I had the same question regarding your doc's familiarity with these products. I use Cytomax Sport, and don't see anything on the ingredient list that would give me pause. Same with Clif blocs and gels. Just be careful to avoid those with caffeine.
That said, you could make your own sport drink (do a search here for homemade sport drink). It's not that complicated, and you know for certain what's in it and what's not. Same thing with energy bars. Beyond that, is it really that big of a deal to carry whole foods? I don't eat much in the way of gels or bars, and I get by just fine!
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher