Curcumin is today one of the most thoroughly researched dietary phytochemicals (1), but its combination of anti-inflammatory and anti¬oxidant properties suggests potential also in other realms of medicine (2).
Within the various activities of curcumin, its neuroprotective effects on cognition have been extensively investigated in terms of epidemiology and in various preclinical and clinical models. Thus regular consumption of curcumin has been related to better cognitive function in the elderly (3), and in India incidence and prevalence of AD is indeed over four times lower than in the United States (4).
A correlation between curry consumption and cognitive level was identified studying a sample of more than 1000 Asians from their sixties to their nineties, and concluded that people on a curry diet performed better on a standard test (mini mental state examination) of cognitive function than those who never or rarely ate curry (3). As an attractive potential mechanism for the management of AD and other types of dementia, the anti-amyloidogenic properties of curcumin were investigated in terms of reduction of plaque burden, an end point related to the potential to reverse amyloid pathology (5-9). Curcumin’s direct radical scavenging activity has been investigated (10,11), but the compound can also reduce radical levels by improving mitochondrial function (12,13). In these studies, it was found that curcumin, by activating various phase II enzymes, can stimulate Nrf2/ ARE-signaling pathways that play a neuroprotective role, also upregulating the intrinsic antioxidant cell defenses (14-16).
An additional indication of curcumin is the management of depression, a major health problem affecting about 120 million people world wide, according to the World Health Organization. The use of curcumin to treat depression is being further supported by the latest research on depression, which emphasizes the importance of neurotoxicity and chronic inflammation (17). Selective serotonin reuptake inhibitors (SSRIs) are the most widely prescribed drugs for depression. At the time of their launch, the potentiation of aminergic signaling was considered the major antidepressant mechanism for this class of compounds. However, the credibility of the monoamine theory and the therapeutic efficacy of these compounds in the treatment of depression has been questioned, and novel mechanism(s) of activity have been proposed. Thus it is now generally expected that the symptoms of depression are closely linked with disturbances in proinflammatory signaling, and SSRIs possess significant anti-inflammatory properties (18).
Preliminary human intervention studies have indeed suggested that curcumin has an antidepressant activity comparable to fluoxetine in the treatment of major depression (19). A mini meta-analysis has concluded curcumin administration reduces depressive symptoms in patients with major depression (20), with benefits occurring in one trial 4-8 weeks after treatment (21).
Anti-inflammatory effects Additionally, inflammation may also play a role in other psychiatric disorders, such as bipolar disorder, schizophrenia, autism, and post-traumatic stress disorder. Curcumin shows anti-inflammatory properties, has an excellent safety profile over extended periods of use, and can stimulate hippocampal neurogenesis, an important pathway to enhance neuroplasticity and repair.
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