DEAR DR. BLONZ: I read that the best calcium supplements are made from bone. I have also heard that milk is not the best source of calcium because of the protein binding. What are your thoughts? -- R.T., Richmond, California
DEAR R.T.: Calcium hydroxyapatite is the key calcium compound found in bones. Because it is bone, it contains all the minerals found in bone, and somewhere along the line, someone came up with the idea that it would be an ideal calcium supplement. But calcium has to be absorbed before it can be utilized, and hydroxyapatite has yet to demonstrate its superiority as a calcium supplement.
Calcium carbonate is the most common form of calcium found in supplements, but if higher absorption is the key, the best bets are calcium citrate malate or calcium citrate.
The bottom line regarding calcium? It is more important to get calcium into your system than to spend time worrying over which form might have a few percentage points' greater absorption in a particular study. And regardless of which form you end up taking, it is widely accepted that the best time to take calcium is at mealtime.
You also bring up the issues of milk and "protein binding." Explaining the idea of protein binding in relation to calcium is a bit more complicated, so bear with me as I walk you through it. First, milk should not be the focus here. The primary issue is that when we consume more protein than the body needs, the excess does not get stored. Rather, excess protein gets directed to other uses. The bulk of protein's amino acids building blocks are converted into energy (fat), something we all know the body is quite efficient at storing.
Changing protein's amino acids into energy creates some metabolic refuse, and this must be eliminated from the body through the kidneys. Compounds being disposed of by the kidneys often grab "escorts" in order to leave the body through the urine. The refuse from the conversion of protein into energy tends to have a negative charge, and the kidneys must buffer this with something that has a positive charge; calcium can serve this purpose.
Calcium is not the first or only choice. In fact, there will be many other "positive" buffering compounds in any balanced diet that contains healthful amounts of fruits and vegetables. If, however, little else is around, calcium can get the call. When calcium leaves the body in this way, more calcium can be pulled from the bones to maintain the required level of calcium in the blood.
The bottom line is that some calcium can be lost when one eats a high-protein diet, but mainly when the diet does not contain the recommended intake of fruits and vegetables. The people who overdo it with protein, unfortunately, are often the ones who do not have a well-balanced diet.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.