Long term, too much
is harmful, just as
is too little. Too much from red meat
is harmful, so the source
is important as well. What we don't have good data on is the long-term effects of a high protein diet that isn't too high, that doesn't go overboard, but so far the results are best for a good old balanced diet of healthy foods high in fish, veggies, and whole grains, and if you eat that way, you're really not going to get a high protein diet.