Vitamin D: How much does it matter in pregnancy and breastfeeding?

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In previous posts, we have touched on how important some nutrients are for pregnant and breastfeeding women, nutrients such as folic acid, iron, choline and Vitamin D. Vitamin D is a fat-soluble vitamin that is essential for the absorption of calcium and is involved mostly in bone health and metabolism.  

The “sunshine vitamin”, as it’s popularly known, can be produced in the body when the skin is exposed to sunlight. In fact, this is our primary source of Vitamin D, and unfortunately diet is a poor source as it is found naturally only in a few foods, such as dairy products, fatty fish, animal fats of pastured animals, liver and egg yolks. Given the few dietary sources, lack of sun exposure in some parts of the world, and/or covering up due to skin cancer concerns or religious/cultural practices, Vitamin D deficiency is very common among people and supplementation is required in almost all cases in order to meet the body’s need.

Interestingly, during winter, people living in latitudes greater than 33-37 degrees produce little to no Vitamin D3. In practical terms, this means people living in regions south of Bunbury in the west of Australia and Sydney in the east of Australia will have minimal synthesis of Vitamin D during the winter months. Australia is also a country familiar with “slip slop slap”, but this may be affecting our nation’s Vitamin D status, as SPF 30 blocks 95% of Vitamin D production. Ethnic groups and those with darker skin colours are also at much higher risk of Vitamin D deficiency.

During pregnancy and breastfeeding, the mothers Vitamin D stores are being used during huge growth periods for laying down bone structures for the infant. It is also needed to work with other nutrients such as Vitamin A, Vitamin K2, calcium, zinc and boron. As a result, being Vitamin D deficient during pregnancy and breastfeeding, will dramatically affect not only yours, but also your child’s health in the long term. Here are some reasons why you need to take enough vitamin D during pregnancy and breastfeeding.

Which factors influence maternal Vitamin D levels?

Maternal Vitamin D status can be altered for several reasons, including the use of sunscreen or covering the skin with clothes, living mostly in an indoor environment or avoiding sunlight, skin hyperpigmentation as well as the sun intensity of where you live or the time of the year.

Why is Vitamin D so essential during pregnancy?

Vitamin D has several key roles during gestation, for example it aids implantation and regulates placental function and placental hormone levels; it also supports the  maturation of fetal lungs and  keeps the endothelium integrity and membrane stability.

During pregnancy, low levels of Vitamin D have been linked with many complications and adverse outcomes for the mother and the baby. For example, a number of meta-analysis studies show Vitamin D deficiency to be associated with an increased risk of preeclampsia, preterm birth, small for gestational age, gestational diabetes mellitus. Other Vitamin D studies have also shown Vitamin D deficiency to be associated withpostpartum depression, caesarean section, recurrent pregnancy loss and prolonged/obstructed labour.

Besides its role in bone health, Vitamin D is also involved in glucose metabolism, and it influences insulin secretion and sensitivity. Therefore, studies have concluded that being Vitamin D deficient, especially in the first trimester during pregnancy could be one of the many factors that increase the risk of gestational diabetes. This was evident in an observational study of 145 pregnant Australian women with gestational diabetes mellitus, which showed that 41% of them had vitamin D deficiency.

Similarly, scientists have found a strong link between lower Vitamin D concentrations and higher risk of preeclampsia. They concluded that supplementing the “sunshine vitamin” along with calcium could reduce the risk of preeclampsia, a potentially dangerous complication characterized by high blood pressure.

And what about breastfeeding?

Vitamin D importance doesn’t end after birth, as it will also ensure the health of the newborn during lactation.

Maternal levels of Vitamin D determine the Vitamin D stores in the baby  at birth. That is, if a breastfeeding mum has low Vitamin D, she might not pass on enough Vitamin D to her baby. This is why some authors proposed to supplement newborns with the vitamin. Exposure to sunlight will also influence the baby’s Vitamin D stores.

Vitamin D deficient children will be at significant risk of skeletal deformities known as rickets. Recently, it’s also been linked to an increased risk of acute lower respiratory tract infections including respiratory syncytial virus infections, poor postnatal growth, bone fragility, increased incidence of autoimmune diseases, allergies, asthma and eczema.

Supplementation

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Mums to be should be supplemented with Vitamin D since supplementation has been shown to be safe and it can lower the incidence of the adverse outcomes mentioned above.

Based on study results, authors suggest a daily (rather than weekly or monthly) supplementation of 1,000 – 2,000 IU of Vitamin D in pregnant Vitamin D deficient women, in order to achieve optimal Vitamin D concentrations. Women who have been supplemented with this amount show fewer pregnancy complications such as preeclampsia, gestational diabetes, preterm labour, caesarean section and infections.

However, recent studies showed that high-dose Vitamin D supplementation of 4,000IU/d of Vitamin D of healthy lactating mothers can increase the Vitamin D concentration of milk to a level that supplies adequate Vitamin D intake for the breastfeeding infant even though both mother and infant were limited in sunlight exposure. Though, some mothers may require greater doses  in order to achieve sufficient Vitamin D levels.

According to the Australian and New Zealand Bone and Mineral Society and Osteoporosis Australia, babies at risk of low Vitamin D, i.e. dark skin or minimal sun exposure, should be supplemented with 400 IU Vitamin D3 daily for at least the first year of their life. Always consult your paediatrician if you think your baby needs supplementation.

Final thoughts

Ensure you incorporate good sources of Vitamin D, like fish oil, salmon and sardines and eggs into your diet. For vegetarians, mushrooms can contain small amounts of Vitamin D2 if grown under UVB light. You can also look for dietary products, fortified foods and nutritional supplements.

Sunlight exposure is important to synthesise Vitamin D. However, no matter where you live in Australia (or the world), you have to be careful about how much sun you and your child gets. Remember that too much sun can lead to sunburn, skin damage and even skin cancer.

I would recommend, if possible, to get your Vitamin D status checked as early as possible prior to or early on in pregnancy, due to its role in implantation and high needs during pregnancy. Vitamin D is an essential vitamin in any stage of life, but it has a significant impact on pregnancy, lactation and newborns. Always ask your doctor and Dietitian if you are concerned about how much you need to supplement during pregnancy or breastfeeding. The same goes if you think your child might need a Vitamin D supplement.

References

ACOG Committee on Obstetric Practice. ACOG Committee Opinion No. 495: Vitamin D: Screening and supplementation during pregnancy. Obstet Gynecol. 2011 Jul;118(1):197-8. doi: 10.1097/AOG.0b013e318227f06b

Agarwal S, Kovilam O, Agrawal DK. Vitamin D and its impact on maternal-fetal outcomes in pregnancy: A critical review. Crit Rev Food Sci Nutr. 2018 Mar 24;58(5):755-769. doi: 10.1080/10408398.2016.1220915.

Casey, C., McGinty, A., Holmes, V. A., Patterson, C. C., Young, I. S., & McCance, D. R. (2018). Maternal vitamin D and neonatal anthropometrics and markers of neonatal glycaemia: Belfast HAPO study. The British Journal of Nutrition, 120(1), 74–80. http://doi.org/10.1017/S0007114518001320

Dawodu, A., & Tsang, R. C. (2012). Maternal Vitamin D Status: Effect on Milk Vitamin D Content and Vitamin D Status of Breastfeeding Infants. Advances in Nutrition, 3(3), 353–361. http://doi.org/10.3945/an.111.000950

Dovnik A, Mujezinović F. The Association of Vitamin D Levels with Common Pregnancy Complications. Nutrients. 2018 Jul 5;10(7). pii: E867. doi: 10.3390/nu10070867.

Hollis, B. W., Johnson, D., Hulsey, T. C., Ebeling, M., & Wagner, C. L. (2011). Vitamin D Supplementation during Pregnancy: Double Blind, Randomized Clinical Trial of Safety and Effectiveness. Journal of Bone and Mineral Research : The Official Journal of the American Society for Bone and Mineral Research, 26(10), 2341–2357. http://doi.org/10.1002/jbmr.463

Lau SL, Gunton JE, Athayde NP, Byth K, Cheung NW. Serum 25-hydroxyvitamin D and glycated haemoglobin levels in women with gestational diabetes mellitus. Med  J Aust. 2011 Apr 4;194(7):334-7

Mulligan, M. L., Felton, S. K., Riek, A. E., & Bernal-Mizrachi, C. (2010). Implications of vitamin D deficiency in pregnancy and lactation. American Journal of Obstetrics and Gynecology, 202(5), 429.e1–429.e9. http://doi.org/10.1016/j.ajog.2009.09.002

Nichols, L. 2018. Everything you need to know about Vitamin D and pregnancy. Webinar accessed 13th July, 2018.

Paxton GA, Teale GR, Nowson CA, Mason RS, McGrath JJ, Thompson MJ, Siafarikas A, Rodda CP, Munns CF; Australian and New Zealand Bone and Mineral Society; Osteoporosis Australia. Vitamin D and health in pregnancy, infants, children and  adolescents in Australia and New Zealand: a position statement. Med J Aust. 2013 Feb 18;198(3):142-3.

Raisingchildren.net.au. (2018). Vitamin D & vitamin D deficiency in kids | Raising Children Network. [online] Available at: http://raisingchildren.net.au/articles/vitamin_d.html/context/204 [Accessed 15 Aug. 2018].