DEAR DR. BLONZ: What are your thoughts about farmed salmon, and how color additives are used to make it look like wild salmon? Do you have issues with farmed fish? -- M.C., Hayward, California

DEAR M.C.: The "you are what you eat" paradigm applies to fish as well as to humans. You may be surprised to learn that the genetically predetermined color of salmon is closer to gray. The characteristic "salmon pink" is a byproduct of their diet -- through their consumption of color compound-rich plants and algae, and also from eating smaller crustaceans or other fish that have eaten those colorful items. A key color compound is astaxanthin, a reddish antioxidant pigment in the carotenoid family. Interestingly, canthaxanthin, a compound related to astaxanthin, is used in tanning pills; when taken as a supplement, their color distributes in the fatty layer of the skin to provide the "tanning" effect (for more on tanning pills, check b.link/3rjug8).

Wild salmon get their color naturally, but farm-raised fish get it only if purposefully fed plants or animals containing the color-causing compounds, or if a color additive is added to their feed. Aside from individuals who might have a sensitivity or allergy to carotenoid compounds, there is no evidence of risk to consumers from astaxanthin when used as a "natural" color compound in fish feed. Check with your health professional if you have any concerns.

Regarding farmed fish in general, I lean toward wild-caught fish when available, but it's not a rigid preference. A wild fish caught in yucky waters offers no health advantage over fish raised in a sustainably managed fish farm.

I encourage consumers to speak with their fish suppliers to learn about the origins of the wild or farmed fish they are considering. Ideally, sellers should have this posted on the package or display case. This information should also be available from supermarket chains, but you may have to ask the manager. Always remember that you are the customer; let them know that if they want your business, they need to be upfront with such information. If you are given the name of a supplier, you can do your own research online to find out more.

It's great to find a fishmonger that does this type of screening for the customer as a matter of routine. This research also makes sense for your meat and poultry purchases. Your question relates to salmon, which is definitely a favorite in our house. We sometimes purchase wild salmon, but often go for sustainably farmed fish, such as that from Loch Duarte, a fish farm in Scotland (cleanfish.com). It's in our local market, but I encourage you to check at your local fish store for this or a similar line of sustainably raised fish, or you can encourage your store to carry one. Stores seek to offer what their customers prefer, but often you need let them know exactly what that is.

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: We just moved to a "hard-water" area that relies on a water softener to keep appliances from getting over-mineralized. Do I need to bypass softened cold water for drinking? How much sodium does one get from softened water, and is it a problem? Does the Brita filter remove sodium? Nobody in the family has issues with high blood pressure. -- E.A., Madison, Wisconsin

DEAR E.A.: The level of minerals in a given water supply varies by geographical location and by how the water gets processed before being consumed. Water with higher concentrations of calcium, magnesium and other minerals is said to be "hard." (For more about geography and water hardness, see b.link/dyjJfm.) Typically, there isn't enough of these minerals to make the water a significant dietary source, but hard water can leave mineral deposits in water pipes and fixtures, on pots and pans, on appliances such as water heaters, coffee makers and tea kettles, and can leave mineral spots on glassware and soap film in the tub and shower.

Water softeners work by exchanging sodium for the water's naturally occurring calcium and magnesium. Sodium is more soluble; the resulting water is said to be "soft." In addition to not leaving mineral deposits, soft water works better with detergents, so your clothes get cleaner. One study at Purdue University found that clothing and household textiles last about 15% longer when washed in soft water.

The amount of sodium in softened water varies because of the level of minerals being replaced; the higher the initial concentration of minerals, the greater the amount of sodium after softening. It is generally not that much, but check with your water softener company to determine the level of minerals in your area and how much sodium would end up in your softened water. For a general perspective, hard water that starts with 15 grains of minerals per gallon will end up with the equivalent of 28 mg of sodium per cup after softening. Given the dietary guideline to stay below 2,300 mg sodium per day, this would make softened water a very low source. This could be an issue for someone on a strict low-sodium diet, so be aware of what is in your water supply and how your softener operates, and check with your health professional. Water-pitcher filters, such as the Brita brand, do not remove sodium from softened water.

It's good news that your family has no problems with blood pressure. While hard water is considered better to drink, one option is to have the house-water softener connected only to the hot-water line. You could also use potassium salts or a mix of sodium and potassium rather than straight, sodium-based softening salts. Another option is to use a reverse osmosis device to remove the sodium from the softened water. Finally, while on the topic, softened water might not be ideal for certain plants, so find out if there might be an issue with what's growing at your place.

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 keep seeing messages that foods are now mineral-deficient, and we need supplements to prevent deficiencies. Which minerals are currently believed to be essential for good health? Are there still as many of these as there used to be, or has modern agriculture made it so foods have less? -- T.S., San Diego

DEAR T.S.: A mineral is loosely defined as anything in nature that is not animal or vegetable. Minerals are inorganic chemical elements required for specific structures or metabolic functions; "inorganic" means they do not contain the element carbon. The body cannot synthesize or change minerals; they don't provide calories and are needed only in small amounts relative to protein, fat and carbohydrate. The body can become more efficient in recycling some nutrients; still, prolonged insufficient intakes lead to a failure to thrive and the development of deficiency diseases, the expression of which depends on the nutrient.

Minerals needed in more significant amounts include calcium, chloride, magnesium, phosphorous, potassium and sodium. Chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium and zinc are equally essential, but needed only in trace amounts. (Check the National Library of Medicine's page on minerals at b.link/5wfsdv.) All the minerals the body needs can be found in food.

Think of plants as miners, pulling the mineral elements out of their environment, unable to grow and thrive if an essential mineral is absent. It follows that essential minerals that leave with the plant at harvest need to be replaced using fertilizer or compost, or subsequent yields will drop.

Minerals that are not essential for the plant can also end up in the food; what enters can vary by mineral, soil and weather -- even among different varieties of the same fruit, vegetable or grain. The plant's overall nutrient content can also vary by the length of time the plant has had to grow. Although the differences might not be significant, a plant picked green that ripens after harvest may not have the same total nutrient content as one allowed to ripen "on the vine."

For example, whole foods grown in iodine-rich or selenium-rich soils tend to have more of these nutrients than the same type of food grown in soils with lesser amounts of these minerals. Of historical interest, iodine-rich soils tend to be close to the coast, with less iodine found in foods grown inland. The incidence of goiter, an expression of iodine deficiency, once correlated with distance from the coast and led to the introduction of iodized salt in 1924. The typical diet in the U.S. is now iodine-sufficient, so iodized salt is no longer needed.

While we may have turned to varieties better suited to transportation and storage, it is incorrect to say today's fruits, vegetables or grains will provide any fewer essential nutrients than the same varieties would have provided in the past. Nutrient data tables, such as those provided by the USDA, present the nutrients expected in a particular food (fdc.nal.usda.gov/). Finally, check the source of the "foods are now mineral-deficient" messages you're seeing; aside from being misleading, you may find they originated from a party seeking to sell supplements.

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.