DEAR DR. BLONZ: What fats do you recommend for baking? Years ago I used shortening, but then shifted to butter because of the trans fat issue. But butter has saturated fats, which are also a problem. -- F.S., Tucson, Arizona

DEAR F.S.: The fats used in baking serve a number of functions. They coat the flour and help to shorten the strings of gluten protein that form when water and flour mix; interestingly, this is the basis for the word “shortening.” The fats also help hold things together, and fats that are more solid help trap the air bubbles that allow baked goods to rise. (This is not much of an issue with cookies, which helps explain why less-solid fats can work there.)

This all means that you need specific performance characteristics from baking fats and oils, but at the same time, you don’t want your food to be a health liability. It makes sense to experiment a bit to see what works with your recipes. Also: Be aware that there are now shortenings without trans fats.

Additional guidance is available at the many websites and blogs covering baking, including bakefromscratch.com, bakerpedia.com, and bakerbettie.com.

DEAR DR. BLONZ: Is salmon safe to eat if it’s been frozen for over a year? Should I just throw it away? -- Y., Hayward, California

DEAR Y.: There shouldn’t be any problems from a safety perspective if the salmon was packaged tightly, ideally in a container or bag meant for this type of storage, and if your freezer has maintained its low temperature. I suggest removing any areas of freezer burn, which show as blotches of discolored fish, usually near the edges.

As the fish defrosts, let your senses be your guide as you check for “off” odors: After the siesta, your fish will not be as flavorful as it was fresh.

DEAR DR. BLONZ: What determines what is classified as dietary fiber in foods? -- D.D., Tulsa, Oklahoma

DEAR D.D.: There are two main categories of dietary fiber: water-insoluble and water-soluble, and their health benefits differ. Both, however, are valuable parts of the diet.

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. To absorb and make use of what’s there, the food has to be disassembled into small, absorbable bits, and our digestive system is that disassembly and absorption line.

Enzymes are the body’s chemicals that break foods down. Fiber is unique in that the human body lacks the enzymes that can take it apart. Instead of being absorbed, it remains in the part that passes on through. As fiber travels through the digestive system, what it does depends on how it’s built.

The average diet in the U.S. contains only about half the fiber we need. Research evidence 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. Quite impressive, when you consider that dietary fiber isn’t absorbed. Recent findings suggest that the interaction between fiber and the flora in our intestines -- our microbiome -- will hold the key here, and this is now an emerging and exciting field of study.

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: 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.