September 12 2008 post: Sherlock sent me another study published last month in “Psychopharmacology” and titled Antidepressant activity of curcumin: involvement of serotonin and dopamine system. See abstract: http://tinyurl.com/5loqab. The study begins with the familiar rundown of the various healing effects of curcumin (antimicrobial, hypoglycaemic, antioxidant, anti-arthritic etc.). It also mentions curcumin’s rapid metabolism and poor bioavailability, about which I have written quite a bit. This is followed by the detailed description of this new (to me) effect of curcumin.
The researchers cite a study (abstract: http://tinyurl.com/5xolvg), published in 2005, in which the Chronic administration of curcumin has been reported to exert antidepressant-like action in olfactory bulbectomy model of depression in rats. I admit that I had to look up “olfactory bulbectomy.” I almost wish I hadn’t! Tender-hearted readers, please skip the next paragraph. All the others may read on.
This procedure removes the olfactory bulbs in rats. In other words, these animals are deprived of their sense of smell. Surprise surprise, this leads to behavioural abnormalities such as hyperactivity, which can be resolved by administering antidepressants.
Some of those same 2005 researchers continued to do research on this topic, publishing another study three years later (see: http://tinyurl.com/62lk79), but the exact mechanism of its antidepressant activity still remains to be explored. The antidepressant activity of curcumin, i.e. That is what this more recent study sets out to do.
Skip, skip, skip through the unintelligible (to me) parts of the study…and also, ugh, through the description of what tasks the mice are forced to perform…the mice are then killed so that the curcumin levels in their brains can be measured, oh dear, this part is a bit gory…skip, skip, skip! If anyone would like to read the whole thing, though, just let me know. I would be happy to forward the study upon request.
I did gather the following: when taken together, curcumin and piperine (=black pepper extract) increased the levels of curcumin in the brain, as opposed to curcumin by itself. That makes sense.
The study then goes through a detailed list of which antidepressant drugs were administered to the mice…when, how much, etc. This part was also not easy to follow, since I don’t know any of these drugs by name and have no time to look up what they are. More skipping.
In the Discussion part we get to the essence of the study: Our results demonstrated a consistent antidepressant-like activity of curcumin in two classical models of depression in mice, namely the forced swim and reserpine-induced immobility models. The researchers found that the effect of antidepressant drugs was stronger when administered to the mice together with curcumin. After reading this, I thought that this synergistic effect might be important in the future treatment of depression.
Another finding: The neurochemical analysis revealed that curcumin (20–80 mg/kg, i.p.) dose dependently increased the serotonin (5-HT) levels. It also increased the levels of dopamine but the effect was observed only at higher doses. Further on, we read that The view that 5-HT has multiple functional roles in depression is supported by the clinical and experimental evidences suggesting that the neurotransmitter (serotonin) is involved in the regulation of mood, sleep, memory, learning, and sexual behavior, all of which are deranged to varying extents in patients with severe mental depression.
So curcumin increases the levels of serotonin, and that is part of its antidepressant activity. Another part concerns its effect on dopamine, a neurotransmitter that affects important brain processes controlling movement and emotional responses (etc.). I read that dopamine has become an important target of antidepressant drugs. The researchers found that these particular drugs are potentiated by curcumin. And, at higher doses, curcumin by itself also significantly increased the brain dopamine levels. Good stuff!
The following quote is for the more scientifically-minded: Based on the present observations, curcumin, at low doses, increased brain serotonin levels via inhibiting its metabolism (MAO-A enzyme inhibition) without significantly affecting the levels of norepinephrine. At high doses, it inhibited the metabolism of dopamine (MAO-B enzyme inhibition) which in turn resulted in the increase in central dopamine levels. Both these activities of curcumin, i.e., by enhancing the availability of serotonin and dopamine in the brain, are responsible for its antidepressant activity.
Brief summary: curcumin can enhance the levels of serotonin AND dopamine in the brain, thereby reducing depression.
The poor absorption of curcumin is mentioned again toward the end of the study. The researchers found that curcumin absorption was enhanced when piperine was added. The study thus concludes as follows: the coadministration of curcumin and piperine may provide a useful natural adjuvant in the antidepressant therapy.
Perhaps my daily intake of eight grams of curcumin is one of the reasons that I am so bloody positive most of the time. I mean, I have always been an upbeat, glass-half-full kind of gal, but maybe my intake of curcumin in the past two and a half years has increased my “happiness” level.