Liver has immense nutritional value ... providing, that is, that it comes from a fairly young animal. Because liver acts as a clearinghouse or filter for substances that enter the body, it tends to store and absorb unwanted chemicals, medicines and hormones that an animal might be fed. Naturally, the older the animal the greater the accumulation of these unwanted substances, which, according to some, offset liver's nutritional value. For this very reason, many people choose the more expensive calves liver over beef liver. There are several ways to distinguish between the two. The color of beef liver is reddish-brown, compared to the paler pinkish-brown of calf's liver. Liver from a mature animal also has a stronger odor and flavor than that from a youngster. Additionally, it will be less tender.
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