This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Alzheimer’s disease (AD) was a progressive neurodegenerative disorder that manifested in aging as memory loss. Progression of AD was associated with deposition of plaques in the brain comprised of amyloid-β peptide. At the time there was no cure for AD, although retrospective studies had linked vitamin D deficiency with cognitive deficit, including risk of AD. Vitamin D3 was produced in the skin upon exposure to sunlight and in limited dietary sources such as oily fish, while low levels of Vitamin D2 were present in some plants and fungi, including mushrooms. The prevalence of Vitamin D deficiency, its links with cognition, and the recent development of methods for stimulating production of Vitamin D2 in mushrooms converged within this research project. In this project, the researcher aimed to determine whether or not vitamin D2-enriched White Button mushroom (VDM) could exert a beneficial effect on learning and memory in mice that were genetically modified to develop pathologies and symptoms associated with AD. The transgenic ‘AD’ mice expressed two human genes linked with familial AD, and consequently displayed progressive memory loss as a result of the brain deposits of plaque, thus modelling key pathologies of AD. Wild type or AD mice were fed either a control diet or a diet supplemented with White Button mushrooms enriched with Vitamin D2 (VDM) for 6 months post-weaning. Key outcomes of the research were as follows:

When compared to the control diet, the VDM-supplemented diet

• Improved memory in both AD and wild type mice and,
• Reduced amyloid-β plaque deposits in the brains of AD mice;

These results suggested that VDM may protect against AD-related memory loss by reducing amyloid-β plaque accumulation in the brain. The effects could be attributed to Vitamin D2 or other components of the mushroom, which were shown to interact with the amyloid-β protein. In addition, the improvement in memory in wild type mice means Vitamin D-enriched mushrooms may have had broader health implications for the general community, presumably affecting additional pathways important in cognitive health. For industry, these research outcomes supported growth in consumer demand for this unique, bioactive food, offering potential population-wide opportunity for promoting brain health.

It was recommended that future research aims to substantiate the findings of the mouse study in humans, either healthy aged or at-risk AD subjects including those with family history of AD or early stages of memory impairment, in order to test the preventative efficacy of Vitamin D mushrooms. Human clinical studies needed to determine the comparative efficacy of Vitamin D2 and D3 for cognitive function and the specific contribution to effects, from Vitamin D2 versus other components of mushroom. Practical usefulness of the outcomes of the mouse study and future human studies to the industry would be achieved by the publication of the research and its subsequent promotion through mainstream media channels.

If human studies proved successful, Vitamin D2-enriched mushrooms may have been confirmed to represent a unique, natural, functional food offering significant benefits for cognitive health. Based on the assumption that Vitamin D was responsible for observed cognitive improvements effects in mice, these results might have inferred that Vitamin D2 exerts differential/superior effects to Vitamin D3 on cognition. Furthermore, the lower bioavailability profile of Vitamin D2 may have in fact, rendered it the safer form of oral supplementation of Vitamin D.