DEAR DR. BLONZ: I know that activated charcoal is the main ingredient in the water filter cartridge I use, but I have seen this same substance sold as a dietary supplement that can act as a blood purifier. Is this possible? -- C.C. Berkeley, California

DEAR C.C.: Activated charcoal is a specially treated and purified form of charcoal. It is a very fine powder, giving it a large surface area. Fine, powdered charcoal is an adsorbent (note the “d”), which means it has an ability to attract and hold on to substances on its surface. Contrast that with an absorbent substance (note the “b”), where liquids are soaked up as if by a sponge. This adsorbency makes activated charcoal useful for water filters, because it attracts and holds heavy metals and unwanted minerals and odors.

Regarding the second part of your question, activated charcoal is often given after an accidental ingestion of poison. Its adsorbent qualities help grab the poison, limiting its negative effects on the digestive tract and preventing the poison from reaching the bloodstream. (According to a statement from the American Academy of Clinical Toxicology, activated charcoal is most likely to produce these benefits if administered within one hour of poison ingestion.)

Given that the activated charcoal itself is not absorbed into the body, it is unclear how it could work as a “blood purifier.” It could prevent a toxin from being absorbed, if used appropriately, but there is no evidence that it could act to purify toxins already in the blood. Also, it’s not wise to consume activated charcoal on a regular basis, especially around mealtime, as it can grab and prevent the absorption of essential nutrients.

DEAR DR BLONZ: I learned in school that the riboflavin in milk is destroyed by light. If that is true, why is milk allowed to be sold in clear containers? Am I wasting my money by paying more for it in opaque containers? -- S.T., Richmond, Virginia

DEAR S.T.: A “waste of money” assessment is a bit of a judgment call, but here are some of the things to consider. Milk is a perishable food, and exposure to light (whether natural or bright fluorescents) can destroy a percentage of certain nutrients. These include riboflavin (vitamin B2), vitamins C and B6. Light can also encourage the development of “off” flavors. Assuming proper storage temperatures are maintained, the duration and intensity of light exposure determines how many of these nutrients will be destroyed. Always check the date on the carton to be sure it’s within the designated period.

All things being equal, opaque containers, such as paper cartons, are best for preventing the type of nutrient destruction you mention. Glass provides the important element of recyclability, although many areas of the country also recycle plastic and cardboard cartons. Then there is the point that glass is heavier and more fragile, which will increase transportation costs. But whether plastic, glass or paper, the jug, bottle or carton will still contain a healthful food.

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: It’s a new year, and I am researching a “100 percent natural” weight-loss tea. So far, I have been unsuccessful in verifying the claims it makes, such as its being able to foster five pounds a week of weight loss. Have you heard of any such tea or herbal weight-loss remedy being able to do this?

Apparently, this product has natural fat-burning enzymes that are quickly absorbed into the bloodstream and are carried throughout your entire body, continuously releasing millions of fat-eating enzymes. It also claims that its first stop is in your digestive system, where its flavonoid enzymes rapidly start to clean and unclog your large intestine’s mucous membrane, which could make you lose three to four pounds within the first 48 hrs. Then, it says your metabolism is forced to accelerate the elimination process to preserve lean muscle tissue and enhance muscle tone. This process is supposed to drain out fat accumulations at the rate of about 454 grams per day (one pound). I know it all sounds too good to be true, but is there any chance it might work? Or is it all a myth? -- E.K., Phoenix

DEAR E.K.: Your last three words, “all a myth,” sum it up well. The idea of a fat-burning enzyme quickly absorbed into the bloodstream that “releases millions of fat-eating enzymes” makes absolutely no sense.

Claims are easy to make, especially when you don’t have to back them up. I would predict a total lack of any objective evidence, mainly because if such stuff were verifiable, science would be all over it. I wouldn’t waste my time or money with such hooey.

Checking the unspoken “big picture” here, excess weight tends to take years to get on board, so to speak. Don’t look for, or expect to find, a quick fix. Rather, you should invest in several subtle ways to tweak your eating and lifestyle habits to foster slow, but steady, progress toward your goal.

DEAR DR. BLONZ: Are almond, rice or coconut milk as nutritious as soy milk? How do they get milk from these foods? -- S.B., Kenosha, Wisconsin

DEAR S.B.: You can get a milky beverage from many foods. In addition to almond, rice, coconut and soy, there are “milks” from oats, hemp and a variety of other plant foods. Most are made by soaking the plant in water for many hours and then grinding it with additional water. There can be filtering to eliminate particulate matter, and some types can be cooked somewhere along the line. Flavors such as chocolate or strawberry can also be added.

Each type of milk will have its own unique flavors and nutrients. Rice milk, for example, is lower in protein and most vitamins and minerals than soy milk, but it is higher in carbohydrates and richer in folic acid.

A variety of “milk” offerings are now fortified with nutrients, especially calcium, to approximate the levels in dairy milk. There can be varying amounts of fat and added sweeteners, so it is essential to read the Nutrition Facts panel and compare your options.

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: My husband has high blood pressure and is watching his salt intake. He doesn’t want me to add salt to our food, and he thinks he is being careful. But I am concerned about the hidden sodium in processed foods. How many milligrams of sodium are there in a teaspoon of salt? And how much should he be having per day? -- M.D., Berkeley, California

DEAR M.D.: There are approximately 2,325 milligrams of sodium in one teaspoon of salt. The Daily Value -- the set of nutritional guidelines developed for food labels -- uses an upper limit of 2,400 milligrams of sodium per day. The average sodium intake in the United States is between 4,000 and 5,000 milligrams per day.

The main concern about excess salt stems from its association with hypertension, or high blood pressure, which currently affects 1 out of every 3 adults. Hypertension is defined as blood pressure readings higher than 140 over 90. The first number (140, in this case) is the measure of the pressure in the arteries when the heart contracts, and the second number (90) is the pressure in the arteries as the heart relaxes between beats.

Hypertension is called the “silent killer” because there are no warning signs until problems such as heart disease, stroke, or kidney disease have already developed. The only reliable way to find out whether you have hypertension is to have regular blood pressure checks.

If your husband has high blood pressure and has been placed on a low-salt diet, you are correct in being concerned about hidden sodium. With the exception of sugar, we add more salt to our foods than any other condiment. About 10 percent of the salt we eat is naturally present in foods; 15 percent is added during cooking and at the table. That means 75 percent of the salt in our diet comes from processed foods.

Salt is added to processed food for a number of reasons. It can slow the growth of certain microorganisms; before refrigeration, salting was the only practical way to keep meat and fish from spoiling. Salt can also play a role in food texture: Processed meats such as bologna, hot dogs and lunch meats contain higher levels of salt because it helps form and maintain the gel-like consistency of these foods. Then, of course, there is salt’s role as a flavor enhancer. Salt can be delicious, but the key is to learn to enjoy foods’ natural flavors, not that which comes from the salt shaker.

There is definitely a relationship between salt intake and high blood pressure, but not everyone with high blood pressure will benefit to the same degree when reducing their intake of sodium. Research tells us that the most reliable way to help reduce elevated blood pressure is to lose excess weight, increase activity and decrease alcohol consumption. (Be sure to check with your physician before beginning any exercise program.)

There have been impressive numbers coming out of the DASH studies (Dietary Approaches to Stop Hypertension), showing how blood pressure can also be lowered by decreasing sodium intake and following a diet that’s low in total and saturated fat but rich in fruits, vegetables and dairy. Not surprisingly, the DASH diet was named again as the best overall diet (tinyurl.com/3j57mmw).

As regards processed foods, check the Nutrition Facts label to see the milligrams of sodium per serving. I suggest you begin making note of the processed foods you and your husband eat and keeping track of how much sodium they contain.

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.