Calcium citrate, sometimes misspelled citrite, is the calcium salt of citric acid, which is most commonly found in citrus fruits. Calcium citrate is a popular type of calcium supplement, but it is also used as a food additive, preservative, flavoring and water softener. Calcium citrate is more absorbable than calcium carbonate because of the additional acidity that citric acid provides for your stomach and intestines. Vitamin D3 often accompanies calcium within supplements because it enhances the absorption and utilization of calcium by your bones.
Calcium Supplements
Calcium citrate and calcium carbonate are the main supplemental forms of calcium on the market, although ascorbate, gluconate, lactate and phosphate forms are also sold. Calcium carbonate is more popular than calcium citrate, probably because it is usually cheaper and more widespread in other products, such as Tums and Rolaids. Vitamin D3, the most biologically active vitamer of the vitamin D group, is often combined with calcium supplements because it can enhance the absorption of calcium and its utilization within your bones, according to the Linus Pauling Institute.
Absorption Rates
Calcium citrate can be taken without food because its acidity allows it to be absorbed in the stomach without the aid of additional digestive juices, which is not the case with calcium carbonate. However, calcium citrate tablets contain only slightly more than half the elemental or atomic calcium that the same-sized calcium carbonate tablets contain. A study published in a 2001 edition of the "Journal of the American College of Nutrition" found that the two types of calcium have equivalent bioavailability and noted that the cost-benefit analysis favors the less expensive calcium carbonate product.
Calcium Recommendations
According to the National Institutes of Health, you should consume at least 1,000 to 1,300 mg of calcium daily depending on your gender and age. These recommendations are based on elemental calcium, but each tablet of calcium citrate contains only about 21 percent of elemental calcium. As such, taking a 1,000 mg tablet of calcium citrate would only yield 210 mg of actual calcium if you absorb all of it, which is unlikely. Chronic lack of calcium increases your risk of mineral-poor bones, or osteoporosis. The development of osteoporosis also depends on low vitamin D and estrogen levels, which is why post-menopausal women are most at risk.
Role of Vitamin D3
Vitamin D3 is made by your skin when exposed to sunshine during summer months, but is also found in some foods. D3 is essential for strong immunity, emotional health, restful sleep and driving calcium into your bones. Specifically, D3 is converted into the hormone calcitriol, which enhances calcium absorption throughout your gastrointestinal system and keeps adequate calcium in circulation to promote bone mineralization and normal muscle tone. It also helps remodel bone by working with parathyroid hormone to release calcium from your bones when dietary consumption is deficient. The National Institutes of Health recommends that adults younger than 70 consume at least 600 IU daily, although that increases to 800 IU beyond the age of 70. Vitamin D deficiency even with adequate levels of calcium leads to osteomalacia, or softening of your bones.
References
- Linus Pauling Institute: Vitamin D
- "Journal of the American College of Nutrition"; Absorbability and cost effectiveness in calcium supplementation; R.P. Heaney, et al.; June 2001
- National Institutes of Health Office of Dietary Supplements: Calcium Fact Sheet
- National Institutes of Health Office of Dietary Supplements: Vitamin D Fact Sheet
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