Background: Millions of people worldwide are suffering from Alzheimer's disease (AD),
and there are only symptomatic treatments available for this disease. Thus, there is a great need to identify
drugs capable of arresting or reversing AD. Constituents of the spice turmeric, in particular, curcuminoids,
seem to be very promising, as evident from in vitro experiments and tests using animal models
of AD. However, most of the clinical trials did not reveal any beneficial effects of curcuminoids in the
treatment of AD. These controversies, including conflicting results of clinical trials, are thought to be
related to bioavailability of curcuminoids, which is low unless it is enhanced by developing a special
formulation. However, there is growing evidence suggesting that other reasons may be of even greater
importance, but these avenues are less explored.
Objective: Review relevant literature, and analyze potential reasons for the controversial results.
Methodology: Recent in vitro and preclinical studies; clinical trials (without a limiting period) were
searched in PubMed and Google Scholar.
Results: While recent in vitro and preclinical studies confirm the therapeutic potential of curcuminoids
in the treatment of AD and cognitive dysfunctions, results of corresponding clinical trials remain rather
Conclusion: The controversial results obtained in the clinical trials may be in part due to particularities
of the curcuminoid formulations other than bioavailability. Namely, it seems likely that the various
formulations differ in terms of their minor turmeric constituent(s). We hypothesize that these distinctions
may be of key importance for efficacy of the particular formulation in clinical trials. A testable
approach addressing this hypothesis is suggested.