DEAR DR. BLONZ: I'm inquiring about the use of activated charcoal to help get toxins out of the body: how much to take and whether it works as a blood purifier. -- L.N., Anderson, North Carolina

DEAR L.N.: Activated charcoal, a purified form of charcoal ground into a fine powder, needs some explanation. Activated charcoal is not absorbed into the body; instead, it acts locally with whatever substance it comes in direct contact with. Its fine powder consistency gives it a large surface area to do its job, and its pure carbon composition attracts and holds onto substances using a process known as adsorbence (not to be confused with absorbance).

Adsorbency is why activated charcoal is used in water filters: It grabs and holds heavy metals, unwanted minerals and odors. Activated charcoal is often used in first aid after accidental poisonings, as it holds on to the poison and prevents it from getting into the blood. (According to a position statement of the American Academy of Clinical Toxicology, activated charcoal is more beneficial if administered within one hour of poison ingestion.)

It is unclear how activated charcoal could work as a blood purifier, because it isn't absorbed into the body. It can keep things out, but there is no evidence it can grab on to toxins already in the body. So unless your doctor instructs you otherwise, there is no reason to consume activated charcoal regularly. It can reduce the absorption of nutrients, but even more concerning, activated charcoal can adsorb medications, rendering them unavailable for absorption. (For more on activated charcoal, see b.link/r65ey55.)

DEAR DR. BLONZ: I drink three to four liters of sparkling (carbonated) water daily that I make from filtered tap water in a home device. I don't like regular water, so I figured this would give me my daily requirements. I often add fresh lemon or lime juice, but no sweetener. I don't drink any sodas.

I was on a plane recently, and after ordering soda water, the man sitting next to me stated that drinking carbonated water affects the nutrients the body absorbs because of the CO2 it contains, and now I'm concerned. I am health-conscious, eat well and work out regularly. Are even unsweetened sparkling beverages bad? -- A.H., Pomona, California

DEAR A.H.: Outside of causing a burp now and then, there is no evidence that the carbon dioxide (or CO2) in carbonated water -- also known as sparkling water or club soda -- causes any nutrient deficits. Albeit a bit more costly, drinking a carbonated mineral or spring water is a perfectly fine way to get your daily water requirements.

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: A holistic doctor featured at a recent wellness conference stated that pasteurization destroys a critical enzyme in raw milk that is needed to absorb calcium. Is this true? -- M.Q., Phoenix

DEAR M.Q.: There are enzymes in raw milk that are broken down by the process of pasteurization, so that part is correct. However, the real issue is whether these enzymes are critical for the body's absorption of the calcium in milk -- and the answer is no. The calcium in dairy has good bioavailability, and there is no clinical evidence that it is significantly better absorbed when consumed in raw versus pasteurized milk.

There are several enzymes in raw milk -- some are from the cow, and others are in the bacteria naturally present in the cow's digestive system. One milk enzyme produced by the cow is plasmin, a protein-digesting enzyme that degrades milk, causing spoilage. Anyone who has seen the clumps or mistakenly consumed spoiled milk can attest to its unpleasantness.

Pasteurization, while not a sterilization process, involves the application of heat to reduce the level of potentially harmful microorganisms that can cause spoilage or disease. It knocks out some, but not all, of the enzymes and bacteria, which allows the milk to remain wholesome through its projected period of storage and use. Refrigeration slows bacterial growth and enzymatic action, which is why milk goes bad if it's allowed to sit out too long. (There are extended storage periods for milk products processed at higher temperatures [ultrapasteurized] or packaged in aseptic containers. For more information on milk expiration, see b.link/qb4mmax.)

The lecture you mentioned sounds like an unscientific milk attack. Some people have no interest in milk, and others feel it is food only for calves. Dairy provides us a healthful package of essential nutrients, but not everyone wants to drink milk, and not everyone needs to.

DEAR DR. BLONZ: I read an article concerning the benefits of selenium, but it recommends taking yeast as a supplement. I seem to have an intolerance to the yeast in bread and cheese, which causes bad stomach pain. Does this mean I shouldn't take selenium? -- N.S., Tulsa, Oklahoma

DEAR N.S.: The selenium present in our foods depends significantly on the selenium content of the soils or waters in which they're grown. The same can be said for yeast, as the mineral will be present only if the yeast is allowed to grow on a selenium-rich medium. Typical food sources for selenium include seafood, such as tuna, clams, oysters and swordfish, nuts (especially Brazil nuts) and seeds, organ meats, and grains such as oats and wheat. (For more on selenium, see b.link/ebgbcf9.)

Selenium deficiencies are uncommon, but if you are looking for a supplement and are concerned about yeast, be sure to find one that's yeast-free. Finally, check with your health professional concerning the stomach pains you have been experiencing.

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 have been using olive oil as much as possible in cooking and salads. Much of the time, and always in baking, I use the "extra light" olive oil from a warehouse store. Recently, I have heard suggestions that the extra light may not have the same healthful fats and other benefits that fruity extra virgin olive oil has. How do the health properties of these two types of olive oil compare? -- O.O., Chicago

DEAR O.O.: The fats in all types of olive oil are comparable, containing approximately 77% monounsaturated, 9% polyunsaturated and 14% saturated fatty acids. The calorie content is also comparable. Extra-virgin olive oil, however, tends to have a greater concentration of healthful phytochemicals and more health attributes than lighter oils.

The phytochemical benefits become apparent when you consider that the olive is the fruit of the olive tree, and the oil is there to nurture the developing seed until it can begin to grow on its own and sprout leaves to gather needed energy from the sun. It would reduce the seed's growth ability if the oil it needed for energy had turned rancid.

Because oils are prone to breakdown, mostly through oxidation, successful plants have evolved to produce protective phytochemical compounds that include different antioxidants. We find some vitamin E and other important antioxidant compounds, known as polyphenols, in the olive. These compounds help maintain the vitality of the olive oil, and many have distinct flavor characteristics that can be detected in premium oils.

If you want the fats provided by the olive and are less interested in its flavorful polyphenols, then the "extra light" version is worth consideration. (For more on olive oils, see b.link/qwngx9ee.)

DEAR DR. BLONZ: I buy raw almonds and roast them at home, baking them in a toaster oven at 250 degrees for about half an hour. I often add spices for unique flavors. After serving them at a party, one of my friends asked whether roasting the almonds causes the oil in the nuts to become saturated fat. I have also heard that heating almonds diminishes their nutritional value, specifically vitamin B. Is this true? Are raw almonds preferable for their nutrition and health value? -- M.C., San Diego

DEAR M.C.: Dry-roasting in a toaster oven is not associated with any meaningful decrease in almonds' nutrient value. The same can be said for oil-roasting, although the oil adds a bit more fat content. Using either method and roasting correctly, the oils in the nuts do not become more saturated.

In terms of nutritional value, any high-heat process can destroy some thiamin (vitamin B1), but the other nutrients, especially the minerals, are relatively unharmed. I consider nuts and seeds to be healthful foods. The choice between raw and roasted almonds, nuts or seeds is simply personal preference. In all cases, be sure to store them properly. (For more information on correct nut storage, see b.link/2xb9aq7.)

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.