Bacteria and lipids

By now, it is apparent that research will continuously reveal new mechanisms by which the mouth and body are connected. Just when we thought we had a pretty good handle on oral-systemic links, along comes a new piece of research reminding us that there is much more we do not know.


Richard H. Nagelberg, DDS

By now, it is apparent that research will continuously reveal new mechanisms by which the mouth and body are connected. Just when we thought we had a pretty good handle on oral-systemic links, along comes a new piece of research reminding us that there is much more we do not know.

A large body of evidence indicates there is an association between chronic periodontitis and atherosclerosis. There is also a considerable body of evidence linking periodontal pathogens and atherosclerosis.

Very recently, in May 2018, a study was published that examined the potential relationship between the total burden of periodontal pathogens and serum lipid profile.1 This clever study design—comprised of 385 participants (176 men and 209 women)—concluded that a higher burden of bacteria was independently associated with lower HDL and higher triglyceride (TG) levels.1 Low LDL and high HDL are the right combination for health; reducing the level of HDL is not good. TGs play a causative role in cardiovascular disease. Lowering the HDL level and elevating the TG level constitutes dysregulation of serum lipid metabolism according to the study authors.1

The bacteria under investigation in the study were Porphyromonas gingivalis (P. gingivalis), Treponema denticola (T. denticola), Tannerella forsythia (T. forsythia), and Prevotella intermedia (P. intermedia)—all of which are highly pathogenic species. The investigators compared the average levels of HDL, LDL, and TG with the individual bacterial species; the total bacterial burden characterized as low, medium, or high (which is a reflection of bacterial population levels); and the combination of bacterial burden and presence of periodontitis.

Obviously, one study does not establish anything as fact. It is, however, interesting to have a new potential mechanism for atherosclerosis development elucidated.

Furthermore, this study found an association between bacterial and lipid levels, apart from periodontitis status. One of the substantially established mechanisms between the mouth and cardiovascular events indicates that the elevated inflammatory burden from periodontitis elevates the risk for a heart attack, stroke, and coronary artery disease. This study indicates that the accumulated burden of periodontal bacteria can affect the regulation of HDL and TG, which are critical risk factors for atherosclerotic diseases, regardless of periodontitis.

The conclusion that the bacterial burden is independently involved in reducing HDL levels and elevating TG levels is followed by a recommendation from the authors for clinicians to consider: “Our findings suggest that bacterial tests in a clinical setting could be a useful approach for predicting the risk of HDL metabolism dysregulation.”1

It is worth noting that previous research regarding periodontal bacteria and atherosclerosis indicated a direct effect of the bacteria on the arterial wall, including the action of Fusobacterium nucleatum (F. nucleatum), creating gaps in the endothelium and exposing the inner wall to invasion by bacteria, LDL, etc., culminating in the development of an atherosclerotic plaque. This research indicates an indirect mechanism in which the bacteria cause lipid metabolism dysfunction leading to unfavorable HDL and TG levels.

The need for bacterial testing for reasons beyond the oral cavity is becoming more and more compelling. This is in addition to the reasons to test having to do with the oral cavity, which are obvious to dental health-care professionals.

The authors of the study also concluded: “Furthermore, screening for the presence of periodontal bacteria could be beneficial to detect lipid changes earlier than atherogenesis, thus reducing the risk for development of atherosclerotic disease.”1

With evidence for the potential mouth-body relationship this study provides, along with the mountain of existing evidence, the need for bacterial testing could accurately be described as imperative. Each individual practitioner needs to decide the lengths to which they will go for their patients. It is past time to be thinking we are working only in the oral cavity, treating pocket numbers, noting caries, and indicating the need for crowns in broken-down old restorations.

As dental professionals, we are in a prime position to positively affect our patients’ total health if we are willing to go the simple extra step of bacterial testing and treating patients as the individuals they are. Patients visit their dentists more frequently than their physicians, and there’s a reason for that. Let’s validate our patients’ trust in us by treating the entire person.


1. Choi YH, Kosaka T, Ojima M, et al. Relationship between the burden of major periodontal bacteria and serum lipid profile in a cross-sectional Japanese study. BMC Oral Health. 2018;18(1):77. doi: 10.1186/s12903-018-0536-0.

Richard H. Nagelberg, DDS, has practiced general dentistry in suburban Philadelphia for more than 30 years. He is a speaker, advisory board member, consultant, and key opinion leader for several dental companies and organizations. He lectures on a variety of topics centered on understanding the impact dental professionals have beyond the oral cavity. Contact Dr. Nagelberg at

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