DEAR DR. BLONZ: The bread offerings at my market continue to expand with not only white and various types of wheat, but other grains and a variety of gluten-free options. I have no issues with gluten, but I remain confused about the relative nutritional merits of all these various bread types. -- B.L., Sun City, Arizona

DEAR B.L.: To better understand these breads, it will help to know a little about the wheat grain, or kernel. The kernel consists of the bran, the endosperm and the germ (tinyurl.com/qjbdk9f).

The bran is the protective outer shell of the grain, composed primarily of a nondigestible dietary fiber (bran) and a small amount of B vitamins. The endosperm, which is mostly starch (carbohydrate) with small amounts of protein, vitamins and minerals, is the central ingredient in the bread-making process. The germ is the embryo inside the grain; if the intact grain were to be planted, the germ would grow into a new plant. The germ contains most of wheat's vitamins and minerals, plus a small amount of essential oils: the nutrients needed by the wheat to fuel development until it can begin getting them from sun and soil. Because there are unsaturated oils in the germ, the wheat grain evolved to include vitamin E and other antioxidants to keep the fats from going rancid.

The internal contents of the grain are used to make bread. Cracked, crushed and whole-wheat flours all contain the entire wheat grain. In cracked wheat, the grains are cut in angular pieces; in crushed wheat, the grains get, well, crushed; and in whole-wheat flour, the entire grain is milled together. Each of these flours create breads of differing consistencies, but comparable nutritional value.

White flour, on the other hand, consists of the endosperm without the bran or wheat germ. Aside from the fact that it's a carbohydrate, it offers less in terms of native nutritional value. For this reason, white flours are usually enriched with added niacin, riboflavin, thiamin and iron to bring them up to the levels found in whole-wheat flour. Unless purposefully added, other naturally occurring wheat nutrients -- including magnesium, zinc, vitamin B6, vitamin E, folate and fiber -- are usually not present in white flour.

To find the healthiest bread options, you will have to read labels carefully. All flours made from the wheat grain can be called "wheat" flour, so it is perfectly legitimate for manufacturers to use the terms "white flour" and "wheat flour" interchangeably.

Don't be fooled by a bread's color: Some companies use white flour, legitimately call it wheat flour, but then add caramel coloring to make the bread appear to be whole-grain. On the flip side, whole-grain breads tend to be heavier in texture, so bread makers often add gluten to make it softer. Some do this by adding white flour, which has more gluten per unit weight, while others add pure gluten to the mix.

The healthiest products are the least refined and have the greatest percentage of whole grains. Look for "cracked," "crushed" or "whole-grain wheat" at the top of the ingredient list, regardless of how many different grains are used.

Whatever your choice, aim for a product that has at least one gram of fiber per slice. Make it a habit to check the Nutrition Facts panel and the list of ingredients when comparing products.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 must begin monitoring my intake of foods that raise my blood sugar level. Could you please provide some basic info about blood sugar? -- Y.M., Berkeley, California

DEAR Y.M.: A good way to begin is to think about rain -- a definite obsession here in Northern California. The rivers, lakes and even the water systems in our homes and towns are set to handle certain amounts of rain. A torrential downpour, or excessive rain on a regular basis, overwhelms the capacities of the various systems, and water ends up in places where it's not expected or desired. The end result, as we have seen in recent seasons, is flooding, property damage and injuries.

Similarly, the human body has various systems designed to handle an influx of carbohydrates.

Set aside the rain analogy for a moment. Glucose, a simple sugar, is the preferred fuel of the brain and the rest of the nervous system. It is an anaerobic fuel that releases energy without extra oxygen. It's what allows us to dash across the room to catch a falling object, or run to catch a bus without first needing to take several deep breaths to increase the level of oxygen in the bloodstream.

The body works best with a metered entry of glucose into the bloodstream, which happens when carbs come from a whole-grain starch and are part of a varied meal. After we eat complex carbohydrates, the digestive system breaks them down into simple sugars (mostly glucose) prior to absorption. After that, there are specific enzyme systems that work on the glucose to provide its unique benefits to the body.

Now back to the rain. With a normal downpour, the gutters on our houses and the drainage systems of our towns handle the water with little incident. But when you consume too much added sugar from sweets or sodas, especially on an empty stomach, it's like a deluge descending on your home.

When an excess of sugar enters the blood, the body has to scramble to assert control. Alternate pathways must be used, and if this occurs on a regular basis, the conditions become right for the development of our most troublesome diseases and conditions: heart disease, diabetes, diabetic neuropathies, obesity, hypertension, arthritis and even cancer. There is no way to sugarcoat the science.

Sugar is not bad in itself, but an excess of it tends to shove our bodies' systems in the wrong direction. A study in the Feb. 3 issue of JAMA Internal Medicine compared U.S. adults who consume no more than 10 percent of their calories from added sugar with those who have more. It reported that individuals who habitually consumed between 10 and 25 percent of their calories from added sugar had a 1.3 times higher risk of cardiovascular mortality. Those having 25 percent or more calories from added sugar had 2.75 times the risk of dying from cardiovascular disease.

Strive to keep your intake under control by opting for a diet that is primarily plant-based with a hefty percentage of whole foods. Read your labels, and pay specific attention to "added sugar" -- not the sugar naturally present in a whole food, but that which is purposefully added during processing. The FDA has proposed a revision of the Nutrition Facts label to include a specific listing of added sugars. I welcome this step forward.

Don't obsess over every gram; think big picture. This message is especially important for the growing bodies of children, teens and young adults.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: We've begun offering nonfat frozen yogurt bars as a snack for our child. The package says there are only 90 calories and, of course, no fat. The package also says "no preservatives," but the ingredient list includes a number of gels and gums, along with polysorbate 80 and carrageenan. If these aren't preservatives, what are they? Are they OK for our 7-year-old? -- FF.,. San Jose, California

DEAR F.F.: None of the ingredients you listed are preservatives. The gels and gums are thickeners, and the polysorbate 80 and carrageenan are emulsifiers designed to keep the yogurt mixture from separating while it freezes. All these components keep the nonfat flavored yogurt from turning rock-solid at freezer temperatures.

These treats usually provide about 100 milligrams of calcium and a small amount of protein. They won't provide the healthful phytonutrients found in a good piece of fruit, but they do represent a good alternative to chips, baked goods or candies. Even so, why not have a snack that's a win-win by making your own bars with fresh fruit and yogurt? You can find an assortment of recipes online, so look for one that appeals to you and your child.

DEAR DR. BLONZ: Is it reasonable to use antacids as a calcium supplement? -- P.R., Sun City, Arizona

DEAR P.R.: Calcium-based antacids tend to contain calcium carbonate, along with flavorings, colorings and a sweetener. And only about 40 percent of the weight of the calcium carbonate is actually calcium. That means that a 500-milligram calcium carbonate antacid will only provide 200 milligrams of calcium, which equates to 20 percent of the daily value for this mineral.

If you're considering such an antacid as a supplement, don't overdo it, especially around mealtime. The first stage of digestion requires an acid environment to begin the separation of foods into their individual nutrients. The excessive use of antacids can make your upper digestive tract alkaline, and that can mess with normal digestion.

As for bone health -- presumably what you're hoping to boost -- remember that it takes more than calcium to make bones. Although a bone is about 90 percent calcium by weight, other minerals such as magnesium, phosphorous, boron and silicon are needed. Vitamin D is also integral to the health of our bones, so you should be sure to have that nutrient in the mix.

For these reasons, food should be your first choice as a source of calcium. Aside from dairy products, calcium can be found in dark green vegetables, such as broccoli, kale, collards and arugula; legumes, such as soybeans and garbanzo beans; almonds; and fruits such as figs and apricots. Finally, aside from the calcium and other bone-building nutrients in your diet, it takes an active lifestyle and weight-bearing exercise to encourage the body to keep its bones strong.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.