Parkinson’s disease is a movement disorder striking 1% of our older population and is the 14th leading cause of death in the United States. We don’t really know what causes it, but we do know that people with a smoking history only appear to have about half the risk. Of course, smoking is hugely damaging to health; any benefit derived from a reduction in risk of Parkinson’s disease is far outweighed by the increased risks of cancer, heart, and lung disease, but this shouldn’t stop us from evaluating tobacco components for possible neuroprotective effects, and nicotine may fit the bill.

If nicotine is the agent responsible for the neuroprotective effects, is there any way to get the benefit without the risks? Well, where does nicotine come from? The tobacco plant. Any other plants have nicotine? Well, tobacco is a nightshade—that means tobacco, tomatoes, potatoes, eggplants, and peppers are all in the same family. And guess what? They all contain nicotine as well.

That’s why you can’t tell if someone’s a smoker just by looking for the presence of nicotine in their toenail clippings, because non-smokers grow out some nicotine into their nails as well. It’s in our daily diet, but how much? The amount we average in our diet is hundreds of times less than we get from a single cigarette; so, though we’ve known for 15 years that there’s nicotine in ketchup, it was dismissed as insignificant. But then, we learned that even just one or two puffs of a cigarette could saturate half of our brain’s nicotine receptors; so, it doesn’t take much. And then, we learned that even just exposure to second-hand smoke may lower the risk of Parkinson’s, and there’s not much nicotine in that. In fact, one would only be exposed to like three micrograms of nicotine working in some smoky restaurant, but that’s on the same order as what one might get eating food at a non-smoking restaurant. So, the contribution of dietary nicotine intake just eating some healthy vegetables may be significant. So, researchers decided to put it to the test.

Looking at nightshade consumption, in general, they maybe found a lower risk compared to other vegetables, but different nightshades have different amounts of nicotine. They found none in eggplant, only a little in potatoes, some in tomatoes, but the most in bell peppers, and so, when that was taken into account, a much stronger picture emerged. They found that more peppers meant more protection, and as we might expect, the effects of eating nicotine-containing foods was mainly evident in nonsmokers, as the nicotine from smoke would presumably blot out any dietary effect.

So, this could explain why protective associations have been found for Parkinson’s and the consumption of tomatoes, potatoes, and a tomato and pepper-rich Mediterranean diet. Might nightshade vegetables also help with treating Parkinson’s? Well, results from trials of nicotine gum and patches have been patchy. So, maybe nicotine only helps prevent it in the first place, or maybe it’s not the nicotine at all, but some other phytochemical in the tobacco and pepper family?

They conclude that their findings will need to be reproduced to help establish cause and effect before considering dietary interventions to prevent Parkinson’s disease, but when the dietary intervention is like eat more yummy, healthy dishes like stuffed peppers with tomato sauce, I don’t see the reason we have to wait.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.