DEAR DR. BLONZ: I keep reading about "buying locally." I can see the good in that it would involve fewer resources, but it seems that if you buy all your food from your area, you wind up with the nutrients only from that area, and might miss others. I am curious about the possible benefits of getting food that is grown all over the world. -- B.K.

DEAR B.K.: "Seasonality," where we are limited to foods available during periods in which they are harvested, is less of an issue in today's fully stocked supermarkets. Much depends on where you live; there is less impact in a state like California, where vast agricultural resources and temperature-controlled transportation methods keep fresh produce available throughout the year. But even with bountiful harvests, there will be periods during which specific foods may not be available. (One of my favorites is dry-farmed Early Girl tomatoes, which are around only a few months of the year. To my palate, no other tomatoes come close.)

Store shelves remain full as grocers purchase fresh foods grown worldwide and organically grown produce available from the Southern Hemisphere when it's winter in the north. We should support local agriculture by buying locally and patronizing farmers markets when possible. Quality can vary, as some regions do a better job with specific foods than others; this is often based on cultural traditions perfected over generations. As for potential health benefits, nutrients reflect more the quality and variety of what you eat rather than where it was grown.

DEAR DR. BLONZ: After I get my dietetics degree, I am considering graduate school, with the goal of working for a food company to develop nutritious foods with less processing, ideally by using controlled atmospheres. I want to develop, test and promote various food products, create new recipes and improve existing ones. Would getting a graduate degree in food science or nutrition be more beneficial? I would appreciate your opinion since this is your area of specialty. -- J.D.

DEAR J.D.: A dietetics degree will provide a foundational understanding of how nutrients work in the body. A graduate food science degree would seem logical if you want to work in the food industry. In addition to learning essential information about food production science, you would be more marketable when looking for a job. Consider a school with food science and nutrition departments; some may have these combined. The Institute of Food Technologists may be a good resource. This professional organization is based in Chicago, and it provides information about careers in the food industry (ift.org).

As you compile a list of possible schools, check online for a list of faculty research interests. Academic departments' successes depend on their faculty's strengths, and reviewing their interests is an excellent way to see how a department is oriented. In graduate school, you will take the required coursework, but will be associated with a professor to guide you on projects. You'll be ahead of the game if you find a school with one or more faculty members that either speak to your current interests, or describe an area of research you want to pursue.

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 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.