The Bone Builder: Calcium

Calcium pills on a spoon.Calcium Benefits

Cal­ci­um is one of the most abun­dant min­er­als in the body.  Most of the cal­ci­um is stored in bones and teeth. This min­er­al is tight­ly reg­u­lat­ed, if not enough cal­ci­um is avail­able through your diet or sup­ple­ments, cal­ci­um is pulled from the bones or teeth, not what you want to hap­pen.

We need cal­ci­um through­out our life­time and for dif­fer­ent rea­sons.   Dur­ing child­hood and ado­les­cents we need cal­ci­um to help build and form bone and start a reser­voir for lat­er years, break­down occurs at a much less­er rate.  As adults the build-up and break­down of bones is about equal, so we need cal­ci­um to help main­tain this bal­ance.  When we reach our 40’s the break­down of bones exceeds the build-up, which can result in osteope­nia or osteo­poro­sis.    There­fore, regard­less of age it’s impor­tant you are get­ting enough cal­ci­um either through your diet or by tak­ing sup­ple­ments.   Besides bone growth, cal­ci­um is need­ed to help build and main­tain teeth, it helps reg­u­late the heart­beat, it helps blood ves­sels move blood through­out your body, it helps con­tract mus­cles, it trans­mits nerve mes­sages of the brain through­out the body and it helps release hor­mones and enzymes.

The Insti­tute of Med­i­cine makes the fol­low­ing RDA for cal­ci­um:

1–3 yrs old         700 mg/day

4–8 yrs old        1000 mg/day

9–18 yrs old      1,300 mg/day

19–51 yrs old    1,000 mg/day

51yrs                  1,200 mg/day

Good food sources of cal­ci­um

Plant-based Sources:

Beans, tofu (made with cal­ci­um sul­fate), spinach, kale, rhubarb, bok choy, sar­dines, Black-strap molasses, Almonds, Orange juice (cal­ci­um for­ti­fied)

Ani­mal-based Sources:

Milk, yogurt, cheese, cot­tage cheese, ricot­ta cheese, but­ter­milk

What to look for when sup­ple­ment­ing for cal­ci­um

There are two forms of cal­ci­um sup­ple­ments:

  1. Cal­ci­um Car­bon­ate
  2. Cal­ci­um Cit­rate

Cal­ci­um Car­bon­ate is best absorbed with food, where­as cal­ci­um cit­rate can be tak­en with or with­out food. They both vary in the amount of ele­men­tal cal­ci­um they con­tain, cal­ci­um car­bon­ate has 40% cal­ci­um by weight and cal­ci­um cit­rate has 21%.  These amounts will effect how much cal­ci­um is absorbed at one time.  The high­er the amount of cal­ci­um the less cal­ci­um is absorbed.  So, in this case more is not bet­ter.  Cal­ci­um is best absorbed in amounts less or equal to 500 mg.  For exam­ple, if you need 1000mg, take one 500mg sup­ple­ment at break­fast and anoth­er 500 mg at lunch or din­ner.

The Role of Exer­cise

Exer­cise, espe­cial­ly weight bear­ing exer­cis­es, help main­tain and retain bone den­si­ty.  The stress on the bone sig­nals cells in the bones to respond by mak­ing the bone denser and stronger. 

Weight bear­ing exer­cis­es include strength train­ing, run­ning, walk­ing, stair climb­ing and rac­quet sports. 

Vit­a­min D

In order to effec­tive­ly absorb cal­ci­um, vit­a­min D needs to be present.  If you are low in Vit­a­min D you are most like­ly defi­cient in cal­ci­um as well.


Estro­gen helps absorb cal­ci­um, if estro­gen lev­els are low, which is what hap­pens after menopause,  cal­ci­um absorp­tion drops as well.

Foods that inhib­it cal­ci­um absorp­tion:

Oxal­ic acid also called oxalate, is one of the strongest inhibitors of  cal­ci­um absorp­tion, it can be found in spinach, rhubarb, and in less­er amounts in sweet pota­toes and dried beans.  Anoth­er inhibitor but some­what less potent is Phyt­ic acid which can be found in fiber con­tain­ing whole grains, wheat bean, beans,seeds, nuts, and soy iso­laes, the yeast used in baked goods con­tains phy­tase which helps break down the phyt­ic acid.

Cal­ci­um also decreas­es iron absorp­tion from non-heme sources such as plant foods and sup­ple­ment and should be tak­en 2 hours apart.

Tan­nins which can be found in tea can bind with cal­ci­um in the intes­tine and can inhib­it its absorp­tion.


Long-term use of cor­ti­cos­teroids and anti-con­vul­sants can affect bone health. 




Linus Paul­ing Insti­tute Micronu­tri­ent Research for Opti­mum Health.

Office of Dietary Sup­ple­ments:  Nation­al Insti­tute of Health.

Har­vard School of Pub­lic Health.  Then Nutri­tion Source: Cal­ci­um and Milk:  What’s the Best for Your Bones and Health.  Accessed April 29, 2011.



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