DEAR DR. BLONZ: My workdays last until the early evening and I don't really have time to cook. This has been my schedule for more years than I want to think about, but as a result, I have never taken the time to learn how to cook. I usually eat out, or rely on single-serving entrees to make at home. My diet is not bad, but it is certainly not where it should be. I haven't really suffered for it yet, as I am in good health. How much will I be helping things by adding a dietary supplement or a vitamin-fortified drink to my daily regimen? -- A.M., San Jose, California

DEAR A.M.: Your question goes to the heart of what nutrition and good eating are all about. The short answer is that it's unrealistic to think that supplements or a vitamin-fortified drink can capture all the goodness that healthful whole foods have to offer. They can't transform a marginal diet into a good one. However, it is not unreasonable to take multivitamin/mineral supplements along with a whole-food fruit/vegetable juice drink.

You will still need to make good choices with the foods you eat. The healthfulness of eating fresh fruits, vegetables and grains has been verified by epidemiology, the science that investigates the connection between people's lifestyles and their health.

The fact that good eating leads to good health is certainly not news. What's relatively new is the technical ability to discover the identity of the beneficial compounds. The essential nature of a nutrient gets discovered when its absence from the diet gives rise to a deficiency disease.

I like to think of whole foods as a symphony of healthful compounds that work together like the instruments in an orchestra. If you rely on supplements, the music gets written by the supplement company and you only get the ingredients that tickle the fancy of the supplement makers. Contrast this with a whole food, where nature has written the musical score: The combination of components has been perfected over millennia to give the plant its best chance for survival and reproduction amidst the various environmental insults that might come its way.

This being said, there are many excellent single-serving entrees in stores, and you can find restaurants that serve healthful foods on a takeout basis. Keeping a supply of healthful snacks in your desk can also be helpful. Juicing can provide a way to include whole foods in a more convenient form. But you should at least consider making the time to take a basic cooking class. It is not that difficult, and it will open up a world of possibilities, such as learning how to prepare and store multiple portions of a meal. You state that you haven't, as yet, suffered because of your dietary habits. Life, however, is a cumulative affair, so why not take this opportunity to make a few positive adjustments?

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: Is there any valid concern about soy products affecting thyroid hormones? I need to take them, and have read that soy can cause problems. -- K.K., Chicago

DEAR K.K.: Thyroid hormones regulate the metabolism of every active cell in our bodies. If, for any reason, a person does not produce a sufficient amount of thyroid hormone, they can be given a medication to stimulate increased production by the thyroid gland, or they can receive a replacement for the hormone itself. (A thyroid deficiency can be diagnosed by your physician with routine blood tests.)

The essential element iodine plays an integral role in the synthesis of thyroid hormone. Isoflavones, a class of phytochemicals found in soy, have an ability to make iodine less available to the body.

Does this mean that having soy could be a problem for you? There are a couple of studies I like to turn to on this topic. The first is from the March 2007 issue of the Journal of Medicinal Food. This study reported that adding soy protein isolate, at a level of 9 milligrams of soy isoflavones per 10 pounds of body weight, did not significantly affect the thyroid function in a population that had an adequate iodine intake. (Isoflavone content can vary from product to product, but 1 cup of soy milk contains about 20 milligrams of isoflavones. The amount in this study would be the equivalent of 2 quarts of soy milk per day for a 180-pound person.)

Next we have the June 2008 issue of the Journal of Nutrition, which contained a review article on soy protein, isoflavones and thyroid function. This paper concluded that soy may reduce the efficiency of thyroid hormone function due to an effect on iodine utilization, but it does not appear to be a problem if soy is consumed as a reasonable part of a mixed diet.

There could be a concern with infants and children if soy products represent a large proportion of their diet. Regarding iodine, the Daily Value is 150 micrograms. There is additional information on iodine at tinyurl.com/27g35fq.

Be sure to follow the directions that came with your thyroid medication, as some need to be taken on an empty stomach to avoid potential interactions with foods, dietary supplements or other medications like antacids. Consult your family physician or a pharmacist if you have further questions.

DEAR DR. BLONZ: How many days after it is opened can sour cream be safely eaten? -- G.T., San Diego

DEAR G.T.: Assuming it was refrigerated properly and opened before the freshness date stamped on the carton, your sour cream could last from one to three weeks. When it's being used, the container should be resealed and returned to the refrigerator after any contents are removed; the fewer the openings, the better. Avoid returning leftover portions to the container, and use a clean utensil every time you take some out. These are general guidelines. It is outside our control whether the product was refrigerated properly along the way from production to your store.

You should toss the product if you find any strange growth or pinkish color, off flavors or odors. Be alert if you begin to discover variability in the quality and shelf life of refrigerated goods from a particular store; there may be issues with that store's equipment or handling practices.

In general, a grocery run to purchase refrigerated/frozen foods should be the last errand before returning home, in order to minimize these foods' time away from the fridge, and cold foods should be unloaded and stored promptly upon arrival home.

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: Please provide some background about the use of chicken soup as a cold remedy. -- M.M., San Francisco

DEAR M.M.: Chicken soup has been used for generations, but a tradition can only go so far if it doesn't deliver. There is science here, but it will help to first understand what happens when you get a cold.

The immune system goes on the attack whenever it detects that a cold virus is attempting to take up residence in the upper respiratory system: the nose, sinuses and throat. A battle ensues, with one side effect being the inflammation that causes swelling of the mucous membranes lining the nose and throat.

At first, the immune system gets trounced, but over time, it learns to make the elements needed to squelch the invading virus. This can take hours, a few days, a week or longer, all depending on the tenacity of the virus and the state of your immune system. The "common cold" normally causes congestion, a runny nose, sore throat, a minor cough and a headache. If the virus persists and spreads down to the lungs, there is an increased risk of laryngitis (inflammation of the larynx/voice box), acute bronchitis and even pneumonia.

Stuffiness and discomfort are side effects, and they don't help the healing process. Congestion actually slows things down; if you rid yourself of the nasal secretions and mucus, you assist your immune system by allowing it to focus on making the weapons to win the battle. Blowing your nose is one obvious step, but care must be taken not to inadvertently force the bad stuff deeper into your sinuses (more info at tinyurl.com/pnfhjcn).

A group of physicians at Mount Sinai Hospital in Miami found that chicken soup was able to help clear the congestion that often accompanies a cold. This was discovered using a controlled experiment that measured the velocity with which mucus congestion was cleared through the nasal passageway. Dr. Irwin Ziment, a pulmonary specialist at the University of California at Los Angeles, attributed some of the soup's powers to the fact that chicken soup contains the amino acid cysteine, which is chemically similar to acetylcysteine, a prescription medicine used to combat congestion.

A cold is not the only instance where chicken soup can lend a hand: It can also help with asthma, where there is a narrowing in the bronchial tubes that carry the air in and out of the lungs. Coughing and mucus production can accompany the labored breathing of asthma, and one of the aims of therapy is to open up the airways and clear the lungs. Anything that helps move the mucus up and out of the body would certainly help.

Dr. Stephen Rennard at the University of Nebraska reported that chicken soup's effect might be due to its ability to block the inflammation and congestion caused by the movement of white blood cells (neutrophils) in the windpipe. In his experiment, the medicinal effect wasn't noticeable until the chicken soup was made with carrots, onions, sweet potatoes, turnips and parsnips.

Chicken soup doesn't have the same abilities as a modern antibiotic, but its powers are more wide-ranging, in a way: Antibiotics are only effective against bacterial infections, whereas soup can aid congestion brought on by either bacteria or viruses (like colds).

When thinking of making chicken soup, there are plentiful recipes to choose from. The basic recipe involves putting pieces of chicken (cooked or uncooked) into a large stock pot, then adding a couple of carrots, a large onion, a few stalks of celery, salt, pepper and enough water to cover. Then turn on the heat. Mimi Sheraton, in her book "The Whole World Loves Chicken Soup" (Warner 1995), supplies over 100 recipes from every corner of the globe.

With chicken soup, you get a satisfying, low-calorie dish that gives your body needed hydration and a potential vehicle for vegetables, protein and fiber. All this, along with an ability to help your body overcome that unwanted visitor. Not bad.

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.