DEAR DR. BLONZ: I read your recent column on cans, solder and BPA. For years, I have been boiling water for tea or coffee in an old kettle, which has green stuff all around its exterior bottom surface. It is obvious that part was soldered. Does the boiling of the water act as a deterrent to any toxins from the kettle's solder? If not, what would the health consequences be in the short or long term? -- H.D., Rio Vista, California

DEAR H.D.: Although the green substance is on the exterior of the kettle, it may have resulted from minerals in your water accumulating over the years. The green color can be from limescale and mineral elements such as copper. You can see whether lead is involved by using a test kit, available online or at most hardware stores.

If you haven't already, review the mineral content of the water coming to your house.

Six ground wells supply the water in your city of Rio Vista, California. If your home is on that municipal supply, you can access your local water report. (Check with your supplier, whose name and contact information should be on your water bill.) The next element to consider is the state of your home's plumbing, which will take more research as it will not be reflected on a municipal water report.

Boiling can destroy microbial elements such as bacteria, viruses, protozoa and parasites. But it does not destroy or remove potentially toxic minerals such as lead, chlorine, arsenic, copper, nitrates or radon, nor does it destroy other toxic chemicals. The only way to eliminate them is through a quality water filtration system.

It isn't easy to generalize about short- and long-term health impacts, as that will depend on the exposure type, level and duration, and your overall state of health. But it is best not to be in the dark about your water.

The U.S. Environmental Protection Agency publishes an annual consumer confidence report on drinking water quality. Check that out (visit b.link/hslf3y), and then look at the CDC's page on water quality and testing (visit b.link/6zbdbg).

DEAR DR. BLONZ: Please settle a dispute at our house. Does removing the skin from chicken before you eat it get rid of a good proportion of the cholesterol? -- F.R., Anderson, South Carolina

DEAR F.R.: No. There is a small amount of cholesterol in the skin and its layer of fat. Once this is removed, however, the greater amount of cholesterol remains; it is present in every muscle cell of both light and dark meat.

This holds true for all animal products, including beef, pork, lamb and seafood. Buying leaner cuts of meats can reduce total fat, but it only slightly affects the dietary cholesterol in the meal.

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 famous medical doctor does these videos where he recommends the elimination of all corn from the diet for optimal mental and physical health. He doesn't refer merely to corn syrup, which I would understand needing to limit, but all corn, in any amount. One of the reasons he gave was the fatty acids in corn. This is all a bit shocking, as this is the time of year I look forward to enjoying fresh, sweet corn on the cob. Is there any basis for such concern? -- H.K., Tulsa, Oklahoma

DEAR H.K.: With the obvious exception of individuals who are allergic to it, the answer is no: You do not need to eliminate corn from your diet. Just like you, I consider it a harvest treasure that can be enjoyed in any healthful diet.

Fresh, sweet corn is a whole food that provides fiber, vitamins and minerals, as well as phytochemicals that are good for our vision (lutein and zeaxanthin). Are corn's fatty acids an issue? Maybe, if your diet was 100% corn. As with most individual foods, corn does not provide every fatty acid and all other nutrients the body needs. But that is a disingenuous argument, and it makes one wonder where these concepts originate -- certainly not with any evidence I have seen.

DEAR DR. BLONZ: I am wondering about nutrient losses when cooking carrots. In one class I took, the instructor mentioned that, when cooking carrots in water to soften them for a recipe, the best way to retain their nutrients was to keep the temperature just below boiling and keep the lid on tight to prevent evaporation. I wanted to question this, but it was presented as family advice passed down through generations, so it did not seem appropriate. -- J.S., Anderson, South Carolina

DEAR J.S.: The primary nutrient that is lost through evaporation is ... water. Higher temperatures can cause some nutrient destruction; the most heat-sensitive nutrients include vitamin B12, thiamine (vitamin B1), riboflavin (B2), niacin (B3), pyridoxine (B6), folate, pantothenic acid and vitamin C.

During cooking, water-soluble nutrients are distributed in the total volume of water, including that found naturally in the food. With increases in water temperature and food surface area, more nutrients end up in the cooking water. For example, being in water helps keep plant cells hydrated and intact. Virtually all the nutrients in intact carrots (greens removed) sitting in ice water remain in the vegetables. Some slicing and steaming, just until tender, will bring more nutrients into the water, but most still remain in the carrot. More will be lost if you do some fine dicing, followed by boiling, and then discard the cooking water. This is one reason that some recipes suggest saving the cooking water for use in a sauce.

Most fat-soluble substances, including vitamin A, vitamin K and any minerals, will remain in the carrot. Other healthful fat-soluble phytochemicals would also remain, as would all the fiber.

Carrots remain a healthful food, even when cooked. Best to be less concerned about minor nutrient losses and more focused on having a variety of healthful ingredients in all your dishes -- prepared in a way that helps you enjoy every bite.

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 family and I left town, and when we returned 48 hours later, I noticed that the stand-up freezer door was partially open. Everything inside was thawed out, except for about 4 pounds of ice from a 20-pound bag. I touched one sealed bag containing salmon, and it wasn't cold. Is this a total loss? -- D.D.

DEAR D.D.: In a power outage, a never-opened freezer can help save food, relying on the unit's insulation to help maintain the temperature. Conversely, a power outage and an open door is a recipe for a total loss. In your scenario -- a working unit with its door open for two days -- the prognosis is not much better.

The unit's compressor was forced to stay on. If it's a frost-free unit, like most are, the fan would also have remained on. Freezer compartments are well insulated and not affected by room air, or by heat from a compressor that only comes on as needed. But here, you had room air mixed with hot air from the ever-on compressor -- all pulled into the food compartment by the fan. I am guessing you noticed the room was warmer than usual when you returned -- not a promising situation.

Tossing defrosted foods that were meant to be stored frozen will always be the safest move. Why assume unnecessary risk? That definitely goes for animal products, including your salmon. There would be a slight chance to salvage some unopened frozen fruits and vegetable products, as long as they contained no dairy or other animal ingredients. The odds might go up for unopened packages that remained chilled -- perhaps those buried and insulated by other products, adjacent to ice or to the freezer's cooling coils. But even then, it's a roll of the dice.

For more detailed salvage options, check foodsafety.gov at b.link/qe5mfi.

DEAR DR. BLONZ: I took a cooking class, and the instructor had recipes for moringa. Apparently, it has been used in many forms in other countries. It is advertised to be a good protein source. Are you aware of it, and is it as good as they say? I have checked, but there are not a lot of studies. Can you give me your opinion? -- P.M.

DEAR P.M.: Moringa is a tree native to South Asia, often referred to as the drumstick tree. Its leaves have beneficial substances, including vitamins, minerals, antioxidants and other phytochemicals. Moringa leaf powder has a slightly bitter taste, similar to matcha green tea.

Moringa has been used in traditional medicine, but is now being promoted in supplements and as a "superfood." There is some protein present, but not enough to be considered a good source, given the amount of powder usually consumed. There are about 25 grams of protein in 100 grams (3.5 ounces) of moringa leaf powder, which translates to less than a gram in a teaspoon. Check how much is being added to those full recipes, and then consider what will end up in an individual serving.

My response is not meant to cast aspersions on what moringa might bring to a recipe, merely to add some practical perspective to any "superfood" touting. Enjoy the flavors. Moringa is a fascinating plant that holds great promise in regional agriculture and in populations with limited access to healthful foods.

For more on moringa, read the article at b.link/5b61l0 about research on this plant supported by the Fogarty International Center, which is a part of the National Institutes of Health that focuses on global health research.

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.