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!
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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 liver:
Beef liver contained 52 ppm arsenic, 0.42 ppm cadmium, 2.18 ppm lead, and 31.47 ppm mercury. Beef kidney contained 47 ppm arsenic, 0.9 ppm cadmium, 2.02 ppm lead, and 50.65 ppm mercury. Beef lean meat contained 46.46 ppm arsenic, 0.33 ppm cadmium, 2.19 ppm lead, and 62.39 ppm mercury. So, liver accumulated the most arsenic (but not by much), less cadmium than kidney but more than lean meat, and significantly less mercury than kidney and especially the lean meat. All three cuts contained roughly equal levels of lead.
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Another study (PDF) examined how aflatoxin, when fed to a cow, was distributed throughout the animal’s tissues, with particular emphasis on the internal organs. Researchers dosed a 160 kg calf with 52 mg aflatoxin per day for five days, then slaughtered the animal and analyzed its tissues for aflatoxin levels. Aflatoxin was found in all cuts, but it was concentrated mostly in the kidneys and, to a lesser extent, the liver. Lean muscle meat contained 12.9 ng/g aflatoxin, heart contained 16 ng/g, spleen contained 18.5 ng/g, kidney contained 145 ng/g, while the liver contained 47.1 ng/g. So, eating a 100 gram portion of liver from this calf would give you 4.6 mg aflatoxin, which is pretty high. Not enough to kill you (the LD50 for baboons is 2 mg/kg bodyweight) on the spot, but it’s probably enough to cause some problems if you make eating aflatoxin-contaminated beef liver a regular habit. Luckily, commercial cattle ranchers aren’t dosing their cattle with 52 mg aflatoxin per day, and aflatoxin doesn’t occur naturally in pasture. It’s a mold that grows on grain stored in damp, humid conditions. Corn, especially improperly-dried corn stored in tropical or sub-tropical regions, is particularly susceptible to aflatoxin.
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Not even the staunchest corn-and-candy feeding cow ranchers want their animals eating aflatoxin-contaminated corn or munching on lead-and-mercury infused feed. It would be bad for business and they monitor this type of thing.
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Liver can accumulate toxins and heavy metals, but so can every other part of the animal. If you avoid liver because of toxins, you should probably avoid the rest of the animal, too. Besides, liver isn’t an everyday type of cut. It’s high in vitamin A and copper, high enough that eating a half pound a day is excessive and counterproductive, even without any toxins getting involved.
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As long as you’re avoiding animals in polluted, toxic environments (and I’m not talking CAFOs here; I’m talking industrial waste and heavy metal runoff) eating contaminated food (which you should be doing anyway, even if you don’t eat liver!), liver is a safe addition to your diet. Livers from organic, pasture-raised animals are obviously going to be tastier (almost sweet, in my experience), more nutritious, and cleaner, but I think you can safely eat the occasional liver meal from conventionally raised animals, too.
Freak, pero ya dijo un poco más arriba que las criadillas tauromáquicas no le iban.
Veterano
Asiduo
Leyenda
Baneado
