If you're drinking it at the start of your ride you probably won't be able to notice how fast it affects you. However if you drink it after your ride when you're a little energy depleted,you'll notice the affect immediately. Ymmv.
I'd stick with what the Doc said, providing your tummy can handle it. If it doesn't agree with you, then look for a replacement. In my experience doctors know more than what we give them credit for.
Last edited by texaspandj; 07-02-16 at 04:54 AM.