DEAR DR. BLONZ: Two weight-loss “miracles” are featured in a constant stream of emails I now receive. (I take responsibility for this mess, having clicked on an ad a few weeks ago.) One of the ingredients is hoodia, and the other is Caralluma fimbriata. The ads discuss how they have been used for centuries in India to suppress appetite. There is also mention of research studies providing evidence that they work to cause weight loss. Are these something you are familiar with? -- M.Q., Lafayette, California

DEAR M.Q.: Hoodia gordonii is a succulent plant found in Africa. There is no reliable scientific evidence to affirm the weight-loss efficacy of hoodia. Indeed, the Federal Trade Commission has taken action against a company for making false weight-loss claims about hoodia.

Caralluma fimbriata is the name of a succulent plant that does, indeed, grow in India. It can be eaten raw or cooked with spices, but it’s also used in pickles and chutneys. Stories in folklore tell of chewing chunks of this plant to suppress hunger while on days-long hunts.

There is a published, peer-reviewed study for Caralluma fimbriata. Let’s go through the details of this study, as it can illustrate how folkloric stories, coupled with aggressive marketing, will not guarantee that a product works.

The research was published in the May 2007 issue of the journal Appetite, and it involves a 60-day study using 50 overweight male and female volunteers. Half the subjects received an extract of Caralluma fimbriata, and the other half received a placebo. Measurements were taken before, midway and at the end of the study, including weight, BMI (body mass index) and body fat, along with appetite variables such as food intake, measures of hunger, thoughts of food and feelings of fullness.

At the end of the study, the group taking Caralluma fimbriata had lost weight, and their BMIs (and a number of other measurements) were lower. I have seen this mentioned in advertisements. But -- and this is key -- what the ads leave out is the fact that similar results were found in the placebo group.

This reinforces why it is absolutely essential to have a placebo group when studying the possible efficacy of substances. Comparing both groups, there was no significant difference in body weight, BMI, body fat or hip circumference. The only difference between the groups was in the measure of waist circumference -- but, given the lack of difference in all other metrics, this is of dubious import.

The Appetite study reported no differences in thoughts of food, feelings of fullness, urges to eat or in the amounts of energy (calories), fat, carbohydrate and protein consumed. The only difference between the groups was in reports of hunger. Even so, when compared to the placebo, the treatment did not have a significant effect on how much the subjects actually ate.

Our bottom line is that there is nothing “miraculous” to report about Hoodia gordonii or Caralluma fimbriata as weight-loss products. A second important takeaway is that we always need to view these types of claims with a critical eye.

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: You have written about high-fructose corn syrup (HFCS), which many of my purist friends consider to be the equivalent of dietary poison. Are they correct in this view? I have read elsewhere that some commercial use of HFCS was originally motivated by the cost/sweetness ratio of the product, particularly with the tariff on imported sucrose and its effect on U.S. sugar prices.

I appreciate your reminders about the beneficial effects of striving for balance in our food consumption; they are refreshing and well-stated. -- F.S., Lafayette, California

DEAR F.S.: The sugar/carb/corn syrup issue can best be appreciated through an understanding that the body gets off-course when overloaded with sweets. When added fructose -- not the sugar naturally present in fresh fruit -- is a major player in any too-sweet diet, a number of unhealthful biochemical shifts tend to occur.

A review article in the American Journal of Clinical Nutrition looked at the potential role of sugar (fructose) in the epidemics of hypertension, obesity, diabetes, kidney disease and cardiovascular disease. The paper suggested that high intakes of fructose are likely to be playing a role, and that certain groups, such as African Americans, are particularly susceptible. The paper correctly points out, however, that there are also illnesses associated with excessive sodium from salt, and with excessive protein.

The issue is not so much that people should reject and run away from any and all sources of HFCS. Bypassing HFCS in favor of an artificial sweetener is not the answer. My read of the evidence is that the way to get ahead of the game is to cast off as many sweetened, processed foods as possible, and stick with the real.

DEAR DR. BLONZ: I am allergic to sulfa antibiotics. Is the sulfur compound produced when eating asparagus also harmful? Should I stop eating it? Which other, if any, vegetables contain compounds of sulfur? -- N.H., Fremont, California

DEAR N.H.: Sulfur is an essential element; sulfa drugs, also called sulfonamides, are particular sulfur-containing compounds. These are not the same as the sulfur naturally found in foods. Methionine, for example, is an essential amino acid that contains sulfur, and is in all complete proteins, as well as nuts, seeds, beans and grains.

DEAR DR. BLONZ: I have a question about mixing fats. I sometimes mix a small quantity of unsaturated fat, such as canola or a mixed-blend oil, with butter when I bake cookies, piecrusts, etc. Would I be inadvertently getting a trans fat result in this simple home blend? -- M.H., San Diego

DEAR M.H.: What you are doing does not present a problem. Trans fats are formed through a multistage, timed industrial process involving high pressure and specialized catalysts. It would be impossible to duplicate this in the kitchen.

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: How do imitation crab meats compare with regular crab in terms of omega-3 fats? I asked my local fish store and was told that imitation crab comes from pollock, and I heard this is a low-mercury fish. I don’t buy it to pretend that it is crab; I buy it because it’s the only way that I can find pollock locally. And it is generally inexpensive, so that makes it a good buy. But does the processing of the pollock -- including the coloring and the flavor infusion -- change any of the omega-3 levels? -- F.M., Tulsa, Oklahoma

DEAR F.M.: While a good source of protein, and low in mercury, pollock is considered a moderate to low source of omega-3 fats -- comparable, actually, to that found in crab. A 3-ounce serving of Dungeness crab contains 383 milligrams of omega-3 fats, while a similar serving of Alaskan pollock contains 418 milligrams. For comparison with other fish, this is about one-fourth the level found in wild salmon.

While pollock isn’t particularly high in omega-3s to begin with, turning it into imitation shellfish (also called surimi) will reduce the levels even further. To make the fish look and taste like crab or lobster, they are typically deboned, rinsed, minced, flavored, colored and reformed to resemble the muscle fiber and taste impression of the desired variety. It is not a process that’s kind to omega-3 fats. A 3-ounce serving of surimi made from pollock will contain only 26 milligrams of omega-3 fatty acids.

DEAR DR. BLONZ: What are the nutritional consequences of discarding the liquid that separates from yogurt in the container? Since discovering Greek yogurt on my trip to Greece last year, I find I prefer the thicker consistency. However, I like to achieve this by purchasing American yogurt, allowing it to settle and then removing the liquid. However, I’m unsure whether I am losing valuable nutrients with this practice. -- A.A., Denver

DEAR A.A.: The liquid on top is mostly water, but also contains whey. Whey contains a bit of protein, some carbohydrates and a few water-soluble nutrients, including calcium, that remain in solution.

The texture of Greek-style yogurt comes from being strained to eliminate extra liquid. More liquid gets removed with Greek yogurt than from pouring out the liquid from a standard type; this explains why, even if you pour off the liquid and spoon out a serving, you will find some water there the next time you open up the container. Greek-style yogurt has less calcium, but a higher proportion of protein per weight.

But all things considered, when compared with the overall healthfulness of yogurt, the nutritional consequences of going Greek or pouring off the liquid from a standard type is not significant. Go with the type that best pleases your palate. Another yogurt plus is that it’s often better tolerated than milk by those with lactose intolerance. This is explained by the fact that active yogurt bacteria produce a lactose-digesting enzyme.

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.