DEAR DR. BLONZ: My husband and I eat fresh Atlantic salmon once weekly. The particular salmon we usually eat is farm-raised and purchased from Whole Foods Market. Recently I have read that the mercury levels in salmon differ depending on type of salmon and where it was farmed or caught. This makes sense to me. Is this correct? To what authority should we refer for safe consumption guidelines of different fish species caught or farmed in different areas of the world? -- E.S., Concord, Calif.
DEAR E.S.: A good start is to visit the site of the Monterey Bay Aquarium (tinyurl.com/23ze8sj), which has an excellent explanation of different fishing methods and can introduce you to the language of the industry. Fish farms are enterprises that can vary in their practices, and they should not be condemned outright. We need to avoid any that do a lousy job cleaning up after themselves, and those that pollute and ruin the environment for other fish, animals and people affected by their output. Once you understand the issues and the potential negatives, you can then consult a site like cleanfish.com to see examples of fish farms that have taken steps to distinguish themselves and provide healthful food with minimal environmental impact.
I always encourage customers to speak with the store where they buy their fish to find out what the sellers know about their suppliers, especially any farmed-fish suppliers. This information should be available from supermarket chains, especially one such as Whole Foods, but you may have to ask, or even insist. Let them know that if they want your business, they need to be upfront with this information. If you are given the name of a supplier, you can do your own research online to find out more. I won't buy farmed fish unless it says where it is from, or unless I have confidence that my fishmonger has done this type of screening for me. This practice also makes sense for your meat and poultry purchases.
You mention salmon, which is definitely a favorite in our house. We enjoy salmon from Loch Duart (lochduart.com), a sustainable fish farm in Scotland. You can find out more about this particular type of salmon at the cleanfish.com site. My local market, Kensington Fine Foods, carries the Loch Duart salmon; you can encourage your store to carry this or another type that meets your needs. Stores want to carry quality items that their customers want, but you have to let them know.
Your question included a concern about mercury and this is certainly a valid concern regarding fish, as mercury is a dangerous toxin. A study in the April 2013 issue of the journal Environmental Science and Technology reported that over 70 percent of the mercury in the human body comes from the mercury present as a contaminant in fish. The good news is that salmon is not one of the fish of serious concern in this regard. The most commonly consumed fish found to have higher levels of mercury contamination include swordfish, shark and certain -- but not all -- types of tuna. For information about the mercury content of fish, gotmercury.org is a site that allows you to assess the risk of different types of fish, regions and fishing methods, and the impact of various levels of mercury intake.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.