DEAR DR. BLONZ: What are your thoughts about milk as a food? You periodically make reference to it in its various forms, but there is so much on the web denouncing milk as a food to avoid -- especially for the elderly. It is something that I grew up with, but has the thinking now changed? -- B.J., Scottsdale, Ariz.

DEAR B.J.: The primary science-based reasons to avoid milk and milk products would include having an allergy to milk protein or a dislike of the possible side effects from the lactose carbohydrate found in milk. Those symptoms include gas or other digestive upset, usually when the milk or dairy product is consumed on an empty stomach. This latter reason would mainly apply to liquid milk, not so much to yogurt and cheeses, but even here, there are products with which problems from lactose can be limited or eliminated.

Some individuals might be consuming whole milk with already high-fat diets that lack sufficient fruits, greens, grains and fiber. In such cases, the fat contributed by the full-fat milk or dairy products could be a concern. This, however, is a balance issue, not a condemnation of milk.

Assuming you are not a vegan, in which case you would be avoiding all animal products, if you enjoy milk or dairy there is little in the way of objective reasons to stop eating them. I wouldn't call milk an "essential" food, but it does have much to offer nutritionally. There are many people spreading all sorts of twists on the "milk is bad" message, such as "cow's milk is meant for calves, not people," but these negative allegations have, thus far, failed to stand up to the light of science.

DEAR DR. BLONZ: How long can carrots be kept in the refrigerator without losing much of their nutrients? -- F.M., Oakland, Calif.

DEAR F.M.: Carrots are available in many forms throughout the year in most parts of the country. As a general rule, I would say that depending on the way they are kept, you should have a good week or two.

Carrots can lose sweetness as they sit, so inspect those sitting on the rack and avoid ones that are dried and cracked. Purchasing carrots with their greens intact provides a good indicator of just-picked freshness. Once purchased, you should remove the tops since they tend to drain water and nutrients from the carrot. This makes sense given the fact that the carrot we eat is actually the root -- the supplier of nutrients for the growing carrot plant.

Carrots store well in a refrigerator set no warmer than 40 degrees F. They should be kept in a sealed plastic bag or container. They will be at their nutritional and flavorful peak for the first few days, and then begin to lose crispness and nutritional quality -- slowly for the first couple of weeks, but then more quickly until they become limp.

Most of the carrots we get in the store are slightly immature, being picked that way to maximize tenderness and flavor. More mature carrots might have a more "woody" texture and although they might not taste as sweet, they can be kept for longer periods of time. In pre-refrigerator days, root crops such as carrots were kept in root cellars for up to six months. Sustenance was the main consideration in those times, and stored "woody" vegetables could always be incorporated into slow-cooked stews.

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 continue to read about fasting and cleansing and their ability to release toxins that have built up in the body. Is there a difference of opinion among professionals in nutrition about the release of toxins in this way? Do you see any potential here? -- S.E., Arizona

DEAR S.E.: The concept of the "release of toxins" during a fasting or cleansing routine is dubious. Many of the arguments are either theoretical ("I think it might work") or anecdotal ("some tried it and thought it worked for them"). To this, we add the fact that there is little if any data or evidence in the journals to support the efficacy of these procedures. As they should, science-trained professionals tend to reject concepts where there is a lack of objective evidence.

Some connect how they feel during fasting/cleansing as an affirmation that their body is casting off toxins. This can be misleading as the lack of food can cause these same sensations. Consider that the body's priorities undergo a massive shift when it stops eating. In some cases, symptoms of chronic ailments might abate, especially those that might be due to previous poor eating habits, food-related allergies or sensitivities. But there is no reason to assume that these feelings are due to actual healing or a removal of toxins.

There is an ongoing dynamic turnover of most cells in the body; they tend to be continually broken down and remade. While all this is going on, the body acts to eliminate whatever toxins it can. While it might seem reasonable to think that fasting might hasten the rate at which toxins are shed, the opposite might actually be the case. Some toxins get stored in the body's adipose (fat) tissue, and during a fast, the body's fat stores are used to supply needed energy. This can actually increase the toxins roaming around the body, but the rate at which the body detoxifies does not increase. When this happens, the body can experience untoward effects from the increasing blood levels of the noxious agents. And then, the lack of food might hamper the immune system at it attempts to detoxify and eliminate.

Some cleansing products claim that the toxins build up in the intestines and colon, and by using cleansing laxatives and stimulants, you force those stubborn toxins out of the body. Consider that the cells that comprise the lining of the intestines are shed periodically, which means that the lining of your intestine changes from month to month. This places on dubious footing the concept that caked-on toxins are able to hang around and wreak havoc with your health. It also casts doubt on the efficacy of the "cleanse."

If there is a potential benefit to these processes, it might be that they can serve as a jump-start to a lifestyle change. One could use a fast or a cleanse to, in effect, cast off the past and change to a more healthful lifestyle, physically, emotionally and spiritually. The fast or cleanse can serve as a time of contemplation, where one considers the status quo and redefines the new quest for a quality of life.

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: How dangerous are the nitrates that are in hot dogs, ham, sausages and deli meats? How do they differ from those found in vegetables? Are they all carcinogens that have to be actively avoided to reduce the risk of cancer? -- F.G., Berkeley, Calif.

DEAR F.G.: Your question involves both nitrates and nitrites; the two are related, but there are important differences.

Nitrites: Food processors use nitrites as preservatives in cured and smoked meat products such as bacon, sausage, smoked and deli meats. These are all meats that tend to be stored under refrigeration for a number of days, and without an appropriate preservative such as sodium nitrite, there's a relatively high risk of botulism -- an often-fatal food poisoning. Nitrites, themselves, represent a risk as they can form cancer-causing chemicals called nitrosamines. These compounds can form when a nitrite (either sodium nitrite or potassium nitrite) reacts with protein at a high cooking temperature. The principle here is that with the exception of freezing or high-temperature cooking, there's no safe way to protect against botulism in a low-acid food such as a cured meat.

Nitrates: Nitrates occur naturally in several vegetables including turnip greens, beets, celery, rhubarb, spinach, radish, parsley and lettuce. They represent less of a risk than nitrites, but a nitrate can be converted to a nitrite in the stomach. This means that nitrosamines can theoretically form in the stomach when you eat a nitrate-containing vegetable and a protein food at the same meal. The important difference is that antioxidant nutrients can help limit nitrosamine formation, and these nutrients, such as vitamin C, E or antioxidant phytochemicals, tend to be found in nitrate-containing foods.

By contrast, in cured meat products such as bacon or sausage, all the ingredients needed to form nitrosamines are in the same package and the nitrosamines can be formed before you eat. In weighing the relative risk from botulism against the presence of the nitrite preservative, scientists decided that if you're going to eat cured or smoked meats, the use of nitrate preservatives is an acceptable risk.

Because there is some risk involved, nitrite preservatives are not permitted in baby foods.

Although most smoked and cured meats contain sodium or potassium nitrite, you can find nitrite-free meat products either as locally made, short shelf-life products, or in the freezer case where the low temperature can effectively inhibit bacterial growth.

A prudent approach is to limit your intake of nitrite-containing cured and smoked meats. If you enjoy these foods, see if a nitrite-free brand is available. You could also look for a product that contains sodium ascorbate (a salt of vitamin C), sodium erythorbate or vitamin E; these antioxidants can help limit nitrosamine formation. Another option is to make sure you have antioxidant-rich foods at the same meal as the nitrite-containing meats. A salad with the meal, some peppers or vegetables on the sandwich, and fruits as dessert are all additions that could help blunt the potential risk.

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.