While diabetes does not interfere with digestion, on the other hand, it does prevent the body from converting an important product of digestion, glucose, which is commonly known as sugar, into energy.
This is the most concise and fluent version. Choice A incorrectly uses the transitional phrase on the other hand, and because it puts which is commonly known as sugar into a nonrestrictive clause immediately after the appositive glucose, the sentence may be confusing. Choice B is grammatically correct but quite awkward, using which three times in one sentence. Choice C inverts the sentence, making it less direct and therefore less clear. Choice E is correct but less direct and slightly more wordy than d because it uses the passive construction (converted by the body).