DEAR DR. BLONZ: If one has a good diet (low in red meat, sugar and fat; high in fruits and vegetables), is it necessary to take a multivitamin? My doctor claims that food is no longer as nutritious as it once was because of soil depletion, so we should take supplemental vitamins and minerals. Do you think this is true? -- H.H., via email

DEAR H.H.: I am skeptical of your doctor's statement. I find the "soil-depletion" argument to be very misleading. Fruits, vegetables and grains, whether grown organically or through conventional methods, require sunlight, water and nutrients -- including nitrogen, phosphorous and potassium -- to develop. The soil must contain the plant's essential elements and if one or more is not available in sufficient amounts, either the plants won't grow or they'll fail to develop normally (and it's unlikely they will ever make it to market).

A plant can absorb minerals from the soil even if it does not need them. For example, foods grown in selenium-rich soil are likely to contain more of this mineral than the same food grown in selenium-poor soil. A plant's mineral content can also vary according to weather conditions, the amount of time it has been allowed to mature and when it's harvested during the growing season.

The idea of "vitamin-depleted" soils makes even less sense. Plants do not get their vitamins from the soil; they are synthesized within the plant itself. The amount of a particular vitamin found in a fruit, vegetable or grain is determined by the plant's genes, not by the amount of this nutrient in the soil. After harvest, vitamin content can decline over time and some vitamins are destroyed during cooking.

It then follows that there isn't really a specific area of the country (or world) where a person can be sure that the fruits and vegetables will be the most nutritious. Variety is key wherever you live, and we are blessed with a transportation system that brings us food from many regions.

As for whether you think it is necessary to take a supplement, I think that is a personal decision based on your diet. I find nothing wrong with taking a multivitamin, but that in no way should be thought of as a substitute for a healthful diet based on fruits, vegetables and whole grains. I like the image of the diet as a musical composition. Whole foods represent a symphony orchestra of nutrients and phytochemicals, all working together. A supplement, by contrast, can be thought of as providing only a few of the instruments.

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 drink milk daily -- sometimes nonfat, sometimes 1 percent or 2 percent. I was recently told that I am heading toward Type 2 diabetes, and when checking the contents on the milk cartons, I noticed that there were 14 grams of sugar per cup in the 1 percent milk and 15 grams in the nonfat milk. Does this mean "sugar" as in "sweet sugar"? How does this relate to diabetes? -- L.W., via email

DEAR L.W.: All sugars are carbohydrates, but not all carbohydrates should be thought of as sugars. Your question relates to the common confusion that "sugar" always refers to "table sugar," the white granular sweetener that's also called sucrose.

From the labeling standpoint, "sugars" refers to the sum of all the single and double sugars present in a particular food. Glucose, fructose and galactose are common single sugars, and a double sugar is when you have two single sugars bound together. For example: Sucrose is a double sugar made up of glucose and fructose, while lactose -- found in milk products -- is a double sugar made up of glucose and galactose. Other common sweeteners include corn syrup (all glucose), high-fructose corn syrup (corn syrup with some glucose enzymatically changed to fructose) and honey (a 50-50 mixture of unbound glucose and fructose).

Glucose is the main form by which carbohydrates travel through our bodies, and when carbohydrates are eaten, they tend to be converted to glucose, usually by the liver (assuming they weren't in the form of glucose to begin with). The blood sugar level, or blood glucose level, is the measure of glucose in our bloodstream. When in good health, the human body has a series of controls designed to keep blood sugar in a defined range.

Insulin, produced by the pancreas, is the hormone that keeps our blood sugar level from getting too high. A rise in blood sugar, such as that typically found after a meal or a sugary snack, triggers the release of insulin. This is the signal for glucose to be removed from the blood and turned into fat. Type 2 diabetes occurs when the pancreas is unable to produce sufficient insulin to do the job.

Different sugars and sweeteners affect this process to varying degrees and at various speeds. Getting back to your question: Lactose should not be considered a "sugary" sugar because it has much less of an impact on the speed at which it raises blood sugar, compared with an equal amount of sucrose.

Excess sweeteners do not cause diabetes, but sugars, carbohydrates, insulin and diabetes are closely connected. Thus, those at high risk for developing diabetes are advised to limit their intake of single and double sugars. Having soda and/or high carbohydrate snacks are particularly troublesome for these individuals, especially when consumed on an empty stomach. Excess body weight is a major factor increasing the risk of Type 2 diabetes because the body's sensitivity to insulin decreases as weight increases. The flip side is that those with extra weight who have been told they are at risk for Type 2 diabetes can see that risk decrease, or even disappear, with weight loss. For more information on diabetes, check the National Institutes of Health page: tinyurl.com/8kfow

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 daughter has been having heavy periods, and she also has iron-deficiency anemia. She told me she takes oral contraceptives, but these do not seem to be helping much. What iron supplement would you recommend? -- N.N., Portland, Ore.

DEAR N.N.: Heavy periods are not unusual, especially in teens who are not yet ovulating regularly and in women approaching menopause. Having said that, I am not a medical doctor, as you know, so keep in mind that other factors can be involved. If your daughter routinely experiences heavy periods, especially those that last longer than a week, it would be wise to have her check with her physician or gynecologist. Do this before you resort to iron supplements.

As for iron, the most efficient way to get it into the body is through food. The body does not efficiently absorb dietary iron, the one exception being the heme iron that is present in meats. Assuming she is not a vegetarian, a reasonable first step would be to include lean meats in your daughter's diet.

In terms of supplements, iron comes in two forms: ferrous and ferric. Of the two, the ferrous form is better absorbed, and it tends to be less irritating to the stomach.

The difficulty with iron supplements is that iron doesn't dissolve easily, and it must be in solution before it can be absorbed. Studies have shown iron supplements tend to work best when they are taken with a glass of orange juice on an empty stomach. This can be a problem for some, however, because iron supplements may irritate an empty stomach.

Whenever your daughter takes her iron pills, try to include acidic foods such as citrus juices or tomato sauce. Even a vitamin C (ascorbic acid) pill will help. The presence of the acid helps to get the iron into solution and maximize the amount your body will absorb.

As all this being said, I want you to be very aware that excess iron intake can be dangerous. Do not start your daughter on iron without first consulting her physician, and make sure that you keep all supplements out of the reach of children.

DEAR DR. BLONZ: What is the difference between a vegetable and a fruit? Also, I'm interested in becoming a certified dietary manager; what are the requirements for this, and how would I go about getting certified? -- S.F., Richmond, Calif.

DEAR S.F.: A vegetable is an edible part of a plant with a soft stem, including leaves (lettuce), roots (carrot), bulbs (garlic), stalks (celery), seeds (peas), tubers (potato) and flowers (cauliflower). A fruit is the mature ovary in a flowering plant -- that fleshy part of the plant that contains the seeds. This means that tomatoes, eggplants, peppers and squashes are technically fruits, even though they are commonly thought of as vegetables.

As for your interest in becoming a certified dietary manager, there are a number of resident and correspondence schools for this field. Once you have the credentials, there are career requirements and a nationally recognized credentialing exam involved with gaining and maintaining certification. For more information, contact the Association of Nutrition and Foodservice Professionals (anfponline.org).

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.