Most people shed over 100 hairs a day, and if your hair is long, it will seem like more, especially if you are looking at a brush!  Unless you are noticing that your hair is becoming significantly thinner, it's not like you are shedding more hair than normal.

If you do notice thinning, there are several people on this board who take supplements to help slow hair loss, with good results.  You might want to read the topics and see what advice others have to offer on the subject :)