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 pre-made 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.

DEAR DR. BLONZ: As you reflect on nutrition globally, and then look back at the U.S. dietary standards, do you believe there are any universal truths in the field of nutrition? What do you see in the future for human health and nutrition, given that here in the U.S., we are not even among the 30 healthiest nations on earth? -- C.A., Las Vegas

DEAR C.A.: Given the (unfake) fact that scientific knowledge continues to evolve, there needs to be an element of flexibility, especially where personal and financial interests and biases are concerned. With each new finding, our thoughts about nutrition and health might require updating or outright change. Bias also comes from one’s worldview. What might be thought of as absolutes for a raw vegan are unlikely to jibe with those held by an omnivore.

This being said, there do seem to be underlying truths that can be gleaned from observations of the plant world, and from a review of human history. The overall theme is that we need to provide our bodies with a broad spectrum of nutrients and whole foods in order to sustain health, ensure longevity and empower our defenses. Essential adjuncts are a physically active, personally satisfying, stress-moderated lifestyle, adherence to basic food safety practices, and the responsible preservation of our land, sea and air.

Scientific findings continue to tweak the detailed chapters and verses, but much depends on who is supplying the research dollars. Dietary standards and recommended intakes, such as those put out by the U.S. government and others, are a mix of science, politics and market forces. There is value to these guidelines as they can provide visual teaching tools, but they tend to be more along the line of lagging indicators rather than bold steps forward.

Concerning your second question, I feel we will continue to have a disappointing ranking among the healthiest nations as long as we, as a culture, continue to have a significant element that can be swayed by instant gratification born of profit-driven market forces. This represents a significant temptation with a proven ability to entice the U.S. populace away from the basic themes of healthful eating -- directing them instead to sidetracks like “value-added food components,” rather than the innate power of whole foods themselves.

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: You often make reference to the “Nutrition Facts” label on packaged foods. Who in the government comes up with the data, and are all foods tested? How reliable are these figures? Why is it that some foods do not have this panel? -- C.C. Walnut Creek, California

DEAR C.C.: All foods regulated by the FDA need to display nutrition labeling. Some exceptions: small businesses with fewer than 100 full-time equivalent employees, with food product sales less than 100,000 units per year (or, for importers, fewer than 10 full-time equivalent employees and sales under 10,000 units annually). Retailers are also exempt if their annual gross sales are less than $500,000, or their gross sales of foods to consumers in the U.S. are less than $50,000.

Many companies not required to display the labels will often do so anyway, because they realize that it is a valuable source of information for consumers.

The accuracy of the information on the Nutrition Facts label is the responsibility of the company selling the food, not the government. Any information on the food label is subject to review, and the FDA goes around sampling, purchasing and analyzing products from store shelves to check for accuracy. The extent and frequency of these checks, of course, depend on the department’s budget.

The FDA allows for a 20 percent margin of error. In 1996, it found that 91 percent of tests on sample food products correctly listed nutrition information. If any infractions are found, fines and product seizures can result, depending on the severity. Food companies, especially larger ones, have a lot to lose from inaccurate labels -- the penalties can be hefty. I consider the information on food labels to be reliable and useful when comparing similar food products.

There are now extensive resources online related to food composition. A searchable database of food composition, amassed by the U.S. Department of Agriculture, can be found at ndb.nal.usda.gov/ndb/. There is also a user-friendly website at nutritiondata.self.com. The site contains food composition data, along with nutritional information for fast-food entrees and a wide variety of diet, nutrition and health tools including a way to find and analyze recipes.

DEAR DR. BLONZ: What do you think of putting desiccant from medicine bottles into a cookie jar to help maintain the cookies’ freshness? -- P.P., via email

DEAR P.P.: It’s a bit at cross-purposes. With medicines, you want to prevent moisture from having a negative effect on the medication. Desiccant packets attract and absorb moisture before it can affect the meds. Dryness is a positive, in other words. But with baked goods, especially cookies, dryness is the negative. You want to maintain a level of moisture consistent with their freshness.

With the medical desiccant packets, there’s also the risk of residual medicinal substances and odors being transferred to the treats. There is also a limited capacity of those small desiccant packs, as only a small amount is needed for already-dry medications.

A check of baker blogs will reveal a number of better methods to retain the freshness of cookies and other baked goods. Check out goo.gl/rBsPuF.

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.