DEAR DR. BLONZ: I would appreciate your thoughts on the discussion about aluminum foil that occurred at a recent dinner event. There was acknowledgment of its many uses and the plus that it is recyclable. There was also mention of a connection between aluminum and the risk of cognitive decline, such as with Alzheimer's disease, and this was a source of underlying concern. My more specific question is whether it is best to use the shiny side or the dull side of the foil when placing it next to the food. The argument in need of clarification was whether the shiny side or the dull side best reflects the heat, and also which side is best for nonstick properties. -- S.R., San Francisco, California

DEAR S.R.: Beginning with your question, the shiny and dull sides of standard or thick aluminum foil are a result of the manufacturing process. They don't reflect any different functional purpose, including differing heat or anti-stick properties. (See an explanation of how aluminum foil is made at b.link/c3wdz7m.)

There are nonstick aluminum foils that use a proprietary food-safe anti-stick coating; check with the brand to see how they achieve their effect. Nonstick aluminum foils will indicate this property on their package label, and in such products, it is the dull side that has the property. If using one, verify it retains its recyclable properties. On a more practical note, rinse food debris off any foil or other recyclable materials before placing them in the recycling bin.

The issue regarding aluminum as a risk factor for disease is somewhat more nuanced, as its primary foundation lies in epidemiology. Epidemiology, often thought of as "population studies," is the science that investigates the connection between specific events, such as the occurrence of a disease, and particular behavior patterns, including elements of diet or exercise. Epidemiological research doesn't explain what's going on; it can reveal suspects and suggest relationships that require clinical studies designed to uncover cause-and-effect relationships, often involving the use of controls, such as a placebo.

Key in epidemiology is the need to understand what causes what. An example can be seen in reports that inner-city children with iron-deficiency anemia are more likely to have lead poisoning. The population study revealed the connection, but it did not identify the cause. Scientists conducted additional studies to uncover the underlying mechanism. In this case, it was discovered that low blood iron (anemia) causes the body to absorb more lead. Inner-city children are at a greater risk for substandard nutrition, coupled with increased exposure to lead that is present in lead-based paints, which may be peeling off the walls.

In some cases, epidemiology yields strange results. I recall a classic example during a graduate course in epidemiology that physicians who eat more meat and consume more alcohol have one-third the risk of dying in a plane crash. Anomalies with no logical relationship can emerge in large population studies, and this particular finding does not justify encouraging doctors to grab a burger and a beer before they board their flight.

Regarding aluminum, there is no evidence that the use of aluminum foil causes problems when consumed at normal levels found in food, as well as those levels added through normal cooking and storage. For a more focused consideration of this aspect, please visit b.link/aluminum.

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: 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.