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.

DEAR DR. BLONZ: Does coffee consumption interfere with attempts to get pregnant? I am 25 years old, in very good health, with no serious health problems. I have two cups of coffee during the morning hours, but nothing more during the rest of the day. I am more than willing to cut back if needed. -- S.T., Tulsa, Oklahoma

DEAR S.T.: Coffee and caffeine represent an ongoing topic of discussion and debate, especially regarding their potential impact on pregnancy. Concerns include the fact that caffeine can cross the placenta, and that the developing fetus has not yet developed an ability to metabolize it as mom can.

In a healthy adult, the half-life of caffeine is about three to four hours; that is the time it takes the body to reduce the level found in the blood by half. In the case of caffeine, that process includes changing it into nonstimulating substances in preparation for elimination. Interestingly, caffeine’s half-life rises for pregnant women to about 15 hours during the last trimester.

As to your specific question, studies have offered evidence on both sides of the risk argument, with some concluding that it is possibly safe, others concluding the opposite. In a typical study, the process would be to take a large population of similar individuals, ordering them according to coffee/caffeine intake. The population would then be split into groups from the lowest to the highest levels of intake, and the incidence of the health issue being studied would be examined to see if it reveals a significant effect.

Here are some examples of the coffee-pregnancy conundrum. One study indicates that having more than three cups a day can significantly affect your ability to conceive, but another finds no such association. Which study to believe?

What about an association between coffee consumption and the risk of miscarriage? A study in the journal Epidemiology reported no increase in risk with intakes of up to 200 milligrams per day, which is what you might find in about two cups of coffee (depends, of course, on the strength of the brew). But there is also a study in the American Journal of Obstetrics and Gynecology reporting an adjusted hazard ratio of 1.42 for caffeine intakes up to 200 milligrams per day. (A hazard ratio of 1.0 means no effect; the higher the number, the more significant the effect.) For caffeine intakes of 200 milligrams or more per day, the hazard ratio was 2.23. And a study in the January 1998 issue of Archives of Diseases of Children found an association between heavy coffee drinking during pregnancy (defined as over four cups a day) and the risk of sudden infant death syndrome (SIDS).

There is little in the scientific literature condemning light consumption of coffee (up to one cup a day). But a couple things should always be kept in mind: that coffee is not essential for the health of your child, and that there is no guaranteed-safe level of intake. Science, after all, has made mistakes, and of all the stages in life, pregnancy is not the time to entertain avoidable risks. Seems reasonable to eliminate caffeine, or at least keep it to an absolute minimum, and err on the side of safety.

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.

DEAR DR. BLONZ: I live by myself and find it difficult to use up an entire loaf of bread before it dries out and becomes stale. I have tried storing bread in the refrigerator, but it never tastes the same. What is it about refrigeration that ruins bread? -- J.W., Las Vegas

DEAR J.W.: Bread turns stale as its starches undergo changes in structure. Although stale bread has a dried-out appearance, a loss of moisture is not the complete explanation -- a loaf will even turn stale in a well-sealed, never-opened package. Temperature, it turns out, is a key.

There are two main types of starch, or carbohydrate, in bread. Over time, each will change from a random to a more rigid arrangement. The first starches set up as a freshly baked loaf of bread cools to room temperature. If you have ever attempted to cut into a loaf right out of the oven, you’ll recall that doughy texture before the first starch sets up. The setting up of the second starch takes about a week. As that second starch changes, the texture of the bread shifts from soft to hard -- or as we call it, stale.

While refrigeration extends the shelf life of many foods, the second starch tends to set up faster at refrigerator temperatures. Your bread could turn stale in about a day. Refrigeration is not recommended for the storage of any raised bread product.

It’s unfortunate that sandwich vendors tend to store their premade sandwiches under refrigeration, but it does make sense: A slight staling of the bread is the price to keep the sandwich’s contents fresh. If buying a premade sandwich, try to get one that was made earlier that day.

As for the bread you keep at home, one solution is to look for breads that use preservatives called emulsifiers. They can slow down the setting up of starch and effectively extend shelf life. The most common emulsifiers used in bread, the monoglycerides and diglycerides, are effective yet harmless additives.

Freezing may be the ideal solution for your issue. Freezer temperatures are cold enough to keep the second starch from setting. If you are unable to get through a loaf before it goes stale, consider splitting your loaf and storing half in the freezer. However you decide to store your bread, make sure the package is always well sealed.

DEAR DR. BLONZ: Carrots in the refrigerator get soft and flexible after a few days, and eventually they shrivel. When are they no longer safe to eat? -- B.B., Chicago

DEAR B.B.: Carrots are a root crop, providing the route by which the water from the soil is taken up and transported to the rest of the plant. The fibrous part of the carrot contains flexible little compartments that hold water until needed by the rest of the plant above.

When the carrot sits, exposed to the air, the water evaporates. Over a matter of days, this will result in the more flexible vegetable you described. Eventually the carrot will wilt and rot. To retain moisture and firmness, carrots should first be washed, the excess water shaken off, and then placed in a plastic bag in the refrigerator crisper. Also, if you buy carrots with greens attached, remove them after purchase, as they tend to draw the water out of the carrot.

Carrots can be considered safe to eat as long as they’re not discolored, overly shriveled or slimy in feel. If a carrot has only lost some of its firmness, it can often be brought back with a soak in ice water.

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.