The liver is the body's nutritional distribution center, the place where nutrients are gathered for circulation to other organs. That makes it a nutritional powerhouse in its own right. Beef liver is one of the best dietary sources of vitamin A, folate and most of the B vitamins, and it has notably high levels of iron, phosphorous, copper, selenium and many other minerals. It's also very low in fat and calories. Even pan-fried, a 100 gram portion of beef liver -- just under 4 ounces -- contains only 175 calories, according to the U.S. Department of Agriculture's database. Its only nutritional downside is high levels of cholesterol.

The USDA's Food Safety and Inspection Service recommends cooking beef liver to an internal temperature of 160 degrees Fahrenheit, to ensure food safety. That's because unlike muscle meats, where potentially harmful bacteria are found only on the surface, liver can harbor pathogens inside its tissues. Cooking to well-done is the only sure way to kill those bacteria. To put this into context for diners, strict adherence to the USDA's temperature guidelines would also eliminate rare steaks and any egg with a soft yolk. As with eggs and steaks, eating beef liver that's less cooked could -- but usually doesn't -- result in illness.

Beef liver that's not cooked to at least medium-rare, or approximately 145 F, has a slightly metallic taste. At temperatures of 160 F or higher it begins to shed moisture, becoming chewy, dry and strongly flavored. It's most palatable when it's cooked to a temperature between those limits, which results in liver that's pink and visibly juicy when cut. How long it takes to reach that temperature varies depending on the cooking method and the thickness of the slices. Quarter-inch slices can be pan-fried to that doneness in just a few minutes, while half-inch slices baked in gravy might require 25 to 30 minutes. Use a thermometer to accurately confirm the internal temperature of the liver.

Beef liver is usually sliced at the butcher shop or supermarket, and usually has most of its veins and protective membrane removed. If you see any visible portions of vein or membrane, cut them away with the tip of a sharp knife before cooking the liver. Soaking beef liver in milk before cooking makes it milder, a piece of longstanding folk wisdom. Soaking the liver in buttermilk or a light brine for at least 30 minutes before cooking can also improve the flavor. Pat the liver dry with clean paper towels before cooking it.

However you like your beef liver cooked, you can minimize your risk of foodborne illness through careful attention to food safety. If you live more than a few minutes from the store, take along a cooler and a gel pack to keep your liver cold on the way home. Scrub your hands, utensils and work surfaces carefully with plenty of hot, soapy water before and after handling the liver. Juices from the liver can harbor bacteria, so scrub anything that comes in contact with them. If the liver drips liquids onto any of your other foods, they're potentially contaminated and should be discarded.