DEAR DR. BLONZ: With increasing weather and power emergencies, I have been keeping an emergency supply of food that needs to be rotated periodically. I prefer having foods that we use regularly rather than buying all-inclusive, emergency full meal kits. I would like to know how to read the dates on some cans that only have codes with no discernible dates. Is there a reliable website that would help? I need to rotate, but I also want to donate the canned foods to a community food bank while they are still wholesome. I hope you can help me. -- M.S., Pima, Arizona

DEAR M.S.: My compliments to you for your attention to emergency food preparedness and for helping distribute food to those in need. (See the University of Georgia’s article at b.link/tzykz88 for information on emergency food preparations.)

As manufacturers and distributors use different coding systems, there is no single information source that applies to all canned foods. Further compounding the problem is the fact that all cans bearing a particular label may not be from the same manufacturer or plant that produced them, or from the same harvest or location. I recommend contacting the individual food company whose name appears on the label. Manufacturers offer a toll-free number to call for questions, and this would include ones about expiration dates. They should be able to crack the codes and give you the information you desire. Also, be sure to label your product when it enters your inventory, so you have at least that level of control.

Canned foods often have codes instead of readable use-by or sell-by dates; they tend to be non-perishable, with shelf lives measured in years, as opposed to days and weeks. If undamaged and stored properly, these lose their taste and texture rather than becoming dangerous. The codes help to identify the date, batch and location of manufacture. They are useful for rotating stock, and if any recalls might be needed. (For more on shelf-life codes, check the article at b.link/2r5flx6, and the USDA’s at b.link/cbsr87.)

As a general rule, when dealing with such foods, you should always ensure that the can is in good shape, with no bulges or deformities that suggest something might have gone wrong. Discard any cans that unexpectedly discharge pressure when opened.

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 found an unopened pint of ice cream in my freezer that had been buried for about a year. I was disappointed to see that it had ice crystals, just like another container I had opened and resealed a number of times. What causes this, can it be stopped, and is there any danger from eating older ice cream in which this happens? -- S.Q., Chicago

DEAR S.Q.: Harmless water crystals can form on the surface of frozen foods during storage as the product's temperature fluctuates above and below freezing. Water typically freezes into large ice crystals, but such crystals in a frozen desert would lend an undesirably coarse texture.

There are methods to keep crystals tiny in ice cream and other frozen desserts; one involves constant stirring while the product is gradually chilled to the final storage temperature. When done correctly, it only allows mini crystals to form, and the dessert retains its smooth texture. Modern techniques chill frozen desserts using liquid nitrogen (-320 degrees F); with this method, the food chills faster than ice crystals can form.

Also important is temperature stability from the time the dessert is made until it is served. We all likely have experience with products whose temperature handling broke down along the way. (If this happens repeatedly, keep track of the particular products you purchased or the stores where you did so. Also investigate whether your freezer may be at fault.)

Ice cream in a carton can have a bit of "dead space" above the product. It is this, and any additional space once the dessert begins getting dished out, where the water in the ice cream can evaporate and refreeze during normal temperature fluctuations. The idea that water can vaporize at freezer temperatures may seem strange, but it can and does, given that the dry air in the freezer can pull the moisture out of the dessert. This rule of physics also helps explain the science behind freeze-drying and why some freezers had to be defrosted periodically (before the widespread use of mechanisms that do it automatically).

The longer it takes to use up a carton of ice cream, the greater the risk of crystal formation; keeping it out at room temperature for any length of time adds to the problem. However, crystal formation can be prevented by putting wax paper or some other moisture barrier on top of the dessert before returning it to the freezer. You may find that lower-fat frozen desserts have a greater tendency to form crystals, as these tend to have more water per unit weight.

DEAR DR. BLONZ: I am not allergic to milk, but I am definitely lactose intolerant. Where can I find a bread spread that contains no milk solids? -- J.B., San Diego

DEAR J.B.: The solids in milk will have proteins that anyone with a milk allergy must avoid. But your concern is lactose, and there is hardly any lactose in spreadable fats. With few exceptions, spreadable fats, including margarine and butter, get 100% of their calories from fat. This means there is no carbohydrate, and therefore no lactose, in these products. A cup of butter, for example, will have only about one-tenth of a gram of lactose.

Check the breakdown of your product on its Nutrition Facts panel to verify the absence of that carbohydrate. Even if there were a couple of grams per serving, it's doubtful that would be enough to cause a reaction in people susceptible to lactose intolerance. You might also consider adopting the European practice of using olive oil as a spread, with added herbs for flavor.

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 have tried intermittent fasting, but I want to know your thoughts on going on a multi-day complete fast for energy, cellular renewal, detoxification and immune system strength. Water would not be stopped, only all food. Thanks. -- A.K., Raleigh, North Carolina

DEAR A.K.: The idea of fasting has been around for a long time and is an integral part of many religions. The origins are intertwined with ancient beliefs that fasting leads to a purification of the soul or spirit. I appreciate your qualifying complete fasting from intermittent fasting, where you only eat during specific times or a limited number of hours a day. This is a more nuanced area with varying approaches and evolving research (for more on intermittent fasting, see the article at: b.link/8pp5ue6).

Up front, let's understand that when you stop eating, your supply of energy and raw materials, as well as the rate of tissue repair, all decrease. Glucose (blood sugar) is the preferred fuel for the brain and nervous system. It is the only fuel that the red blood cells use, and it is the body's primary source for instant energy. Glucose allows you to transition from resting to running without first taking deep breaths to increase the level of oxygen in your blood. There are small stores of a form of glucose in the liver and muscles, but it doesn't last very long. When in short supply, the body craves glucose to the point that it breaks down its muscles and organs to get at the specific amino acids it can modify into glucose (glucogenic amino acids).

Daily protein intake provides amino acids to replace worn-out cells, but during a fast, the body must recycle its amino acids. It comes up short because some are recruited to form the needed glucose. During the first days of a fast, approximately 75 grams per day of the body's protein gets used to satisfy our need for glucose; this slows tissue growth and repair.

One of the claimed benefits of fasting is that not eating allows the digestive system to rest, thereby freeing energy to help the body detoxify and improve overall health. This is illogical. Normally, about 10% of dietary energy is used to digest, absorb and metabolize what's in food. Fasting for this purpose would be like quitting your job to save commuting expenses.

As for detox claims, toxins are often fat-soluble compounds that distribute themselves throughout the stored fat in the body while awaiting elimination. With a fast, the mobilization of fat calories can result in increased blood levels of these unwanted substances and contribute to the general weakness experienced. There is much to consider. A healthy diet and lifestyle are important goals, and many paths can take you in that direction. I encourage you to look behind rosy portrayals of total food fasting as critical to that objective.

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.