Turmeric has been used as a common kitchen spice for ages. It is also used for a wide range of medicinal and scientific purposes for over 100s of years. The recent scientific investigations into the exact method of action and the bioactive components of turmeric is what led to the discovery of curcumin. (1)
Curcumin’s chemical name is (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) or diferuloylmethane! Which is a mouthful, so let's stick to referring to it as curcumin. Curcumin is the primary natural polyphenol found in turmeric. It has been shown to target multiple signalling molecules and have activity at the cellular level. All of which has led to providing valuable evidence to its multiple health benefits. (2)
The enol and keto forms of curcumin are common structures of the drug
Curcumin has been proven to improve systemic markers of oxidative stress. There is evidence showing increased serum activities of antioxidants such as superoxide dismutase (SOD), Catalase, Glutathione peroxidase (GSH) and lipid peroxides. By modulation of the activity of GSH, SOD and catalase enzymes neutralization of free radicals can be achieved. Curcumin can also scavenge different forms of free radicals like reactive oxygen and nitrogen species (ROS and RNS, respectively). Curcumin can also inhibit ROS-generating enzymes such as lipoxygenase/cyclooxygenase and xanthine hydrogenase/oxidase. In addition curcumin also has a chain-breaking antioxidant mechanism similar to Vitamin-E
Crystallized powder of curcumin.
Inflammation has been identified in the development of many chronic diseases such as Parkinson's disease, Alzheimer’s Disease, Multiple sclerosis, epilepsy, cardiovascular disease, cancer, diabetes and the list goes on. Tumor necrosis factor α (TNF-α) is a major mediator of inflammation in most diseases and this effect is regulated by the transcription factor, nuclear factor (NF)-κB.
In addition being activated by TNF-α, NF-κB is also activated by gram-negative bacteria; various-disease causing viruses; environmental pollutants; chemical/physical/mechanical/psychological stresses; high glucose; fatty acids; cigarette smoke; ultraviolet radiation; and other disease-causing cause. Therefore any agents that can downregulate NF-κB production and/or NF-κB–regulated gene products have potential efficacy against many of these diseases. Curcumin has been proven to block NF-κB activation. (2)
Curcumin Also suppresses inflammation through many other mechanisms, for those readers who would like to know more details and scientific explanations: refer to reference list (4) and (5).
Treatment of Arthritis:
One disease that is associated with inflammation is Osteoarthritis(OA). This can happen as a chronic or acute joint condition. While there is no cure, pharmaceutical treatment options can be costly and usually have undesirable side effects. Leading to an increased interest in alternative treatments such as dietary supplements and herbal remedies. Several studies show the anti-arthritic effects of curcumin in humans with OA and rheumatoid arthritis (RA).(2)
For more details on those studies, check reference list (7), (8), (9) and (10).
Regardless of the mechanism, curcumin does appear to have beneficial effects on several aspects of OA as suggested by a recent systematic review and meta-analysis which concluded:
The root of turmeric.
“This systematic review and meta-analysis provided scientific evidence that 8–12 weeks of standardized turmeric extracts (typically 1000 mg/day of curcumin) treatment can reduce arthritis symptoms (mainly pain and inflammation-related symptoms) and result in similar improvements in the symptoms as ibuprofen and diclofenac sodium. Therefore, turmeric extracts and curcumin can be recommended for alleviating the symptoms of arthritis, especially osteoarthritis”. 
The fact that curcumin can reduce/cut down systemic inflammation has other implications beyond the treatment of arthritis. Systemic inflammation is associated with many other conditions affecting many systems. Metabolic syndrome(MetS) is one such condition which includes hyperglycemia, elevated triglyceride levels, elevated low-density lipoprotein cholesterol (HDL-C), low high-density lipoprotein cholesterol (HDL-C), insulin resistance and obesity, mainly visceral obesity. (2)
Curcumin has shown to reduce several aspects of MetS by suppressing adipogenesis, improving insulin sensitivity, reducing oxidative stress, inflammation and elevated blood pressure. In addition there is evidence that curcuminoids modulate the activity of enzymes and expression of genes involved in lipoprotein metabolism which leads to a reduction in cholesterol and plasma triglycerides. They also increase HDL-C concentrations. Both obesity and overweight are linked with chronic low-grade inflammation thereby releasing pro-inflammatory cytokines. These cytokines are thought to be involved in the center of the complications involved with cardiovascular disease and diabetes. Ergo, addressing the inflammation is vital. (2)
In healthy people:
Chronic Low dose of curcumin can provide health benefits for people who do not have a diagnosed health condition such as improvement in working memory/mood; significantly reduce total and LDL cholesterol; improve muscle recovery time improving performance during and following exercises; reduce exercise-induced muscle soreness (DOMS) and potential anti-anxiety effects in otherwise healthy obese individuals. (2,11,12,13,14,15)
Bioavailability of curcumin when ingested was a major problem, mainly due to poor absorption, rapid elimination and rapid metabolism. Many agents were tested to increase curcumin’s bioavailability by tackling various mechanisms. Most of these were based on blocking the metabolic pathway of curcumin leading to and increase in bioavailability.
One such agent is piperine, a known bioavailability enhancer. Piperine is actually the major active component of black pepper and is associated with a whopping 2000% increase in bioavailability of curcumin. Ergo, the problem with curcumin’s poor bioavailability when ingested is resolved by adding agents such as piperine and creating a curcumin complex. (2,16,17,18)
Curcumin has finally gained the world's attention for its multiple health benefits essentially falling under the “superfoods” category. The golden dietary supplement, acts primarily through its anti-inflammatory and antioxidant mechanisms. These benefits are best attained when combined with agents such as piperine to increase bioavailability.
Research shows that curcumin can help in the management of arthritis, anxiety, hyperlipidemia, metabolic syndrome, oxidative and inflammatory conditions. Curcumin may also help in the management muscle soreness and inflammation which are induced by exercise which in turn helps with faster recovery and subsequent performance in physically active individuals. Curcumin can additionally provide health benefits for individuals who have not been diagnosed with health conditions. (2)
Hewlings, S. J., & Kalman, D. S. (2017). Curcumin: A Review of Its' Effects on Human Health. Foods (Basel, Switzerland), 6(10), 92. doi:10.3390/foods6100092
Zhang, Dongwei & Fu, Min & Gao, Si-Hua & Liu, Jun-Li. (2013). Curcumin and Diabetes: A Systematic Review. Evidence-based complementary and alternative medicine : eCAM. 2013. 636053. 10.1155/2013/636053.
Aggarwal B.B., Harikumar K.B. Potential therapeutic effects of curcumin, the anti-inflammatory agent, against neurodegenerative, cardiovascular, pulmonary, metabolic, autoimmune and neoplastic diseases. Int. J. Biochem. Cell Biol. 2009;41:40–59. doi: 10.1016/j.biocel.2008.06.010.
Panahi Y., Hosseini M.S., Khalili N., Naimi E., Simental-Mendia L.E., Majeed M., Sahebkar A. Effects of curcumin on serum cytokine concentrations in subjects with metabolic syndrome: A post-hoc analysis of a randomized controlled trial. Biomed. Pharmacother. 2016;82:578–582. doi: 10.1016/j.biopha.2016.05.037.
Daily J.W., Yang M., Park S. Efficacy of turmeric extracts and curcumin for alleviating the symptoms of joint arthritis: A Systematic review and meta-analysis of randomized clinical trials. J. Med. Food. 2016;19:717–729. doi: 10.1089/jmf.2016.3705.
Henrotin Y., Priem F., Mobasheri A. Curcumin: A new paradigm and therapeutic opportunity for the treatment of osteoarthritis: Curcumin for osteoarthritis management. SpringerPlus. 2013;2:56. doi: 10.1186/2193-1801-2-56.
Belcaro G., Cesarone M.R., Dugall M., Pellegrini L., Ledda A., Grossi M.G., Togni S., Appendino G. Product-evaluation registry of Meriva®, a curcumin-phosphatidylcholine complex, for the complementary management of osteoarthritis. Panminerva Med. 2010;52:55–62.
Belcaro G., Hosoi M., Pellegrini L., Appendino G., Ippolito E., Ricci A., Ledda A., Dugall M., Cesarone M.R., Maione C., et al. A controlled study of a lecithinized delivery system of curcumin (meriva®) to alleviate the adverse effects of cancer treatment. Phytother. Res. 2014;28:444–450. doi: 10.1002/ptr.5014.
Chandran B., Goel A. A randomized, pilot study to assess the efficacy and safety of curcumin in patients with active rheumatoid arthritis. Phytother. Res. 2012;26:1719–1725. doi: 10.1002/ptr.4639.
DiSilvestro R.A., Joseph E., Zhao S., Bomser J. Diverse effects of a low dose supplement of lipidated curcumin in healthy middle-aged people. Nutr. J. 2012;11:79. doi: 10.1186/1475-2891-11-79.
Cox K.H., Pipingas A., Scholey A.B. Investigation of the effects of solid lipid curcumin on cognition and mood in a healthy older population. J. Psychopharmacol. 2015;29:642–651. doi: 10.1177/0269881114552744.
McFarlin B.K., Venable A.S., Henning A.L., Sampson J.N., Pennel K., Vingren J.L., Hill D.W. Reduced inflammatory and muscle damage biomarkers following oral supplementation with bioavailable curcumin. BBA Clin. 2016;5:72–78. doi: 10.1016/j.bbacli.2016.02.003.
Drobnic F., Riera J., Appendino G., Togni S., Franceschi F., Valle X., Pons A., Tur J. Reduction of delayed onset muscle soreness by a novel curcumin delivery system (Meriva®): A randomised, placebo-controlled trial. J. ISSN. 2014;11:31. doi: 10.1186/1550-2783-11-31.
Esmaily H., Sahebkar A., Iranshahi M., Ganjali S., Mohammadi A., Ferns G., Ghayour-Mobarhan M. An investigation of the effects of curcumin on anxiety and depression in obese individuals: A randomized controlled trial. Chin. J. Integr. Med. 2015;21:332–338. doi: 10.1007/s11655-015-2160-z.
Anand P., Kunnumakkara A.B., Newman R.A., Aggarwal B.B. Bioavailability of curcumin: Problems and promises. Mol. Pharm. 2007;4:807–818. doi: 10.1021/mp700113r.
Han H.K. The effects of black pepper on the intestinal absorption and hepatic metabolism of drugs. Expert Opin. Drug Metab. Toxicol. 2011;7:721–729. doi: 10.1517/17425255.2011.570332.
Shoba G., Joy D., Joseph T., Majeed M., Rajendran R., Srinivas P.S. Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Med. 1998;64:353–356. doi: 10.1055/s-2006-957450.