DEAR DR. BLONZ: I have been interested in taking niacin for my cholesterol but am concerned that it might be harmful. I get some pretty bad rashes when I take it, like an allergic reaction, but I can’t imagine that I might be allergic to a vitamin. Is this normal and safe? -- H.C., Berkeley, California

DEAR H.C.: Doubtful that you are allergic to niacin, which is indeed an essential nutrient. The daily value for niacin for adults and children (aged four or older) is 16 milligrams per day. What you are probably experiencing is appropriately referred to as a "niacin flush." This is nothing more than a dilation of the small blood vessels near the skin that can occur when a high dose of niacin is taken, usually about 10 times the daily value. It varies from individual to individual, and some can experience a “flush” at much lower doses. You can avoid the flush effect by lowering your intake of niacin, taking it in divided doses, or opting for an extended-release form. There are flush-free forms of niacin, such as nicotinamide or inositol hexanicotinate, but the evidence does not support these as having the same cholesterol-lowering effect. Niacin (also known as vitamin B3, or the related compounds nicotinic acid and nicotinamide) is required for normal cell metabolism and energy release from carbohydrates. Niacin also plays a role in the synthesis of hormones and DNA. Food sources include organ meats, poultry, seafood, nuts, green vegetables and legumes. For more on niacin and its use regarding cholesterol, check b.link/medlineplus54.

DEAR DR. BLONZ: I recently got lightheaded and blacked out. I have no idea why. Could it be from dehydration? Not enough salt? The reason I was not that concerned is that I am in good shape and I bike and run. I have had problems with heat exhaustion in the past. Just curious what you might think it was. I had been getting dizzy when I got up from sitting earlier in the day after a hefty workout. I got up and stood for a minute, and next thing I knew, I was on the floor. Not a big deal, I think I was out for only a few seconds. Any thoughts? -- W.R., via email

DEAR W.R.: I am not a physician, and I have no real handle on other health issues in your life; my advice is that such episodes need to be checked out by your physician. There can be risks in delay, so why take a chance? That said, there can be many explanations for an unexpected loss of consciousness. You have mentioned a few. It could have been a freak intersection of factors that ended up leading to a rapid drop in blood pressure (vasovagal episode). Staying hydrated is important, and if you tend to perspire heavily, it is reasonable to replenish fluids and lost electrolytes when exercising. Anemia is also a possibility. I encourage you to find out what is involved with your situation now, with the help of your doctor.

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: Cereals and fruit have been a part of my breakfast for decades, but about two days after switching to a new brand of cereal, I started to feel that I had become violent, moody and so depressed. I could hardly pick myself up off the floor. Of course, I stopped eating the cereal, and the symptoms did fade. The cereal is the only new food I can recall. Could this have caused this reaction? Any help would be greatly appreciated. -- S.C., Sacramento, California

DEAR S.C.: The first thing to do was to stop consuming any suspect item(s), but also to make a note of any novel experiences or exposures, including eating out, that occurred during this time. It is good that your problem went away, but the cereal, while reasonable to suspect, may not be the answer. It could have been any of a number of things, from something you ate -- including food poisoning -- to an insect bite, to a reaction to a medication you are taking. Given the nature of the reaction, it is in your best interest to do more checking. You don’t want to take on a food fear if it’s not responsible. Consider contacting your family physician or a specialist competent in the areas of allergy and immunology. Seeking assistance makes sense as it is never a good idea to experiment on oneself, especially when missteps might evoke the type of reaction you describe. If your health professionals believe that a food is a likely suspect, they can help you strategize whether and how to test suspect item(s) or to look elsewhere for clues. Uncovering suspect food reactions is a bit of a detective game, and a knowledgeable approach is key. I have heard from many individuals who have written foods or food components off their menu based on faulty logic. You can read more about food allergies and untoward reactions to food components at the website for the American Academy of Allergy, Asthma, and Immunology: b.link/food32. Also, check out the Food Allergy Network: www.foodallergy.org.

DEAR DR. BLONZ: Is it true that black pepper is very bad for you and that it is not eliminated by the body and collects in the kidneys? -- L.A., via email

DEAR L.A.: It is important to appreciate that nature represents a difficult environment, and successful plants will have evolved to produce a custom collection of phytochemicals to assure their growth and continued reproduction. Along these lines, there are compounds in black pepper (Piper nigrum) that might pose a problem, but only if an excessive amount of crushed peppercorns was a big part of your diet. Assuming there are no contaminants in the pepper, and that there is no individual sensitivity to its components, there is no evidence that black pepper is bad for you when used as a seasoning. The idea that something in black pepper collects in the kidneys does not jibe with any information that I have ever seen.

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: Our soccer-playing son has grown about four inches during this past year (he is now 12 years old), which has been fantastic. My concern relates to periods of muscular pain and pain on the soles of his feet while he plays. It is annoying, slowing him down a bit, but never to the point that he needs to stop. The coach is aware of the situation and encourages him to stretch and warm up before any practice or game. His diet is a concern as he does not make great food choices. What might you suggest? -- F.T., Hayward, California

DEAR F.T.: Rapidly growing adolescents can experience minor aches and pains as their bodies transition from "child" to "adult." It is good that his coach is aware of the issue, but you should also discuss your concerns with your family physician. It may be that the discomfort is nothing more than muscles and tendons that have become too snug for the more rapidly growing long bones. These types of "growing pains" are most often experienced at night, as that is when most growing takes place, but they can take place during the daytime as well, especially during and after the stress of his demanding exercise.

You mention the pain in your son's feet. Each foot contains 26 separate bones (one-eighth of the number in our entire skeleton), and there are a number of tendons that pass around the ankle to control the movements of the foot. It is possible that his pain could be a byproduct of his rapid growth. Stretching before a workout plus periods of rest during the game may be of help. Keep in mind, though, that whenever there is recurrent pain during growth involving the knees and legs, it is reasonable to have it checked by a physician. For foot pain, there is also the possibility of visiting a podiatrist. And let's not forget the obvious: A child's rapidly growing body can run through clothes and shoes quickly, so make sure that your son's shoes -- especially those soccer cleats -- are always fitting correctly.

As for your nutrition concerns, any period of rapid growth involves the creation of new body tissue, and that means a need for an ample supply of healthful foods to supply the raw materials to keep the process fueled and on an even keel. Good eating habits are very important, but they are often given short shrift during adolescence. At times, we, as parents, might wonder how our children are able to grow and remain in good health given what we see them eat.

There are limits to what a parent can accomplish during their child’s adolescence. Playing a parental-power card may backfire, as these are the very years during which children may have that urge to establish their independence. What you have been doing over the years can hold great sway, so set a good example and forgo any “do what I say, not what I do” approach. Adolescents take pride in seeing their bodies change and mature. You can foster healthful habits through tactful reminders that what they eat and how they take care of their body will help determine who stares back at them in the mirror. Go to b.link/teenagers50 for more on teenager nutrition from the National Institutes of 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.