Kerry Briggs had trouble keeping track of the supplements. To help, her husband, John Briggs, created a spreadsheet with rows for ashwagandha, Omega-3 and curcumin extract. There was ginseng, lion’s mane mushroom and the antioxidant liposomal glutathione, too.

Ms. Briggs, 64, had started taking the supplements last July, a daily regimen that grew to include 34 capsules and tablets along with two scoops of powder. When it became too much, Mr. Briggs began blending them into a shake, to which he added brown food coloring so it looked less like its natural “sickly” olive shade.

Ms. Briggs was taking them all because a doctor had told her that with enough supplements and lifestyle modifications, her Alzheimer’s symptoms could not only be slowed, but reversed.

It is an idea that has become the focus of television specials, popular podcasts and conferences; the sell behind mushroom supplements and self-help books.

But the suggestion that Alzheimer’s can be reversed through lifestyle adjustments has outraged doctors and scientists in the medical establishment, who have repeatedly said that there is little to no proof for such a claim, and expressed concern that the idea could harm a large group of vulnerable Americans.

Mr. Briggs had come across the idea after learning about Dale Bredesen, who had been performing a series of small and unconventional studies through which he claimed to have designed a set of guidelines to reverse Alzheimer’s symptoms.