if u eat a balanced diet than zero (0) is enough.
protein shakes are a supplement so ur better of eating plenty of chicken & fish. make sure u have a bit of protein in every meal.
However, their is nothing wrong with protein shakes, to get maximum benifit
1. weigh yourself, the maximun amount of protein u can absorb in a day is:- 2g for every 1kg of body mass (so if u weigh 50kg u can have 100g)
2. read the label, to find out how much protein is in 1 shake, and decide according to no.1
3. drink the shakes throughout the day (perhaps 1/2 a shake 2 or 4 times a day) because as well as a daily limit to protein absorbtion, u can only absorb 15g to 20g in a sitting. any more than that and ur just gonna pee it out!
4. the best time to take in protein is straight after ur workout (i'm gonna assume u lift weights, cos if u dont i wouldnt bother at all!) to make sure ur body has something to burn so it dosnt attack ur muscle.
5. go for a shake that has carbs as well as protein, the carbs act as a buffer so ur body will burn them instead of ur valuble muscle building protein.
6. make sure it tastes good theres no point torturing urself!
yea and make sure its just a protien shake and not a meal replacement shake or you'll be brining in ALOT more calories then you realize though meal replacement shakes are great if you do not have time to eat properly...