Turmeric, a staple of almost any Indian dish, may hold the clue to fighting the Alzheimer's disease, researchers have said.

In a major study the researchers -- Dr Milan Fiala of the David Geffen School of Medicine and the VA Greater Los Angeles Health Care System and Dr John Cashman, director of the Human BioMolecular Research Institute in San Diego -- said they have isolated bisdemethoxycurcumin, the active ingredient of curcuminoids, a natural substance found in turmeric root, that may help boost the immune system in clearing amyloid beta, a peptide that forms the plaques found in Alzheimer's disease.

Using blood samples from Alzheimer's patients, researchers found that bisdemethoxycurcumin boosted immune cells to clear amyloid beta. In addition, researchers identified the immune genes associated with this activity.

'This is one of the first studies which pays attention to what we believe may be the crucial problem in Alzheimer's disease -- a defective immune system. The research presents further evidence that curcuminoids may improve the function of the innate immune system of patients with Alzheimer's disease by helping it clear the brain of amyloid beta  -- the waste products that accumulate in the brain of patients with the disease,' Fiala said in a press statement.

The study provides more insight into the role of the immune system in Alzheimer's disease and points to a new treatment approach. The researchers say that it may be possible to test a patient's immune response with a blood sample in order to individualise treatment.

The genes involved in the process, called MGAT III and Toll-like receptors, are also responsible for a number of other key functions in the immune system. The results also suggest a new drug development approach for the disease that differs from the amyloid-beta vaccine.

The new approach relies on the innate immune system, which is present at birth rather than on antibodies produced by B cells, which is a later developed part of the active immune system.

'We think that medications based on curcuminoids and on the isolated active ingredient, bisdemethoxycurcumin, may be useful, but more work needs to be done,' the statement said.

'The natural curcuminoid substance is available in pill form at health food stores but it is not clear yet how much is being absorbed when taken orally or how much active ingredient is available in these supplements. The next step is clinical trials, which are going on at UCLA and elsewhere,' the statement said.