Turmeric, a member of the ginger family, is a widely used spice in South and Southeast Asian cooking. It is also used as a colouring agent in foods and textiles, and in traditional Indian medicine.
Curcuminoids are polyphenolic compounds that give turmeric the distinctive yellow colour. Curcuminoids consist of curcumin (80%), demethoxycurcumin (18%) and bisdemethoxycurcumin (2%).
Curcumin is the primary curcuminoid that possesses wide ranging preventive and therapeutic properties.
Properties of Curcumin
Therapeutic Potential of Curcumin
Curcumin has been extensively studied for its safety and efficacy against numerous diseases.
Some promising effects have been observed in patients with various pro-inflammatory diseases including cancer, cardiovascular disease, arthritis, uveitis, ulcerative proctitis, Crohn’s disease, ulcerative colitis, irritable bowel disease, tropical pancreatitis, peptic ulcer, gastric ulcer, idiopathic orbital inflammatory pseudotumor, oral lichen planus, gastric inflammation, vitiligo, psoriasis, acute coronary syndrome, atherosclerosis, diabetes, diabetic nephropathy, diabetic microangiopathy, lupus nephritis, renal conditions, acquired immunodeficiency syndrome, ß-thalassemia, biliary dyskinesia, Dejerine-Sottas disease, cholecystitis, and chronic bacterial prostatitis. Curcumin has also shown protection against hepatic conditions, chronic arsenic exposure, and alcohol intoxication.1
Despite its impressive health benefits, the effectiveness of curcumin is limited by its poor availability. After oral ingestion of curcumin, very little reaches the systemic circulation.
There are several contributing factors to curcumin’s low bioavailability:
- poor absorption
- rapid metabolism
- rapid systemic elimination
- poor aqueous/water solubility
- short biological half life
Several appproaches have been undertaken to improve curcumin bioavailability, such as:
- piperine to interfere with glucuronidation
- use of liposomal curcumin
- curcumin nanoparticles
- use of curcumin phospholipid complex
- use of structural analogues of curcumin (eg.EF-24)
While there are several brands of bioavailability-enhanced curcumin, very few offer the free or active form of curcumin.
Free (or Parent) Curcumin Vs Curcumin Metabolites
Most ingested curcumin is excreted via faeces. In the liver and intestines, the remaining small portion of curcumin undergoes rapid metabolism to be converted to metabolites. It is conjugated to yield mainly curcumin glucuronides and sulfates, and/or reduced to hexahydrocurcumin and tetrahydrocurcumin. These metabolites do not possess the same biological activities as free curcumin and are either biologically inactive or less active.
In addition, free curcumin readily crosses the blood-brain barrier. Hence, it may have therapeutic potential for diseases of the central nervous system such as Alzheimer’s disease.
Almost All Studies on Curcumin Bioavailability Are Misleading
There are several formulations that increase bioavailability of curcumin. However, almost all the papers/studies on curcumin bioavailability measure curcumin metabolites and not curcumin per se.
When testing blood levels for free curcumin, most studies use glucuronidase/sulfatase enzymes to break down metaboolites and then estimate curcumin. This number does not represent the amount of curcumin that is free and active in the bloodstream. And yet, several manufacturers equate curcumin metabolites with free curcumin, thus claiming improved bioavailability of curcumin in their formulations!
So when choosing a curcumin supplement, bioavailability is just one factor. You want to look for a formulation that offers enhanced bioavailability of the free form of curcumin (free curcumin).
1. Therapeutic Roles of Curcumin: Lessons Learned from Clinical Trials: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535097/