Priobiotic for Oral (PRO) Health

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Who is conducting this Study?

The Probiotic for Oral Health (PRO Health) Study is led by Dr. Jennifer Smilowitz, PhD, at the UC Davis Foods for Health Institute in collaboration with Dr. Mark Underwood MD, at the UC Davis Medical Center.

This study has been reviewed and approved by the UC Davis Institutional Review Board.

What is the purpose of the study?
The purpose of this 5-week study is to determine if a probiotic supplement, given for 14 days to healthy adults, increases levels of beneficial bacteria in their mouth. The effects of the probiotic supplement on oral bacteria will be compared to the effects of a placebo-control supplement. Both the probiotic and placebo-control supplement contain xylitol, a sugar alcohol with well-known beneficial effects on oral health.  

Who can participate?

  • Healthy adults who are 21-45 years old;
  • Individuals who practice good oral hygiene;
  • Individuals who consume alcohol in moderation or consume no alcohol;
  • Individuals who are willing to avoid binge drinking during the study period;
  • Individuals willing to refrain from consuming raw onions or garlic during the study period;
  • Individuals willing to use the study toothpaste to brush their teeth and refrain from using other oral-care products during the study period;
  • Individuals willing to refrain from smoking or chewing tobacco or smoking or vaping marijuana during the study period. 


Who is NOT eligible to participate?

  • Individuals who are pregnant;
  • Individuals with a history of periodontal disease or gingivitis;
  • Individuals who have received a routine dental cleaning within the past 4 weeks;
  • Individuals with any oral surgery or intensive oral procedures within the past 4 weeks;
  • Individuals with dental trauma or injury to the teeth, periodontium, and/or nearby soft tissues in the past 4


  • Individuals who have consumed probiotics, kombucha, yogurt, or kefir in the past 7 days;
  • Individuals who have consumed probiotics containing S. salivarius within the past 8 weeks;
  • Individuals who have taken oral or IV antibiotics within the past 8 weeks;
  • Individuals who currently smoke or chew tobacco, or have smoked or chewed tobacco within the past year;
  • Individuals with a recent history of illicit drug use;
  • Individuals who frequently smoke or vape marijuana;
  • Individuals who use alcohol excessively.


What is expected of me during the study?

This study lasts up to 5 weeks. During the study period you will be asked to do the following: consume a probiotic powder supplement for 14 days; collect 7 saliva samples using swabs; and fill out daily logs regarding your health and dietary intake. Study personnel will instruct you on how to consume the supplement and how to collect samples. You will be asked to store the collected samples in a cool, dry place until your scheduled campus visit. You will be asked to come to the UC Davis Robert Mondavi Institute in Davis, CA on 4 different occasions.

Will I be compensated for participation?

Participants may receive up to $100 in gift cards.  

For more information please contact the Human Studies Coordinator, (888) 217-5355 or email at:

Visit the Study Website: