priority reasons

Investigating the effect of smoking and smoking cessation on the intestinal microbial composition and function. The investigators wish to determine whether the alteration in gut microbiome drives the significant weight gain seen in humans after smoking cessation, and find the mechanism by which the gut microbiome contributes to this phenomenon.

Cigarette smoking causes a variety of health problems, including cardiovascular disorders, cancer, pulmonary diseases, autoimmune diseases, premature birth, and certain birth defects. Health benefits of smoking cessation start very fast after the last smoke. However, smoking cessation has significant side effects including weight gain. Several theories have been proposed to explain weight gain after smoking cessation.

Microbiome research is an upcoming, extensively followed research field that has found unsuspected connections between human health and gut occupants. Many recent studies established important roles for the gut microbiome in regulating obesity, and metabolic diseases.

The general aim of this study is to investigate the effect of smoking and smoking cessation on the intestinal microbial composition and function.

This study follows 200 healthy participants who will be recruited according to their affiliation to one of three groups:

Group 1: Non-smokers for at least 10 years Group 2: Cigarette smokers that do not plan to quit. Group 3: Cigarette smokers who plan to quit smoking. Participants who are planning to quit cigarette smoking will be offered to join a program for smoking cessation. The study will start 8 days before cessation group volunteers will stop smoking and will continue for one year after. Participants of all groups will be followed-up for one year.

During the study, the participants will collect stool and oral samples which will be used for microbiota profiling. At every meeting anthropometric measurements, blood samples will be taken, and body composition performed. Participants will be connected to a continuous glucose monitor and will be asked to log a food diary using a designated mobile phone application.

Inclusion Criteria:

1. Non-smokers for at least 10 years, hereinafter 'control group'.
2. Cigarette smokers for at least 2 years, 5 or more cigarettes per day, that do not plan to quit hereinafter 'smoking group'.
3. Cigarette smokers for at least 2 years, 5 or more cigarettes per day, who plan to quit smoking hereinafter 'cessation group'.
4. Age - 18-70
5. BMI<28
6. Capable of working with the smartphone application in Hebrew or English.

Exclusion Criteria:

1. Consumption of antibiotics/oral antifungals/ probiotics 3 months before the first day of the experiment.
2. Constant consumption of drugs (cannabis etc..) in the last 2 years
3. Pregnancy in the last 6 months, breastfeeding, and active fertility treatments within the past year
4. Diagnosis of type 1 or type 2 diabetes
5. Chronic disease (infectious, autoimmune, endocrine, metabolic, neurodegenerative)
6. Cancer and recent anticancer treatment within the last 5 years
7. Neuro-psychiatric disorders
8. Coagulation disorders
9. Inflammatory bowel diseases (IBD)
10. Bariatric surgery within the last 5 years
11. BMI>28
12. Alcohol or substance abuse