DEAR DR. BLONZ: Are some calcium supplements better than others? I had been using oyster shell calcium, but read there are risks of a contaminant. Is this form safe? -- B.B., Milwaukee, Wisconsin
DEAR B.B.: Calcium supplements from natural sources are the ones at higher risk for lead contamination, mainly because they tend to form in areas where lead is also hanging around. These sources include oyster shell, dolomite and bone meal.
Oyster shell calcium can become a problem when the oysters developed in lead-contaminated waters. Dolomite, also called dolomitic limestone, is a mined mineral that’s composed primarily of calcium carbonate and magnesium carbonate, plus some other elements. If the mineral happens to be in areas that contain elevated amounts of lead, this natural source would also have its share of this unwanted mineral.
Bone meal makes sense as a calcium supplement because, in addition to the calcium, it contains the other trace elements used to make bones. The problem is that an animal’s bones often serve as storage tissue for heavy metal contaminants in the diet. Animals allowed to graze near sources of industrial pollution can become sources of higher-than-normal levels of these contaminants in their bones and other tissues.
This doesn’t mean that all natural sources are contaminated; it is just to let you know that when you choose a calcium supplement made from any of these compounds, you need to check the source. That means verifying that the company providing the supplement has tested their product and can provide assurances of its purity. Opt only for those brands that state their product is low-lead or lead-free. In general, only purchase supplements that provide you with the quality assurances that you, as a customer, need in order to be comfortable.
DEAR DR. BLONZ: I appreciate your science-based, respectfully written column, and never miss it. But I have a small correction to a recent answer about chelation therapy. You stated that the EDTA in lavender blood-collection tubes prevents blood from clotting by chelating the iron. Actually, it chelates the calcium in the plasma; the iron in cells is not accessible to the EDTA because the cells remain intact. -- E.B., retired clinical lab scientist, via email
DEAR E.B.: Thanks much for this correction.
DEAR DR. BLONZ: I was surprised when I read that the pH of lemon juice was actually lower than that of vinegar, making it more acidic. I can drink lemon juice straight, but vinegar takes my breath away. I have always been under the impression that if I substituted lemon juice for vinegar in a dressing or recipe, I should use slightly more lemon juice, which now seems unnecessary. -- B.G., San Diego, California
DEAR B.G.: pH is a measure of acidity, and it does not necessarily equate with taste. The vinegar used in foods comes from acetic acid, a substance that is produced during spoilage. It is pure acetic acid, so your taste buds get a real shot of that one component. In lemon juice, we have citric acid with a few other organic acids, but there are other flavor qualities to balance out the sensation. Vinegar acidities can vary, but most are about 5 percent. Lemon juice is in the same range. Your reactions make more sense when you consider the larger flavor context.
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