Health Effects
[3.0] What are the health effects of smokeless tobacco?
Contrary to popular belief, smokeless tobacco is not a major health hazard. In fact, it has not been definitively linked to any deadly disease. More important, to the extent that it causes any risks, the scientific evidence clearly shows that the risks are very small.
This probably comes as a huge surprise to most readers. We will admit that it was equally surprising to every one of us when we first learned it. Because there is so much misinformation about smokeless tobacco, much of it spread by otherwise legitimate health authorities, it has been difficult to learn the truth. Below, we take up the question of how to sort out truth, lies, and genuine scientific uncertainty. Here, we present what the scientific evidence actually shows.
[3.1] Doesn't smokeless tobacco cause oral cancer (cancer of the mouth)?
Maybe, but if so, only very rarely. There is overwhelming evidence that any risk for oral cancer from smokeless tobacco is very low.
This is a very important question in understanding smokeless tobacco, so it is useful to provide some background before expanding on the evidence. Oral cancer (cancer of the mouth and surrounding areas) is a fairly rare disease in Western countries, and in most cases it is caused by smoking. Yes, you read that right: Oral cancer is almost as much a disease of smoking as is lung cancer. The U.S. government attributes about 3/4 of all oral cancer deaths in that country to smoking. Smoking increases your risk of oral cancer by a factor of 8 or 10, much more than even the worst-case-scenario estimate for smokeless tobacco. In other words, the best thing someone can do to reduce the risk for oral cancer is to not smoke, and whether a smoker quits by using smokeless tobacco or some other way hardly matters at all.
Just as important, even if smokeless tobacco did cause a measurable increase in oral cancer risk – a fairly common claim is that it multiplies the risk by a factor of 4 – the total risk would not be that large. (That figure of 4 turns out to be a myth, which we explain below.) The "baseline" risk for oral cancer (the risk for people who do not smoke or drink a lot of alcohol, the other major cause) is quite low. So even if smokeless tobacco multiplied that risk by 2 or even 4, the total risk of dying from it would still be very small compared to the risks of the much more common lung and heart diseases caused by smoking. (Consider if you had a choice between doubling your chances of dying by getting hit by lightning versus doubling your chances of dying in a car crash. Doubling your risk from lightning would be no big deal because it is so rare in the first place – two times a very small number is still a very small number. But doubling your risk from a car crash would be a lot more worrisome.)
Thus, in one of the most remarkable marketing successes ever (which is a nice way of saying it is a lie), anti-smokeless-tobacco advocates have convinced people that, "if I switch from smoking to dipping, I will just trade lung cancer for mouth cancer." About half the smokers we talk to say something very close to that. (You probably thought that too, right?) In reality, switching from cigarettes to smokeless tobacco will dramatically reduce your oral cancer risk (in addition to your risk of lung disease, heart disease, and many other diseases), and even if that were not true, the tradeoff would still be a good one because the risk of oral cancer for non-smokers is so low in the first place.
Having said all that, what is the answer to the original question? What does the scientific evidence say about the risk for oral cancer from smokeless tobacco?
It turns out that the evidence clearly shows there is very little risk. When looking at scientific research, it is necessary to look at the entire collection of research, not just one or two particular studies. As with most things we study in health science, the results vary. A few studies find that people who use smokeless tobacco have a higher risk for oral cancer (one fairly large study found that quadrupling of risk we mentioned). But most studies have found that the risk is very low. Some even show a negative association – which is to say, if someone just picked out those studies and ignored the rest, they might conclude that using smokeless tobacco protects you against getting oral cancer. Of course, picking just a few studies with extreme results is bad science, so we are not suggesting anyone do that.
When we look at the all the scientific evidence, it averages out to there being either no risk or very little risk (it is impossible to tell the difference between those two conclusions because health science methods are always imperfect). By "very little", we mean that using smokeless tobacco might cause a 10% or 20% increase in the risk for oral cancer compared to not smoking or not drinking heavily. The evidence shows it is extremely unlikely that the increase in risk is as high as 50%(which is still much less than the risk from smoking).
If you do not want to delve into the technical details, the previous points and our calculation of the comparative risk of smoking and smokeless tobacco are all you need to know.
[3.1.1] But doesn't smokeless tobacco cause oral lesions which can become cancerous?
Much of the following is taken from Rodu and Godshall's Tobacco harm reduction: an alternative cessation strategy for inveterate smokers. See the original for further reading or for details on the research behind the conclusions.
Oral leukoplakia is an ominous sounding term used frequently in discussions about oral lesions resulting from ST use. The term literally means "white plaque," and it is used to describe areas of the mouth lining that become thickened by ST use or smoking. The World Health Organization has determined that leukoplakias resulting from ST use are considerably different from those resulting from smoking. The distinctions are based on the frequency of occurrence, the location in the mouth, and how often these leukoplakias result in mouth cancer.
The condition is rare, occurring in less than 1% of the general population, primarily in long-time smokers 40 to 60 years old. Smoking-related leukoplakias most commonly involve the undersurface of the tongue and throat area, locations that account for 75% of oral cancer in the U.S..
Oral leukoplakias occur in up to 60% of ST users, within 6 months to 3 years of starting ST use. They primarily occur at the site of ST use and are largely a result of local irritation. The frequency of appearance depends on the type of ST that is used. Moist snuff, which is more alkaline than chewing tobacco, more often leads to leukoplakia. However, moist snuff in pre-portioned pouches (like snus) causes fewer cases of leukoplakia than does the loose form.
There are distinct differences in how often ST and smoking leukoplakias show pre-cancerous changes called dysplasia. Dysplasia is seen infrequently in ST leukoplakias (less than 3%). Furthermore, even when dysplasia is present in ST leukoplakia, it usually is found in earlier stages than in leukoplakias amng smokers, where it is seen in about 20% of cases.
ST leukoplakias only rarely progress to cancer. For example, one study found no case of cancer in 1,550 ST users with leukoplakia who were followed for 10 years, and a second study reported no case of oral cancer among 500 regular ST users followed for six years. A retrospective study of 200,000 male snuff users in Sweden found only one case of oral cancer per year, an extremely low frequency. In comparison, a follow-up study reported that 17% of smoking leukoplakias transformed into cancer within seven years.
In conclusion, oral leukoplakia occurs commonly in ST users, but it primarily represents irritation and only very rarely progresses to oral cancer.
[3.2] Does smokeless tobacco cause other cancers?
Again, the answer has to be that there is no conclusive evidence that it does, but it is certainly possible that it does at some very low level. There is no clear evidence that smokeless tobacco causes any cancer (and for cancers other than oral cancer, there is not even the one large study that suggests otherwise). Hence, the evidence indicates that if there is any risk, it is small.
Other than oral cancer, the cancers that seem most likely to be associated with smokeless tobacco are laryngeal, esophageal (throat), and gastric (stomach), since those are the other parts of the body that come in contact with the tobacco. For these cancer sites, along with a few others, there is a lot of scientific evidence that there is no substantially elevated risk. As with oral cancer, researchers have looked for an association and have failed to find one. For other cancer sites there are few or no studies, so we do not have any evidence one way or the other. However, studies that look at all cancers combined have failed to find an increase among smokeless tobacco users, so there cannot be a very big increase for any particular cancer.
[3.3] Does smokeless tobacco cause heart disease or stroke?
Yet again, the answer is that there may be some small risk, though there is no definitive evidence. As with the studies of cancer, most studies of cardiovascular disease and smokeless tobacco have found no increased risk. However, because nicotine is a mild stimulant, it might increase the risk of certain cardiovascular outcomes, such as stroke. Many stimulants have been linked to some risk for fatal cardiovascular events. This does not prove that nicotine (or any product containing it) causes such risk, but it suggests that it is plausible.
The available evidence shows that if there is any risk from smokeless tobacco, it is low, perhaps a 10% or 20% increase in risk (for comparison, smoking is estimated to roughly double this risk, a 100% increase). This is potentially more important than a similar percentage increase in oral cancer risk, since cardiovascular disease is a lot more common. If the risk of cardiovascular disease increases by as much as 20% then smokeless tobacco might cause 3% or 4% what the risk from smoking is. That is still a lot better than smoking, of course, but worse than one percent. Fortunately, most of the evidence suggests that nicotine without the smoke is not actually quite that bad. But it would be useful to do more research to find out more. Unlike with oral cancer, there is not enough available research about cardiovascular disease for us to feel entirely comfortable in our conclusions.
[3.4] What does this all mean for the total risk compared to smoking?
Quite simply, it means that the risk is tiny compared to smoking. There are various estimates that you might hear, but as far as we know, we are the only ones who have actually done the calculation. Our calculations show that if we take a worst case scenario and assess the risks for cancer and cardiovascular disease, the total risk from smokeless tobacco is only a few percent of that from smoking. Fairly conservative estimates put the risk at about 1%, which is why we summarize by saying a 99% reduction. Some reasonable estimates get risk figures that are even lower.
Due to the limitations of health science, we cannot be sure exactly how the risks compare. But we can be very sure that the total risk of dying from smokeless tobacco use is less than 5% of that from smoking. That is, for any plausible levels of risk for disease from smokeless tobacco – any values that are not clearly ruled out by the science – the total risk is less than 1/20th that from smoking. (Helpful hint: If anyone claims the risk is higher than this, ask them what disease risk estimates they used to get their total. We bet they do not even have an answer.) So, there is no legitimate scientific doubt that someone's risk drops by at least 95% by using smokeless tobacco instead of smoking, and it is probably closer to 99%, and might even be better than that.
[3.5] So why do so many people say "smokeless tobacco is not a safe alternative to cigarettes"?
The main reason that this phrase is so common is that the U.S. and Canadian governments require a version of it to be printed on packages of smokeless tobacco products. This is very unfortunate, since most people read the phrase "not safe" and think "very dangerous". They read the phrase "not a safe alternative to cigarettes" as "just as bad as cigarettes". So long as people get those messages, they will never realize the potential for harm reduction.
Strictly speaking, the statement is true. If we interpret "safe" to mean "100% safe; creating no health risk at all" then smokeless tobacco is not "safe" (and neither is anything else – chances are that somewhere, sometime, somehow, broccoli has killed someone). Smokeless tobacco may not be a "safe" alternative, but neither are any of the other products used to help people stop smoking. Certainly trying to quit and failing, or smoking for another year or two before quitting are not "safe" either. Smokeless tobacco is tremendously safer, however, and that is what matters.
Think about this: Driving safely and properly is not a safe alternative to speeding while drunk and not wearing a seatbelt. But it is very close. It might even reduce the risk by as much as 99%. Somehow, there seems to be no confusion about which of those options we think someone should choose. There should be no confusion about tobacco products either – smokeless tobacco is much less harmful, and the fact that it is not 100% safe does not change this.
[3.6] Are you saying that smokeless tobacco is harmless?
No, and as far as we know, no one else is saying that either. As we noted, it is possible that smokeless tobacco causes cancer or other deadly diseases at some very low level. We know that the nicotine has short-term cardiovascular effects which may be a little bit harmful. Nothing is 100% harmless, and this includes smokeless tobacco. This does not change the fact that it is a much less harmful alternative to smoking.
If you think about it, "harmless" is a rather ridiculous standard. The only people who ever use this term are people who oppose tobacco harm reduction, who point out that smokeless tobacco is not harmless, and try to suggest that this is an argument against a harm-reduction strategy. This is a classic way to try to confuse people when you do not have the truth on your side: Imply that people who disagree with you (harm reduction advocates) would only be right if a certain claim were true (that smokeless tobacco were completely harmless), and then show that the claim is not true . Of course, this is clearly wrong. The harm reduction argument does not depend on that claim. In fact, a harm reduction strategy is all about making something safer or more healthy, rather than trying to make it as safe as could possibly be imagined.
Another classic method for confusing people is the "straw man argument", when you misrepresent someone's position, and then argue against the misrepresentation. It is certainly a lot easier to claim that someone is saying something absurd, and then prove them wrong, than it is to respond to what they are actually saying. We all agree that smokeless tobacco is not 100% harmless.
[3.7] What about all the chemicals in smokeless tobacco that I have heard about?
Sometimes people who are opposed to harm reduction or any use of smokeless tobacco present a list of potentially harmful constituents. What they do not tell you is that many of those chemicals are in other plants, including the healthy vegetables that you eat, not just tobacco. A little bit of all the metals on Earth end up in everything, including cadmium, polonium, and others that are quite bad for you in large quantities. They are in tobacco, carrots, wheat, and even the water you drink. There are also organic molecules like formaldehyde in most every life form on Earth, including tobacco. Again, concentrated in large quantities, you would certainly want to stay away from some of these chemicals, but the amount that naturally occurs in plants (and in your own body) is not a problem. We should be glad that there are not a lot of anti-broccoli advocates out there trying to trick you into not eating it because it contains some cadmium.
One particular set of chemicals that are talked about a lot in the science are nitrosamines, or tobacco-specific nitrosamines (TSNAs). Nitrosamines are a class of chemicals that we are exposed to in food and through other pathways. Some of these chemicals are known to be carcinogens in some quantities. Whether the TSNAs might be carcinogens is the subject of debate. Fortunately, it does not matter whether these chemicals might cause cancer since we have actual evidence about whether smokeless tobacco itself causes cancer. As we pointed out above, the evidence shows that people who use smokeless tobacco do not have measurable increases in cancer rates or mortality. So it does not really matter what chemicals are there.
Think about this: If you met a thin person who always ate huge amounts of food, would you tell him that eating all that food is making him overweight? Obviously not, since you can directly observe that he is not overweight. All this talk about chemicals is like that. If all you knew about a person was that he always overeats, it might suggest that he would be overweight. Similarly, if you only knew about the chemicals and had never observed the actual health effect of the products, the chemical analysis could suggest that there might be a health effect. But once you observe that someone is thin (or observe that smokeless tobacco users do not have elevated disease rates), the suggestive evidence is no longer informative. It can only be used to trick you into thinking there is a health effect when the evidence actually says otherwise.
[3.8] ] Doesn't smokeless tobacco contain fibreglass?
No, the fiberglass thing is a complete myth. There is no evidence that this is true, though it gets repeated by anti-smokeless-tobacco activists who are not too concerned about whether they are telling the truth. We have heard the claim that fiberglass creates little cuts which allows absorption of nicotine. However, nicotine is absorbed quite well through intact mucosa (the inside surface of your mouth), so there would be absolutely no reason to do this. It actually seems more likely that creating holes in the mucosa, and thus bleeding, would interfere rather than promote absorption.
The only reference we have been able to find for the use of fibreglass in tobacco products is in some cigarette filters.
This myth may come from people not understanding that you can absorb things through your mucosa (or even your skin), and thinking that there need to be holes through to the bloodstream. Or it could just be part of the vilification of tobacco companies, trying to suggest that they are intentionally harming their customers.
[3.9] ] I know someone (or read about someone) who got cancer from using smokeless tobacco. How do you explain that?
We offer our sympathy if someone in your life got cancer, but it wasn't necessarily caused by smokeless tobacco. The same is true for the various oral cancer victims whose stories are used in the anti-smokeless-tobacco literature. Just because two things coincide does not mean that one caused the other. These cases are almost certainly coincidences.
You can understand the statistics behind this point without needing much math. In a large population (like North America), even if we are talking about something that relatively few people are exposed to (e.g., smokeless tobacco) and a fairly rare disease (e.g., oral cancer), there will still be quite a few people who fall into both categories just by chance. For example, if 1-in-100 people has a particular exposure, and 1-in-1000 people gets a particular disease, then by chance (coincidence) alone we would expect about 1-in-100,000 people to both have the exposure and get the disease (1/100 x 1/1000 = 1/100,000).
That does not seem like a lot, until you realize that there are over 300,000,000 people in North America (where most of the anti-smokeless-tobacco propaganda comes from). So it is not surprising then that you will find someone with oral cancer who happened to use smokeless tobacco. Inevitably, there will be quite a few such people, just by chance. In our example above, 3000 people would have both the exposure and the disease by chance alone. That is why epidemiology (the science that explores whether a disease is caused by an exposure) always uses a "comparison group" – people who do not have the exposure – to see if those with the exposure have more cases of the disease. The evidence does not show that smokeless tobacco users have more cases of various diseases than the regular population, but of course they will have some cases.
Consider this analogy: Some people read a lot of mystery novels (the exposure); some people get pancreatic cancer. If we told a scary story about a mystery fan dying of pancreatic cancer, and posted gory pictures on the web, would that be evidence that the novels caused the disease? Obviously not.
But the anti-smokeless-tobacco propaganda is actually even worse than that. Since oral cancer is usually caused by smoking, finding someone who never smoked who has oral cancer means looking for something unusual and misleading. It is as if someone collected pictures of people who had died in car crashes while wearing seatbelts and tried to argue that seatbelts are bad for you. We know that wearing a seatbelt is a lot better than not wearing one, but there will still be people who die even when they choose the less risky course. It is completely irresponsible to emphasize those people and discourage people from choosing the safer course (which is exactly what the anti-smokeless-tobacco advocates are doing).
As an interesting aside: Smoking is much more popular than smokeless tobacco use, and is known to cause a lot of oral cancer. A quick calculation suggests that there are about 100 times as many smokers who get oral cancer (most of them caused by smoking) than there are smokeless tobacco users who get oral cancer (most or all of them just by chance). Why is it that anti-tobacco advocates never put any of the smokers on display? We think it is because if people realized that smoking is the leading cause of oral cancer they would realize that smokeless tobacco is a safer alternative, and that is exactly what these advocates don't want you to know.
But what about cases where someone, perhaps a physician, said that smokeless tobacco caused a particular disease? Well, there is a strong human tendency to look for a specific cause, especially for highly traumatic events, even when such a determination is impossible to make. Causes for some diseases are easy to see (if you acquire a broken arm while falling down, it is pretty clear what caused it), but this is not true for cancer and cardiovascular disease. So, when people have been told (inaccurately), over and over again, that smokeless tobacco is a terrible health hazard, it is not surprising that they end up concluding that it caused a disease, despite opposing scientific evidence.
For a few diseases and exposures, we can conclude that it is likely that the exposure caused the disease. If someone who has smoked for fifty years gets lung or oral cancer, we know that it is quite likely that this was caused by smoking. But we know that because when we compare smokers to non-smokers, the disease rates for smokers are much higher. If smokers have 9 times the risk of non-smokers for a particular disease, when one of them gets that disease there is a 90% chance it was caused by the smoking (and a 10% chance that it would have happened anyway).
As a final, more technical note, most of the oral cancer victims who are exploited in the anti-smokeless-tobacco propaganda suffered from tongue cancer at a fairly young age. To the extent that any evidence suggests there is a link between Western smokeless tobacco and oral cancer, the related cancer occurs at ages greater than 60, after many decades of use, (and it is not cancer of the tongue). In developed countries, almost all oral cancer occurs at age 60 or 70, or older. By contrast, there are a small number of young people, generally under 30, who get tongue cancer (in the range of one to two hundred per year in North America, which has increased over the last three or four decades). These cancers do not appear to be associated with smoking and heavy drinking (the usual causes of oral cancer), nor with smokeless tobacco use. We do not know what causes these cancers, other than knowing that it does not seem to be any of the usual suspects. Of course, by coincidence, one or two of these victims every year will be smokeless tobacco users (and about 40 of them smokers, some heavy drinkers, and so on). Taking scary pictures of one of those unfortunate individuals provides absolutely no evidence about the dangers of smokeless tobacco, and for a health related initiative, is highly inappropriate.
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