Is it true that if you use whey protein shakes your muscles will go away and be flabby at an older age like 50?

My brother bought a bucket or what ever those things are called of whey protein and I started using some as well. My dad saw me and told me not to use that because when I will be older (like 50) my muscles will go away. My dad is 52 and still has huge arms and still some of his 6 pack and he said he never used that crap. Is this true? And also is using whey protein at 15 ok?