DEAR DR. BLONZ: In my new apartment, I am living with a group that primarily eats raw foods. Their explanation is that "cooking removes the vitamins and minerals." These are my friends, so while I detect a slight bit of sanctimony, there is no serious rejection of the fact that I am an omnivore. Is eating nothing but raw foods, or even mostly raw foods, a good idea? One of my roommates says her new diet is really helping her lose weight. What are the pluses and minuses? -- S.T., Oakland, California

DEAR S.T.: Diets that strictly limit what you can eat can result in weight loss simply because you are paying closer attention to the foods you select. When you stick to raw, you definitely limit the types and amounts of foods you can eat. As for whether a raw food diet is a good idea, it depends on how it is done.

First, let's add some perspective to any blanket statement that cooking removes vitamins and minerals. Minerals are not affected at all, and while the levels of a few vitamins are reduced by heat (notably vitamin C, thiamine and folic acid), most are not affected. Cooking can actually help make other nutrients more bioavailable. Proper cooking also makes certain foods easier to digest. The idea that cooking destroys certain vitamins is not a serious issue if the food involved is not the main source of that nutrient. We get our vitamin C, for example, from fruits, not from cooked foods. Cooking can help make foods safer, helping to destroy foodborne organisms as well as some natural toxicants.

There is absolutely nothing wrong with eating raw foods. It can be an exciting way to eat, but it is not something that should be embraced blindly. It takes information and effort to do it correctly, as the body still requires a full complement of nutrients.

DEAR DR. BLONZ: I am in my 30s, with two children, and I have been taking multivitamins for most of my adult life. My mother has just been diagnosed with osteoporosis, and I want to add 1,200 milligrams of calcium to build my bones before I start to lose them. Is there a best time of day to take calcium and multivitamins? At present, I take mine after breakfast so I can flush out the excess vitamins with water throughout the day. -- T.M., Eureka, California

DEAR T.M.: There is definite wisdom to building bones during the first decades of life while the door is open. If you are going to take a calcium supplement based on calcium carbonate (the most common type), it is best to take it with or after a meal. Don't take more than 500 milligrams at a time, as this is about as much as your body can handle at once. Also consider calcium-rich foods, such as yogurt, or calcium-fortified beverages, such as orange juice.

Your multivitamin should include vitamin D, an important nutrient for bone health. Experts are now recommending up to 1,000 IU daily for adults. An active lifestyle, with weight-bearing exercise, plays a big role in building bones. It tells your body that your bones are needed, and the body responds by keeping them strong. There is a more detailed discussion of calcium at tinyurl.com/866w4sa.

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: 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.