DEAR DR. BLONZ: There has been no clear clinical evidence that food causes behavioral issues in children. I am interested in your thoughts on this issue. -- R.D., Los Angeles

DEAR R.D.: The role of food allergies in childhood behavior remains controversial, but it is not unreasonable to at least consider this as a possibility when other avenues have been unproductive. It is essential, however, that one proceeds cautiously, calling upon a clinician experienced in this area.

One issue is that the connection between the behavior and the offending substance(s) might not be readily apparent. You have to consider what happens if the wrong substance is blamed, or if one simply turns to generalities, such as blaming all food additives. Such cases can give rise to changes in parental behavior that can then act as programming for the child: "You shouldn't eat that, it will make you sick." It can all turn into a march down an unproductive road with ever-growing limits placed on the child's ability to eat and enjoy life.

The ironic thing is that a parent might observe improvements in a child's behavior even if the wrong substance is identified. Such changes might take place because they are expected -- the essence of the placebo effect. You haven't accomplished much if the underlying problem was not allergy-related or if it was caused by an item not originally suspected. If the symptoms resurface, other foods or food categories might get added to the "banned" list, further restricting the child and the parents.

I raise this scenario to highlight the importance of a reasoned, systematic approach. Parents can assist the process by maintaining a diary of foods consumed and reactions observed; this aids the experienced health professional in compiling a list of the likely suspects for further testing.

Once suspects are identified, testing in a controlled clinical environment is essential to remove any possible bias from all concerned parties. A gold-standard often relied upon is the double-blind, placebo-controlled food challenge. I would encourage you to discuss this with a physician. I often refer people to an excellent review article, "Manifestations of Food Allergy: Evaluation and Management," which appeared in the January 1999 issue of American Family Physician.

DEAR DR. BLONZ: One of my favorite times of year is when the new crop of potatoes comes to the market. My question has to do with the nutritional value of these fresh potatoes. I checked the USDA database, which says that a medium-sized baked potato, or a similar amount of French fries, is supposed to contain about 17 milligrams of vitamin C. You have mentioned that heat destroys vitamin C, among other nutrients. If this is the case, how can these "heated" potatoes still be a good source of vitamin C? -- J.J., San Diego

DEAR J.J.: The high heat involved in the preparation process does indeed destroy a number of vitamins, including vitamin C and thiamin (vitamin B1). That level of vitamin C does reflect a reduction from the amount in the raw potato. French fries will have a bit less due to their increased surface area.

A good source for any nutrient is one that provides between 10 and 19 percent of the daily value for that nutrient. An excellent source is one that provides at least 20 percent of the daily value. Seeing as the daily value for vitamin C is 60 milligrams, one serving of "heated" potatoes would actually be an excellent source.

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 recently went on a detox/cleansing diet routine, complete with a drink and pills, that was recommended by my close friend. I was able to drop almost 10 pounds in a few days. It was incredible until the intensive part of the routine was over, and the weight began to return within a week. Did I do anything dangerous to my body? Was there anything I could have done so that the weight stayed off? -- G.M., San Jose, Calif.

DEAR G.M.: The goal of losing "weight" can actually be a bit deceptive, because the number on the scale can vary for many reasons. More appropriately, the goal should be to reduce excess body fat. Some regimens can be very successful at taking off pounds, while failing to make any significant dent in our stores of unwanted body fat.

As the body's most calorie-dense material (nine calories per gram), fat is our main form of energy storage. Whenever the intake of calories exceeds the demand at the moment, all the excess, whether from carbohydrate, fat or protein, gets converted to fat and then shuttled away to storage. That means that at mealtime, the flow is toward storage, while between meals the flow is from our fat stores to the working muscles and organs.

A pound of body fat is estimated to contain about 3,500 calories of potential energy. It is reasonable to consider, therefore, that the number of calories burned has to exceed dietary intake by something in the neighborhood of 3,500 for every pound of body fat to be lost.

In the 2010 Dietary Guidelines for Americans, adult men reported an average daily intake of 2,640 calories, while women reported consuming an average of 1,785 calories each day. These numbers can vary according to age, body size and level of activity, but you can see that even if one were to cut one's food/calorie intake by half, it's difficult to lose much more than a couple of pounds of body fat a week.

How to explain your results? Cleansing routines often talk about pounds of "toxins" clinging inside your intestines, but there is not much evidence to support such claims. What is known is that there is usually a quantity of fecal matter in queue for normal elimination. Any "cleansing routine" that includes laxative ingredients will cause a temporary -- albeit dramatic -- weight loss due to the physical weight of this matter. If it also contains diuretic ingredients, the cleansing product can cause a loss of water weight; again, a temporary effect. Neither of these are the same as weight loss that involves a decrease in body fat from the adipose stores. Once the cleansing regimen is finished, the body reestablishes balance and the numbers on the scale return to where they were.

Success takes determination and a good plan. There has never been a quick fix that has withstood the test of time. Relying on a cleansing diet drink, or diet pills, does not bode well for long-term chances. Better to find a plan that includes a healthy, balanced diet, a good selection from all the food groups and a solid activity component. By tweaking your food choices, lowering calories and increasing activity, your new routine can bring lasting success.

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: Other than price, what is the difference between organic sugar made from evaporated cane juice, and regular granulated sugar? Are both products stripped of their nutrients, and if consumed regularly, harmful to my health? Also, where do brown sugar and honey fit in? As a very active young adult (21 years old), should I replace some sugar products with a natural sweetener like honey? I am trying to create a healthy lifestyle. -- F.F., San Diego

DEAR F.F.: Bottom line: Nutritional value is not a reason to choose evaporated cane juice over granulated sugar, as they are essentially the same. Granulated sugar, whether from cane or beets, is pure sucrose -- plain and simple. There are flavor differences between sugar and evaporated cane juice, and the latter can also contain trace amounts of minerals and vitamins, but not enough to qualify as a source. Evaporated cane juice is less processed and requires less energy to produce, but as you point out, it also costs more.

As for brown sugar, don't let the color fool you into thinking that it's more nutritious. The only nutrient-rich component in sugar cane is the unprocessed molasses -- the fluid that is left after the sugar is crystallized out of the cane or beet juice. Brown sugar is not made by leaving the molasses in, but rather by adding a specially refined molasses juice to a refined white sugar. The nutritional differences between white and brown sugar are practically nil.

Honey is actually sweeter than an equivalent weight of granulated sugar or dried cane juice. (One note of caution: Honey is not recommended for infants less than 1 year old.) One advantage with honey is the way it's constructed and absorbed.

Both sucrose (from granulated sugar or cane juice) and honey are made up of equal amounts of two sugars: glucose and fructose. The glucose and fructose in sucrose are bound together, while with honey, the glucose and fructose are separate. This makes a difference in the speed at which the carbohydrate enters the body and is metabolized.

In the body, sucrose gets actively absorbed. This means there is a special mechanism that actively pulls it into the body when it comes in contact with the absorptive surfaces in our intestines. Glucose, when by itself, is also actively absorbed. Fructose, by contrast, is passively absorbed, which means it comes into the bloodstream at a slower rate.

The implication here is that when you eat honey, only half the carbohydrate (the glucose) is rapidly absorbed. With sucrose, both the glucose and the attached fructose are rapidly absorbed. 

Sugary foods quickly satisfy the body's immediate energy needs, but once these needs are met, the blood sugar level begins to rise, causing insulin to be released. This signals a shift into "energy storage mode" and the sugar calories get changed into fat.

Sugars can certainly fit into a healthy lifestyle; their main use in cooking should be in small amounts to bring out or complement another food's natural flavors. Sweet treats, where the sugary taste is in the foreground, should only be consumed sparingly. Assuming you have no problems with blood sugar regulation, other factors to consider are the amount of calories your body requires, the risk of tooth decay and the fact that when you consume sugar calories, you have less room for food with more healthful attributes.

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.