man, thats totally ridiculous...i'd be just as pissed as you were if some physician gave me that b.s. about the "putting stress on kidneys". of all the supplements out there, whey protein is by far the safest and cleanest one in my mind. I take 5 shakes of whey per day, 35 grams in each shake. This helps me account 2 grams of protein for every pound I weigh, and as a result, i've seen myself gain quality lean muscle, along with a proper diet and proper weightlift routine. I say you drink that stuff up, just your doctor does have a point, so i'd advise that you drink each shake with 2 cups of water (or milk if thats how you do it) to satisfy him and possibly your parents aswell. and your set!