Known for its important role in skeletal health and the prevention of osteoporosis, a reduced dietary calcium intake and an increased physiological need can have a profound effect on the individual beyond bone health. In this article, we review the functions of calcium within the body and look at dietary and supplemental sources of calcium. We take a closer look at the rationale for supplementation across the lifespan and showcase the role of calcium D-glucarate supplementation, looking at its unique role in hormone regulation.
Calcium is an essential macronutrient found in abundance in the body, with 99% stored in teeth and bone.1 This mineral is involved in several biochemical processes, including:
- Hormonal secretion
- Nerve impulse transmission
- Muscular function
- Vascular contraction
- Vasodilation
- Intracellular signalling. 1,2
Lifespan calcium requirements
Calcium plays an important role in women’s health, with intake requirements differing across the lifespan.
Higher doses of calcium are required during pregnancy and breastfeeding3 to:
- Minimise bone mineral loss
- Aid skeletal growth of the child4
- Support milk production4
- Prevent pre-eclampsia.3
Higher doses are also needed for menopausal and post-menopausal women, as the drop in oestrogen necessary for bone formation causes more bone resorption, increasing the risk of osteoporosis and osteoporotic fractures.5
Calcium deficiency
With the wide-ranging role of calcium throughout the body, Fig. 1 depicts some of the physical expressions of calcium deficiency.
Calcium in the diet
Meeting the requirements for calcium can be challenging - 1 in 10 Australians do not meet their daily calcium requirements through diet.6 While dietary intake of calcium in childhood is generally sufficient, intake drops during adolescence in Australia.7 A staggering 90 per cent of women between the ages of 12-18 years and over 50 years were found to have insufficient dietary calcium in Australia, despite an increased need.6 The number of Australians choosing to avoid animal products and switching to plant-based alternatives is increasing and while plant-based milk and dairy alternatives provide a dairy replacement from a taste perspective, unless they are fortified with calcium, they often do not provide the calcium benefits of dairy products.7
Generally, dietary intake of calcium is sufficient for most people, provided their diet contains no restrictions. There are, however, some individuals who may benefit from supplementation including individuals who:
- Take corticosteroids
- Diagnosed with osteopenia or osteoporosis
- Follow a vegan or dairy-free diet or those with a lactose intolerance
- Women with amenorrhea
- Residents of aged / long-term care facilities
- Individuals with gastrointestinal (GI) diseases, given dietary calcium is largely absorbed in the small intestine.2,8
Supplemental calcium
The two most common forms of supplemental calcium include calcium carbonate and calcium citrate, followed by calcium hydroxyapatite. Several factors for consideration when prescribing are outlined in the table below (See Tables 1 and 2). Regardless of the form chosen, absorption is best when taken with food, in divided doses of 500mg or less at a time and when given concurrently with vitamin D.9
Calcium supplementation for specific conditions
Calcium supplementation and cardiovascular disease risk in women
Research on calcium supplementation and cardiovascular disease (CVD) has been divisive, with studies producing contradictory results. In some studies, lower doses of calcium supplementation (600 mg/day) decreased CVD risks,2 while others demonstrate a considerable increase with doses of 700–1000 mg/day.18 The assumption being that increased calcium may contribute to raised serum calcium levels potentially hastening coronary artery calcification.2 With no conclusive outcome, and generally favourable results on CVD in the literature, calcium supple- mentation is still believed to be beneficial overall.2
Calcium supplementation, osteoporosis and falls risk in women
Calcium requirements increase for women during and post menopause, as reduced levels of oestrogen precipitate a decrease in the absorption and preservation of calcium. This reduction of calcium absorption and preservation can affect bone mineral density and lead to osteoporosis. When combined with weakened muscles, curvature of the spine or poor postural control experienced with ageing, these women tend to also have a higher risk of falls and fracture.19 Research supports supplementing with both calcium and vitamin D, as a deficiency can further inhibit calcium absorption in older women to positively impact calcium homeostasis, mitigating these concerns.7,20
Calcium supplement for pre-eclampsia prevention during pregnancy
Pre-eclampsia is a complication that can occur in pregnancy and commonly affects 2-5% of pregnant women. It is a multisystem condition characterised by hypertension (≥140 mmHg/≥90 mmHg) and proteinuria (≥300 mg/day) typically presenting after 20 weeks’ gestation. Other symptoms may include neurological and haematological complications, in addition to liver abnormalities and acute kidney injury.21,22
Current research supports calcium supplementation during pregnancy to reduce the risk of pre-eclampsia onset. Doses between 1-2 g/day are considered safe and effective and this is especially important for women with a low dietary intake of calcium, or those with predisposing factors putting them at risk of developing pre-eclampsia.23, 24
Kidney stone formation associated with calcium supplementation
Where once the recommendation in the management of kidney stones was dietary calcium restriction,25 more recent research highlights that a dietary calcium intake greater than 500 mg/day may be protective against the formation of kidney stones by decreasing the absorption of oxalates and reducing urinary oxalate levels.2 In contrast, supplemental calcium may increase the risk, which could be mitigated by taking the supplement with food, though this is currently speculative.2
Gastrointestinal effects and calcium supplementation
GI side effects may occur with high-dose calcium supplementation and are often associated with calcium carbonate.2 Symptomsaremostlyminorandmayinclude an increased prevalence of abdominal pain, bloating, flatulence, severe diarrhoea and constipation.26 In some instances, adverse effects from larger supplement doses can be severe and may require hospitalisation.26
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Image references
Fig 1.
Bora S. Calcium deficiency: Symptoms, causes, treatments, etc.. [Internet]. YoHindi. 2020 [cited 2022Nov7]. Available from: https://www.yohindi.in/blog/what-is-calcium-deficien- cy-and-its-causes/
Fig 2.
Calcium D-glucarate monograph [Internet]. FX Medicine. [cited 2022Nov7]. Available from: https://www.fxmedicine.com.au/ blog-post/calcium-d-glucarate-monograph