My original post on the microbial effects of smoking led to a line of inquiry that is still ongoing, and which I plan to return to shortly. But since that original post, I’ve come across quite a few pieces of data and supporting evidence for the broader smoking/microbial link, and I think it’s worth recording them.
An NPR article last week reported that probotics — specifically Lactobacillus reuteri — have been found to greatly reduce the symptoms of colic in babies (a condition that results in excessive and uncontrollable crying in infants). It’s a condition that affects 8 to 15 percent of babies, and can take a major toll on families. Not only does the probiotic reduce the symptoms, but if given during the first few weeks of life, it can actually prevent colic.
I found this pretty intriguing, but I don’t know much about colic. So I read up on it. Guess what’s been shown to be strongly associated with colic? Smoking during pregnancy. According to a Danish epidemiological study in 2005, mothers who smoked 15 or more cigarettes a day were twice as likely to have babies with colic. Furthermore, studies have found that a) smoking leads to an increase of a hormone (motilin) secreted in the digestive tract; and b) baby colic is associated with an increase in this hormone, thus pointing to a mechanistic link.
According to that study, half of all women smokers continue to smoke during their pregnancies — 12% of all women who give birth.
Inflammatory Bowel Diseases
Crohn’s Disease and Ulcerative Colitis are the twin inflammatory bowel diseases — the first affects the small intestine, the second affects the large intestine. If any kind of disease has a strong microbial connection, it is inflammatory bowel disease. As I mentioned in this post, even animals with IBD present with the dysbiosis pattern found in humans.
What does this have to do with smoking? It’s well known in research circles and those afflicted with IBD that a strange paradox exists between smoking and these diseases. In Crohn’s sufferers, smoking exacerbates the disease. In Ulcerative Colitis sufferers, smoking ameliorates the disease.
The fact that smoking has such a profound effect on the course of two diseases with such a strong microbial connection — negative or positive — is further corroboration of the smoking/microbial link.
Cigarettes, Live Bacteria, Nicotine
Since the original post, I’ve gotten a few questions about how cigarettes may be inducing this effect, and what role nicotine plays in all of this. As I mentioned in that post, cigarette tobacco has been shown to contain gram-negative bacteria, and can introduce endotoxins directly into smokers. What I didn’t quite make clear is that cigarettes introduce live bacteria — and known human pathogens — into smokers:
The research team found 15 different classes of bacteria and a number of potentially pathogenic organisms. The most notorious organisms present were Acinetobacter, Bacillus, Burkholderia, Clostridium, Klebsiella, Pseudomonas aeruginosa, and Serratia. These bacteria were found in more than 90 percent of all cigarette samples tested. Also found in the samples were the pathogens Campylobacter, Enterococcus, Proteus, and Staphylococcus.
Apparently, it is the fermentation of tobacco leaves that creates extremely dense concentrations of bacteria. The bacteria, dead or alive, and the endotoxins they produce can lead to disease:
Even dead bacteria produce endotoxins that can activate cells that cause inflammation. He says there is some concern that the chemicals and bacteria might work together to speed up the malignancy of cancer cells.
This information would indicate that nicotine is not involved with the microbial effect. But more importantly, we also have evidence that nicotine is not involved in the broader smoking/heart disease correlation. Many like to explain smoking’s heart disease correlation by blaming nicotine’s inducement of abnormal heart rate (arrhythmia) and high blood pressure, which can lead to ischemia (insufficient blood flow to the heart). However:
- Pipe-smoking, which exposes smokers to much less nicotine, has not been found to be any safer.
- Nicotine patches do not contribute to arrhythmia or ischemia.
- Epidemiological studies have found that smokers have a slightly lower blood pressure than non-smokers.