Nurturing The Brain – Part 8, Turmeric (Curcumin)by Sara Adaes, PhD | December 10, 2015
Turmeric is a yellow dietary spice extracted from the rhizome of a plant in the ginger family named Curcuma longa. Turmeric has some well-known beneficial properties and it has been widely used for medicinal purpose for centuries, mostly in Asian countries. There are thousands of research articles describing the multitude of curcumin’s effects, as well as many clinical trials currently assessing its effects.
Tumeric‘s medicinal properties are due to the active ingredient curcumin. First isolated 200 years ago, only the last few decades have seen detailed research on the effects of curcumin.
Biochemically, curcumin is a polyphenolic compound able to modulate different signaling molecules including pro- and anti-inflammatory molecules, enzymes, and tumor suppressor genes, for example. Curcumin has been proven to have anti-oxidant, anti-inflammatory, anti-microbial, hypoglycemic, anti-rheumatic, wound healing and anti-cancer activities. That’s a rather impressive list. Furthermore, a number of studies have shown that curcumin undergoes metabolism upon oral intake with almost every metabolite produced having some advantageous effect.
Among all of curcumin’s properties, its strong anti-oxidative and anti-inflammatory properties pop out. These two properties combined can account for most of its biological actions. Experimental and clinical data have demonstrated time and again that chronic inflammation, oxidative stress, and most chronic diseases are closely associated. This is true for vast number of conditions, including cardiovascular diseases, arthritis, diabetes, pulmonary diseases, cancer, and neurological diseases. Oxidation and inflammation are also the main driving force in aging.
Curcumin can hence potentially modulate all of the above, and research has indeed supported this possibility.
The therapeutic action of curcumin
Inflammation is one of the major causes of cardiovascular diseases, and oxidative stress plays a key role in causing hypertension. In animal studies, curcumin has demonstrated cardioprotective properties by being effective in decreasing hypertension and vascular damage, for example.
Cardiovascular disorders can sometimes stem from chronic renal failure. In animal models of renal injury, curcumin has also been able to reverse some of the consequences of renal damage, including not only oxidative stress, but also hyperfiltration, renal structure alterations, and hemodynamic alterations, therefore protecting both the kidneys and the cardiovascular system.
Because of its anti-inflammatory and antioxidant properties, curcumin also emerged as a promising therapeutic option for diabetes. Its hypoglycemic effect has drawn attention to its therapeutic potential in diabetes and its associated complications. Animal studies have shown that curcumin can improve insulin sensitivity, decrease glucose intolerance, and reduce fasting blood glucose and urine sugar levels.
Inflammation in the gastrointestinal tract is also quite common. Inflammatory bowel disease, for example, occurs due to production of pro-inflammatory molecules and oxidative stress. By counterbalancing these effects, curcumin is able to ameliorate its symptoms.
Curcumin and cancer therapy
A number of reports have described curcumin’s ability to modulate tumor-related genes. Curcumin can inhibit key signaling pathways in cancer, contributing to the prevention of tumor formation, migration, and invasion. This effect seems to be due to the ability to induce apoptosis (cell death) in tumor cells and to anti-angiogenic properties, that suppress the ability to form new blood vessels supplying the tumor.
Emerging evidence has been suggesting that curcumin may exert its anti-cancer activities by targeting cancer stem cells. These cells are able to originate all cell types found in a tumor and can be a source of new tumor cells even after tumor growth is stopped. Curcumin has shown beneficial effects in experimental models of a wide variety of cancers, including colorectal cancer, pancreatic cancer, breast cancer, brain cancer, and head and neck cancer.
Curcumin and the brain
In recent years, there has been increasing scientific evidence of the therapeutic potential of curcumin against a number of neurological diseases. Curcumin possesses a set of biological properties that can potentially modulate a multitude of pathological processes in neurological pathologies.
In experimental Parkinson’s disease, curcumin has been able to counteract oxidative stress and inflammation, preventing alfa-synuclein aggregation and fibrillation, the hallmark of this disease. Similarly, in Alzheimer’s disease, experimental evidence has shown that curcumin can bind to amyloid-beta to inhibit its toxicity and its accumulation and aggregation into amyloid plaques in the brain.
There have also been indications of a protective effect in amyotrophic lateral sclerosis, multiple sclerosis and traumatic brain injury. There have even been signs of antidepressant properties through an interaction of curcumin with dopamine receptors and an increase in brain dopamine levels.
Experimental research has shown that curcumin also has anti-aging properties. It has been able to increase the mean lifespan of the nematode roundworm, of the fruit fly Drosophila, and of the mouse. Curcumin inhibited the oxidative stress response, up-regulated expression of anti-oxidant genes and down-regulated expression of several age-related genes.
Curcumin’s actions are quite impressive. So why hasn’t its use been generalized? There’s a big limitation to curcumin’s action: its limited oral bioavailability. Only a fraction of the ingested curcumin is absorbed and it is rapidly metabolized. To be used in therapeutic trials, it has to be modified or used in combination with other agents.
Nevertheless, curcumin is regarded as benign and well-tolerated. The U.S. Food and Drug Administration has deemed curcumin as generally safe, and it is non-toxic even at high doses of up to 8 g per day (which is a lot!).
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