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.

DEAR DR. BLONZ: Do I need to be concerned about taking calcium supplements if I am also taking a calcium channel blocker? If so, how do you manage osteoporosis when on this medication? -- P.T., Phoenix

DEAR P.T.: Although calcium is involved in both situations, there are important differences. Calcium channel blockers are often prescribed for hypertension (high blood pressure) because they prevent the contraction of certain smooth muscles that surround the blood vessels. For the muscle around the vessel to contract, a small amount of calcium has to pass through a channel in the membrane (outer skin) of the muscle. Calcium channel blockers are so named because they slow the movement of calcium through these channels, thereby keeping the blood vessels relaxed.

There is little connection between the calcium in your diet and the ability of a calcium channel blocker to do its job. If you have any questions about any medication you are taking, be sure to discuss the issue with the prescribing physician, or the pharmacist where you have your prescriptions filled.

DEAR DR. BLONZ: I am uncertain where else to go with this one: I have seen my regular doctor, an urgent care doctor, my dentist and an allergist and none of them have had any idea what to tell me. I am not an allergic person in general, but have had geographic tongue on and off for the last two years. My lips, tongue, gums and interior walls of my mouth swell and get numb. Then my lips peel and the numb sensation takes a week or so to go away. I’ve kept a diary of what I’ve put in my mouth the preceding six hours or so of each episode. There doesn’t seem to be too much in common. Later, I will eat some of the same foods, and have no reaction. One time I awoke at 5:30 a.m. with my tongue so swollen I couldn’t talk, and my lips were the most swollen I’ve ever seen. After swishing with a liquid antihistamine, the swelling went down.

This has been very periodic, every two weeks or so, for the last couple months. This last month, I’ve also had a very metallic taste in my mouth. Any suggestions? My next stop is an oral surgeon (a head and neck specialist). I have a feeling he’ll say the same thing. -- D.S., San Jose, California

DEAR D.S.: I am not a medical doctor -- my training is as a nutritional biochemist -- so there are limits to what I might say or can recommend. I think you have assembled a reasonable team, consulting with dentists (for teeth), physicians (for sinuses, etc) and allergists (to see if there is a provocative agent responsible).

If there are concerns about an allergy, has anyone suggested you go on an elimination diet to remove all suspected allergens? Are there new pets/animals in the house or in the neighborhood? Might there be some sort of allergenic substance already present or being brought into your environment by others? Any new dietary supplements or changes in brands of foods? New cookware? Recent dental work? New cosmetics? Have you traveled away from home during all this, and do the symptoms change when you are away?

I encourage you to give thought to all possible variables and put together a list of suspects to discuss with your health professionals. I wish you quick success on this detective hunt.

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 am hoping you will answer these questions about vitamins and minerals. Is it OK to take water- and fat-soluble vitamins at the same time? Should vitamin C be taken with foods that contain vitamin C, or is it just as effective taken alone or with water? Should calcium be taken alone or with other nutrients, such as vitamins E, C and the Bs? What's the best time of day to take vitamins? Thanks for all your help. -- G.T., Las Vegas

Dear G.T.: There is no problem taking water-soluble and fat-soluble vitamins at the same time. You can take vitamin C with or without C-containing foods. As a general rule, it is preferable to take supplementary vitamins and minerals at mealtime. When food is present, the body is more attentive to the digestive system, and its blood supply heads that way to pick up the incoming nutrients.

There are two key points to be raised here. The first is that it is more important that you get the nutrients than to be overly concerned about when during the day you get them. Second, and more on point, is the fact that it is the foods you eat that deserve the starring role. Supplements are just that: supplements. Taking supplements does not provide the equivalent of the whole-food symphony of substances produced by the plant for its growth, development and defense of the plant -- substances which then become available to benefit your body when you eat that food.

Dear Dr. Blonz: We found a couple of bottles of oil given as gifts that were tucked away in the cabinet. They have been on the shelf for approximately two years, kept away from heat and light. They are both top quality, extra virgin olive oils and have not been opened. Am I correct in thinking that they should present no problem when used? – O.S., San Jose, California

Dear O.S.: Unlike wine, oil does not improve in the bottle. An extra virgin olive oil will be at its best when first put in the bottle (or can), and it’s all downhill from there. Oils should be tightly covered and stored away from heat and light. An unopened container of a refined vegetable oil -- properly stored -- can maintain quality for about a year. Some oils, including extra virgin olive oils, claim they can last up to two years, so yours are certainly worth a check. But don’t wait! Given that they were stored properly after being opened, you have about six months. As a general rule, the more unsaturated the oil, the shorter the shelf life after being opened. Oils that have been sitting for questionable periods of time should get a sniff and taste test before being used. It is always best to buy your oil in containers that match an expected rate of use. To help you keep track, mark on the label the date of purchase, and the date the container was first opened.

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.