If you have an ailment, there's a good chance that someone, somewhere, is studying whether turmeric can treat it. There are more than 15,000 manuscripts published about curcumin, the active ingredient in turmeric, and about 50 manuscripts added to this collection each week, according to the National Institutes of Health

"It's really taken on sort of panacea-like properties in terms of the things it's being studied for and the things it has been reported to be useful for," said D. Craig Hopp, deputy director of the Division of Extramural Research at the National Institutes of Health's National Center for Complementary and Integrative Health

What is turmeric?

Turmeric is a popular spice similar to ginger, known for its bright yellow color and use in curry powders and mustards. Also called "Indian saffron," the plant grows across India, other areas of Asia and Central America. Turmeric flavors a range of dishes, is a vital component of certain religious rituals and has been used for medicinal purposes for nearly 4,000 years

"There are plenty of studies currently being done but already good evidence that turmeric can help control knee pain from arthritis as well as decrease the likelihood of a heart attack after bypass surgery," said Dr. Sanjay Gupta, CNN's chief medical correspondent.

Turmeric is one of many plants used in ayurveda, a traditional South Asian system of medicine, according to the National Institutes of Health. It is used to treat issues such as breathing problems, rheumatism, fatigue and pain.

"There's a distinction that's very important to make between turmeric, which is the plant and the spice, and what people often study, which is the curcumin, which is the proposed active constituent in turmeric," Hopp said. "And even curcumin, as it's usually sold or researched, is not a single compound. It's usually a collection of three or four compounds that are called curcuminoids, collectively."

The exact amount varies, but the turmeric root contains up to 5% of these curcuminoids typically, the National Institutes of Health says.

A gap between theory and practice

Extracting the curcumin and translating its power into a successful treatment is still a major challenge for researchers, experts say. There is epidemiologic evidence that people who eat a diet rich in turmeric can potentially attribute their substantial health benefits to the spice, Hopp said, citing a lower incidence of colon cancer in the Indian subcontinent.

"But it's very difficult to sort of project what you see in terms of an activity in a cell to what's going to actually happen in the human," he added. "There's a sort of a disconnect between what appears to be a lot of very promising activity in vitro, which is just in the cells. And contrast that with where it's been studied in clinical trials as humans, where there's been virtually no evidence of benefits."

One reason for that disconnect is that apart from turmeric, curcumin has biological properties that make it poorly bioavailable: It is rapidly metabolized and excreted, and very little of it gets absorbed into the body. The chemical doesn't make it to the places where it could be of help.

The context in which turmeric is traditionally used is important as well, Hopp said. Black pepper is often found alongside turmeric. Piperine , the substance that gives pepper its bite, increases curcumin's bioavailability.

"It keeps the door open," Hopp said. "As things go into and out of cells, piperine is sort of like a doorstop that allows things to go in and out of the cells much more readily."

Photos: 12 healthy herbs and spices: A closer look Our ancestors used herbs and spices to flavor foods and soon learned that some of them seemed to improve their health. Today, science is looking more closely at those claims. Read on to find out the latest research on these historically healthy spices and herbs. Hide Caption 1 of 13 Photos: 12 healthy herbs and spices: A closer look One of the most commonly used spices in the world, cinnamon has been linked in various studies to improvement in cholesterol and blood sugar control, and it seems to have antibacterial and anti-inflammatory effects.



Enjoy it on your food, but hold off on using capsule supplements, says Academy of Nutrition and Dietetics spokeswoman Lauri Wright. There's not enough research on dosage and long-term impact, and if you have liver issues, it could be dangerous. Hide Caption 2 of 13 Photos: 12 healthy herbs and spices: A closer look



have shown that rosemary has strong anti-inflammatory properties and seems to improve memory in mice and



As with any herb, be careful. There are compounds in rosemary oil that could worsen bleeding or seizures and be harmful if taken by mouth.

Uniquely fragrant, rosemary has historically been known for its impact on memory. Shakespeare wrote about it in Hamlet, when Ophelia says to her brother Laertes, "There's rosemary; that's for remembrance." Studies have shown that rosemary has strong anti-inflammatory properties and seems to improve memory in mice and humans , making it a promising target for Alzheimer's research. Its natural antioxidant abilities persuaded the European Union to approve rosemary extract as a food preservative As with any herb, be careful. There are compounds in rosemary oil that could worsen bleeding or seizures and be harmful if taken by mouth. Hide Caption 3 of 13 Photos: 12 healthy herbs and spices: A closer look Turmeric, a common spice in curry powder and other Indian dishes, is another powerhouse spice often touted for its anti-inflammatory properties. The National Center for Complementary and Integrative Health says that claim isn't yet supported but points to studies that show it can control knee pain as well as ibuprofen, reduce the number of heart attacks after bypass surgery, and reduce skin irritation after breast cancer radiation treatment. Be aware that using turmeric in high doses or over a long period could cause stomach distress. Hide Caption 4 of 13 Photos: 12 healthy herbs and spices: A closer look Ancient records from Greece, Rome and Egypt mention the use of mint as a healing herb; today, we often see peppermint used for colds, headaches and digestive issues. Studies of peppermint oil show that it may improve irritable bowel symptoms when taken in capsules and when applied topically may lessen tension headaches, but there's no evidence that it can help the common cold or other conditions. Be warned: Excessive doses of peppermint oil can be toxic. Hide Caption 5 of 13 Photos: 12 healthy herbs and spices: A closer look

When used as a spice, ginger is considered safe, but there is some concern that it could interact with blood thinners and increase the flow of bile, which might affect anyone with gallstone disease. Asian medicine has used dried ginger for centuries for stomachaches, nausea and diarrhea. Scientific studies show that ginger could help control nausea from cancer chemotherapy when used along with conventional medications, and it may reduce morning sickness among pregnant women, who should be sure to consult with an OB/GYN first.When used as a spice, ginger is considered safe, but there is some concern that it could interact with blood thinners and increase the flow of bile, which might affect anyone with gallstone disease. Hide Caption 6 of 13 Photos: 12 healthy herbs and spices: A closer look Garlic is the edible bulb of the lily family and is widely promoted as a health aid for high blood pressure, cancer, cholesterol and the common cold. But the National Center for Complementary and Integrative Health says the research into these claims is inconclusive. The center recommends adding garlic to foods but warns that it can increase the risk of bleeding in those on warfarin or needing surgery and can interfere with some drugs, including one that treats HIV. Hide Caption 7 of 13 Photos: 12 healthy herbs and spices: A closer look It takes 75,000 saffron blossoms to produce one pound of saffron, making it one of the world's most expensive spices. Studies have shown that it may help with depression, menstrual discomfort, and possibly Alzheimer's, but research is inconclusive for a positive impact on erectile dysfunction, asthma, cancer and many other conditions.



Use in food is considered safe, but when taken medicinally, large doses may be toxic. Even smaller doses could cause miscarriage and heart and blood pressure issues. Hide Caption 8 of 13 Photos: 12 healthy herbs and spices: A closer look



Evidence is sparse for the use of sage for cancer, asthma and stomach pain. Use in food is considered safe, but supplements are not advised during pregnancy or if you have seizures, high or low blood pressure or a hormone-sensitive cancer such as breast or ovarian cancer. Sage is a potent herb often used in stuffing and butters. Studies have shown that it may be helpful for memory, cholesterol and menopausal symptoms if taken by mouth. In one study, a mixture of sage and rhubarb on cold sores was nearly as effective as the antiviral medication acyclovir.Evidence is sparse for the use of sage for cancer, asthma and stomach pain. Use in food is considered safe, but supplements are not advised during pregnancy or if you have seizures, high or low blood pressure or a hormone-sensitive cancer such as breast or ovarian cancer. Hide Caption 9 of 13 Photos: 12 healthy herbs and spices: A closer look Holy basil, sometimes known as hot basil, is revered by Hindus and used in Ayurvedic medicine as a way to counter life's stresses. Studies have shown that chemicals in the herb may decrease blood sugar, reduce anxiety and depression, lessen stress and improve sleep, while its high antioxidant properties have researchers looking into the impact of holy basil oil on certain cancers.



Avoid the herb when pregnant, when breast-feeding or two weeks before any surgery: It has anti-blood-clotting effects, and its use during pregnancy has not been studied. Hide Caption 10 of 13 Photos: 12 healthy herbs and spices: A closer look



see Look beyond the sweet taste of this powerful spice: Nutmeg, used unwisely, can poison you. It's been used over the centuries as a psychedelic, to stimulate menstruation and induce abortions, and to fight infections, including the Black Plague. Its popularity as a poor man's hallucinogen -- it takes only two tablespoons to have effects -- became legend when Malcolm X wrote about using it in prison. Poison control centers see teenagers get into trouble trying it out; in addition to an uncomfortable high, they suffer abdominal pain, nausea, vomiting, an unsteady heart rate and and severe confusion. Dr. Leon Gussow wrote in Emergency Medicine News that "Many individuals who take nutmeg once as an available, inexpensive high vow never to do it again." Hide Caption 11 of 13 Photos: 12 healthy herbs and spices: A closer look Eating the flowers, leaves and oil of the herb thyme, either alone or in conjunction with other herbs, may have some benefit for symptoms of colds and bronchitis, especially coughs. But research into other uses, such as agitation, hair loss and movement disorders, is still inconclusive.



Use in food is considered safe, but the use of supplements is not advised before surgery or if you have a bleeding disorder or a hormone-sensitive cancer such as breast or ovarian cancer. Hide Caption 12 of 13 Photos: 12 healthy herbs and spices: A closer look

Stay away from medicinal uses during pregnancy, as it has not been studied, and before surgery, as it might increase the risk of bleeding. Oregano, a frequent player in Italian food, seems to contain chemicals that may reduce coughs, spasms and digestive issues, including killing some parasites in the intestines. There's insufficient evidence for other uses, such as for wound healing, asthma, arthritis and heart conditions.Stay away from medicinal uses during pregnancy, as it has not been studied, and before surgery, as it might increase the risk of bleeding. Hide Caption 13 of 13

Turmeric's link to glaucoma and Alzheimer's

Curcumin also does not dissolve easily, and much of it does not enter the bloodstream, said researchers in a study investigating the effects of turmeric in treating glaucoma, recently published in the journal Scientific Reports . One would need to take as many as 24 500-milligram tablets of curcumin a day to get an effective dose, increasing the risk of gastrointestinal side effects like vomiting and diarrhea.

"If you think about it, in a curry, there's only 700 milligrams of turmeric," said Dr. Francesca Cordeiro, professor of ophthalmology at Imperial College London and one of the authors of the study. "You'd need to eat 200 curries a day to get that therapeutic level."

Instead of choosing capsules or cuisine as their method of treatment delivery, Cordeiro's team used eye drops infused with a stabilizer that increased the curcumin's solubility on their rat subjects twice a day.

"We used nanotechnology," Cordeiro said. "The advantage of it being so small is it can cross into the eye as an eye drop into the back of the eye. Once it enters, it can affect the nerve cells there, and that direct effect can lead to them not dying. It's what we call neuroprotection."

Three weeks later, the untreated control group had a 23% reduction in retinal cells compared with the eye drop group. This loss was prevented by treatment with curcumin, Cordeiro explained.

The researchers' next steps include clinical trials and exploring the possibility of using the retina as a "window to the brain" by developing the drops into a diagnostic resource for Alzheimer's disease.

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"Curcumin is fluorescent," Cordeiro said. "If you put the correct wavelength to it, it fluoresces, and it binds to the parts that are implicated in Alzheimer's, the beta amyloid plaque," one of the substances in the brain that is a hallmark of the condition.

Even if the risks of taking turmeric as a supplement appear to be limited, Hopp recommends discussing such treatments with a doctor, "especially if they're taking other medications, so that the doctor has a full picture of what the patient is consuming and can manage that care properly," he said.