Turmeric, a common cooking spice with powerful health benefits
Curcumin, (diferuloymethane) is the main polyphenol found in the spice turmeric or Curcuma longa; a herbaceous perennial plant belonging to the ginger family. The medicinal properties of turmeric have been known for thousands of years, with Curcuma longa being traditionally used in Asian countries to treat many ailments due to its antioxidant, anti-inflammatory, antimicrobial and anti-carcinogenic properties. Many populations worldwide consume curcumin in a variety of forms. In India, turmeric is used in curry. In Japan and Korea, it is prepared in drinks and in China and the United States it is utilised as a colourant and preservative.
Poor bioavailability is the major obstacle hindering the ability of curcumin to elucidate health benefits, primarily due to poor absorption. This can be overcome by taking curcumin with a known bioavailability enhancer such as piperine, the major active component of black pepper, which can produce a two-thousand-fold increase in curcumins bioavailability. Curcumin undergoes a biotransformation during absorption from the bowel and also in the liver. This leads to the production of several curcumin metabolites (curcumin glucuronides/sulphates or hexahydrocurcumin) 75% of which are excreted of via faeces.
Most of the beneficial effects associated with curcumin can be attributed to its antioxidant and anti-inflammatory activity. There are several mechanisms by which curcumin can curtail the effects of free radicals. Namely, curcumin possesses a beta-diketone group which allows it to scavenge reactive oxygen and nitrogen species, thus inhibiting their deleterious effects. Additionally, curcumin may enhance the activity of several antioxidant enzymes, such as catalase, superoxide dismutase and glutathione peroxidase, all of which play a role in the arrest and neutralization of free radicals. Curcumin may also inhibit free radical generating enzymes such as lipoxygenase and cyclooxygenase. Curcumin is a lipophilic compound, making it efficient at scavenging peroxyl radicals. Hence, like vitamin E, curcumin is also considered a chain-breaking antioxidant.
The inflammatory cascade plays an important role in the development of chronic illnesses. Its pathological processes being closely related to those of oxidative stress; inflammatory cells release reactive species producing oxidative stress at sites of inflammation. Inflammation is implicated in neurodegenerative, cardiovascular, autoimmune and endocrine disease. Curcumin can decrease inflammation by interacting with many inflammatory processes. For instance, tumour necrosis factor -alpha is a major mediator of inflammation in most diseases and is regulated by the activation of a transcription factor, nuclear factor (NF)-kB. Curcumin has been shown to block NF-kB activation (through inhibition of IkB kinase), increased by several different inflammatory stimuli. This produces a down regulation of oxidative stress and the subsequent inflammation. Curcumin also inhibits inflammatory cytokines, such as interleukins and chemokines.
The antioxidant and anti-inflammatory activity of curcumin confer an anticancer property upon it; preventing the initiation, promotion and progression of cancerous cells. Cancer is a disease characterised by the dysregulation of multiple cellular signalling pathways. Despite this, current treatments of cancer generally only act on one target; those which affect multiple cancer forming pathways are costly and produce undesired effects. Curcumin, however has been identified as a substance that is able to disrupt multiple pathways in carcinogenesis, whilst being safe and cost effective. Several clinical studies have demonstrated the therapeutic and chemo-preventive effects of curcumin. These effects have been studied extensively in colorectal cancer, with the administration of curcumin reducing the amount of aberrant crypt foci in individuals with colorectal tumours by 40%. As well as improving cancer patient’s general health by enhancing the expression of p53 causing apoptosis of the tumour cells. In pancreatic cancer patients, curcumin can halt the progression of disease through down-regulation of NF-κB, cyclooxygenase-2, and phosphorylated signal transducer and activating transcription 3 (pSTAT3).
The good news doesn't stop there, with evidence of curcumin playing a beneficial role in the prevention and treatment of other major diseases of the industrialised world, including Alzheimer's and cardiovascular disease. The ability of curcumin to modulate targets such as antioxidant enzymes, inflammatory cytokines, transcription factors, kinases and growth factors account for its neuroprotective effect. This has been demonstrated in a variety of nervous system cells, including neurons, cortical and spinal cord cells. Again, these benefits may be attributed to curcumins antioxidant and anti-inflammatory properties. Furthermore, curcumin has been observed to decrease the neuro-inflammation present in degenerative brain diseases by inhibiting the expression of interleukins -1 and -6 as well as tumour necrosis factor. A pathological feature of Alzheimer’s disease is defective phagocytosis and a subsequent accumulation of Amyloid plaques. In vitro, curcumin can promote microglial phagocytosis, increasing Amyloid plaque clearance in vitro.
The association between inflammation and cardiovascular diseases risk has been well established. As discussed earlier, curcumin decreases the expression of inflammatory molecules, thereby reducing the risk of inflammation related cardiovascular risk. Curcumin has also been shown to exert an inhibitory effect on the platelet aggregation and eicosanoid metabolism, further bolstering its cardio protective nature. Curcumin was responsible for reducing serum very low-density lipoprotein, LDL cholesterol and triacylglyceride in a human study of coronary heart disease, all of which are biomarkers for cardiovascular disease.
Curcumin has a long-established safety record and along with all other curcuminoids, has been approved by the US Food and Drug Administration as 'Generally Recognized As Safe', with good tolerability and safety profiles demonstrated in clinical trials, even at high doses. Despite this well-established safety, some negative side effects have been observed, including diarrhoea, headache, rash, yellow stool and an increase in serum alkaline phosphatase and lactate dehydrogenase.
Curcumin has received worldwide attention for its multiple health benefits, which appear to act primarily through its anti-oxidant and anti-inflammatory mechanisms. Thus, curcumin has an important role to play in the fight against leading causes of death like cancer, neurological, and cardiovascular diseases. A relatively low dose can provide health benefits, even for people that do not have diagnosed health conditions. These benefits are best achieved when curcumin is combined with agents such as piperine, which significantly boosts its bioavailability.
References
Hewlings, S. J., & Kalman, D. S. (2017). Curcumin: A Review of Its' Effects on Human Health. Foods, 6(10). doi:10.3390/foods6100092
Kunnumakkara, A. B., Bordoloi, D., Harsha, C., Banik, K., Gupta, S. C., & Aggarwal, B. B. (2017). Curcumin mediates anticancer effects by modulating multiple cell signaling pathways. Clin Sci (Lond), 131(15), 1781-1799. doi:10.1042/CS20160935
Marchiani, A., Rozzo, C., Fadda, A., Delogu, G., & Ruzza, P. (2014). Curcumin and curcumin-like molecules: from spice to drugs. Curr Med Chem, 21(2), 204-222.
Pulido-Moran, M., Moreno-Fernandez, J., Ramirez-Tortosa, C., & Ramirez-Tortosa, M. (2016). Curcumin and Health. Molecules, 21(3), 264. doi:10.3390/molecules21030264
Shoba, G., Joy, D., Joseph, T., Majeed, M., Rajendran, R., & Srinivas, P. S. (1998). Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Med, 64(4), 353-356. doi:10.1055/s-2006-957450