Eating red meat should be kept to a minimum. It also really depends on the person as to how much red meat should be eaten. Red meat requires a high amount of stomach acid in order to efficiently digest and metabolize the proteins contained in it.
According to the Blood type diet written by Dr. Peter J. D'Adamo, those with blood type O are best suited for eating red meat. This is because type O blood types tend to have high stomach acid content. However, one also needs to be aware that stomach acid concentration declines with age, and it is a known fact that as many as 40 percent of postmenopausal women lack sufficient stomach acid. People over 60 years of age produce only approximately 25% of the stomach acid they produced when they were 20 years old.
Due to its high phosphorus content, eating too much red meat also interferes with calcium absorption.
You should always eat vegetables with meat proteins to avoid over-acidification, which can lead to disease.
According to the blood type diet, Type O's can have 3-4 ounces (after cooking) of lean red meat 4-6 times per week if you are of caucasian ancestry. I still think that's too much. Type A's should not have any red meat at all. Type B's can have red meat 2 times per week, but I also think that's still too much. Type AB's can have red meat 1 time per week.
If you follow the blood type recommendations, you would do best to eat lamb more than beef for red meat. It is also highly beneficial and should be organically raised.