In this article, we will take a look at one of the studies that has found a link between nicotine and Parkinson's and uncover why this relationship might exist.
Here are some key points about Parkinson's and nicotine. More detail and supporting information is in the main article.
- Parkinson's affects millions of people worldwide, and there is still no cure
- Plants of the family Solanaceae are an edible source of nicotine
- Researchers are currently investigating whether a nicotine patch might slow Parkinson's progression
- Nicotine may protect the brain by helping the body deal with badly organized proteins
What is Parkinson's disease?
Despite affecting millions of people, there is still no cure for Parkinson's.
Parkinson's disease is a progressive condition that affects the brain, increasingly disrupting the way that it works.
It is the second most common degenerative disease of the brain, after Alzheimer's disease. There are 60,000 new cases diagnosed each year in the U.S.
Parkinson's disease causes disruptions in movement and coordination because of degeneration in the central nervous system.
The disease is caused by the loss of brain cells that produce dopamine, an important chemical messenger (neurotransmitter).
Men have a 50 percent higher risk of developing the disease compared to women. In the majority of cases, symptoms start to appear after the age of 50.
Symptoms develop gradually and may begin with small tremors in one hand. Parkinson's symptoms can include:
- Facial, hand, arm, and leg tremors
- Balance difficulties
- Slower movement
- Stiff limbs
Sadly, there is no cure for Parkinson's, which currently affects around ten million people worldwide. To date, treatment and medication can only ease some of its symptoms.
Nicotine and Parkinson's
Studies have found an association between smoking tobacco and a reduced risk of Parkinson's disease. However, experts aren't yet 100 percent certain if it is the nicotine or another component of tobacco that prevents the development of the disease. It might simply be that Parkinson's patients were never the "smoking types."
Certain species of a flowering plant family called "Solanaceae" are edible and contain nicotine. This family includes peppers, chilis, and tomatoes. Could this type of plant be useful in the prevention of Parkinson's disease?
What is the evidence?
One finding, published in Annals of Neurology, revealed that consuming certain foods that contain nicotine, such as plants belonging to the Solanaceae family, could help lower Parkinson's risk.
The study, led by Dr. Susan Searles Nielsen and her colleagues from the University of Washington in Seattle, included 490 patients who were diagnosed with Parkinson's disease and 644 individuals without Parkinson's (the control group).
The researchers gave the participants questionnaires asking about their diet and tobacco use.
They found that people who ate higher levels of edible Solanaceae were at a lower risk of Parkinson's disease compared to those who didn't eat as much. Of all the foods that contained nicotine, the best protection seemed to come from eating peppers.
The protective effects of consuming foods containing nicotine were most noticeable in people who never used other tobacco products.
"Our study is the first to investigate dietary nicotine and risk of developing Parkinson's disease. Similar to the many studies that indicate tobacco use might reduce 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."
Dr. Searles Nielsen
How does nicotine prevent Parkinson's?
"Misfolded" proteins may be the key to understanding nicotine's effects on Parkinson's.
Scientists know that some of the tremors of Parkinson's are linked to a loss of neurons that produce dopamine (dopaminergic neurons).
Although the mechanisms behind the death of neuronal cells are not well understood, there are clues. It seems that, in people with Parkinson's, cell proteins that fail to fold properly are not removed from the system, as they are in healthy people.
These misfolded proteins then build up within otherwise healthy cells, eventually killing them.
A 2016 study published in the Journal of Neuroscience examined how nicotine affects dopaminergic neurons.
By simulating the conditions that cause proteins to misfold, the study authors found that, in the presence of nicotine, the dopaminergic neurons were more resistant to the toxic effects of the misfolding proteins.
The authors think that nicotine may both reduce the level of misfolding and also prevent any proteins that have misfolded from accumulating in cells. If this is the case, then the findings suggest that nicotine-based medicines that do not pose the health risks associated with smoking may warrant further investigation for use among people with Parkinson's.
In 2015, geneticists at the University of Alabama (UAB) attempted to map what genetic mechanisms may underpin an association between nicotine exposure and reduced risk of Parkinson's (resource no longer available at www.nature.com). Their study found that regular smokers had a remarkable 25 percent lower risk for Parkinson's, compared with people who had never smoked.
The UAB study identified a gene - SV2C - that may play a role in lowering Parkinson's risk among regular smokers. This gene is "biologically plausible," the authors explain, because nicotine enhances the release of dopamine through synaptic vesicles - the part of the neuron that stores neurotransmitters - and SV2C encodes a synaptic vesicle protein in a part of the brain called the substantia nigra that is damaged during Parkinson's.
The Michael J. Fox Foundation for Parkinson's Research
One of the most famous people with Parkinson's is the actor Michael J. Fox. In 2000, he founded the Michael J. Fox Foundation for Parkinson's Research, which is committed to finding a cure and developing improved therapies for the disease. One study currently being conducted by the Foundation is "Disease-modifying potential of transdermal Nicotine in early Parkinson's disease," or NIC-PD for short.
The NIC-PD study is investigating the therapeutic potential of nicotine patches for people who are in the very early stages of Parkinson's disease. In the trial, 150 participants were randomly assigned either nicotine patches or placebo patches over a treatment period of 12 months. The study is assessing the effect of nicotine on slowing or stopping the progression of Parkinson's using standardized clinical rating scales.
If NIC-PD demonstrates that nicotine can slow the progression of Parkinson's, then the Michael J. Fox Foundation believe that the substance may also show potential to treat other neurodegenerative diseases.