DEAR DR. BLONZ: Why is it best to get vitamins from food rather than from supplements? Does the human body make the distinction, and if so, to what extent? -- R.S., Boston

DEAR R.S.: A vitamin is the same whether it comes from food or from a synthetic formula. To the human body, it's a chemical that fills a need. My response would be different if you had asked whether getting nutrients from whole foods is better.

We now has effective methods to diagnose nutrition deficiencies, and much of this data comes from population studies. However, science has only begun to investigate how certain health or genetic issues might affect what is best for a particular individual. Interactions with medications, and even between nutrients and herbs, must be considered. (For more on drug interactions with supplements and herbs, see b.link/ejz74zb.)

Modern science has come a long way, but we are far from knowing all there is to know. The human body may not be able to distinguish between a particular nutrient from food versus the identical substance provided as a supplement, but nature's whole foods typically contain complementary substances that help the nutrient do its job most effectively. Thus, it is always best to get the entire team, which comes from a nutrient in its whole-food context.

DEAR DR. BLONZ: I work to have a whole-food diet, as you recommend. Still, when I recently purchased vitamin and mineral supplements, I noticed that my mineral supplement contains calcium amino acid chelate, and my vitamin supplement contains D-calcium pantothenate. Why is this calcium compound in my vitamin? I have read that too much calcium can be toxic, so I want to ensure that I'm not taking too much calcium if both products provide similar ingredients. -- S.T., Dover, Delaware

DEAR S.T.: In the same way that its chemical name, ascorbic acid, also refers to vitamin C, the compound known as vitamin B5 can go by its chemical name, pantothenic acid.

The calcium in D-calcium pantothenate is indeed an essential mineral, but it would be best to think of it as a "salt" of pantothenic acid made from two molecules of the pantothenic acid joined with one calcium molecule. When dissolved, the calcium and the pantothenic acid go their separate ways, leaving the B5 to be available as the vitamin. The amount of calcium is negligible.

To illustrate: Say you took the adult daily value of pantothenic acid (5 milligrams) as D-calcium pantothenate. This would add less than one-half of one milligram of calcium to your daily total for this mineral, which has an adult daily value of 1,000 mg. Anything, including calcium, can become toxic if taken in excess. However, there is no issue here.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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 know you're not a medical doctor, but I was hoping for some general guidance about the care my mother, who was diagnosed with thyroid cancer, is receiving. We are in a managed-care plan through my father's job, and I was hoping you might have some idea of how we could go about getting a second opinion to confirm her diagnosis and treatment plan. My friends have been telling me many different things, but my parents seem content with whatever the doctor says. Advice? -- F.E., New York

DEAR F.E.: I deeply sympathize with your situation. Getting a second opinion regarding diagnosis and treatment can be an important part of the approach to any complex medical situation.

Cancer is not a singular entity with consistent features. As such, the diagnosis of cancer can depend on interpretation of medical evidence, and indicators of any cancer's unique characteristics are not always clear-cut. Doctors can differ in their approaches; some are conservative, while others are more aggressive. And medical facilities can differ in their familiarity with and use of evolving technologies.

You should work with your parents to voice your concerns and verify that your mother's diagnosis and treatment strategy make medical sense. If you feel it is appropriate, raise the issue of getting a second opinion. Most physicians will respect the request for a different set of eyes to review a case, and insurance may cover it. If possible, find a cancer center or a university-affiliated teaching hospital, ideally with faculty who have researched the type of thyroid cancer affecting your mother. The National Institutes of Health provides information on finding cancer centers and doctors at b.link/y55yveu. In addition, check the American Cancer Society's Cancer Survivors Network at b.link/yxhhe8q for discussions from other patients who have been down this road. My best to you and your family during this difficult period.

DEAR DR. BLONZ: I learned in school that riboflavin in milk is destroyed by light. If that is true, why is milk sold in clear containers? Am I wasting my money by paying more for milk in opaque containers? -- S.T., Tulsa, Oklahoma

DEAR S.T.: Milk is a perishable food, and exposure to natural or bright fluorescent light can destroy a percentage of riboflavin (vitamin B2), vitamin C and vitamin B6 and, over time, encourage the development of "off" flavors. Light intensity, duration of exposure and time away from refrigeration will determine how much these nutrients are affected.

A healthful diet should include nutrients from many sources, so minor losses from one food should not negate the nutritional value of that food. That said, storage in an opaque container, such as a paper carton, seems to be best in preserving milk's nutrients, while clear glass -- while aesthetically pleasing, and recyclable -- is not. Always check the product's date to be sure you are enjoying fresh milk. (Read more on food product dating at b.link/cbsr87.)

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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 returned from a trip with a cold. Two close friends, who don't know each other, brought over their homemade chicken soup to help me recover. I recall my grandmother bringing it over when we were sick during childhood. Is there anything special about chicken soup for a cold, or is it the soothing of the warm liquid that does it? -- S.F., New York

DEAR S.F.: With winter comes cold and flu season, and many have the misfortune to succumb. I compliment your friends for offering homemade chicken soup. Not only does it help with its soothing warmth and taste, but it can also work with your body's immune system to help it gain the upper hand. History and science help make this case.

Chicken soup was noted as a remedy in ancient Rome, where Pedanius Dioscorides, Nero's army surgeon, wrote about its benefits in "De Materia Medica." In the second century, Greek physician Aretaeus of Cappadocia described chicken soup's use in treating respiratory disorders. Perhaps most notably, in the 12th century, Moses Maimonides, a prominent medical scholar, recommended chicken soup for colds, flu and asthma.

To understand the role chicken soup can play in fighting illness, it helps to review the sequence of events when a sufficient dose of the cold virus enters your upper respiratory system.

Recognizing a foreign microbe, our immune system reacts, assembling its team to isolate and defeat the virus. Inflammation is an element of the battle plan, which results in congestion and symptoms that include a runny nose, sore throat, minor coughing and headache. If the virus spreads to the lower respiratory tract, it can lead to more serious conditions like laryngitis, bronchitis or pneumonia. (Read more about the common cold at b.link/kuxxk6q.)

Congestion, while evidence of the immune system at work, can slow the healing process if it collects more rapidly than it can drain. Thinning and moving congestion out of your system can hasten recovery, so doctors recommend you stay hydrated, and will often suggest the use of an expectorant.

A classic study at Mount Sinai Medical Center in Miami found that chicken soup helps to clear congestion. Dr. Irwin Ziment, a pulmonary specialist at UCLA, attributed this to the amino acid cysteine found in chicken soup, which is similar to acetylcysteine, a medicine used to break up congestion. Chicken soup can also help some symptoms of asthma -- Maimonides recommended it because he found it helped clear mucus from the lungs.

Other research physicians, including Dr. Stephen Rennard of the University of Nebraska, reported that chicken soup might block inflammation and congestion caused by white blood cells in the windpipe. His experiment used a soup made with carrots, onions, sweet potatoes, turnips and parsnips, prepared by his wife, Barbara.

A basic chicken soup recipe involves cooking chicken in water with carrots, onions and celery. My personal recipe uses a roasted chicken to take advantage of its special flavor. Mimi Sheraton's James Beard Award-winning book "The Whole World Loves Chicken Soup" offers more than 100 chicken soup recipes from around the globe.

Chicken soup has a number of powers. Note that colds are caused by viruses, not bacteria, which explains why doctors resist prescribing antibiotics for colds. So, enjoy your chicken soup -- it would make your grandma proud.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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.