Books that promote unscientific practices typically suggest that the reader consult a doctor before following their advice. This disclaimer is intended to protect the author and publisher from legal responsibility for any dangerous ideas contained in the book. Both author and publisher know full well, however, that most people won't bother asking their doctor. If they wanted their doctor's advice, they probably wouldn't be reading the book in the first place. From what I have seen, nearly every information source that uses this type of disclaimer gives bad advice.
Disclaimers can even accompany testimonials.
We have no competent or reliable scientific evidence to suggest that the testimonial experience is due to the use of our products. These testimonials are not intended to recommend any supplement as a drug, as a diagnosis for specific illnesses or conditions, nor as a product to eliminate diseases or other medical conditions or complications. We make no medical claims as to the benefits of any of our products to improve medical conditions. There is no logical reason to believe that taking oxygen pills or potions will provide the slightest health benefit. The company apparently hopes that the testimonials will have greater impact that the disclaimer.