Liver confuses and confounds many of us. It looks weird, gives off an odd mineral smell, and has a unique texture. We try to reconcile our horrible memories of Mom’s bone-dry renditions of the stuff with all the ethnographic literature describing how hunter-gatherers share precious slivers of the raw trembling organ immediately after a kill. We appreciate and acknowledge the superior nutrient profile of four ounces of beef liver compared to five pounds of colorful fruit even as the shrink-wrapped grass-fed lamb liver direct from the organic farm sits in the freezer untouched. And then we wonder whether it’s even safe to eat, because, you know, it’s the “filter” – the only thing standing between an onslaught of environmental toxins and our vulnerable bodies – and filters accumulate the stuff they’re meant to keep out. See colanders, coffee filters, water purifiers. Liver, then, is many a Primal eater’s Everest. Tantalizing but fraught with seeming danger. Okay, the question: Mark, I was reading your post about organ meats. I have always heard liver was nutritionally valuable, but I hear the same thing about bread. Maybe I am wrong, but isn’t the liver a filter? Doesn’t it filter poisons and toxins from the body?  If I eat liver, am I ingesting the poisons and toxins of the animal? Seems to me there will always be residual poisons in liver. What are your thoughts on this? Chris To call the liver a simple filter is incorrect. If we want to maintain the metaphor, it’s more like a chemical processing plant. The liver receives shipments, determines what they contain, and reacts accordingly. It converts protein to glucose, converts glucose to glycogen, manufactures triglycerides, among many other tasks, but its best-known responsibility is to render toxins inert and shuttle them out to be expelled – usually in the urine via the kidney. It doesn’t just hang on to toxins, as if the liver is somehow separate from the body and immune to contamination. The liver is part of the body! If your liver contains large amounts of toxins, so do you! Okay, so we’ve established that the liver is a processing plant by design, rather than a physical filter whose express purpose is to accumulate toxins, but what about animals raised in industrial, intensive operations? The liver from a pasture-raised cow with a perpetually cud-filled maw can undoubtedly handle its relatively light toxic load; the liver from a CAFO-cow feeding on grain and exposed to environmental pollutants is surely another matter entirely. Right? Sorta, although it’s more complicated than that. The liver can definitely accumulate heavy metals, but it is not alone in that, nor does it always particularly excel. A 2004 study (PDF) of liver, kidney, and lean meat from cattle, sheep, and chickens randomly selected from ranches in Lahore, Pakistan, found that all three tissues accumulated significant amounts of certain metals. Let’s see how the metals were distributed throughout the various cuts of beef, since that’s what most of us are eating for … Continue reading Dear Mark: Does the Liver Accumulate Toxins?