Medical cannabis may shift oral bacteria levels without changing saliva flow | Research

The takeaway

In 16 patients starting medical cannabis, saliva volume and pH stayed stable over four weeks, but Lactobacillus levels increased significantly.

Dental health researchers and medical cannabis users interested in oral health effects.

Lactobacillus levels rose significantly within one week of starting cannabis

What the researchers found

Lactobacillus growth scores rose significantly at both week 1 (p=0.033) and week 4 (p=0.025) compared to baseline. Streptococcus mutans showed a non-significant trend toward increase at week 4 (p=0.058). Saliva flow and pH remained unchanged.

Why it matters

Cannabis is typically consumed orally (smoked, vaped, or ingested), meaning the oral cavity is the first biological system exposed. Changes in oral microbiome composition could have downstream effects on dental health.

The numbers in context

16 patients enrolled, 14 female, mean age 52.8 years. Lactobacillus scores: 2.59 (baseline), 3.1 (week 1, p=0.033), 3.3 (week 4, p=0.025). S. mutans scores: 1.8 (baseline), 1.6 (week 1), 2.4 (week 4, p=0.058).

How the study worked

Prospective study of 16 rheumatology patients newly approved for medical cannabis. Saliva samples were collected at baseline, week 1, and week 4, then measured for volume, pH, and microbial growth of S. mutans and Lactobacillus using a specialized culture kit.

What this study cannot tell us

Very small sample (16 patients). No control group. Short follow-up (4 weeks). Most participants were female fibromyalgia patients, limiting generalizability.

How to read the evidence

Very small sample size with no control group and short follow-up period.

When this study was published

2021 study from a single clinic in Israel.

The bigger picture

Higher Lactobacillus levels in the mouth are generally associated with increased cavity risk. If cannabis consistently shifts oral flora in this direction, it could have practical implications for dental care among regular users.

Questions still open

Do these microbial shifts persist beyond four weeks? Does the route of cannabis consumption (smoking vs. oral ingestion) matter? Would these changes translate to measurable dental health outcomes?

Common questions

Did medical cannabis cause dry mouth in this study?

No. Saliva flow remained stable across all three measurement points (baseline, week 1, and week 4), with no significant changes.

What oral bacteria changed with cannabis use?

Lactobacillus levels increased significantly at both week 1 and week 4. Streptococcus mutans showed a trend toward increase at week 4 but did not reach statistical significance.

Read the original research

The impact of medical cannabis consumption on the oral flora and saliva.

PloS one, 16(2), e0247044

View on PubMed ↗Publisher’s paper ↗

Citation

Habib, George; Steinberg, Doron; Jabbour, Adel. (2021). The impact of medical cannabis consumption on the oral flora and saliva.. PloS one, 16(2), e0247044. https://doi.org/10.1371/journal.pone.0247044