Question for you experienced long distance runners out there.

I have always been a runner, ran cross country in high school but stepped away from it while my daughters were young. Running took a back seat in my life until about 5 years ago. Getting back into it all these years later, I find that I don't have the stamina I used to have.....maybe older age, extra weight, who knows....

Anyhoo, while training for the Minneapolis Monster Dash I suddenly became ill and was diagnosed with hyponatremia and was admitted to ICU after my heart stopped. It was also discovered that I had an autonomic disorder, neurocardiogenic syncope which was aggravated during training from adrenal fatigue and the hyponatremia. I have been instructed by my cardiologist to no longer consume any type of sugar or caffeine because it causes NCS symptoms. After getting the go-a-head to resume running, I began to train for the Rock 'N Roll half marathon. So, my question is does anyone have any good advice on how to fuel that does not involve sugar?? No heavy carbs, no processed foods, etc. I can tolerate fruit but in small amounts. I have been looking on runnersworld.com but no articles address my situation, which isn't surprising.

Any advice is helpful!

Nicole