Friday, March 1, 2013

Lead in chicken broth?

After the lead and crime article in Mother Jones last month, I've been more aware of lead in the environment.  Perhaps that is why a paper finding lead in organic chicken stock in the journal Medical Hypotheses alarms me, at least slightly and hypothetically.  The researchers found concentrations of 9.5 mcg/L and 7 mcg/L, still below the EPA's "action level" of 15 mcg/L for drinking water, but the EPA in the same publication says that no concentration of lead is acceptable:  i.e., the goal level concentration is zero. 

As is the nature for a hypothesis-generating publication, the study used only one batch of chicken stock of each type:  one with bones, one with skin and cartilage, and one with meat.  Perhaps they picked a bad chicken, or perhaps it is only chicken from the UK.  It's impossible to know without more tests.  People always ask us statisticians what would have happened if the sample size would have been larger, and it's important to remember that we're statisticians, not fortune-tellers:  we can't know what results would have been without having the actual results.  It's strange and frustrating that with 3 authors on the paper, they couldn't be bothered to get a few more chickens to test.  At least they did a control of plain water boiled for the same period of time, which found near-zero concentrations, under 1 mcg/L.  (Chicken meat broth by contrast was just over 2 mcg/L.)

The authors neglected to mention that the technique of saving bones for stock from every piece of meat you eat is almost universally recommended by cookbook authors including Melissa Clark and Nigella Lawson, to ensure that you always have stock available when it's called for.  Cookbooks say that there is no substitute for stock, and if you don't have stock around, use water rather than canned.  It's disappointing that there might be dangers from what is considered a best practice for cooking, not to mention one that I've just started following myself!  The lentil soup made from homemade beef stock was amazing, and one guest told us that he'd never tasted anything like it. 

I will still use the chicken stock in my freezer, but I'd be reluctant to continue this habit if pregnant or if I had children, given how dangerous lead is during critical formative periods. I do wish that the authors had gotten their act together to get at least an n=10 from geographically dispersed chickens.  How hard would that have been, seriously? 

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