The Gemara on our daf continues with a discussion of medicinal recommendations of the Talmudic sages. One teaching that is presented is that there are eight things which are harmful in large quantities but in small quantities are beneficial, namely, traveling, sexual relations, wealth, work, wine, sleep, hot baths, and blood-letting.
Including blood-letting in this list is an example of the value that was placed on this practice, at least in measured amounts. For many generations physicians believed that blood-letting was a powerfully helpful remedy for the human body, both as a cure and as a general preventative therapy that would keep a person healthy. Based on this belief, many people arranged to have blood-letting on a regular basis, and in fact the Gemara forbids a scholar from living in a community that did not have a professional blood-letter. At the same time, there was recognition that blood-letting weakened the body in the short-term, and could potentially be dangerous. Recognizing this, the Gemara offers lists of things that a person should be careful to avoid at the same time as blood-letting. These include having blood-letting immediately after returning from a trip, getting up immediately after blood-letting, or engaging in relations immediately after blood-letting.
In offering this advice, it appears that the sages were sensitive to the potential problems that could be caused by physical exertion immediately before or after blood-letting. For this reason the Gemara also includes a list of foods that should be eaten after blood-letting, all of which offer a ready supply of calories that can be used by the body to recover. Many of these suggestions appear to be similar to advice offered by contemporary medical professionals after a person donates blood.
Today it is well-established that blood-letting is not effective for most diseases. Indeed it is mostly harmful, since it can weaken the patient and facilitate infections.