Turmeric is widely grown both as a kitchen spice and for its medicinal uses. Two closely related plants, Curcuma petolata and Curcuma roscoeana, are natives of Cambodia and are grown for their decorative foliage and blossoms.
All curcumas are perennial plants native to southern Asia. They grow in warm, humid climates and thrive only in temperatures above 60°F (29.8°C). India, Sri Lanka, the East Indies, Fiji, and Queensland (Australia) all have climates that are conducive to growing turmeric.
The turmeric plant is identifiable by both its characteristic tuberous root and the leaves that extend upward from erect, thick stems arising from the root. Turmeric root is actually a fleshy oblong tuber 2–3 in (5–10 cm) in length, and close to 1 in (2.54 cm) wide.
It is tapered at each end, and its exterior can be yellow, tan, or olivegreen in color. The interior of the root is hard, firm, and either orange-brown or deeply rust-colored, with transverse resinous parallel rings.
M. Grieve, in A Modern Herbal, states that the root is dense and breaks into a powder that is lemon yellow in color. Turmeric root has a fragrant aroma and a somewhat bitter, peppery, biting taste reminiscent of ginger. When eaten, it colors the saliva yellow and leaves a warm sensation in the mouth.
The root contains a bitter volatile oil, brown coloring matter, gum, starch, calcium chloride, woody fiber and a yellowish coloring material that is known as cucurmin. In addition to the root, the turmeric plant produces rhizomes, which are underground stems growing parallel to the ground that produce roots below and new shoots from their upper surface.
Turmeric rhizomes have also been used for medicinal purposes. The plant’s leaves are divided, lance-shaped and narrower at each end. They are close to 2 ft (61 cm), lustrous and deep green. The flowers arise from those leaves, and are a pale yellow color, growing in groupings of three to five.
The addition of turmeric to such oils as olive or sesame oil extends their shelf life due to its antioxidant properties. In addition, some orange and lemon drinks are now colored with turmeric, which is considered safer than artificial colorings derived from coal tar.
The powdered root of turmeric has been used for making a deep yellow dye for fabrics for hundreds of years, though it does not produce an enduring color-fast tint. It is also used as a coloring for medicines at times.
A less familiar use of turmeric is in chemistry, in the making of papers to test for alkaline solutions. White paper soaked in a tincture of turmeric turns reddish-brown and dries to a violet color when an alkaline solution is added.
Though its use in Western herbal medicine has declined over the years, turmeric has long been used and continues in use in Eastern medicine, both Oriental herbal medicine and Ayurveda, the traditional system of medicine from India.
R.C. Srimal, in Turmeric: A Brief Review of Medicinal Properties, describes the herb as having the ability to protect the liver against toxic substances, especially such heavy metals as lead; to prevent the formation of gallstones or decrease the size of stones already formed; and to increase the flow of bile.
Some studies have demonstrated that turmeric exhibits anti-inflammatory properties that are useful in the treatment of both osteoarthritis and rheumatoid arthritis. Alcohol extracts of turmeric have been found to reduce blood sugar, which could eventually affect the treatment of diabetes.
A substance known as a lipopolysaccharide isolated from the turmeric root has shown a capacity to stimulate and increase the activity of the immune system. In addition, research has shown turmeric to be effective in destroying gram-positive salmonella bacteria in vitro. Turmeric also demonstrates antifungal properties.
Turmeric has long been used as an Eastern folk remedy for eye discharges and as a cooling, soothing skin lotion. In Chinese herbal medicine, under the name of jiang huang, the turmeric rhizome is used in many different formulas as an anti-inflammatory pain reliever, especially for shoulder pain.
It is believed to invigorate and improve the movement of blood and stimulate menstruation. The turmeric tuber, which is called yu jin in Chinese medicine, also has many important uses. It is given for jaundice, pain in the liver area, agitation, and insomnia.
The cucurmin found in turmeric is being studied as a possible treatment to prevent cancer. Cucurmin appears to lower the rate of genetic mutations in experimental animals.
It has also been shown to induce apoptosis, or cell self-destruction, in leukemia cells. In addition, recent studies done on tissue samples from the human digestive tract indicate that cucurmin may help to prevent colon cancer.
In India and Pakistan, turmeric is dissolved in water for use as an eyewash, and in milk to make a soothing skin lotion.
Practitioners of Chinese herbal medicine advise against using turmeric during pregnancy.
Like other anti-inflammatory agents, turmeric has been found to contribute to the formation of stomach ulcers.