Concern about heavy metal toxicity is a very real thing as the world becomes more laden with chemical residue. Concern about mercury in fatty fish, sources of Omega 3 fatty acids, is seemingly good for the vitamin business (buy omega 3 capsules), but bad for people who believe that food should be our primary source of nutrition. Preganant women are warned to limit eating tuna, or just forget about it. Now Jean Carper, in USA Weekend Magazine, reports from Wm Lands, expert on fish oil benefits, that you can eat any and all fish IF the fish are "loaded" with selenium. "Mercury is toxic in the absence of selenium." "selenium ...neutralizes the danger."
Selenium, in food and in supplements, has been shown in studies to have strong cancer preventive activity, but I find this report confusing. Are the warnings just a mistaken case of taking the part (mercury toxicity) for the whole (balance of poison and protection found in the same food)? Can we take the chance that he's right and eat all the fish in sight? (And what about the issue of overfishing and the probability of no fish in the sea after 2048?) I don't know!
What about Vitamin D? It's the hottest "new" vitamin. In 1976 my trusted reference Laurel's Kitchen said, "Amounts (of Vitamin D) over 2000 IU per day can produce dangerously high levels of calcium in the body, leading to the deposit of calcium in unwanted places like the blood vessels and the kidneys...never exceed the recommended daily allowance of 400 IU." Now it's 2007 and almost everyday I hear "my doctor wants me to take 1000, 2000, even 4000 IU's of D" because tests show deficencies, specifying the D-3 (natural) form. There is a shift taking place which seems to be leading to less calcium, more D, a good change toward better absorption rather than sending the calcium down for cement. And where should we get it? Sunshine is the most natural source (safest in moderation); fish liver oils have it, but it's removed when the dread mercury is removed by molecular distillation (some add it back and it may not be the natural D-3/cholecalciferol but the less beneficial D-2/ergocalciferol; get Nordic Natural's D enhanced oil); and the latest, MegaFood's D-3 from lanolin, prepared with their special process (good for sun-sensitive vegetarians like me). Keep watching as we see more of the benefits of Vitamin D (cancer, MS, IBD) and promising food sources (mushrooms!).
Follow-up: Another complex: Thank you Michael Pollan, author of the eye-opening "The Omnivore's Dilemma" -- 10/15/06, New York Times Magazine -- "The Vegetable-Industrial Complex." More thought for food.