Eating even small amounts of foods containing edible nicotine, such as capsicums and tomatoes, may reduce the risk of developing Parkinson’s Disease, according to new US research from the University of Washington.

The research, published 9 May 2013 in the Amercian Neurological Association and Child Neurology Society’s journal Annals of Neurology, found that people who ate plants belonging to the ‘solanaceae’ family showed a reduced risk of developing Parkinson’s.

Parkinson’s Disease is a movement disorder caused by a loss of brain cells that produce dopamine. Symptoms include facial, hand, arm, and leg tremors, stiffness in the limbs, loss of balance, and slower overall movement.

According to advocacy and support agency Parkinson’s Australia, one in every 350 Australians lives with Parkinson’s Disease, making it Australia’s second most common neurological disease. The number of Australians living with the disease has grown by 17 per cent since 2007. In the US, 60,000 new cases of Parkinson’s are diagnosed every year and the US-based Parkinson’s Disease Foundation reports that up to ten million individuals globally live with the disease.

Study results

For the new study, Dr Susan Searles Nielsen and colleagues from the University of Washington in Seattle recruited 490 patients newly diagnosed with Parkinson’s Disease from the university’s Neurology Clinic or a regional health maintenance organisation, the Group Health Co-operative. Another 644 unrelated individuals without neurological conditions were also studied as controls.

Questionnaires were used to assess participants’ lifetime diet and tobacco use. Researchers defined tobacco use as “ever smoking more than 100 cigarettes or regularly using cigars, pipes or smokeless tobacco”.

Vegetable consumption in general did not affect Parkinson’s disease risk, but as consumption of edible ‘solanaceae’ increased, risk of developing the disease decreased. Consumption of capsicum displayed the strongest association with a decreased risk of the Parkinson’s.

Researchers noted that the apparent protection from Parkinson’s occurred mainly in men and women with little or no prior use of tobacco, which contains much more nicotine than the foods studied.

Previous studies have found that cigarette smoking and other forms of tobacco, which is also a ‘solanaceae’ plant, reduced the relative risk of Parkinson’s Disease. However, experts have not confirmed if nicotine or other components in tobacco provide the protective effect, or if people who develop Parkinson’s Disease are simply less apt to use tobacco because of differences in the brain that occur early in the disease process, long before diagnosis.

“Our study is the first to investigate the dietary nicotine and risk of developing Parkinson’s Disease,” said Dr Searles Nielsen. “Similar to the many studies that indicate tobacco use might reduce the risk of Parkinson’s, our findings also suggest a protective effect from nicotine, or perhaps a similar but less toxic chemical in peppers and tobacco,” she said.

The authors of the study recommend further research to confirm and extend their findings.

Experts respond with caution

Responding to the findings, other scientists have also called for further study in the area, saying that the current study is limited.

“Although this study offers some interesting clues about how diet may affect risk of Parkinson’s developing, we need much larger studies in older populations before we know whether eating peppers can be added to this list,” said Claire Bale, Research Communications Manager at Parkinson’s UK. “Currently there’s no evidence that eating certain foods containing nicotine can slow Parkinson’s progression,” she said.

Other experts said that the way we eat foods from the ‘solanaceae’ family might also play into the decrease in the risk of developing Parkinson’s Disease.

“As the authors neatly explain in the discussion section, the devil is in the detail. Plants that we eat contain thousands of biologically active constituents, many of which have potential for protecting us against chronic disease,” Catherine Collins, Principal Dietitian at St George’s Hospital NHS Trust in the UK.

“We also choose to eat plants in a variety of ways – which may also influence the effect on our health. Peppers and chillies are rarely eaten alone, and it may be the foods cooked with these vegetables that confer some protection,” Ms Collins said.

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