DEAR DR. BLONZ: I would like your opinion on the use of over-the-counter sleeping aids, as I am concerned about long-term use. My wife and I use doxylamine succinate nightly. I've researched OTC sleep aids to some degree using Google Scholar, and am not finding any serious evidence against long-term use that outweighs the importance of getting a full night's sleep. There is enough, however, for me to be concerned.

We take 12.5 milligrams (half of a 25 mg tablet) and also take 5 mg of melatonin each. We are 70-ish, not overweight, and are healthy eaters and exercisers. On the "bad" side, we drink a bottle of wine every night. I have no caffeine intake; my wife has a cup of strong coffee in the morning. -- J.I., via email

DEAR J.I.: Sleep is our primary restorative, but there can be complex issues at play when it isn't working. Given that we spend about a third of our life asleep, it would be best if it accomplished its purpose. I am hopeful this response, with plentiful reading suggestions, will provide some guidance and assistance.

Here are some resources you may find helpful:

-- A primer on sleep: "How Sleep Works" from the Sleep Foundation (b.link/7nd2as).

-- Information on insomnia: "Why Can’t I Sleep?" from the University of California at San Francisco (b.link/p7ca8s).

-- An additional insomnia resource: the "What Is Insomnia?" page from the National Institutes of Health (b.link/qmmjr7), which includes a downloadable guide to healthy sleep.

-- Many sleep disorders exist, and some experts estimate that about one-third of adults have a sleep disorder of some kind. Peruse the National Library of Medicine's list for details (b.link/uu944y).

-- There are dozens of "sleep hacks" -- tweaks to our activities and behaviors -- to try. See one long list from CNN Health (b.link/h26bmv).

One basic fix is to limit time spent in front of a screen prior to bedtime, especially if it is a screen without a blue-light filter. These filters reduce light frequencies that can impede the release of melatonin, a hormone normally released by the pineal gland to prepare the body for sleep. (Many, including you, I note, take melatonin as a dietary supplement.)

Then there is the role of alcohol in sleep disruption. A daily shared bottle of wine is pushing it for a 70-ish couple. While it can facilitate the initial doze, this is not "normal" sleep. Your body's metabolic attention is prioritized on breaking down the alcohol, which is considered a toxin. Higher intakes of alcohol disrupt sleep, particularly during the second half of the night. Studies also show that alcohol may exacerbate sleep-disordered breathing, such as snoring and obstructive sleep apnea.

Doxylamine is an antihistamine sold as an OTC sleep aid. It is approved for occasional sleeplessness, but not recommended for regular use. Alcohol is not advised when taking doxylamine, as it affects its breakdown.

I realize there is a lot to digest here. You have much in order regarding diet and lifestyle, but it is wise to be concerned about the long-term use of any OTC medication not being taken at your physician's direction. It is always best to check with your family physician to rule out any health problems.

Lastly, remember that changing routines can take time, so give your body a chance to adapt to new behaviors.

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: Besides fresh and frozen vegetables, I often use canned, especially tomatoes. I buy organic when available, and periodically they are imported. I recall lead solder used to be used in many brands of canned foods, mainly the imported ones. This type of solder seemed especially dangerous for acidic foods like tomatoes. Does the fact that the can is airtight make it safer, or are protective substances added to make it so the food won't react with the metal? -- F.S., San Jose, California

DEAR F.S.: Cans used to be made in three pieces: top, bottom and the cylindrical body, all soldered together into the familiar shape. Lead is an ideal soldering material, but its use where there would be contact with foods turned out to be risky business when we learned of its toxic effects in the human body. Lead is hazardous during pregnancy, infancy and childhood. (Read more about lead poisoning from the National Library of Medicine at b.link/c5yt9r.)

Domestically produced cans were the first to stop using lead solder; canned food manufacturers in the U.S. reported having stopped using it by 1991. Cans are now welded together or extruded into a two-piece shape that eliminates the need for the side seam. In all cases, the can materials are formulated to inhibit the leaching of metal ions into the food -- even when the goods inside are acidic. This sometimes involves using an enamel or vinyl liner substance designed to not react with the contents.

Food companies in developing countries have moved toward lead-free cans, but it is difficult to say that all are there yet. For those cans, the Food and Drug Administration has an action level of 250 parts per billion of lead in the food, a level considered to be safe. If a can exceeds that level, it can be seized by the FDA.

Although this may provide some comfort, it's not a safety guarantee. It is prudent to check the labels on any imported canned food, especially if it is one you would be purchasing on a regular basis. If there is no information on the label or product website, check with the supplier. Another option is to use test kits with swabs that turn a particular color when exposed to lead. These inexpensive kits, good to have around the house, can be used on cans, pottery, crystal, pitchers or any food-contact surface you want to examine.

While not raised in your question, another substance raising concern in food containers is bisphenol A, known as BPA, which is often used in can-lining materials. (Learn more about BPA at b.link/dzukfd.) The FDA regulates how much BPA can be present, and no longer permits its use in packaging and containers that will hold materials for infants. Manufacturers continue to phase out the use of BPA in cans; for more, see an article from the Environmental Working Group at b.link/48wu35.

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 would like your help to settle an argument at a recent dinner. There seems to be such a push to restrict salt consumption in general, but the only hazard I am aware of is that salt can raise blood pressure in some people. Is there any other risk associated with salt, aside from high blood pressure? -- H.T., via email

DEAR H.T.: The main issue with excess salt intake is, as you mention, its association with high blood pressure (hypertension). But this is nothing to be dismissive about. High blood pressure currently affects roughly half of adults. It's called "the silent killer" because there are no warning signs until problems such as heart disease, stroke or kidney disease have already developed. The only reliable way to determine whether you have hypertension is to check your blood pressure regularly.

Salt and sodium are not automatically antagonistic for everyone, even those with high blood pressure. But there is no health benefit from excessive salt -- only liability. For those at high or uncertain risk about their blood pressure, it is best to keep salt to a minimum. Another point to consider is that one's sensitivity to salt, and ability to consume it safely, can change over time.

Finally, saltiness is one of our basic tastes. Salt helps to bring out the flavors in food. But the point should be to enjoy the natural flavor of foods, rather than that which comes from the salt shaker. Consider it a warning sign if you routinely reach for the shaker before you taste the food.

See b.link/2qkdb4 for more on high blood pressure.

DEAR DR. BLONZ: I work with second and third graders as a student teacher. We would like to know: How do scientists determine the levels of protein and other nutrients in fruits, vegetables, meats or processed foods that contain them all? And where can I take my students to show them scientists analyzing foods? -- T.T., Chicago

DEAR T.T.: To analyze foods, representative samples are put through a series of laboratory tests that measure the amounts of macronutrients -- such as protein, fat and carbohydrate -- and micronutrients in the item. ("Macro" means larger amounts of the nutrient, whereas "micro" means smaller amounts. Read more at b.link/33chvc.) Each nutrient has its own test. Independent laboratories around the country perform these analyses, although food companies often have their own labs, as well.

You should check in your area for food manufacturers with in-house labs that offer tours. Consider creating a list of options and allowing the students to vote for their selection. I grew up in the Chicago area, and a trip like that was one of my most memorable class outings. I predict you will find companies willing to open their doors to your students.

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.