DEAR DR. BLONZ: What exactly determines what gets classified as dietary fiber in foods? -- C.D., Elgin, Illinois

DEAR C.D.: Fiber refers to the materials found in plant foods that the human body cannot digest.

Think of the foods we eat as a complex combination of nutrients and non-nutrient ingredients. In order for your body to absorb and make use of the nutrients, food has to be disassembled into small, absorbable bits. Our digestive system is the disassembly line, and enzymes are the body's chemicals that break the foods down. Fiber is unique in that the human body lacks the right enzymes to take it apart. Instead of being absorbed, it becomes part of the bulk that passes on through.

As fiber travels through the digestive system, what it does depends on how it's built. An important distinction is whether the fiber dissolves in water. There are two main categories of dietary fiber: insoluble and soluble, and their health benefits differ. Both, however, are valuable parts of the diet.

The average diet contains only about half the fiber we need. Research suggests an increased fiber intake (a total of 25 to 30 grams per day) helps control heart disease, certain cancers, diabetes, diverticular disease, constipation, diarrhea, weight, hemorrhoids and ulcerative colitis. This is quite impressive when you consider that dietary fiber isn't even absorbed.

DEAR DR. BLONZ: Is salmon safe to eat if it's been frozen for 6 months? Or should I just throw it away? -- Y., San Diego

DEAR Y.: If your salmon was packaged tightly -- ideally in a container or bag meant for freezer storage -- and your freezer has maintained a constant low temperature, there shouldn't be any problems from a safety perspective. The quality of the frozen fish, however, will decline after a few months. After its siesta, the fish won't be nearly as flavorful as it would have been if eaten fresh, but it should be safe.

When you remove it from the freezer, be sure to trim off any areas of freezer burn. These will show as blotches of discolored fish, usually near the edges. As the fish defrosts, let your senses be your guide as you check for any weird smells. If the fish looks OK and has no "off" odors, try to find a recipe that adds plenty of flavor so that the focus won't be on the fish.

DEAR DR. BLONZ: Please tell me what you think about "detox food patches." These are pads you place on the bottom of the feet to promote natural detoxification and the pulling of toxic metals from the body. They also claim to improve circulation, combat fatigue, jump-start metabolism and promote a better night's sleep. According to the literature, you place one on each foot every other night for 30 nights, then use them about once every three weeks. The pictures show how wearing the patches gives rise to a black buildup on the patch, which is evidence that it is working. -- S.F., via email

DEAR S.F.: Using scientific evidence as the benchmark by which such claims should be measured, these products are pure, unadulterated nonsense.

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: Please tell me what you know about "imitation crab meat." I know it doesn't contain crab, and the type I buy is actually made from Alaskan pollock. Do the treatment, coloring and flavoring processes change the amount of omega-3 fats in it? -- E.E.

DEAR E.E.: It is a good source of protein, but pollock is considered a moderate to low source of omega-3 fats. It is comparable to that found in actual crab: a 3-ounce serving of Dungeness crab contains 383 milligrams, while a similar serving of Alaskan pollock contains 418 milligrams. The levels in these are about one-fourth of those found in salmon. Read more about Alaskan pollock at tinyurl.com/mnsfevl.

The processing of pollock into an imitation shellfish, however, will bring the level down quite a bit. The fish will be deboned, rinsed and minced, then flavored, colored and reformed to resemble the muscle fiber and taste impression of the desired variety of crab. It is not a process that's kind to the omega-3 fats. A 3-ounce serving of pollock surimi contains only 26 milligrams of omega-3 fatty acids.

DEAR DR. BLONZ: It has often been my habit to swallow my vitamins with a cup of hot coffee. My friend was shocked that I do this. My question is whether the hot liquid affects the quality of the pills. My friend believes that I am negating the effect that the pill is meant to achieve. -- S.C.

DEAR S.C.: Aside from the risk of ruining your ability to enjoy the taste of your coffee, there is no basis to fear that you are negating any effects the pills are meant to achieve, to use your words.

DEAR DR. BLONZ: Thank you for your explanation of high fructose corn syrup. I have heard various other things on this topic. I asked a local physics professor why it was not good for you, and he said, "It has a component in it that interferes with the body's ability to know when one is full. In essence, it keeps the door open." Then, on TV, a man explained that it was bad for the liver because with soft drinks in an empty stomach, for example, the liver gets too much to process at once. Are you aware of these factors? -- E.P.

DEAR E.P.: Sweetened soft drinks would not be considered a healthful beverage in any situation, and especially not when consumed on an empty stomach, consumed to excess, or as a part of an overall unhealthful diet. Studies reporting negative effects are usually collected using these types of circumstances.

In such situations, there is no real compelling evidence that one (HFCS) is worse than the other (sugar); they are both bad. You shouldn't be having sweetened beverages on an empty stomach. As for it being bad for the liver, this again would relate to the level of intake. The concept of excessive consumption is the basis for most of the bad effects reported on sugars in scientific literature.

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 eat well and exercise regularly, but despite these good habits, I have noticed weight gain around my middle. It's very bothersome to me. Is this just part of getting old? I can't improve my diet much more, and am frustrated at this bulge. Nothing has really changed except the shape of my body. -- S.S., San Dimas, California

DEAR S.S.: There is a natural decline in the amount of energy (calories) the body requires as the years go by. Couple this with the typical decrease in activity as we age, and it's easy to understand the impact on the shape of our bodies. The slowdown in calorie burning is gradual, and it represents a problem for those who continue to ingest the same daily calories that they always have, or even more.

The body needs energy to operate, and there are three basic categories of body energy. First and foremost is the resting metabolic rate (RMR). These calories represent the energy needed to keep the body ticking. This is our caloric "cost of living," and it represents about 60 to 75 percent of our daily caloric requirement. Next is the energy used for activity, which amounts to about 15 to 30 percent of the caloric requirement for the average individual. Finally we have the thermic effect of food (TEF), which is the energy burned as a direct result of eating. It represents about 5 to 10 percent of daily calories. Weight tends to remains stable as long as we consume the number of calories our body requires.

An older body, however, will burn fewer calories than a comparable younger body, even if both ate the same and had the same level of physical activity. A study in the February 2005 issue of the European Journal of Clinical Nutrition reported that the decline associated with aging is not solely a function of the fact that we tend to lose lean body mass (muscle, organ weight and bone) as we age.

No question, it is best to remain active, as this will help slow down the slowdown. Staying active not only burns the calories associated with the activity, it also helps maintain your muscle mass. Muscle is active tissue, and similar to the way an eight-cylinder car burns more gas at idle than a four-cylinder car, having more muscle mass burns additional calories even when you are at rest. Studies in the February 2006 Journal of Physiology and the August 2007 Journal of Applied Physiology provide independent confirmation how the TEF component of our daily calorie requirement is greater in those with regular exercise habits.

If you will allow a personal observation, I noticed a couple of years ago that there was -- slowly but surely -- getting to be a bit more of me. So I added 15 minutes of aerobic time to my three-times-a-week exercise sessions and that helped me to regain control of the trend.

We all need to keep up with our activities and find a way to make exercise a fixed part of our routine. There should be an aerobic element as well as resistance exercises. If you have health issues, you can touch base with your physician. If you have any physical limitations or concerns, consider speaking with a certified trainer at a gym to develop a personalized program.

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.