Because the blood from the lungs reaches the brain very rapidly, a smoker’s brain is exposed to extremely high nicotine levels within seconds after the first puff. Because of this, many researchers have concluded that cigarettes are the most addictive nicotine delivery device. In a snus user, nicotine is absorbed to the blood through the oral mucous membranes. The blood here needs to go through the entire circulatory system before it can reach the brain so the brain is never exposed to the same high nicotine levels as among smokers. That said, clinical studies seem to indicate roughly the same potential for dependence with snus compared to cigarettes.
The amount of nicotine absorbed by an individual snus user is determined by complex links between several factors. Significant product characteristics include nicotine content, pH level, moisture, particle size of the ground tobacco, and size & physical form of the pouch. The individual consumer is also important. Manipulation with the tongue or chewing of the pouch increases absorption. The saliva (amount, chemical properties, enzymatic activity etc) are other potentially relevant factors. This means that the nicotine extraction from a standard pouch may vary between 10-50% among individual users. Extraction rate tends to be higher for loose snus, products with higher moisture content, and for smaller pouches.
The pH level determines the speed with which the extracted nicotine can be absorbed through the oral mucosa. Nicotine is a plant alkaloid which in a solution (such as the saliva) occurs in two forms: “free” nicotine, and protonated nicotine. The balance between these two forms is determined by the pH: high levels imply more free nicotine and hence a more rapid uptake. The pH target value for Swedish snus is about 8.5 which mean that about 75-80% of the nicotine is “free”. The high pH contributes to the “tingling” or “burning” feeling of a snus pouch that some users have difficulties to accept. The high pH level is traditional and has remained unchanged since the early 1800s when “modern” snus was invented. pH stabilization is achieved through sodium carbonate, a food-approved additive found in many common consumer products, such as, German pretzels and tooth paste.
After the fast increase in blood nicotine concentration during smoking, the nicotine is eliminated quite rapidly from the blood stream. With snus the nicotine concentration plateaus after the pinch has been taken out. The more prolonged elimination of nicotine among snus users has been attributed to continued absorption of nicotine released from the mucous membrane or to absorption of nicotine that has been swallowed. On average, only about 10 to 20 percent of the total nicotine content in a snus portion reaches the bloodstream although this may vary greatly among individual users.
Snus pH declines during storage, it can never increase. This is part of the normal “ageing process” for snus. Storage in a cooler helps to slow down the ageing and also preserves moisture content and product freshness.
Nicotine is a potentially addictive substance. The rate at which nicotine reaches the brain is by many considered to be the most important determinant of the addictiveness of a nicotine product. Within seconds after smoking a cigarette, the brain is exposed to levels of nicotine in the arterial blood that are 8-10 times higher than the maximum levels seen with snus. A recent scientific report from the European Commission on the health impact of smoke-free products includes a discussion of whether the higher nicotine absorption rate associated with smoking could mean that cigarettes are more addictive than smoke-free tobacco products.
Like smokers, snus users may experience abstinence-related problems, caused mainly by nicotine withdrawal, when they stop using snus. Studies of various measures of subjective nicotine addiction typically reveal no significant differences between snus users and smokers in terms of self-experienced addiction, craving for tobacco, or difficulties in cessation of tobacco use. Many ex-smokers who now use snus but want to quit all forms of tobacco sometimes report that it was less difficult to switch from cigarettes to snus than to switch from snus to “nothing”. It is likely that such experiences have contributed to the misconception that snus results in a stronger nicotine addiction than smoking. However, a more likely explanation is that it is more difficult to stop using nicotine completely than it is to switch between different tobacco products.
Based on studies of tobacco habits among identical and fraternal twins, it is evident that hereditary factors play a central role for addiction to nicotine. Around 50 percent of the probability that an individual starts to smoke can probably be explained in terms of genetic factors. Genetically determined differences in the ability to release dopamine and other signal substances in the brain could be part of the explanation for these results.
The addictive properties of the nicotine in snus represent a moral dilemma for individual users as well as for manufacturers. Products with a lower nicotine delivery profile (such as nicotine gums or patches) have a lower potential for dependence but are conversely less satisfying among consumers as an alternative to cigarettes. Snus with its higher nicotine delivery is used by many ex-smokers, but is also clearly addictive. This circumstance appears to have become the main driver of the current highly polarized debate about the pros and cons with endorsing products such as snus for tobacco harm reduction purposes.
Dr. Lars-Erik Rutqvist; MD, PhD
Reporting at SnusCENTRAL.org