Dear Dr. Blonz: I wanted to comment about the column you wrote on stomach upset from taking supplements. I, too, need to watch these. I learned to take them right before the meal, not after. This way the pills are not sitting high in my stomach causing great discomfort. I also do better with tablets than capsules. Capsules seem to feel like they get stuck. Interestingly, I have no trouble eating food, including fat and meat. Indigestion is very rare for me. If it does happen, I just pop a few papaya tablets. Just FYI. -- E.

Dear E: It helps to appreciate that the body doesn't really "know" from dietary supplements. After we swallow supplementary vitamins and minerals, for example, they enter the digestive tract and come in contact with its absorptive surfaces. This is a process that will take considerably less time when the supplements are consumed on an empty stomach. With a meal, nutrients enter gradually, but with a supplement on an empty stomach, the constituents can end up on the absorptive surfaces and in our bloodstream at a more rapid pace. From the body's perspective, the physical (supplement) objects and the increased vitamins and minerals get read as an indicator that it has just eaten. Our digestive motor kicks into gear as the entire digestive system gets cranking to process and absorb the full meal. For some, this may contribute to discomfort. While there may be exceptions, this explains why it's reasonable to take such products with food; either right before, with or after we eat.

DEAR DR. BLONZ: I know there are concerns about mosquitoes and the viruses they might carry. Over 20 years ago, I was advised to take 100 milligrams of vitamin B1 twice a day. Believe me, it has worked. I have told many people about this, and it has worked for them. -- B.N., Los Angeles

DEAR B.N.: Definitely wonderful to become unattractive to mosquitoes. There are anecdotal reports that some are able to achieve this using vitamin B1 (thiamine), but independent research has failed to confirm that this works with any degree of reliability. Scientists at the University of Wisconsin, Madison tested vitamin B as a home remedy against mosquitoes and published their results in the June 2005 issue of the Journal of the American Mosquito Control Association. They found individual variability but the bottom line was no reliable effect as a repellent. Great if it works for you, even better if it also works for your friends. But I do have concerns about recommending a megadose of a nutrient without more substantiation. The daily value (DV) for thiamine is 1.5 milligrams, so you are taking 67 times what your body requires. (Read more about thiamin at tinyurl.com/zn8ogbf.)

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 am 70 years old, in good health and hope to stay that way. I tend to get at least five or six servings of fruits and vegetables each day, and a lot of grains. I also take a multivitamin that contains between 100 percent and 200 percent of the recommended value of everything. Most of the vegetables I eat (cauliflower, broccoli, carrots, celery and lettuce), and a lot of the fruits, are raw. Is that good, bad or indifferent? I take my vitamins with breakfast; is that OK? I am at the top end of the normal bracket for cholesterol, so I am very careful with fats. I haven't been active recently due to an ankle condition that has finally healed, so I am anxious to get moving. -- J.D., Chicago

DEAR J.D.: This all sounds like you are doing your body a solid. Having your vegetables raw is neither good nor bad; having them is what's most important. The way they are prepared is all a matter of taste. It is best to take a supplement with a meal, but the choice of meal is up to you. What you are doing with your diet sounds good to me, and staying as active as possible will also help your cholesterol. Touch base with your doctor before you start up again.

DEAR DR. BLONZ: I read that acid is important for the absorption of iron. What acid in the body absorbs iron? How exactly does the iron work once it is absorbed? -- J.M. Seattle

DEAR J.M.: It is not an acid that is at play with the absorption of iron. The body produces an iron-binding protein that is released in the digestive tract. Its job is to grab on to dietary iron and help it through the absorption process. The amount of the binding protein present tends to reflect the body's need for iron.

The connection with "acid" that you saw probably relates to the fact that iron needs to be in solution (dissolved) before it can be absorbed, and iron is more soluble in an acid solution. From a food standpoint, acid foods might include tomato-based products, foods that contain vinegar (acetic acid), orange and other citrus juices, or vitamin C supplements (ascorbic acid).

There is one exception to the iron/acid pairing, and that is a form of iron found in meat, fish, eggs and other animal products. This type, called "heme iron," is absorbed at a much more efficient rate and doesn't require acid. Other iron sources include enriched cereals and breads, nuts, seeds, legumes, dried fruits, and dark-green leafy vegetables.

Iron, regardless of where it comes from, is used in a number of enzymes, but its main use is as the focal ingredient in heme, which is an oxygen-carrying substance. Perhaps this is why iron that is already incorporated into heme has an easier time being absorbed.

Heme becomes hemoglobin inside the red blood cells, and there it carries oxygen from the lungs to metabolically active cells in our body. The cells use the oxygen, giving off carbon dioxide as a waste product. The hemoglobin then carries the carbon dioxide back to the lungs, where it can be exhaled in exchange for fresh oxygen that is picked up for a return trip to the cells.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 eat well and have a pretty active lifestyle. I take a daily packet of multivitamins and minerals -- nothing fancy or excessive, just a small group of pills that should provide 100 percent of the body's needs. My husband is also taking this product; it is our form of "insurance." About four or five months after we started them, my husband was complaining of nausea an hour or two after taking them (even though he made sure to take them right after breakfast). He discontinued them, then tried them again a couple of weeks later and had the same problem. Is there a particular vitamin or mineral that could be doing this? He is less inclined than I am to eat fruits and vegetables, so I want him to take some sort of supplement. -- J.M., New York

DEAR J.M.: Your obvious priority is to focus more on what's not on his plate, than any side effect of what is in those packets. The tone of your letter would suggest that this may be the topic of an ongoing discussion, and I encourage you to keep up whatever diplomatic pressure you can to get his diet and lifestyle on a healthful footing. That represents the foundation of good health, and supplements should be thought of as extra.

That obligatory sermon delivered, some individuals can experience mild nausea or some other untoward reaction after taking a multivitamin supplement. It is not that common, and there may not be one particular nutrient responsible -- it could be the fact that you are taking a number of pills and capsules all at the same time. When they dissolve together, they can potentially irritate the stomach.

It is good that you are taking them with a meal, and the more complete the meal (protein, fat and carbohydrate), the better. If breakfast is a small meal in your house, you might consider taking your supplements with a more substantial meal, or splitting the contents of the packet between two meals.

I also encourage you to contact the manufacturer and tell them of your experience. And there is always the option of switching to another product.

DEAR DR. BLONZ: Last year, you advised me to seek advice from a gastroenterologist. After tests from A to Z, I was diagnosed with irritable bowel syndrome (IBS). It's been a long and difficult journey. I now use IBS hypnotherapy tapes, developed in the U.K. where they have taken IBS very seriously. Do you happen to have any new information on the subject? -- J.R., via email

DEAR J.R.: It is good to have an answer, even in the form of a diagnosis that you may not welcome. I don't have more information on IBS, but in addition to working with your gastroenterologist, you might consider joining a group such as ibsgroup.org. Be aware that such groups tend to be patient-led; while they can be empowering, be sure to exercise care with any advice given. This means consulting with your physician to check that any new action, however well motivated, won't counteract what you're already doing.

I remain hopeful that you will continue your travels down the road to better understanding and health.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.