DEAR DR. BLONZ: Please explain more about placebos and controls and whether they can actually bring about health benefits. -- G.B., Anderson, South Carolina

DEAR G.B.: When early research results confounded expectations, scientists began to suspect that effects could occur simply because they were believed to be due -- even if no active ingredients were present in the treatment being given. (Key side note: And, yes, this may shed light on what's going on with "miraculous claim" supplement products that lack objective testing, but go heavy on product promotion. It is why potential customers should demand clinical evidence, rather than testimonials, before they buy.)

Scientists began using placebo controls in their studies to provide inactive treatments that appeared and tasted similar to the active treatments. When only the subjects do not know what treatment they are receiving, it is a "single-blind" study. However, many subjects wanted to know which group they were in, so they tried to pick up clues from anyone working on the research. Researchers often asked subjects at the end of the study whether they had learned which group they were in and how they had come to know it. When subjects have such knowledge, it thwarts the reliability of findings.

Quality researchers stepped in to design studies in which no one -- from the subjects, to those administering the treatments, to the researchers conducting the analyses -- could know who was in which group. Codes are used and are not broken until all the data has undergone final analyses. When placebos are used and nobody knows who's getting what, it's called a "double-blind, placebo-controlled" study, a premier method in clinical research.

An interesting side story was when an important concept was discovered using control treatments. In one study, grapefruit was used to mask the taste of a drug being tested so that subjects could not discern between the active treatment and the placebo. In this study, they found unusual results in the placebo group, revealing the profound impact grapefruit can have on drug absorption and metabolism. This finding led to our understanding and caution about the "grapefruit effect" with certain medications (see b.link/8mqcd for more).

DEAR DR. BLONZ: Is there any basis to the advice that the body shouldn't have fruits and vegetables at the same meal? Is this nothing more than a widely circulated, long-standing myth? If so, it dies hard. Thank you. -- A.S., Raleigh, North Carolina

DEAR A.S.: There is no one way of eating that works for everyone. We all have our quirks and preferences, food-prep abilities, social circumstances and takes on the physiological rules of the day. If there were to be a generalization in this matter, though, it would be that there is no evidence that fruits and vegetables have to be consumed separately.

Our digestive system is well-designed for mixed meals, having specific areas for the sequential breakdown, processing and absorption of the food's nutrients. The "die hard" aspect relates to period romances with misinformation from folklore that preceded evidence and our understanding of how things work in the body. For a more detailed view of our digestive system, see b.link/vq7rpkz.

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: As an Oakland, California, resident, I appreciate each of your columns in the East Bay Times. The recent column on protein was timely, as I am a 71-year-old, just over a hip replacement, and working via lifting, cycling, and yoga to gain and maintain muscle mass. In your response to a recent question about protein, you stated that "active individuals may benefit from up to ... 27 grams of protein for every 30 pounds of weight." By my calculations, as a lean 153-pound male, that equates to about 135 grams of protein per day. That amount seems very high and unreachable for anyone other than a professional bodybuilder. Is your recommended grams per 30 pounds a misprint or miscalculation? I would appreciate a response so I can target my nutrition on a daily basis. -- D.P., Oakland, California

DEAR D.P.: Thanks for your kind comments. No recalculation is needed for that level, which was described as being for "athletes and intensively active individuals." That would characterize competitive weightlifting/powerlifting, Ironman, long-distance cycling, and military basic training types of workouts -- things that would be done five to six days a week. The food/calorie intake is high at that level of physical demand; the need for protein is up as well. You will have to decide where you fit with your routines, but please understand that excess dietary protein, i.e., more than the body needs, is not a health asset.

Having recently undergone a total knee replacement and relying on physical therapy, with a 3x weekly workout and steam at the Y, I am now back with a much better knee! I continue to eat well, but I did not see the need for extra protein during that process. I wish you the best with your recovery.

DEAR DR. BLONZ: In a recent column on protein, you failed to address an important side element in the question. The writer mentioned that the gym offered collagen protein drinks for building muscles. Collagen protein is not ideal for muscle building due to its amino acid content, specifically that it is low in leucine, an essential amino acid, compared to the levels in milk/whey protein. -- D., El Cerrito, California

DEAR D.: You raise a valid point, but it would not be an issue unless collagen was a primary protein in the diet. If one is already getting their requirement for high-quality (complete) protein, the difference between a collagen drink and a different type, such as whey, or a vegetarian source, would make little difference.

That element might have added unnecessary complexity to the main issue involving the value of extra protein. There is some research on the value of added collagen for connective tissue, but most of these studies involve individuals with marginal protein intakes. You are correct that whey, which comes from dairy, would be a preferred source when supplementary protein is needed, but there are attractive vegetarian sources as well. Consider checking the essential amino acid contents of any product you are considering.

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: This is about a solution to the stomach problems that were experienced by my daughter. We were not sure whether it was some medical condition, stress, or even a food allergy. At a periodic wellness visit with our family physician, many questions were asked, including whether she had gum and sugar-free mints. I remember you had written about this, and that she always chews sugarless gum, but I never made the connection. This turned out to be the answer. I wanted to pass along that since she stopped, her stomach problems have disappeared. -- S.A., Martinez, California

DEAR S.A.: My hat's off to the family doctor and to your family for having periodic wellness visits. The sweeteners most commonly used in sugarless gums and mints are xylitol, mannitol and sorbitol, all members of the sugar alcohol family. Even though they are indeed carbohydrates considered to be sugars, they merit the "sugarless" label because, despite their sweet taste, they don't promote tooth decay. Sugar alcohols possess this quality because, unlike other carbohydrates, the bacteria in and around our teeth cannot metabolize them to produce the enamel-destroying acid associated with tooth decay.

One negative characteristic of sugar alcohols is that they attract water when they're in the digestive tract. Substances with this quality contribute to digestive upset that includes diarrhea and cramping. Also, sugar alcohols are not efficiently absorbed, so they tend to remain in the digestive tract and reach the large intestine. There, they serve as food for our microbiome, many of which produce intestinal gas as a byproduct.

The symptoms are mild when small amounts are consumed, or if they are eaten with or soon after a meal. If, however, larger quantities are consumed, such as several mints or sticks of sugarless gum, and if they are eaten on an empty stomach, the result can be the type of upset your daughter experienced. Read more about sugar alcohols and how they are shown on food labels at b.link/e7gfcew.

DEAR DR. BLONZ: I wanted to say thanks for an earlier column in which you covered positive benefits from chocolate. My question is whether the antioxidants you described are in the cocoa powder or in the cocoa fat. If it is in the fat, would that mean that the only way to get the benefits is to have full-fat chocolate? -- D.M., Benicia, California

DEAR D.M.: Research on chocolate has indeed identified the presence of beneficial compounds. These compounds, known as flavonoids, are found in the cocoa solids, not the cocoa butter. This means that they are in the cocoa powder, and, of course, in the whole chocolate confection. Dark chocolate, which has more cocoa solids, tends to contain more flavonoids than milk chocolate, and white chocolate (no cocoa solids) contains very few flavonoids, if any.

As for whether having cocoa powder is a "better" way of getting the benefits of the chocolate, that, I think, is a matter of personal preference. There are plenty of foods with wonderful attributes. Eat chocolate because you enjoy it, not because you think it's good for your health.

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.