The spice turmeric is the rhizome of Curcuma longa and has been used as a medicine, spice and colouring agent for thousands of years.  It is a native of India and South-East Asia, but is now cultivated in many countries, but India still accounts for a large proportion of the current world production.  It is estimated that India grows 487,000 metric tonnes annually with 27,750 metric tones being exported.  Turmeric became an important spice when it was observed that the addition of turmeric powder into foods preserved freshness, improved the nutritional value as well as palatability.

Description

Turmeric is a stemless, leafy perennial plant that closely resembles ginger and is a member of the same plant family the Zingiberaceae, and has broad hairless leaves arising from near ground level.  The fleshy rhizomes range from bright orange to yellow inside and the plant bears attractive pale yellow flowers containing three petals that appear close to ground level [i].  The rhizome consists of two parts, an egg shaped primary rhizome and several cylindrical and branched secondary rhizomes growing from the primary rhizome ³.  These where once differentiated in the spice trade as C. rotunda and C. longa respectively and as we shall see the distinction has been maintained in traditional Chinese Medicine.

Aroma and flavour

Dried turmeric powder has a slight peppery aroma with a hint of wood.  The taste is slightly warm and musky with a slight bitter aftertaste [ii].

Medicinal actions and uses

In India, turmeric is regarded as a stomachic, tonic and blood purifier and is used for poor digestion, liver disorders, fevers, skin conditions, and vomiting in pregnancy.  Externally it is used for conjunctivitis, skin infections, cancer, sprains, arthritis, haemorrhoids, and eczema.  Indian women are known to apply turmeric to the skin to reduce hair growth and to lighten and soften the skin, which has lead to the widespread use of turmeric in topical creams and soaps in India.   In China the tuber and rhizome are attributed different uses, as the tuber is seen as being more cooling.  The rhizome is said to be a blood and Qi (vital energy) stimulant with analgesic properties.  It is used to treat chest and abdominal pain and distention, jaundice, frozen shoulder, amenorrhoea due to blood stasis and postpartum abdominal pain due to stasis.  It is also applied topically to wounds and injuries.  The tuber being more cooling is used for hot conditions and has been used for viral hepatitis [iii].

In recent years turmeric has attracted a considerable amount of clinical and pharmacological research and for this reason Western herbalist regard turmeric as having antiinflammatory, antiplatelet, antioxidant, hypolipidaemic, choleretic, antimicrobial, carminative and depurative (blood purifying) properties.

The effectiveness of turmeric as a topical remedy has lead to a recent controversy. In 1995, the US Patent and Trademark Office granted a patent to the University of Mississippi for the use of turmeric powder as a wound-healing agent.  The patent protected both the oral and topical administration of formulations of turmeric with other ingredients, as food supplements, capsules, tablets, ointments and creams as well as nasal, intravenous and suppository dosage forms.  Of course this rang alarm bells in India and the patent was challenged in 1996 by the Indian Council of Scientific and Industrial Research on the grounds that it did not satisfy an important criteria, novelty.  There was worldwide concern that patents of this nature would have far reaching consequences and threaten the traditional medicine knowledge base that is in the public domain and particularly that of the third world.  The challenge was well presented and as a result the patent on turmeric was overturned in 1997. Ironically the “inventors” of the product are Indian born faculty members of the University of Mississippi’s medical centre.

Culinary uses

Turmeric is best known as an ingredient in curries and curry powder where it contributes both flavour and the characteristic yellow colour.  It also finds use in many chutneys and pickles particularly piccalilli, Indian rice dishes such as kedgeree, as well as vegetable and dhal dishes ².  There are various Curcuma species each with unique flavours that share similar culinary and medicinal uses and include C. zedoaria (Zedoary), C. xanthorrhiza (Javanese turmeric) and C. aromatica (Wild turmeric).  Zedoary for instance has a musky aroma with a hint of camphor and is often mixed with turmeric and ginger to make a spice paste for lamb and chicken curries ².

Due to the rise in the use of natural ingredients in foods, turmeric is now used by the food industry as a colouring agent for mustards, butter, cheese and liqueurs [iv]^,2.

Phytochemistry

There are three classes of compounds that are important, the yellow pigments termed phenolic diarylheptanoids which includes curcumin and methoxylated curcumins, aromatic essential oils (3-5%) including the sesqueterpene turmerone as well as zingiberine, cineole and borneol as well as polysaccharides ⁴.

Much of the research has focused on curcumin, whose chemical structure is shown below.

Pharmacological studies

Antiinflammatory effects

Inflammation is a non-specific, defensive response of the body to tissue damage, whether that damage results from infection or trauma.  It results from a complex interaction of immune system cells and represents the immune systems attempt at disposing of the invading microbes and is the first stage in the healing process.  However uncontrolled inflammation due to the nature of the immune system cells that are attracted to the area, may itself cause further damage and so needs to be reduced.  Curcumin has displayed inhibitory effects on many of the mediators of inflammation in vitro, such as inflammatory cytokines, which are locally acting hormones produced by immune cells to increase the magnitude of inflammation [v].  Curcumin appears to be an inhibitor of both of the enzymes that mediate the inflammatory pathway of arachidonic acid (AA) metabolism ^3,5.  Aspirin has a strong inhibitory effect on one of these enzymes, termed cyclooxygenase, in contrast to a mild effect with curcumin.  Consequently curcumin lacks significant analgesic and antipyretic activity ³.

One of the first cells to migrate to an area of inflammation are the macrophages, which release proteolytic enzymes in an attempt to kill the invading microbes. These enzymes can also damage tissue. Macrophages are also prevented from leaving the area by the T cell production of macrophage migration inhibiting factor (MIF).  MIF also induces proteolytic enzyme release from macrophages.  Curcumin has displayed inhibitory effects on both proteolytic enzyme release from macrophages and MIF production by T cells ^5,[vi].

In summary it is likely that curcumin inhibits several mechanism which contribute to inflammation such as the locally produced and acting cytokines that promote inflammation, enzymes that mediate the production of inflammatory prostaglandins from the cell membrane AA and proteolytic enzyme release from macrophages.

Antioxidant effects

There is now an overwhelming amount of evidence that free radicals and oxidative stress are associated with cellular damage, cancers, mutagenesis and the degenerative process of aging.  The discovering of the antioxidant properties of curcumin explains many of the therapeutic actions of turmeric.  Curcumin is an effective antioxidant and neutralizes the superoxide radical, hydrogen peroxide and nitric oxide from activated macrophages ⁵.  As previously mentioned macrophages are immune cells that engulf microbes and kill them by releasing proteolytic enzymes as well as bombarding them with free radicals termed the oxidative burst.  These free radicals generated by macrophages can be released into the interstitial fluid in a process termed frustrated phagocytosis exacerbating the whole inflammatory process.  Curcumin has also displayed significant ability to inhibit lipid peroxidation ^3,5.

Inhibition of platelet aggregation

Phytochemicals that cause an inhibition of platelet aggregation may be useful in the prevention and treatment of cardiovascular degeneration.  The metabolism of AA produces platelets mediated by the enzyme cyclooxygenase, which aspirin strongly inhibits, explaining the widespread use of aspirin to thin the blood.  As well as inhibiting this same enzyme curcumin inhibits several other pathways involved in platelet aggregation such as platelet activating factor (PAF) and thromboxane A2 ^3,5.  Thus curcumin acts on platelet aggregating pathways which aspirin does not effect.

Anticancer effects

Cancer results from a series of molecular events that fundamentally alters the normal properties of cells, such as the disabling of the control systems that prevent cell overgrowth and the invasion of other tissues.  This cellular anarchy usually results from mutations in the protein coding genes that regulate cell division.  Cancer cells do not respond to the usual cells signals for programmed cell death termed apoptosis and thus become immortal.  Curcumin has demonstrated in a variety of models to induce apoptosis ⁵.  Curcumin appears to inhibit cancer at all three stages of cancer, initiation, promotion and development ³.

Clinical studies

Antiinflammatory effects

In a short term, double-blinded trial on rheumatoid arthritis patients, curcumin was compared to phenylbutazone.  A significant symptom improvement occurred with curcumin but phenylbutazone showed a greater improvement probably due to its analgesic activity [vii].  Curcumin showed greater effects over phenylbutazone and placebo for postoperative inflammation [viii].

In a double-blind, placebo-controlled crossover trial, 42 osteoarthritis patients received either a herb/mineral mixture containing turmeric of placebo for 3 months. Treatment with the herb/mineral mixture produced a significant drop in the severity of pain, however radiological assessment did not demonstrate any difference between the groups [ix].

Hypolipidaemic effects

An uncontrolled trial on 16 patients in China using 50g of turmeric per day resulted a significant reduction in cholesterol and triglycerides, which was at least equivalent to clofibrate.  These results were replicated in another similar study on 90 patients ³.  In both of these trials the use of turmeric ameliorated the symptoms of angina.

Chemoprotective effects

Turmeric given to smokers in doses of 1.5gm per day for 30 days significantly reduced urinary mutagens, whilst there was no change in controls [x].  The use of turmeric in India is said to contribute significantly to the low rates of colorectal, prostate and lung cancers in that country [xi].

Digestive tract

A randomised, double-bind, placebo-controlled trial using 2gm per day of turmeric for 7 days on patients with dyspepsia demonstrated an effect significantly greater than placebo [xii].  A recent trial using turmeric on patients with Irritable Bowel Syndrome demonstrated a significant reduction in symptoms [xiii].

HIV/AIDS

18 HIV positive patients took an average of 2gm of curcumin for 127 days, which resulted in a significant increase in CD4 and CD8 T lymphocyte counts.  A follow up phase two trial failed to show any benefit on viral load or CD4 count in HIV positive patients ³.

Scabies

A paste of turmeric and neem was used in the treatment of scabies in 814 patients which resulted in cure in 97% within 3-15 days of treatment ³.

Conclusion

Turmeric is an inexpensive spice and medicinal agent, which offers a wide range of protective effects against many of the chronic lifestyle diseases impacting modern society.

[ii]

[iii] Mills S., Bone K. 2000, Principles and Practice of Phytotherapy, Churchill Livingston, Edinburgh.

[iv] Heinrich M, Barnes J, Gibbons S, Williamson EM. 2004. Fundamentals of Pharmacognosy and Phytotherapy, Churchill Livingston, Edinburgh

[v] Joe B, Vijaykumar M, Lokesh BR. 2004, Critical Reviews in Food Science and Nutrition, 44: 97-111

[vi] Joe B, Lokesh BR. 2000, Molecular and Cellular Biochemistry, 203: 153-161.

[vii] Deodhar SD, Sethi R, Srimal RC. 1980, Indian Journal of Medical Research, 71:632-634.

[viii] Satoskar RR, Shah SJ, Shenoy SG. 1986, International Journal of Clinical Pharmacology, 24:651-654.

[ix] Kulkarni RR et al. 1991, Journal of Ethnopharmacology, 22(1-2):91-95.

[x] Polasa K et al. 1992, Mutagenesis, 7:107-109.

[xi] Sinha R, Anderson DE, McDonald SS, Greenwald P. 2003, Journal of Postgraduate Medicine, 50:222-228.

[xii] Thamlikitul MD et al. 1989, J Med Assoc Thai, 72:613-620.

[xiii] Bundy R et al. 2004, J Alt Compl Med 10:1015-1018.