Reply to B. Meunier’s Letter to the Editor Re: Brewer G. J.; Nutrients 2015, 7, 10053–10064

In a letter to the editor, Meunier [1] apparently attempts to discredit the copper-2 hypothesis for causation of the Alzheimer’s disease (AD) epidemic in developed countries proposed by myself in a review in this journal [2]. Briefly, the review laid out the following scenario: First, that AD was rare, perhaps at about a 1% prevalence level, in developed countries prior to 1900. The evidence for this is that esteemed clinicians of the period, Osler [3], Gower [4], and Freud [5] did not report any patients with an AD-like disease, and pathologists of the period, such as Boyd [6], did not report brains at autopsy with amyloid plaques and neurofibrillary tangles, hallmarks of AD brain pathology. Second, developed countries have undergone a huge increase in AD prevalence during the 20th century, an “AD epidemic”. Third, that undeveloped countries have not shared in the AD epidemic, remaining, at about 1% prevalence. All of this was well documented by very solid referencing [2]. Fourth, that the huge difference in AD prevalence in developed countries between the 19th and 20th centuries was not due to a lack of old people in developed countries during the 19th century, which is relevant because aging is a major risk factor for AD. Fifth, that the above four facts can only be explained by an environmental cause in developed countries in the 20th century. In other words a new environmental agent or agents had to have emerged in the 20th century in developed countries to cause the AD epidemic. Sixth that increased divalent copper, or copper-2, ingestion was at least part of that environmental causal change. Lack of space here precludes reiterating in detail all the evidence for copper-2 causality which was carefully laid out in my review. In brief, copper-2 ingestion from drinking water in AD animal models greatly enhanced the AD-like disease [7] and copper-2 ingestion in copper supplement pills in humans caused rapid loss of cognition [8]. It was shown that the AD epidemic in developed countries closely paralleled time-wise the huge increase in use of copper plumbing [2] and that enough copper was leached from copper plumbing to be causal of AD using the animal models as a guide [2]