As the final show in the series on the doctors who've helped me back to health, I interview Dr. Andrew Rostenberg who specializes in a new, cutting edge DNA test that showed my body had a hard time absorbing B vitamins - a problem tens of millions of other Americans have as well and don't know it. This test, and the simple change in my vitamins, have been key to my feeling better, having more energy, and being able to think again. Dr. Rostenberg explains how easy it is to get the test, and what it might reveal - another simple step to better health. This is Part 4 in my Doctor Series.