DEAR DR. BLONZ: I often read your column and know you preach a varied, plant-based diet with fruits, vegetables, nuts, seeds and lean meats. But I keep seeing things on television and in the paper, and have even heard from a friend, that sugar/carbs are bad and should be limited. When I told my friend that I fix a yogurt and fruit smoothie every day, she said I shouldn’t be having all that sugar from the fruit. I countered with the idea that fruit’s sugar is natural and unprocessed, and that it also contains other good things like fiber and minerals. But am I missing something? -- A.T.B., via email

DEAR A.T.B.: The message that “sugar/carbs are bad” needs some context. If one has a healthful diet, such as the one you describe, sugars and carbs can become an issue if they are over-represented. Only then do they become “bad.” The rather simplistic take on this matter can lead well-meaning friends to inappropriately condemn healthful foods, such as fruits.

I’m unclear on the specific formula for your smoothie, but using whole fruits as sweeteners makes healthful, and flavorful, sense to me.

DEAR DR. BLONZ: Over the years, I have given my family honey for allergies, coughs and sore throats. My son, who has a problem with high blood sugar, says he should not take honey as it is sugar. But I thought honey’s sugar was different from other sugars. Please inform me if it is safe to take honey if you have high blood sugar. -- E.S., El Cerrito, California

DEAR E.S.: Honey is most definitely a sugar, and in addition to its unique qualities as a product of bees, it has assets and liabilities associated with other caloric sugars. Regular table sugar, also known as sucrose, is composed of equal parts glucose and fructose. With sucrose, each glucose is attached to a fructose in a structure referred to as a disaccharide. Honey also has glucose and fructose, but they are present as separate compounds, each referred to as a monosaccharide, or single sugar.

To widen this circle a bit, consider that high-fructose corn syrup (HFCS), a manufactured sweetener, is -- similarly to honey -- made up of glucose and fructose as monosaccharides. The carbohydrate difference is that honey has nearly equal portions of glucose and fructose, while HFCS, because it is manufactured, can have varying levels of its two monosaccharides. It usually favors more fructose than glucose.

For anyone with blood sugar issues, honey should be consumed with the same caution as any caloric sweetener.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 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: In a lecture at my community college, there was a statement that the turkey we have at Thanksgiving contains specific enzymes that make us feel sleepy after we eat. I had always thought that this was a myth, but was reluctant to challenge the professor. Is that statement valid? If so, what is in turkey that makes us feel sleepy after we eat it? -- M.M., Phoenix

DEAR M.M.: As a prelude to every holiday season, we hear the commonly held belief that turkey causes tiredness, but I had never heard it phrased as “specific enzymes.” Since this was an academic setting, you should not have been reluctant to ask more about these enzymes and how they supposedly cause tiredness. This is a new one, and I am always interested in learning the rationale behind such beliefs. I must confess, I am quite puzzled, given that the cooking of the turkey would destroy any enzymes in the meat.

Let’s put some other aspects of the turkey-tiredness legend in perspective. One key is tryptophan, one of the amino acid building blocks of protein. When this amino acid gets in the brain, it can be converted into serotonin, a compound that elicits relaxation and calmness. (One reason that a certain class of anti-anxiety drugs works is that it helps to maintain serotonin in the brain.) Turkey, as a complete protein, will indeed contain tryptophan, but it doesn’t contain that much more than other complete proteins, such as chicken or other meat.

Why, then, would turkey have the reputation for causing sleepiness, and not other proteins? It turns out that the tiredness you feel is more likely due to the carbohydrates often consumed along with turkey at the holiday feast.

To explain this, you should know that there is an important barrier between the blood that flows in the general circulation of the body and that which flows around the central nervous system. Called the blood-brain barrier, it helps protect the brain and control the compounds allowed to circulate in and around delicate brain tissues.

After a protein-based meal, the enzymes in our digestive system help break down the proteins into their constituent amino acids building blocks. Amino acids can pass through the blood-brain barrier, but they compete with each other to cross. Tryptophan is at a disadvantage because it’s found in smaller amounts in foods relative to other amino acids. Carbohydrates, however, can tilt the odds in tryptophan’s favor. Carbohydrates cause insulin to be released, and insulin causes amino acids to enter muscles and other body tissues, but tryptophan to a lesser extent. With its competition thus reduced, tryptophan is better able to enter the brain, turn into serotonin, and bring about the relaxation. 

Thanksgiving turkey tends to be paired with carbohydrate-rich foods such as cranberries, potatoes, stuffing and pumpkin pie, all of which raise our blood sugar level and ease the way for tryptophan to do its thing. Such logic would also explain why those who partake of other main courses -- such as ham, duck or even a vegetarian dish -- might feel that same post-feast tiredness.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 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: What do you know about coral calcium? I was at a lecture where the speaker attributed anti-cancer properties to this so-called “unique” form of calcium. I just sat and shook my head, but was never given an opportunity to question the claims. I remain very suspicious, but wanted to ask you if there is any substance there. -- C.B. Seattle

DEAR C.B.: Coral calcium might be considered “unique” in that it comes from the structural matrix of ocean coral, but there is no evidence that it provides anything more significant or miraculous than “regular” calcium, an essential mineral nutrient.

The origins of coral calcium as a dietary supplement include an association with the long life of the people on the island of Okinawa. There have been unscientific statements about how these people’s intake of coral calcium has prevented or cured a veritable laundry list of diseases. There is also talk of coral calcium neutralizing toxic materials, and bringing the body into balance due to its alkaline (as opposed to acidic) nature. These statements are all sales pitch, and no evidence. A case brought by the Federal Trade Commission reflects these issues (tinyurl.com/m4t8d2y), but the products continue to be sold and the nonsense lives on.

Coral calcium is a type of calcium carbonate, the most common form of calcium supplements. And guess what? All forms of calcium carbonate are already alkaline. This is why it’s a common ingredient in many antacids. There is nothing special about the alkaline properties of coral calcium. As for the ability to “neutralize toxins” and cure or prevent disease, again, there is no evidence of efficacy.

As with all essential minerals, we need calcium. No surprise there. But there’s nothing miraculous about this particular type. You were right to be skeptical.

DEAR DR. BLONZ: What are the best food sources for niacin, thiamin and riboflavin, and what do these nutrients do? -- D.F., Charlotte, North Carolina

DEAR D.F.: All three of these B-vitamins are essential nutrients, ones that must be provided by the diet, as the body cannot produce them in sufficient quantities by itself. They are all involved in facilitating the release of energy, i.e., calories, stored in proteins, fats and carbohydrates.

Thiamin, also known as vitamin B1, is also required for normal functioning of the heart and nervous system. Food sources of thiamin include animal products (eggs, poultry, fish, meats and organ foods), whole grains, legumes, nuts, potatoes, and any food fortified with this vitamin. Niacin, also known as vitamin B3, is also required for normal cell metabolism and in the synthesis of hormones and DNA. Food sources include organ meats, poultry, seafood, nuts, green vegetables and legumes.

Riboflavin, also known as vitamin B2, is important for the health of the skin, the lining of the digestive system, and the lungs. Food sources include liver, enriched milk and milk products, meats, seafood, enriched grains, asparagus, broccoli, avocados, Brussels sprouts, eggs and green leafy vegetables. For more information on these and other vitamins, see medlineplus.gov/vitamins.html.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 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.