Yes, it is harmful. Eating too much protein has its side effects. It can cause diarrhea, dehydration, constipation, weight gain, and bad breath. It can even lead to kidney and liver damage. The maximum protein that these organs can deal with is around 3.5 to 4.5 grams per kilogram of weight, which is 238-306 grams of protein a day for a 150-pound woman (12). Prior consultation with a doctor is mandatory for those who choose to up their protein portion and have an existing medical condition. It applies to people even with a past kidney ailment.