Alzheimer's disease is a debilitating and ultimately lethal neurodegenerative disorder that currently afflicts about 18 million people worldwide. The incidence of the disease increases exponentially with age and, with life expectancy rising in many parts of the world, global prevalence is expected to double by 2025. Alzheimer's disease is characterized by progressive intellectual deterioration; starting with memory loss that is followed by intellectual impairment, poor decision making, uncoordinated movements, speech impediments and loss of recognition of familiar people and places. Although the incidence of Alzheimer's disease is increasing rapidly in many developing countries, on the Indian subcontinent it remains rare, even among the high-risk age groups. Recent studies have associated this reduced risk primarily with the high levels of consumption of turmeric that, together with several other spices, has been shown to have protective and possibly curative effects against the disease. This discovery has led to intensive research into the potential use of spices as natural treatments for Alzheimer's disease.

The causes of Alzheimer's disease are not fully understood, but there are several pathological processes that occur in those afflicted with this illness. The most prominent of these is the deposition of an abnormal protein, beta-amyloid, in the brains of Alzheimer's disease sufferers. ?-amyloid is deposited in the form of plaques between the neurons and also accumulates in the walls of small blood vessels in the brain, where it impedes the flow of blood to brain tissues. The aggregation inside the neurones of abnormal amounts of tau protein filaments is another pathological feature of Alzheimer's disease. A further process associated with this malady is atrophy (wasting) of nerve tissue which leads to the loss of synapses and their associated neurotransmitter chemicals from key areas of the brain. In all cases, the precise causes of these pathological processes are unclear but they, and certain other factors, appear to increase the risk and aggravate the development of Alzheimer's disease.

Factors implicated in Alzheimer's disease are: Metals like aluminum, copper and zinc; oxidative stress and chronic inflammation. Genetic factors may also play a role in the development of Alzheimer's disease.

Confirming epidemiological pointers that diet plays a key role in the low incidence of Alzheimer's disease in India are several promising laboratory studies of the phytochemical, curcumin. Found in large quantities in turmeric, curcumin has been shown to inhibit the deposition of ?-amyloid in the brain and, in some cases, actually reverse this process. Studies have also shown that rosmarinic acid, present in rosemary and several other spices as well as gingerol and zingerone found in ginger (which also contains curcumin) have similar protective effects. Although these are the most thoroughly researched spices in respect of Alzheimer's disease, evidence is accumulating that several others, including garlic, have similar preventive effects against this disorder. Moreover, it is almost certain that the list of spices shown to protect against Alzheimer's disease will continue to grow.

If we look at the known underlying factors that are thought to cause Alzheimer's disease we can see the reasons why spices have the potential to prevent and even alleviate this condition.

Chelation: Several spices have chelating properties. Chelating agents are substances that attach to toxins (such as heavy metals) and help the body to excrete them. There is a strong possibility that the chelating characteristics of some spices help to rid the body of toxic metals like aluminium, copper, lead, mercury and zinc. Coriander and turmeric are two of the most potent chelating spices.

Inflammation: An inflammatory process is also likely to be an underlying cause of Alzheimer's disease. Many spices contain high levels of anti-inflammatory compounds like salicylates. Curcumin (found in turmeric) is one of the most important anti-inflammatory phytochemicals.

Antioxidants: Spices are the richest source of antioxidants and, as oxidative stress is one of the processes underlying this malady, one would expect that they would be useful natural treatments for Alzheimers's disease.

Alzheimer's disease could affect any one of us and, as spices may be one the only defenses we have against this debilitating illness, we should eat more of these remarkable foods. The most important spices known to help Alzheimer's disease are turmeric, garlic and rosemary.