DEAR DR. BLONZ: I made the shift to high-fiber, organic, whole-grain cereal with fruit for breakfast. But after a couple of days of eating the new cereal, I became violent, moody and so depressed I could hardly pick myself up and get on with the day. Things have settled down a bit, but the breakfast change is the only new dietary thing I can recall. Could my new breakfast have caused this reaction? -- B.C., San Jose, California

DEAR B.C.: Health, mood and well-being can be affected by a single element or a complex interaction of many. A coincidence of unrelated factors can give rise to fingers being pointed in the wrong direction.

When you do suspect that a certain food is the cause, the first thing to do, of course, is to stop consuming any suspect item(s). If the problem abates, you may think you have your answer -- and that may indeed be the case -- but that's not necessarily so; it could simply be that the problem was of short duration.

I recommend you contact a physician specializing in allergies 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 reactions you describe. Working with the health professional, you can decide whether it is appropriate to retry the suspect food, do some additional types of testing or to look elsewhere for clues.

Uncovering suspected food allergies is a bit of a detective game, and a knowledgeable approach is key. I have heard from many individuals who have written foods or nutrients off their menus based on hasty responses and faulty logic. Read more about food allergies and untoward reactions to food components at the website for the American Academy of Allergy, Asthma and Immunology: tinyurl.com/b8cnsr6. Also, check out this article on food allergies and intolerances in the Berkeley Wellness Letter: tinyurl.com/m425slg.

DEAR DR. BLONZ: Can you please tell me the nature of the fat in chocolate? The Nutrition Facts label lists its total fat, but what is the source? -- V., via email

DEAR V.: The fat in chocolate, called cocoa butter, is primarily made up of stearic acid (34 percent), palmitic acid (20 percent) and oleic acid (30 percent), with small amounts of other acids making up the rest. Both stearic and palmitic acids are saturated fats; oleic acid is the monounsaturated fat that is also found in olive oil.

DEAR DR. BLONZ: Is it true that black pepper is toxic, that it is not eliminated by the body and that it collects in the kidneys? -- L.A., Los Angeles

DEAR L.A.: There are compounds in black pepper (piper nigrum) that might pose a problem if crushed peppercorns were a big part of your diet, or if you had ongoing kidney disease. But there is no evidence that black pepper is bad for an otherwise healthy individual when used as a seasoning. The idea that something in black pepper collects in the kidneys is not consistent with information I have read.

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: What are your thoughts about liver as a food? We used to eat it every now and then, but stopped with the rise in concerns about cholesterol and food safety. There have been some changes in the demonic view of dietary cholesterol, so is it OK to indulge as long as it comes from a healthy source? -- H.S., Walnut Creek, California

DEAR H.S.: The liver is a rich source of many vitamins and minerals (see tinyurl.com/k3ju22s). It is also a major processing and detoxifying organ of the body. You could think of it as a transportation hub, with absorbed nutrients heading there to be processed and packaged so that they will be in the correct form when they reach their eventual destination. Many medications and foreign substances also end up in the liver, where they get broken down or inactivated in preparation for elimination from the body.

It is a remarkably resilient organ, with a healthy liver even having the power to regenerate itself. It has an undeserved reputation as the body's toxic waste dump, and while it does serve as a clearinghouse for unneeded or unwanted substances, the liver does not hold on to its products -- it works to ship them out. If, however, there is an ongoing exposure to a dangerous compound, it is likely that the liver will be in the midst of the battle to re-establish health.

For those in good health with an otherwise healthful diet, an occasional serving of liver should not be a problem. A healthful option is to opt for grass-fed organic beef, and pastured organic poultry. Another alternative is to seek out a provider with a stated philosophy of raising animals without hormones or feed additives. You can often find such providers at farmers' markets and natural food stores.

DEAR DR. BLONZ: Do you consider meats to be the best source of dietary iron? What are some other options? -- V.H., El Cerrito, California

DEAR V.H.: Red meats are definitely a prime source, mainly because the iron is in a highly bioavailable (easy to absorb) form. This being said, there are many non-meat sources as well, including apricots, oysters, spinach, legumes and raisins. Periodic use of cast-iron pans is another way to add iron to the diet. When acidic foods, such as spaghetti sauce, are prepared in cast iron, a small amount of iron dissolves into the food. The actual amount of iron drawn into food depends on the condition of the cookware; a cast-iron pan that's frequently seasoned with oil tends to give off less iron, although it will still provide some.

In any discussion of iron, it is important to remember not to overdo it. Excess iron can be dangerous. Most bodies do a good job of regulating iron, and there is a protein needed for iron absorption; less becomes available when the body's iron stores are full. There is, however, a serious genetic iron-storage disease called hemochromatosis that does not allow the body to rid itself of excess iron. There is an excellent discussion of this at the National Institutes of Health (tinyurl.com/95opbcj).

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: Thank you for your column on intestinal gas. There is one thing you could add that might be helpful next time the subject comes up: Some parasitic infestations cause chronic cyclical gas episodes.

As a Peace Corps volunteer in the 1960s, I was exposed to many African parasites, and brought at least one of them home. For the next 15 years, I was afflicted with periodic bouts of noxious flatulence, about two days every two weeks. I repeatedly sought medical help (and received lots of ineffective information) before I found a doctor who had experience with tropical ailments. He said, "I don't know what you've got, but Atabrine might clear it up." I took the Atabrine for a week, and it was over. Thus, with one bottle of pills, a 15-year social problem was ended.

Most likely, I learned afterward, the culprit was Giardia lamblia. This organism has become very widespread in the past few decades -- possibly due to folks like me coming home from Africa, then going backpacking in the mountains and woods.

Giardiasis is not particularly debilitating. After a single initial siege of sulfurous burping, the only long-term symptoms seem to be the periodic attacks of stinky gas. I suspect that lots of folks are living with giardia, and occasionally casually asking their doctor about it. Just as I did for a decade and a half, they are receiving suggestions to avoid beans, cabbage or processed meats. Since a bout of gas only lasts a couple of days, the "cure" seems to work, but the trouble will be back in a couple of weeks.

Atabrine, an older quinine drug, probably isn't used much anymore, but there are plenty of newer drugs that will clear giardia up quickly; the trick is finding a doctor who has experience with parasites. Since parasites in general are less common in the U.S. than in Africa, this can take a while. The worst thing that can happen is to get misdiagnosed and mistreated for something else. -- D.R., Orinda, California

DEAR D.R.: Your informative letter speaks to the necessity of seeking assistance from someone with expertise in the area of concern, and of giving your complete background to your health professionals. There is so much information available online, but that places the responsibility on us to be diligent in where and how we search. Stick with academic sites (ending with .edu) or others that rely on evidence-based medicine. I have a list of medical resources at blonz.com/med.htm that can serve as a guide.

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.