Vegetables, mainly green leafy ones and some others like beets, are a rich source of nitrate. Nitrate metabolism has shown benefits to the body and there are recent studies that agree that the consumption of nitrates from vegetables can modify the oral microbiota by increasing species with nitrate-reducing capacity, which are also bacteria that are associated with oral health.

Background. Periodontitis (PD) is a chronic, multifactorial and inflammatory disease caused by the imbalance resulting from the proliferation of certain pathogenic bacteria that alter the symbiotic community and cause oral dysbiosis. Non-surgical periodontal treatment (NSPT) helps to eliminate the pathogenic plaque present and it is of interest to look for adjuvant treatments that contribute to an improvement in oral health, given that, with the passage of time, a recolonization of pathogenic bacteria has been observed, as well as a relapse in patients. The oral microbiota plays a key role in the nitrate reduction process in humans, as certain bacteria reduce exogenous nitrate to nitrite, which is subsequently converted in the body to nitric oxide. Vegetables, mainly green leafy vegetables and some others such as beets, are a rich source of nitrate. Nitrate metabolism has shown benefits for the body and recent studies agree that consumption of nitrates from vegetables can positively modify the oral microbiota. Therefore, we hypothesize that the consumption of vegetables may be an adjuvant in the recovery and improve the condition of patients receiving NSPT and possibly prevent relapse.

Objective. To evaluate the effect of nitrate-rich vegetable intake on salivary levels of inflammatory molecules, nitratoreductive capacity and oral microbiota composition in patients with PD.

Material and methods. A parallel randomized clinical trial (RCT) will be conducted in 60 PD patients who are candidates for NSPT and they will be randomized into two groups. The control group will receive the NSPT and instructions to continue with their usual diet, while the intervention group, in addition to the NSPT, will receive a nutritional intervention to promote the daily consumption of vegetables rich in nitrate. The nutritional intervention will be based on the theory of the wheel of behavior change to achieve the consumption of vegetables rich in nitrate that provide ~ 350 mg of this compound. Both groups will be evaluated before and after the study: clinical, dental, and nutritional parameters. Blood samples will also be taken for blood chemistry and saliva to perform a nitratoreduction test, quantify the amount of nitrates and nitrites and determine the levels of inflammatory molecules, as well as subgingival plaque and tongue scraping, from which DNA will be extracted to be sequenced and to obtain the diversity and abundance of bacteria at the beginning, end of the RCT, 6 months and 12 months later in both groups.

Inclusion Criteria:

• Men and/or women from 30 to 65 years old
• Voluntary participation and signing the written informed consent
• Not receiving nutritional treatment at the time of uptake
• Availability to attend all scheduled visits
• Have an indication to receive nonsurgical periodontal treatment (NSPT)
• Interdental clinical insertion loss ≥3mm and ≥5mm in the buccal or oral area of two or more non-adjacent teeth
• Detectable depths ≥ 5mm in two or more teeth
• Radiographic evidence of periodontal bone loss

Exclusion Criteria:

• Trauma-Induced Gingival Recessions
• Cervical caries
• History of bleeding diathesis
• Pregnant or nursing women
• BMI <18.5 kg / m2
• History of any of the following self-reported diseases: type 2 diabetes mellitus, high blood pressure, kidney or liver disease, inflammatory bowel diseases, autoimmune diseases and/ or use of medications to control these diseases.
• Having or presenting a high risk of infection by tuberculosis, hepatitis B or Human Immunodeficiency Virus (HIV)
• Use of antibiotics (including antibiotic oral rinse) 6 months prior to or during the study
• Having received specialized periodontal treatment in the previous 6 months.
• Smoking habit
• Require an interpreter or not understand Spanish to attend or provide written material.

Single blind. Dentists in charge of assessing dental clinical parameters, as well as researchers performing the analysis of the oral microbiota, will be unaware of the group assignment.