DEAR DR. BLONZ: This is about a solution to the stomach problems that were experienced by my daughter. We were not sure whether it was some medical condition, stress, or even a food allergy. At a periodic wellness visit with our family physician, many questions were asked, including whether she had gum and sugar-free mints. I remember you had written about this, and that she always chews sugarless gum, but I never made the connection. This turned out to be the answer. I wanted to pass along that since she stopped, her stomach problems have disappeared. -- S.A., Martinez, California

DEAR S.A.: My hat's off to the family doctor and to your family for having periodic wellness visits. The sweeteners most commonly used in sugarless gums and mints are xylitol, mannitol and sorbitol, all members of the sugar alcohol family. Even though they are indeed carbohydrates considered to be sugars, they merit the "sugarless" label because, despite their sweet taste, they don't promote tooth decay. Sugar alcohols possess this quality because, unlike other carbohydrates, the bacteria in and around our teeth cannot metabolize them to produce the enamel-destroying acid associated with tooth decay.

One negative characteristic of sugar alcohols is that they attract water when they're in the digestive tract. Substances with this quality contribute to digestive upset that includes diarrhea and cramping. Also, sugar alcohols are not efficiently absorbed, so they tend to remain in the digestive tract and reach the large intestine. There, they serve as food for our microbiome, many of which produce intestinal gas as a byproduct.

The symptoms are mild when small amounts are consumed, or if they are eaten with or soon after a meal. If, however, larger quantities are consumed, such as several mints or sticks of sugarless gum, and if they are eaten on an empty stomach, the result can be the type of upset your daughter experienced. Read more about sugar alcohols and how they are shown on food labels at b.link/e7gfcew.

DEAR DR. BLONZ: I wanted to say thanks for an earlier column in which you covered positive benefits from chocolate. My question is whether the antioxidants you described are in the cocoa powder or in the cocoa fat. If it is in the fat, would that mean that the only way to get the benefits is to have full-fat chocolate? -- D.M., Benicia, California

DEAR D.M.: Research on chocolate has indeed identified the presence of beneficial compounds. These compounds, known as flavonoids, are found in the cocoa solids, not the cocoa butter. This means that they are in the cocoa powder, and, of course, in the whole chocolate confection. Dark chocolate, which has more cocoa solids, tends to contain more flavonoids than milk chocolate, and white chocolate (no cocoa solids) contains very few flavonoids, if any.

As for whether having cocoa powder is a "better" way of getting the benefits of the chocolate, that, I think, is a matter of personal preference. There are plenty of foods with wonderful attributes. Eat chocolate because you enjoy it, not because you think it's good for your health.

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: We had great-tasting grilled frozen swordfish steaks at a friend’s place, prepared according to the package instructions. I would appreciate your comment on whether this is a good fish to have, given concerns about mercury content. My main question comes from my learning that the leftovers had inadvertently been left in a sealed container on the counter overnight, rather than being put in the freezer as planned. My friend told me she put them in the freezer the next morning. I questioned the wisdom of this, and she told me that the original grilling would have killed the existing bacteria on the uncooked fish, and that freezing (even if begun the next morning?) would kill any bacteria that might have grown during the night. Then, when it came time to have the leftovers, reheating would finish the job. I questioned this, and she said it was a common practice, and no one had ever gotten sick. Is this a safe? Does freezing kill bacteria? Not to mention what it might taste like, and the general safety of swordfish.

-- W.N., Portland, Oregon

DEAR W.N.: You certainly are a good friend, and I hope you will pass this reply to your neighbor before they consider having those leftovers. Freezing would not kill bacteria in this situation; all that freezing does is to suspend the growth of microorganisms. It is essential to realize that freezing does not make food fresher than it was before it was frozen. Whenever a food is defrosted, bacterial growth resumes exactly where it left off. Eating foods left out on the counter is an unnecessary roll of the food-safety dice. There could be no guarantee of safety, even after reheating the next day. The idea of them being in a sealed container on the counter provides no reassurance, as cooling foods can draw the bacterial wild card of external air into the container while the food is temperature-sensitive. In my considered opinion, the best course of action would be to discard the items.

As for the healthfulness of eating swordfish, it provides an excellent source of protein, vitamins D and E, most of the B vitamins, along with omega-3 fatty acids. There are, however, real concerns about its mercury content. Fish are the main dietary source of this toxin for humans. As healthful as fish can be, estimates in the scientific literature are that about 90% of the mercury in our bodies comes from fish, typically from varieties high up on the marine food chain. The most commonly consumed higher-mercury fish include swordfish, shark, orange roughy, tilefish and certain types of tuna. (Side note: Salmon is not a fish of concern in this regard.)

Mercury is distributed throughout a fish, so cleaning and the method of preparation can’t solve the problem. It’s best to have no more than one serving per month of any high-mercury fish. Pregnant women and children should be at the lower end of that range, if you get my meaning. For more on mercury in fish, see b.link/pb677p5. Low- or no-mercury fish can be consumed more frequently. Check seafoodwatch.org for fish recommendations.

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 been eating more nuts and seeds, and also adding them to our children's lunches. Walnuts are a favorite. I would like to know their effect on blood lipids and triglycerides. In your reply, I hope you will provide a simple explanation of the difference between blood lipids and triglycerides. -- R.J., Raleigh, North Carolina

DEAR R.J.: "Lipids" is an umbrella term for a group of chemicals that includes fats (solid at room temperature), oils (liquid at room temperature), fatty acids, phospholipids, waxes and steroids. They are all composed primarily of carbon atoms in the form of chains or ring structures. Each type of lipid has a structure that sets it apart from the others. All lipids share one characteristic: They cannot dissolve in water, but instead dissolve in organic solvents such as mineral spirits or cleaning fluids. Some lipids can have water-soluble elements attached. Triglycerides also belong to the lipid family, but they're the form in which fats and oils are packaged in the body. And to complete the picture, cholesterol, a type of steroid, is another member of the lipid family.

About 80% of the calories in walnuts come from fat. Eating walnuts could have a variable effect on one's blood triglyceride level, depending on the amount eaten, other items in the meal and any predisposition one might have toward elevated blood lipid levels.

An interesting side note is that nuts, when eaten as a pre-meal snack, can contribute to satiety and decrease caloric intake. A classic study involving university students found that consuming one ounce of walnuts as a pre-meal snack was associated with a reduction in total calories consumed (nuts plus the meal). One ounce of walnuts (14 halves) provides 185 calories, 18 grams of fat and 2 grams of dietary fiber.

There can be differences in health effects between the various types of nuts and seeds, but the general impacts are comparable. There are similar results with peanuts, often regarded as nuts but actually classified as legumes. On a personal note, I rotate between individual nuts and blends of almonds, cashews, pistachios, walnuts, peanuts and pecans, often making a trail mix with added dried fruit and a few dark chocolate chips.

DEAR DR. BLONZ: What is vitamin A palmitate? I know palmitic acid is one of the saturated fats. Is it harmful in diets for those of us who have a cholesterol problem? Why is this form of vitamin A in so many foods? -- V.H., San Diego, California

DEAR V.H.: Vitamin A can exist in several related chemical forms. One of these compounds is made from vitamin A and palmitic acid, a saturated fatty acid. This form of vitamin A is stable and relatively inexpensive, making it the compound of choice for fortifying foods. The small amount of palmitic acid you would receive from vitamin A palmitate (also called retinyl palmitate) would be of little consequence to your cholesterol problem.

To put some numbers here, the daily value of vitamin A is 900 μg RAE (micrograms of retinol activity equivalents), also referred to as 3,000 IU. This level will be in 1.65 mg of vitamin A palmitate, which contains a paltry 0.8 mg of palmitic acid.

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.