On Nutrition

DEAR DR. BLONZ: I need a clarification about the meaning of “elemental” as it applies to the minerals in the diet. My confusion comes from the lack of consistent terminology in books, online, and on products I have seen. I have also asked “knowledgeable” clerks in supplement stores, and the responses tend to be all over the place. I am anxious to hear a reliable answer, especially regarding calcium and how much potassium we need. -- R.Q., Phoenix

DEAR R.Q.: Minerals are often referred to as “mineral elements.” They are found in foods and dietary supplements as compounds made up of the mineral, plus an “escort” substance.

The escort has an opposite charge to the mineral, as this is how mineral elements exist in biological systems. For example, calcium can be paired with carbonate, phosphate, citrate, gluconate or other escorts. Calcium compounds have differing characteristics, including bioavailability (how effectively the calcium is absorbed), how well they will function in a given food system, and, of course, cost. There are practical implications, as well. Calcium carbonate is approximately 40 percent calcium by weight. Compare this with calcium citrate, which is approximately 20 percent calcium. For a given amount of calcium, you would have to take twice as many pills (or have pills twice as large) if you took calcium in the citrate form, as opposed to the carbonate.

In terms of bioavailability, the calcium has to separate from its escort before it can be absorbed; carbonate comes apart best in an acid medium, while calcium citrate (and a related form known as calcium citrate-malate) do not need acid to separate. That explains why calcium carbonate is best taken at mealtimes, but calcium citrate can be efficiently absorbed either during or between meals. Because of their higher solubility, calcium citrate and calcium citrate-malate are often recommended for those who do not produce sufficient stomach acid. There have been some issues of late on the amount of calcium in our diets, and possible dangers from excessive intakes. For more on this, see b.link/calcium29.

Potassium is involved in the transmission of nerve signals -- for example, it helps keep the heart beating, and it is also important for regulating the water balance inside the cells and the body’s acid-base balance. A reasonable goal is about 4,700 milligrams a day. Potassium is in a variety of fresh, whole foods such as potatoes, greens, tomatoes, bananas, citrus fruits and avocados. Avoid having too much potassium; supplementation is not usually needed unless there is a specific health problem, or medications are being taken that drain the body’s supply of the mineral. For more on potassium, see b.link/potassium21.

On a separate issue, you are right to be wary about health-related answers from online sites and store clerks. It’s a bit of a wild card, as some sources provide information based on facts and an understanding of the issues, while others can be of a lesser stripe. It’s always best to have an understanding of the basic concepts in mind. A reasonable strategy when looking online is to seek out information from recognized educational institutions or government agencies.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

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