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Olive oil and Alzheimer's disease

Friday 2 October 2009

“Olive oil could hold key to defeating Alzheimer’s,” reported the Daily Express . The newspaper said that a compound found in the oil has been shown to slow down changes in the brain that lead to Alzheimer’s disease. According to the paper, researchers believe that the antioxidant that gives the oil its "peppery bite" will become a key ingredient in new drugs.

This laboratory study investigated the effects of an olive oil extract (oleocanthal) on chemicals thought to be involved in Alzheimer’s disease. It found that nerve cells exposed to oleocanthal were better protected from the effects of these potential neurotoxins (toxins that damage or destroy nerve cells).

However, this study does not indicate that eating more olive oil will protect people from Alzheimer’s disease. The olive oil extract and other similar molecules may be important in the future development of drugs for Alzheimer’s disease, but these will require considerable further research and development. It will be some time before the direct relevance of these findings to preventing Alzheimer’s are clear, but this is the first step in the process.

Where did the story come from?

The research was carried out by Dr Jason Pitt and colleagues from the Northwestern University, the University of Pennsylvania, Western Illinois University and Rutgers University in the US and the Universidade Federal do Rio de Janeiro in Brazil.

While the authors provide grant numbers (reference numbers for that particular study) for the supporters of their research, it is unclear which funding organisations provided these.

The study was published in the peer-reviewed medical journal Toxicology and Applied Pharmacology .

What kind of scientific study was this?

Alzheimer’s disease is the most common form of dementia, affecting around 420,000 people in the UK. It is a degenerative brain disorder. The exact causes aren’t well understood, but plaques and tangles made of proteins form around brain cells, eventually leading to their damage and death. This causes a range of symptoms that can include confusion, mood swings, poor memory and forgetfulness and more severe symptoms such as delusions or obsessive behaviour.

Research has demonstrated that fibres in the brain called Aβ-derived diffusible ligands (ADDLs) are the main chemicals responsible for the initiation of Alzheimer’s disease. In this laboratory study, researchers explored the neuroprotective (protects brain cells) properties of a chemical called oleocanthal, which is derived from olive oil.

The researchers prepared ADDLs in the laboratory and investigated the effects of various concentrations of oleocanthal on these molecules. They assessed the effect of this extract on the primary molecules (monomers) that make up the ADDLs and also on the formed ADDLs (which are chains of monomers).

They also explored the effects of oleocanthal on nerve cells from the hippocampus, an area in the brain that largely controls memory and learning. The hippocampus is one of the areas in the brain affected by Alzheimer’s disease. Previous research has established that ADDLs of a certain size can bind at the synapses (junctions between neurones in the brain) The loss of synaptic function that results is a crucial first step in the development of Alzheimer’s disease.

What were the results of the study?

The study found that in the presence of the chemical oleocanthal, the ADDLs became more immunoreactive (i.e. more likely to provoke an immune response) and less soluble (which may lead to a decrease in toxicity).

When the chemical was applied to the brain cells, ADDLs formed in the presence of oleocanthal were less likely to bind to the synapses and this was accompanied by reduced deterioration of these cells.

What interpretations did the researchers draw from these results?

The researchers say their results suggest that oleocanthal is capable of altering the chemicals implicated in Alzheimer’s disease and can also protect against the effects of these compounds on synapses in the brain. They say that this suggests oleocanthal may be a key compound in the development of treatments for Alzheimer’s disease.

What does the NHS Knowledge Service make of this study?

Previous research has indicated that phenols (a group of chemical compounds) such as oleocanthal may have neuroprotective properties, and this laboratory study has uncovered some of the complex reactions that may explain these effects.

More research is needed to establish how it protects nerve cells (for example, whether it reduces binding at the synapses or whether the protective effect is due to the changes in the structure of ADDLs that it causes).

The researchers report that, overall, their findings are consistent with other studies that have investigated phenolic compounds such as oleocanthal and demonstrated protective effects. This extract from olive oil and other similar molecules may be important in future development of drugs for Alzheimer’s disease, but these will require further research and development. The drug development process is a long one, which starts with studies such as these in the laboratory and later move on to  animal testing then, to safety and efficacy studies in humans.

While the chemical being tested here – oleocanthal – is an extract from olive oil, it has not yet been tested in humans with Alzheimer’s. Whether these particular effects will be derived simply from eating olive oil is not clear from these findings.

Olive oil is likely to be part of a traditional Mediterranean diet, which is also high in vegetables, fruits and fish. While there is some evidence that a Mediterranean diet reduces the risk of Alzheimer’s disease, it is not clear what specific role olive oil has to play in these benefits. Only further studies can answer these questions.

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Olive oil could hold key to defeating Alzheimer's.

Daily Express, 2 October 2009

Extra virgin olive oil could prevent Alzheimer's disease.

The Daily Telegraph, 2 October 2009

Links to the science

Pitt J, Roth W, Lacor P, et al.

Alzheimer's-associated Aβ oligomers show altered structure, immunoreactivity and synaptotoxicity with low doses of oleocanthal.

Toxicology and Applied Pharmacology 2009; 240: 189-197

Further reading

Birks J, Grimley Evans J, Iakovidou V, Tsolaki M.

Rivastigmine for Alzheimer's disease.

Cochrane Database of Systematic Reviews 2009, Issue 2

Birks J.

Cholinesterase inhibitors for Alzheimer's disease.

Cochrane Database of Systematic Reviews 2006, Issue 1