Does Smoking Really Protect Against Parkinson’s Disease?

The Centers for Disease Control and Prevention recently celebrated the 50-year anniversary of the landmark 1964 Surgeon General’s report on smoking, considered one of the great public health achievements of our time and the first of 30 other such reports from the Surgeon General on smoking. Internal tobacco industry memos, which you can see in my Is Something in Tobacco Protective Against Parkinson’s Disease? video, document their response. Major criticisms of the report include a “[c]avalier treatment of costs of smoking”: The Surgeon General argued that smoking costs the United States billions, but the tobacco industry noted that “smoking saves the country money by increasing the number of people dying soon after retirement,” so we don’t have to pay for Social Security, Medicare, and the like. In fact, the industry argued, if we were truly patriotic, maybe we should encourage smoking to help balance the budget!

The tobacco industry also criticized the Surgeon General for a “[l]ack of balance regarding benefits of smoking,” asserting that “[o]ne has to search pretty hard to find any concession anywhere in the Report that smoking is not all bad.” This is something the tobacco industry liked to bring up when testifying before Congress, saying that health benefits include “the feeling of well-being, satisfaction, and happiness and everything else.” But beyond just all the happiness the Surgeon General was trying to extinguish, he failed to even mention that smokers appear protected against Parkinson’s disease.

“Quite unexpectedly…[m]ore than 50 studies over the last half century consistently demonstrated reduced prevalence of Parkinson’s disease among smokers compared with never-smokers.” Now there are more than five dozen studies.

But smokers are probably dying before they even have a chance to get Parkinson’s, so is that the explanation? No, that didn’t seem to be it. Researchers found a protective effect at all ages. Maybe it’s because smokers tend to be coffee drinkers, and we know coffee consumption alone appears protective. But, no. The protective effect of smoking remained even after carefully controlling for coffee intake. Well, maybe we inherit some propensity to not smoke and to get Parkinson’s. If only we could clone someone to have the same DNA. We can! They’re called identical twins. And still, the relationship remained, suggesting “a true biologic protective effect of cigarette smoking.”

Not so fast. Maybe finding unusually low rates of Parkinson’s among smokers is an example of reverse causation. That is, maybe smoking doesn’t protect against Parkinson’s—maybe Parkinson’s protects against smoking. Could there be something about a Parkinson’s brain that makes it easier to quit? Or perhaps failure to develop a smoking habit in the first place is an early manifestation of the disease.

To put that to the test, researchers studied children exposed to their parents’ smoke. If they grew up to have less Parkinson’s, that would confirm the protective link—and indeed they did. So, smoking really does seem to be protective against Parkinson’s disease, but who cares? How does that help us? “More than 20 million Americans have died as a result of smoking since the first Surgeon General’s report…” Even if we didn’t care about dying from lung cancer and emphysema, even if we only cared about our brain, we still wouldn’t smoke because smoking is a significant risk factor for having a stroke, as well.


Is there a way we could get the benefits of smoking without the risks through our diet? I discuss this in my Peppers and Parkinson’s: The Benefits of Smoking Without the Risks? video.

Other Parkinson’s videos include Preventing Parkinson’s Disease with Diet and Treating Parkinson’s Disease with Diet.

Diet may play a role in other movement disorders. For example:

Surprised about the potential benefits of coffee? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

In Late Pregnancy Moderate the Intake of Powerful Anti-inflammatory Foods

The right side of the heart pumps deoxygenated blood from the body to the lungs, where it can fill up with oxygen, and then the left side of the heart pumps oxygen-rich blood from the lungs to the rest of the body. So, blood travels from the body to the right side of the heart to the lungs to the left side of the heart and back to the body.

But what happens in the womb? Fetuses’ lungs don’t work because they’re filled with fluid. How does the heart bypass the lungs and spread the oxygen-rich blood coming in through the umbilical cord to the rest of the body? Before we’re born, we have an extra blood vessel—the ductus arteriosus—that directly connects the right side of the heart with the left side of the heart, bypassing the fluid-filled lungs. When the baby is born and takes a first breath, this blood vessel closes. In about 1 in 10,000 births, though, the blood vessel closes prematurely before the baby is born, necessitating an emergency C-section, as I discuss in my video Caution: Anti-inflammatory Foods in the Third Trimester.

Most cases for which there’s a known cause are thought to be related to taking anti-inflammatory drugs such as aspirin or ibuprofen. This is because the way the body keeps this blood vessel open is with a class of inflammatory compounds called prostaglandins. If you take an anti-inflammatory drug, you can undermine your body’s ability to keep it open, and it could constrict closed prematurely. That’s why most authorities recommend that these nonsteroidal anti-inflammatory drugs (NSAIDs) be avoided in the third trimester. The likelihood that anything bad will happen is extremely remote, but it’s better to be safe than sorry.

Sometimes this premature constriction happens even when women are not taking drugs, so-called “idiopathic” cases, which is doctorspeak for “we have no idea what causes it.” If anti-inflammatory drugs can cause it, though, what about anti-inflammatory foods? A few years ago, in my video Chamomile Tea May Not Be Safe During Pregnancy, I profiled two incidents apparently caused by pregnant women drinking chamomile tea. One of which reversed in that the ductus opened right back up once the tea was stopped, but, in the other case, the other baby had to come right out. Since then, there have been other case reports of this occurring––for example, when a woman had been drinking a few ounces of an acai berry drink every day and when another woman had been drinking prune juice and a violet vegetable juice containing a blend of fruits and veggies. Pregnant women should, therefore, take special care when consuming lots of these powerful anti-inflammatory berry nutrients.

What about berries themselves, green tea, and all the other wonderful anti-inflammatory foods and beverages out there? A group of researchers in Brazil compared ultrasounds of the hearts of third-trimester babies whose moms ate a lot of these anti-inflammatory foods with those whose moms ate less, and they could tell a difference. The speed of blood through the ductus in the moms consuming the anti-inflammatory diet was higher, suggesting it was narrower, just like when you pinch the opening of a hose closed and can make water shoot out faster. Also, the right sides of the hearts of the babies whose moms were consuming the anti-inflammatory diet were larger than their left sides, suggesting some blood backup, again an indicator of a tighter ductus. The researchers suggested changes in late pregnancy diets may be warranted, but critics replied that the differences they noted might not have any clinical relevance, meaning it may not matter if the vessel is a little more open or closed. We don’t want to alarm women because many of these anti-inflammatory foods may be beneficial––such as cranberries, for example, which may be useful in preventing urinary tract infections, which can be a risk factor for premature birth. Consuming cranberries is attractive from a public health and cost standpoint if it can prevent some premature births.

Before cutting down on a healthy food such as cranberries, we’d want some stronger evidence that they’re potentially harmful. What about confounding factors? For example, women who ate lots of anti-inflammatory foods might have had other characteristics that could affect fetal blood flow. What we needed was an interventional trial in which pregnant women change their diets and see what happens, but we didn’t have such studies… until now.

A study has shown that cutting back on anti-inflammatory foods such as tea, coffee, dark chocolate, grapes, and citrus for a few weeks during the third trimester did indeed seem to open up the ductus during normal pregnancies. In women whose fetuses had abnormally constricted vessels, a few weeks of eliminating polyphenol-rich foods reversed the ductal constriction in 96% of cases. Importantly, researchers didn’t follow these babies after birth to see if it made any difference. That complete closure only happens in 1 in 10,000 births; we’re not sure what effects relative levels of constriction may have, so it’s too early to be instituting a ban on dark chocolate for pregnant women.

At this stage, what we’re left with is a note of caution. During the rest of your life, I recommend eating healthy foods such as berries and cocoa powder, but from about 28 weeks until birth, pregnant women may want to cut back until we know more.


In Chamomile Tea May Not Be Safe During Pregnancy, I profile those two case reports I mentioned above. As I noted in Anti-inflammatory Antioxidants, highly antioxidant foods are, in general, highly anti-inflammatory foods.

For comparisons between the strength of anti-inflammatory foods and drugs, see Watermelon for Sore Muscle Relief, Anti-inflammatory Life Is a Bowl of Cherries, and Which Spices Fight Inflammation?

The videos provide more information about healthy (and unhealthy) diets in pregnancy:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Who Should Avoid Coffee?

Do coffee drinkers live longer than non-coffee drinkers? Is it “wake up and smell the coffee” or don’t wake up at all? I discuss these questions in my video, Coffee and Mortality.

The largest study ever conducted on diet and health put that question to the test, examining the association between coffee drinking and subsequent mortality among hundreds of thousands of older men and women in the United States. Coffee drinkers won, though the effect was modest, a 10-15% lower risk of death for those drinking six or more cups a day. This was due specifically to lower risk of dying from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.

However, another study that amount of coffee was found to increase the death rate of younger people under age 55. It may be appropriate, then, to recommend that you avoid drinking more than four cups a day. But if you review all the studies, the bottom line is that coffee consumption is associated with no change or a small reduction in mortality starting around one or two cups a day, for both men and women. The risk of dying was 3% lower for each cup of coffee consumed daily, which provides reassurance for the concern that coffee drinking might adversely affect health, or at least longevity.

A recent population study found no link between coffee consumption and symptoms of GERD, reflux diseases such as heartburn and regurgitation. If you actually stick a tube down people’s throats and measure pH, though, coffee induces significant acid reflux, whereas tea does not. Is this just because tea has less caffeine? No. If you reduce the caffeine content of the coffee down to that of tea, coffee still causes significantly more acid reflux. Decaf causes even less, so GERD patients might want to choose decaffeinated coffee or, even better, opt for tea.

Coffee intake is also associated with urinary incontinence, so a decrease in caffeine intake should be discussed with patients who have the condition. About two cups of coffee a day worth of caffeine may worsen urinary leakage.

A 2014 meta-analysis suggested that daily coffee consumption was associated with a slightly increased risk of bone fractures in women, but a decreased risk of fractures in men. However, no significant association was found between coffee consumption and the risk of hip fracture specifically. Tea consumption may actually protect against hip fracture, though it appears to have no apparent relationship with fracture risk in general.

Certain populations, in particular, may want to stay away from caffeine, including those with glaucoma or a family history of glaucoma, individuals with epilepsy, and, not surprisingly, people who have trouble sleeping. Even a single cup at night can cause a significant deterioration in sleep quality.

We used to think caffeine might increase the risk of an irregular heart rhythm called atrial fibrillation, but that was based on anecdotal case reports like one of a young woman who suffered atrial fibrillation after “chocolate intake abuse.” These cases invariably involved the acute ingestion of very large quantities of caffeine. As a result, the notion that caffeine ingestion may trigger abnormal heart rhythms had become “common knowledge,” and this assumption led to changes in medical practice.

We now have evidence that caffeine does not increase the risk of atrial fibrillation. Low-dose caffeine—defined as less than about five cups of coffee a day—may even have a protective effect. Tea consumption also appears to lower cardiovascular disease risk, especially when it comes to stroke. But given the proliferation of energy drinks that contain massive quantities of caffeine, one might temper any message that suggests that caffeine is beneficial. Indeed, 12 highly caffeinated energy drinks within a few hours could be lethal.


To learn more about various health aspects of coffee, see my videos Coffee and Cancer, What About the Caffeine?, Preventing Liver Cancer with Coffee?, and Coffee and Artery Function.

What else can we consume to live longer? Check out Nuts May Help Prevent Death, Increased Lifespan from Beans, Fruits and Longevity: How Many Minutes per Mouthful?, and Finger on the Pulse of Longevity.

And, for more on controlling acid reflux, see Diet and GERD Acid Reflux Heartburn and Diet and Hiatal Hernia.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: