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.

DEAR DR. BLONZ: We are entering the season where farmers' markets become loaded with fresh fruits and vegetables, and I wanted your take on juicing. Is it more healthful to eat fruits or vegetables, or to juice them? How about fiber, because you pretty much throw that away? -- T.T., Hayward, Calif.

DEAR T.T.: Farmers' markets are a great way to see what's in season, support local agriculture and get some walking in as well. In answer to your question, let me say that it is very healthful to consume lots of fruits and vegetables, period! Whichever way you choose will work in the big scheme of things.

Some advantages to eating fresh produce (without juicing) are that you get individual tastes, textures and an appreciation of how flavors differ between varieties, growers and throughout the growing season.

Another big plus is that it tends to take more time to eat the produce than to drink its juice -- an aspect that should not be discounted. It takes a while for the brain to get the signal that the body has had enough to eat, and when we rapidly eat until stuffed, we've usually had too much. Wolfing down a meal is not advised, whether the meal is a paragon of healthfulness or fast-food dreck. The slow enjoyment of a fresh fruit or vegetable keeps control in the loop.

Juicing, particularly if fibers are not present, can provide a load of sugars in easy-to-consume form. As with any eating, portion control needs to be exercised, but the flavors can be seductive. The great advantage of juicing is that it can provide a convenient way to include new varieties of fruits and vegetables in your diet.

As for juicers, there are three basic types: extractors, masticators and blenders. Extractors are the most popular type. They grind the food with a high-speed spinning dish that traps the pulp, and often have an ejector that deposits the pulp in a convenient bin. The masticator type of juicer "chews" up the food at a slower speed, then makes juice by mechanically pressing the ground-up mash against a screen.

Finally, there are specialized blender/juicers that grind the entire fruit or vegetable, pulp and all. This is the one type of machine that doesn't remove the pulp; as a result, juices from these machines retain the food's fiber. The tradeoff, however, is that the output can end up more slushy than juicy.

Price vary greatly among juice extractors, with the differing price tags -- from about $45 to well over $300 -- often reflecting the power and noise-dampening of the motor, the pulp capacity and the ease of cleaning. The masticators and blender/juicers tend to be in the $200 range.

There is really no "best" method; it's all a matter of taste and affordability. Be sure to sample some juice from the type of machine you are considering before you buy: Find a juice bar in your area, or arrange for a demonstration at the store where you are considering making your purchase. It is also essential that you know how a prospective model needs to be cleaned. If cleaning is a bother, the machine may sit crusty and unused.

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.