DEAR DR. BLONZ: Forgive the basic nature of this question, but what is the difference between a vegetable and a fruit? Also, I am interested in becoming a Certified Dietary Manager. How would I go about this, and what are the requirements? -- R.K., Indianapolis, Indiana

DEAR R.K.: A vegetable is an edible part of a plant that has a soft stem. These parts can include leaves (such as lettuce), roots (carrots), bulbs (garlic), stalks (celery), seeds (peas), tubers (potatoes) and flowers (cauliflower). A fruit is the mature ovary in a flowering plant: the fleshy part of the plant that contains the seeds. This means that tomatoes, eggplant, peppers and squashes are technically fruits, even though they are commonly thought of as vegetables.

There was actually a Supreme Court decision in 1893 stating that a plant part typically eaten with the main course was a vegetable, while a plant part typically eaten as an appetizer or dessert was a fruit. (The clarification was sought by a tomato importer looking to avoid vegetable tariffs by classifying his wares as fruit.) I wonder what those justices would say if they had a chance to savor today's cuisines, many of which make use of fruits throughout the meal.

As for your interest in becoming a Certified Dietary Manager, there are a number of resident and correspondence schools that offer training. After that, gaining and maintaining certification means meeting certain career requirements and passing a nationally recognized credentialing exam. For more information, check the site for the Certifying Board for Dietary Managers: cbdmonline.org.

DEAR DR. BLONZ: What is maltodextrin made of? I have called a soup company, two cereal/bread companies and two nutrition stores, and no one knows. I ask because my grandson is allergic to barley. We associate the word "malt" with grains, so we have omitted any product with maltodextrin from his diet, just to be safe -- and it's in a lot of products. I am hoping you can tell me exactly what it is. -- M.S., Sun City, Arizona

DEAR M.S.: Maltodextrins are easily digestible carbohydrates made from starch. The starch is cooked and then broken into smaller pieces -- similar to what happens when starch is digested. As additives, maltodextrins serve as texturizers or flavor enhancers. According to FDA regulations, manufacturers should use use corn, potato or rice as the source of the starch for any maltodextrins used in foods. Note that this may not be the case for maltodextrin used in medications.

Where allergies are involved, it is best to use caution; even though there are regulations, there is no guarantee that a particular manufacturer won't use a different source for its starch. For any specific products your grandson might consume, you should consider contacting the manufacturer and requesting further information about their maltodextrin supplier.

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: There are a number of weight-loss teas at my drug store, and I was wondering which, if any, are worth consideration. -- S.C., San Jose, California

DEAR S.C.: As a basic concept, consuming liquids with (or before) a meal can help you feel fuller, and can therefore cut down the volume of food you eat. While many claim to have special metabolic powers, "weight-loss teas" usually rely on this most natural phenomenon to accomplish their goal.

Some such products might include herbal diuretics, such as couch grass, buchu, dandelion, uva-ursi and butcher's broom. The taking of a diuretic tea can decrease the total amount of water in the body, which will impact the numbers on the scale. But it is only water you are losing, not excess body fat. What's worse, it tends to be a short-term effect, with the water weight usually returning once the regimen is stopped.

Tea is a great beverage, and we are learning that some of the compounds found in green, black and oolong teas offer health benefits. That should be the motivator for drinking it -- not the promise of weight loss. Dramatic claims of success should be viewed with great skepticism.

One product I recall came in a package that displayed a slim woman on the front. The literature indicated that drinking the tea would facilitate the shedding of unwanted weight, but the product was nothing more than a plain black tea of modest quality. If you looked inside the package, there was a piece of paper that explained that you had to eat less and exercise more for the weight-loss plan to work. What a novel approach.

DEAR DR. BLONZ: Have you written about noncaloric sweeteners such as stevia and sucralose? Some of my friends are concerned about the safety of these sweeteners. -- S.S., Portland, Oregon

DEAR S.S.: Sugar substitutes provide few or no calories and have minimal effect on blood sugar, which is a plus for people with diabetes. Then there is the fact that they do not contribute to tooth decay. But while a sugar-substituted dessert, for example, succeeds in putting fewer calories on the plate, there is no reliable evidence that it works as a weight-loss strategy.

A paper by Richard Mattes in the 2009 American Journal of Clinical Nutrition reported that the addition of noncaloric sweeteners to diets posed no benefit for weight loss, or reduced weight gain, unless accompanied by energy (calorie) restriction.

I refrain from encouraging the consumption of noncaloric sweeteners -- not because they are necessarily dangerous, but because I don't encourage seeking out excessive sweetness. The Berkeley Wellness letter has a simple and straightforward piece on the various options: tinyurl.com/zxwf6zs.

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 see articles on the benefits of "folate," but the nutrition and supplement facts panels only list "folic acid." Is folate the same as folic acid, or is it something different? -- T.T., Dallas, Texas

DEAR T.T.: Folic acid and folate are essentially the same active compound. Throughout its history, this vitamin has gone by many different names, including Wills factor, anti-anemia factor, PGA, vitamin M, vitamin Bc, factor R, SLR factor, vitamin U, factor U, vitamin B9, vitamin B10 and vitamin B11.

The different names can be explained by the fact that various laboratories were doing research on the same substance at the same time, and many were working on related compounds. There was a level of competition to discover essential compounds, and very little information sharing. Scientific prestige and naming rights were a side benefit to the individual or lab whose findings stood the test of time.

"Folate" is a generic term referring to a family of related compounds, the simplest of which is folic acid. You can think of the folates as folic acid with a side-chain component attached. In nature, it is active in metabolic reactions, and often referred to as folate. When spoken about as a nutrient, or when listed on a product label, it is called folic acid.

Whatever you want to call it, folic acid is a key compound in human nutrition. An inadequate intake of this nutrient is associated with a number of different ailments, including heart disease and certain birth defects. But you don't need megadoses to avoid these problems; one can get all the folate they need from a healthy diet. Good sources include leafy greens, organ meats, legumes, orange juice, beets, avocado and broccoli.

DEAR DR. BLONZ: Does pressure-cooking vegetables deplete their vitamins tremendously? -- E.R., San Jose, California

DEAR E.R.: All forms of cooking deplete nutrients to some degree. The actual nutrient losses during cooking depend on a number of factors, including temperature, cooking time, type of food, size of the food pieces and how much water is used (if any). With all these variables, the amount of loss will vary with the type of nutrient.

Cooking water, if discarded, will deplete some of the water-soluble vitamins. Heat, regardless of its source, can affect the fat-soluble vitamins, vitamin C and thiamin. The most stable of the nutrients are the minerals. Unless a large amount of water is used to cook a food that has a small particle size, and that water is then discarded, these nutrients will remain in the finished product.

Because cooking in a pressure-cooker typically uses less water and shortens cooking times, more of the nutrients will remain.

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.