According to Francis Bacon's "Of friendship" describe the three fruits of friendship.

One of the first fruits he describes as
follows:

A
principal fruit of friendship, is the ease and discharge of the fulness and swellings of
the heart, which passions of all kinds do cause and
induce.

With the
understanding of the view of the human body at the time, that it was full of humors that
sometimes needed to get out in order to be healthy, one of the main benefits of having
friends was that you could get out the "fulness and swellings of the heart" so that the
body would remain healthy.  Obviously you can talk and share with a friend, and at the
time this was seen as connected to bodily health as well as
spiritual.

The second he describes
thusly:

For
friendship maketh indeed a fair day in the affections, from storm and tempests; but it
maketh daylight in the understanding, out of darkness, and confusion of
thoughts.

The idea that a
friend can help you to understand the thoughts that rattle around in your head is
another that Bacon points out as one of the principal
benefits.

The third I will leave to you to
find.