I did some digging into Dr. Bredesen's work and the study you mentioned didn't have a control group. If you don't have a control group and you're changing dozens of variables simultaneously, you're not doing science.

This is not to say that his patients don't enjoy some subjective benefits, or that diet and exercise and mental stimulation aren't helpful, but Dr. Bredesen cannot have any scientific insight into Alzheimer's until he does an actual study.