From the Guidelines
Calcium is not synthesized by the human body and must be obtained through dietary sources or supplements, with adults generally requiring 1000-1200 mg daily. The human body relies heavily on calcium for various physiological functions, including bone health, muscle contraction, nerve transmission, and blood clotting. According to the Institute of Medicine guidelines, as reported in the New England Journal of Medicine 1, the recommended dietary intake of calcium varies by age and sex.
Key points to consider when evaluating calcium requirements include:
- More than 98% of the body's calcium is stored in the skeleton, which serves as a reservoir for calcium that can be released when needed 1.
- The recommended dietary allowances for calcium are based on requirements for healthy populations, while the recommended upper intake levels are based primarily on the risk of nephrolithiasis observed in studies of calcium supplementation in postmenopausal women 1.
- Calcium absorption is increased in pregnant and lactating women, but the recommended calcium intake for these women does not differ from that for other women in the same age group 1.
- Dairy products are the primary source of dietary calcium, with more than 70% of dietary calcium coming from these products 1.
For individuals requiring calcium supplementation, options such as calcium carbonate and calcium citrate are available. It is essential to maintain adequate vitamin D levels, typically 600-800 IU daily for adults, to ensure proper calcium absorption. The body regulates calcium levels through hormones like parathyroid hormone and calcitonin, which control calcium release from bones, absorption in the intestines, and excretion through the kidneys to maintain proper blood calcium levels.
From the Research
Calcium Synthesis
- Calcium synthesis is crucial for maintaining strong bones and preventing osteoporosis 2, 3, 4
- The combination of calcium and vitamin D is effective in reducing the incidence of non-vertebral and hip fractures 2
- Calcium citrate is a preferred form of calcium supplement due to its high solubility and absorption rate, especially when taken between meals 2, 3
- Vitamin D is necessary for bone health and is often deficient in individuals, making it essential to combine calcium with vitamin D supplements 2, 3, 5
Forms of Calcium Supplements
- Calcium carbonate is the most cost-effective form of calcium supplement, but it should be taken with a meal to ensure optimal absorption 3
- Calcium citrate can be taken without food and is suitable for individuals with achlorhydria or those taking histamine-2 blockers or protein-pump inhibitors 3
- Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements 3
Dosage and Administration
- The maximum dose of elemental calcium that should be taken at a time is 500 mg 3
- Calcium supplements should be taken in divided doses to minimize gastrointestinal side effects 3
- The combination of calcium and vitamin D should be taken at respective dosages of at least 1200 mg and 800 IU per day 2
Adverse Effects and Interactions
- Potential adverse effects of calcium supplementation include gastrointestinal complaints, kidney stones, and hypercalcemia 3, 6
- High calcium intake (>1500 mg/d) has been associated with an increased risk of advanced and fatal prostate cancer 3
- Calcium supplements may interact with other medications, such as histamine-2 blockers and protein-pump inhibitors, affecting their absorption 3