diet may benefit from calcium supplementation when pregnant if they are unable to increase the calcium through their diet naturally
Overall, it appears that any harm of lactational bone loss is temporary for most women and that having breastfed in your lifetime generally confers a long-term neutral or protective effect on the future risk of fracture in most studies
References:
Aguado F, Revilla M, Hernandez ER, Menendez M, Cortes-Prieto J, Villa LF, Rico H. Ultrasonographic bone velocity in pregnancy: a longitudinal study. Am J Obstet Gynecol 178: 1016–1021, 1998.
Kovacs CS, Ralston SH. Presentation and management of osteoporosis presenting in association with pregnancy or lactation. Osteoporos Int 26: 2223–2241, 2015.
Christopher S. Kovacs Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery Physiological Reviews 2016 96:2, 449-547
Kovacs CS. Bone development and mineral homeostasis in the fetus and neonate: roles of the calciotropic and phosphotropic hormones. Physiol Rev 94: 1143–1218, 2014.