DEAR DR. BLONZ: A recent magazine article suggested that daily vitamins aren't necessary for adults over 65. Do you agree? -- T.G.

DEAR T.G.: I don't see it that way, but let me share the backstory. I do not favor using daily vitamins as an excuse for not making efforts toward a healthful diet and lifestyle. And it is incorrect to think that getting all of the "essentials" in a pill will cover all the nutritional bases. Vitamins can supplement healthful eating, especially when you need certain essential nutrients not typically present at recommended levels in your foods.

History is instructive here. Essential nutrients were discovered when things went wrong in experiments where all known essentials were thought to have been provided. Subsequent reviews discovered that one or more missing substances were responsible for the results, which were then studied and eventually added to the list of essentials. The different vitamin letters and numbers show that this has been an ongoing process -- and we are not done yet. (Check b.link/67v67w for a story of vitamin history.)

Next, consider that most discoveries were made when short-term studies found unexpected outcomes. We seem to have done well with substances where deficiencies give rise to immediate effects, but what about those needed to impact long-term outcomes for aging and chronic disease? My advice is to look to nature, where the successful evolution of plants serves as an object lesson. With plant-based, whole-food eating, we get "known" essentials packed with partner substances to complement their action. (My prediction is that those partner substances will be where future essentials will be discovered.)

Nutrients work with teams of substances in complex biochemical reactions. Similar to how exceptional talent is valued in an orchestra, sports team or business, the entire ensemble is needed to succeed -- the system is only as strong as its weakest link.

Whole foods evolved by making teams of interacting protective substances to protect the plant and facilitate its ability to produce its next generation. When such foods are at the core of our eating plan, we import these benefits into our bodies. Evidence can't say the same thing regarding poor eating habits. For example, vitamin C -- ascorbic acid -- is a powerful antioxidant and free-radical scavenger. It works well when part of a whole food, such as citrus, where it comes with other nutrients, dietary fiber and a support staff of "co-worker" antioxidants to help. If you add a bunch of vitamin C to junk-food eating, it will still do its dance. But without any support staff, the vitamin C -- particularly if taken in excessive amounts -- can become a pro-oxidant and cause the very damage that it was taken to prevent.

Back to your straightforward question: Plant-based whole-food eating must be primary; a multivitamin can supplement such a diet. If healthful eating is on the scene, I have no problems with their use.

Read more about vitamins at b.link/zhf8g6. You can also check out Consumerlab.com, a subscription site that tests and reviews various multivitamins and 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.

DEAR DR. BLONZ: On the subject of sea salts, I am less concerned about contaminants in Himalayan sea salt because it is 3 million years old. However, I am skeptical of, and would not knowingly use, sea salt from the Caribbean and Southeast Asia. We have traveled there a lot to scuba dive. Almost all the islands discharge raw sewage and industrial waste directly into the ocean -- the source of the seawater that can flow into evaporation ponds to make and export table salt. I am concerned that the inorganic contaminants, although present in low concentrations in the seawater, would be concentrated by the process of evaporation to salt crystals. -- B.T.

DEAR B.T.: Your experiences present reasonable sources of concern, but products meant for human consumption must be tested and found safe before being marketed in the U.S.

Seawater is not safe to drink, as it is full of impurities. That would also be the case for salt obtained directly from seawater. Sea salt approved for sale in the U.S. must undergo more than simple evaporation -- typically, a washing process sufficient to remove impurities.

Gourmet salts, like other foods, can come from protected geographical areas in which quality can vary. The output from some regions may be suitable for humans, while others may only produce salts suitable for animals. Note that if a familiar brand indicates it is for animals, it cannot be assumed safe for humans unless expressly stated on the label.

The United States and other countries have geographically protected areas for the production of certain goods. Products from these areas must meet certain standards of quality and include the name of the locale on the label. For more on such U.S. areas, called "geographical indications," see b.link/sggetj. For European Union designations, see b.link/gpmy3s.

The one thing all salts share is that they are predominantly salt (sodium chloride), with only minimal amounts of other minerals -- not nearly enough to count as good dietary sources. While the other minerals can affect how the salt tastes on the tongue, this tends to get lost when used in a recipe.

DEAR DR. BLONZ: One of your recent columns mentioned the coloring used to make "salmon pink." I'm surprised you didn't reference the Monterey Bay Aquarium's Seafood Watch program. It provides a wealth of information about which fish -- farmed or wild -- is best to eat, which to avoid and why. You can explore seafood and the industry from different angles and read the stories behind some fishery operations. The goal is to keep the oceans, and us, healthy. The program even provides printable pocket guides to take to the market to help us make the best choices around sustainable seafood buying and eating. It's an excellent resource, and makes for some eye-opening reading. -- L.M.

DEAR L.M.: My thanks for mentioning Seafood Watch (seafoodwatch.org). It is very informative, but relies on generalities about different types of fish. There can be good, bad and ugly players all over, so it is important to check about individual purveyors to see if they are doing it right. (Having a trusted fishmonger do this for you is a plus.)

On a related note, I recommend visiting the Monterey Bay Aquarium, as it provides a unique educational experience for the whole family.

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 a question about minerals and absorption. Let's say that our body can only absorb 50% of the minerals in a supplement, and that supplement label shows it supplies 100% of the RDA. Does that mean you must take twice the dose to absorb the RDA? How does this apply to food labels? -- S.M.

DEAR S.M.: Dietary recommendations consider the body's absorption efficiency -- they reflect the average amount an individual should eat daily to satisfy their requirements. If, for example, science determines that the average body should have 300 milligrams of a particular mineral every day, and if the research indicates that we absorb only about 30% of this mineral in our food, then the recommended dietary allowance (RDA) for that mineral would be 1,000 milligrams per day (30% of 1,000 = 300). This allows us to take RDA figures literally. Still, an additional heads-up is needed in relation to your question.

Foods and dietary supplements make use of the Facts labels (Nutrition Facts and Supplement Facts), and this system uses the Daily Value (DV), not the RDA. The RDA is based on research data to establish requirements according to gender and age. The DV, by contrast, presents one set of numbers for all adults. The intended role of the DV was to help consumers decide between foods by providing a way to check which provides the preferred nutrient profile. DVs are based on the RDAs, but are not as precise. Read more on Daily Values at b.link/mq2sqr.

DEAR DR. BLONZ: You debunked the ice hack, but it left me wondering whether there is a potential for drinking too much water that could possibly hurt the body or the kidneys. -- P.O.

DEAR P.O.: You can overconsume most things, and water is no exception. With water, it is referred to as overhydration, which can progress to water toxicity. That's right: pure water, the toxin!

This risk is based on the fact that the body cannot eliminate pure water. An amount of electrolytes, present in all bodily fluids and essential for nerve transmission, gets shown the door with every drop of urine and sweat. Sodium, the main element in salt (sodium chloride), is our primary electrolyte in body fluids and tissues; this explains why perspiration has its salty taste. Our body requires specific concentrations of items to work. Overhydration forces the elimination of the excess to bring concentrations back into line, which can drain sodium to dangerous levels (hyponatremia).

Low sodium becomes particularly problematic for folks with cardiac issues, such as congestive heart failure, but taking in too much water also becomes a serious issue for those with existing kidney disease. Plain water is the culprit; there is less of a risk when water comes with electrolytes, such as in well-made sports drinks. For more information on drinking water, see the National Library of Medicine info page at b.link/7b55s4.

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.