Calcium is a critical component of a healthy diet. It is required for growing and maintaining healthy bones, for muscle contractions and for transmitting messages throughout the nervous system. It is available in an abundance of food products and in nutritional supplements. But how can we ensure that we are getting the maximum benefit from the calcium we ingest? And in what form is it best absorbed?
Calcium can be found everywhere in a healthy diet. Though dairy may be the first food group that comes to mind, there are a variety of other foods that can be eaten to boost intake. Plant-based foods such as dark green leafy vegetables, tofu and almonds contain a substantial amount of calcium, as do fortified cereals and nondairy milks.
One of the greatest advantages of getting calcium through food as opposed to supplements is that you ingest other nutrients found in the whole food you are consuming, rather than just isolated calcium. In addition, calcium in food may be more readily absorbed due to the presence of certain additional nutrients, such as vitamin D. (Beware, however, there are some circumstances where calcium absorption can be negated by other nutrients, such as oxalic and phytic acid in some vegetables.)
In general, by aiming to meet calcium requirements via food intake, it is likely you will be making a more nutritious choice.
Supplementation of calcium has its place, especially in populations where calcium needs are increased or calcium-rich foods are lacking. When deciding what type and how much calcium to supplement, you should assess how much calcium is missing from your diet and what form of calcium supplement is most appropriate for your individual circumstances.
There are two main forms of calcium found in supplements: carbonate, which is 40 percent calcium by weight, and citrate, which is 21 percent calcium. However, as the percent of elemental calcium increases, absorption decreases, which means that calcium citrate is actually more readily absorbed. This form is also better tolerated by people who have low amounts of stomach acid.
However, citrate is also less readily available and more expensive than carbonate. But all is not lost. If you are on a budget or have already purchased a bottle of calcium carbonate, you can enhance absorption by making sure you take it with food.
Take note that absorption also is optimized when less than 500 mg of calcium is ingested, so no matter what form you choose, make sure to separate your supplementation schedule into doses smaller than 500 mg.
Optimally, you should aim to meet your calcium needs with a rounded, whole food diet. If and when deciding to add a calcium supplement, choose the calcium form that best fits your individual needs.
— Christina Troutner, dietetic intern, and Debra A. Boutin, MS, RD, chair and dietetic internship director, Department of Nutrition and Exercise Science at Bastyr University.