DEAR DR. BLONZ: Please provide more information about the xanthan gum and cellulose gel that I find in my fat-free salad dressings. I tend to eat a lot of salad, and the dressings taste fine, but is there a reason to be concerned about eating these components on a regular basis? -- S.F., San Jose, California

DEAR S.F.: Dressing provides a flavor accent for the salad components, but to do this effectively, it must provide a light, easily distributed coating, and leave a pleasant mouth-feel. The two ingredients you mentioned serve these purposes in commercially produced dressing.

Xanthan gum is made from a specially fermented cornstarch syrup. It was created in the 1960s at the U.S. Department of Agriculture’s research station in Peoria, Illinois, as part of a project to find new uses for surplus corn. Xanthan gum helps to thicken foods’ texture and stabilize components in a mixture. It has proven to be quite versatile: Aside from salad dressings, it’s used in puddings, sauces, baked goods and desserts. Because it is made from corn, xanthan gum should be avoided by those who are allergic, but aside from that, there do not appear to be any problems associated with its use.

Cellulose gum is made from the fibrous cell walls of plants. It is a naturally occurring thickener used in dressings, ice creams and puddings.

Neither compound brings nutritional assets to the party, but they appear to be quite safe as food additives for use on a regular basis. Always read the rest of the ingredient list and the Nutrition Facts panel to see what else the product has to offer.

DEAR DR. BLONZ: I was surprised to see a dietary supplement proclaim oxygen as one of its active ingredients. How could that work? If it does, would it be a concern that effectiveness diminishes with prolonged use? -- H.B., Walnut Creek, California

DEAR H.B.: Let’s not get ahead of ourselves by assuming effectiveness. Oxygen is essential for carbon-based forms of life due to the many ways that carbon and oxygen can react together, and in the process, absorb or release energy. Oxygen is also involved in other metabolic processes.

The supplement angle makes little sense, as the body is designed to take in and utilize its needed oxygen via a gaseous exchange in the lungs, not as a dietary supplement that comes in through the stomach. This is not a route to deliver oxygen to the body. While there may be legitimate products out there, the Federal Trade Commission has gone after such dubious claims in the past (see tinyurl.com/q9k8cvr).

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: I wanted some information on the advantages of liquid colloidal mineral supplements. My concerns are about the risk of osteoporosis, which runs in my family, and I would be happy to switch to a product that would be more effective in preventing it. These products are more expensive than the other minerals I take, but the expense would certainly be justified if the product has a higher level of absorption, as is claimed. Is there any substance to these claims? -- B.E., Hayward, California

DEAR B.F.: Colloidal mineral products are not new. There remains a lack of competent, reliable scientific evidence to support any claims that these types of dietary supplement products bring anything special to the table.

A colloid, or colloidal suspension, is a physical state in which solid particles are suspended in a medium, such as a liquid, in a way that the solids do not settle out. The source of colloidal mineral supplements is usually clay or humic shale deposits.

Mineral absorption takes place, for the most part, in the small intestine. Pills, tablets or capsules are designed to dissolve before they reach the absorptive surfaces of the small intestine. The key question is whether, all else being equal, the body will absorb more minerals in the form of a colloidal liquid than it will from a similar amount supplied as a standard pill, powder, tablet or capsule.

Think about what you would accept as proof. Would you want positive statements and testimonials from individuals who want to sell you their products? Or would you demand some form of solid science, such as the publication of unbiased research in a peer-reviewed journal? Hopefully you would opt for the latter. Unfortunately, there is no reliable published evidence to support claims of enhanced bioavailability from minerals in a colloidal form versus similar compounds in more standard supplement forms.

Minerals are all considered inorganic elements because, unlike protein, fat, carbohydrates and vitamins, they do not contain the element carbon. A unique thing about minerals is that they cannot be synthesized or changed by the body. Like vitamins, minerals are only needed in trace amounts, and they don’t provide any calories.

The minerals in our diet are distributed throughout the foods we eat. Calcium, for example, is found in dairy products, a number of green, leafy vegetables and some nuts; magnesium is present in nuts, bananas, legumes and whole grains; and zinc is present in meats, whole grains and seafood. The distribution of the various minerals among the different foods (the same theme holds true for vitamins) is the basis for the advice to focus on variety when it comes to food selection.

Finally, there are proven strategies to help combat the risk of osteoporosis. Check out the articles at tinyurl.com/yda34bj7 and tinyurl.com/yanjrxkc.

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: I was told to take a calcium supplement, but the one I purchased says to consult your doctor if you are taking estrogen, which I am. Why is that? -- J.D., Anderson, South Carolina

DEAR J.D.: Product cautions are not to be taken lightly. But for some perspective, these warnings serve the dual purpose of alerting consumers to potential concerns while affording the product's manufacturer a measure of liability protection. There are always possibilities for unforeseen interactions. When there is a known risk, or at least a suspected one, these tend to get notations on the product label or insert.

As for the particulars of your question, calcium supplements are commonly used along with hormone replacement therapy. Other ingredients in that supplement may be responsible for the caution. Get clearance from your physician, which may only involve a simple phone call.

The bottom line is that these decisions are best made with the health professional most familiar with your particular situation.

DEAR DR. BLONZ: Is there any significant difference between the protein in red meat and that found in seafood, such as shrimp? I reduced my meat intake to once a week, but I'm concerned that I’m not getting enough protein. I do a cardio workout three days a week and also work out with weights. I am interested in adding some seafood to the menu, but wondered if that protein is as good as that found in meat. -- SF, Phoenix AZ,

DEAR S.F.: There are minor differences between the proteins found in red meat and seafood, and these are mainly different amounts of the various essential amino acids. Both are considered high-quality “complete” proteins, in that they both contain good amounts of all the amino acids the body needs to make its protein. To answer your question, you should consider them comparable.

Scientists score proteins by looking at the types of amino acids they contain and then comparing them with the amino acids in our body's protein. Those that compare most favorably have the highest score. Egg whites (albumin) are usually considered to be the ideal protein, followed by dairy, fish, beef and poultry. Contrast this with lower-scoring vegetable proteins, such as corn, wheat and rice, which contain some protein but lesser amounts of one or more of the essential amino acids. Be aware that the protein listing on the Nutrition Facts label does not address protein quality.

Most people have no problem getting the protein they require. In fact, in this country, we tend to eat more protein than our bodies need. We also have fewer of the plant foods that can help provide the dietary fiber and valuable phytochemicals that support our health.

The key is to have a mix of high-quality protein foods and other protein-containing foods, including grains, legumes, vegetables, nuts and seeds.

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.