DEAR DR. BLONZ: What is your advice regarding spray dietary supplements? I am also interested in dietary supplement foot pads, which are promoted for detox and weight loss. Are these safe and effective, as the ads promise? I would appreciate your opinion. -- M.C., San Jose, California

DEAR M.C.: Dietary supplements are substances taken orally; in other words, there is a swallow involved. The substances are regulated as foods, not drugs. Read the “FDA 101: Dietary Supplements” at tinyurl.com/yaaugh5f for a larger perspective.

Dietary supplements, by definition, are a category of food intended for ingestion as a tablet, capsule, powder, softgel or liquid. The “spray vitamins” I am aware of involve spraying a mist into your mouth, followed by a pause -- ostensibly for the active ingredients to be passively absorbed (in theory) through the highly vascular tissues in your cheeks, under the tongue and elsewhere in the mouth.

If we stopped there, this would not fit the regulatory definition of a dietary supplement. Simply put, there has to be a swallow somewhere in the process. To skirt this issue, spray products often include instructions to swallow after use. Absent this inclusion, there is a risk of a regulatory “knock on the door” at some point. Irrespective of regulations, it cannot be assumed that any spray product’s active ingredients will make it into the body when the product is used as directed.

The topic of drug delivery through the tissues in the mouth has been discussed in scientific literature. There have been studies showing that small amounts of vitamin B-12 can be absorbed through the vascular membranes in the mouth and nose, which would have some application for individuals who have problems with B-12 absorption, but any advantage for others is questionable. Only certain types of compounds can pass through oral membranes. The science here is rather heady, but there is an application with certain types of pharmaceuticals: Oral absorption can be facilitated by additives designed to assist with the process, but these artificial, nonfood compounds are not allowed in dietary supplements.

The bottom line is that mouth and cheek tissue can serve as a portal for certain substances, but it is far from an open-door policy.

As for foot pads, there is obviously no “swallow” involved, so these are not even dietary supplements. They are a drug or a medical device, and unapproved at that. Such products cannot legally bear a “Supplement Facts” label. I could find no evidence that these types of products are effective with “detox,” weight loss or any medical condition.

Consumer protection organizations, including the Federal Trade Commission and attorneys general of the states, have acted to stop the marketing and sale of such products. The fact that you might see them for sale should not be taken as an indication of their efficacy or legality.

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 actually controls how much cholesterol the body makes? Can the body manufacture more cholesterol than it gets in food? -- D.D., Philadelphia

DEAR D.D.: Cholesterol is an essential structural element in every cell of the body. It is also a raw material for many hormones, including estrogen and testosterone. Given these points, you would wonder how vegans survive -- without eating animal products, they have no source of dietary cholesterol.

The answer is that the body does, indeed, make cholesterol on its own. It is a waxy substance and, like other lipids, does not dissolve in our body’s water-based blood. As a result, it needs to be shuttled around the blood inside fat-carrying proteins called lipoproteins.

Most of the body’s cholesterol is manufactured in the liver. When cholesterol is present in the foods we eat, the liver is programmed to make less. There are a number of genetic conditions in which the body makes more cholesterol than it needs, but they are rare. More common is the condition in which a person has an unbalanced diet heavy in meat, fat and simple carbohydrates, and light on whole grains, greens, fresh fruits and vegetables. Couple this with an inactive, stress-filled lifestyle, and elevated blood cholesterol comes knocking at the door.

This is a concern for many, so I encourage you to read more on the topic at tinyurl.com/ya489wua and tinyurl.com/ycu2s63m.

DEAR DR. BLONZ: At least once a day, three fingers on my right hand turn white, then purple. They feel tingly and usually become numb. My doctor has never seen it happen. He has not known how to approach the situation, so it gets ignored. What do you think it could be? Is it related to allergies or anything I am eating? I’m a 78-year-old woman in otherwise great health, but this is quite annoying. -- L.E., via email

DEAR L.E.: I need to remind you up-front that I am not a medical doctor, so I cannot diagnose your problem or dispense medical advice. But I can say that your issue is not likely to be related to nutrition. The National Institute of Health has information about a condition known as Raynaud’s phenomenon at tinyurl.com/y7wm4rcv. I would recommend that you read this and determine if it fits your situation.

Then -- and this is most important -- make an appointment to discuss the issue with your physician. You can take the information from the NIH (or not, if it doesn’t apply). If you don’t get the attention you need from your current health professional, seek another. Your health is on the line, and you should not be ignored.

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’m wondering about the differences between the protein found in red meat, such as steak, and that found in seafood, such as shrimp. I only eat red meat a few times a month, and am concerned about whether I’m getting enough protein. I take a multivitamin every day, but know that nutrients from food are more important. On the physical side, I do a cardio workout every other day, working with weights on the alternate days. I don’t smoke, drink minimally and am overall very healthy. My only concern is nutrient-based. How does the quality of the protein in shrimp compare with the protein from steak? -- L.W., Madison, Wisconsin

DEAR L.W.: Think of protein as what we are made of. The list of body proteins includes hair, skin, muscles, organs, blood cells, nerve tissue, brain tissue, hormones, antibodies, DNA, RNA, and even the enzymes used to digest the foods we eat. It’s fitting that the word “protein” comes from the Greek “proteios,” which means “primary” or “first.”

Proteins are made up of long chains of assorted amino acids. They tend to be too large to be absorbed intact, so after being eaten, our stomach releases acid to denature the protein and facilitate the action of the digestive enzymes in the small intestine. Enzymes separate proteins into their amino acid constituent parts, which can then get absorbed into the body. Once in the body, these amino acids serve as building blocks for the body to make any of the proteins it needs. The human body can actually make its own amino acids, but there are exceptions; the ones we can’t make are referred to as the essential amino acids, and they must be provided in the diet.

One of the ways that scientists “score” proteins is by looking at the types of amino acids they contain, and then comparing this with the amino acids in our body proteins. Those that compare most favorably have the highest scores. 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, where there can be plenty of amino acids, but lesser amounts of one or more of the essential ones. This lessens the overall score.

There are minor differences between the proteins that make up 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 own protein. To answer your question, you should consider them to be comparable.

Most people have no problem getting the protein their body requires. The key is to have a mix of high-quality protein foods, together with other protein-containing foods, including grains, legumes, vegetables, nuts and seeds. Vegans accomplish this by sticking to plant foods to satisfy their requirements.

Be advised that in this country, we tend to eat more protein than our bodies need. Excess protein doesn’t give you more muscles; it becomes nothing more than calories that get turned into body fat. Let me close by saying that you have my admiration for your healthy exercise habits.

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.