Bone Development and the Need for Calcium and Vitamin D

Abstract: The two principle nutrients required for bone health and development are calcium and vitamin D, which are critical during pregnancy. Calcium is highly regulated within the body with stores located in bone. However, if nutrient intake of calcium is not sufficient, then calcium is sacrificed from bone. During pregnancy, the developing fetus requires calcium for bone development which may be enhanced with vitamin D.

Bone care for the developing baby during pregnancy is reliant on maternal intake of essential nutrients, particularly calcium and vitamin D. The development and maintenance of bones is under hormonal control within the body, which tightly regulates the amount of calcium in bone and circulating in the bloodstream. Bones are a unique reservoir of calcium, which begins to fill during development in the womb, reaching a peak just after the age of 20. Vitamin D is critical in the absorption of calcium from the diet, improving delivery of calcium to bloodstream and to the developing fetus.

The Importance of Calcium

Calcium is a very active substance within the body, as it is extensively required by the nervous system for neurotransmission, proper functioning of nerves, and cell signaling. Therefore, the body needs to keep levels of calcium in the blood fairly constant within a fairly narrow range. So how does the body do this? When the body has excess calcium in the blood, calcium is stored in bones for use at a later stage. In times of need for extra calcium, parathyroid hormone and vitamin D enhance absorption of calcium from the diet and also result in the release of calcium from bone to meet the needs of the body via the blood. However, if there isn’t enough calcium within the diet, the main source of calcium must come from bone and over time may become depleted resulting in osteoporosis. For the developing baby, sufficient calcium is required to provide for the structure of new bone.

The importance of many nutrients for fetal development is evident in the observations that premature babies have significant health disadvantages, as they lack the nutrient gains from the later stages of pregnancy. Efforts are made to replicate the nutrient supply during pregnancy with supplement formulas, which contain essential minerals calcium and vitamin D. A total of 30g of calcium is accumulated in the fetus, most of which is received in the third trimester of pregnancy through active transport through the placenta. Various studies conducted in different countries have shown that low maternal intake of calcium result in significantly lower bone mass in newborns. Infants who do not receive the required amount of calcium are prone to the clinical syndrome rickets, and fractures can become common [1]. Therefore, it is recommended that pregnant women seek to achieve optimal calcium intake, particularly those with multiple pregnancies and teen pregnancies requiring a higher need for calcium.

The Importance of Vitamin D

Vitamin D is very important for bone growth and development, by regulating the amount of calcium absorbed in the diet. Interestingly, infant bone mineral density was greater in those born in the winter months compared to summer, in a study conducted in the United States [2]. As vitamin D requires sunlight for its synthesis within the body, this study highlights the need for vitamin D in early bone development and indicates the increased level of vitamin D in the summertime before pregnancy and in the early stages of pregnancy for those whose babies were born in winter. During the third trimester, concentrations of vitamin D is elevated in the maternal bloodstream and is also further synthesized in the placenta. It has been suggested that vitamin D aids in the transport of calcium across the placenta to the developing fetus, by increasing calcium-binding proteins [3].

Supplementation of vitamin D during pregnancy produces beneficial effects for fetal bone health and general health at one year. In a study of over 100 women, it was shown that maternal vitamin D supplementation significantly improved fetal calcium levels, birth weight and length, and showed signs of progressive bone maturation in the fontanelles [4]. During fetal development, vitamin D is required for skeletal mineralization and growth of bones and muscles. It is thought that during pregnancy, the development of the skeletal can have long term effects in later life in relation to fractures, falls and osteoporosis [5]. Obtaining optimal levels of vitamin D is significant for bone development and maintenance.

There is no doubt that calcium and vitamin D play crucial roles in the development of health bone in the fetus, with health benefits that are long lasting. Pregnant women at risk of calcium and/or vitamin D deficiency should be extra prudent when considering the nutritional needs for a healthy baby. Adequate calcium and vitamin D should ensure
your child has strong and healthy bones.

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References
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birth. Clin Chim Acta 2003, 333(1):1-11.
3. Belkacemi L, Simoneau L, Lafond J: Calcium-binding proteins:
distribution and implication in mammalian placenta. Endocrine 2002, 19(1):57-64.
4. Brooke OG, Brown IR, Bone CD, Carter ND, Cleeve HJ, Maxwell JD,
Robinson VP, Winder SM: Vitamin D supplements in pregnant Asian women: effects on calcium status and fetal growth. Br Med J 1980,
280(6216):751-754.
5. Pasco JA, Wark JD, Carlin JB, Ponsonby AL, Vuillermin PJ, Morley R:
Maternal vitamin D in pregnancy may influence not only offspring bone mass but other aspects of musculoskeletal health and adiposity. Med Hypotheses 2008, 71(2):266-269.