Introduction:
Many studies highlighted variations in prevalence of Dietary Supplements (DS) use and its determinants across countries. However, survey data for DS use and its determinants amongst general population of Greece remain limited.

Objective:
The aim of this study was to investigate DS use among Greek people following different types of diets (free, low in fat, low in carbohydrates, low in calories, vegetarian).

Methods:
The sample size was 30,901. Participants were interviewed face-to-face using a standard questionnaire. Data analysis (Pearson’s Chi-Square test, Z-test, Correlation Analysis) was performed using SPSS.

Results:
The overall prevalence of DS use was 54.1%, and it was higher in low in fat diet followers (64.2%) and lower in “free” diet followers (51.1%). Participants reported that the replenishing of inadequate nutrients (36.2%) and the treating and prevention of diseases (37.2% and 26.3%) are reasons of DS use, without significant differences among diets. Participants reported that the fear of side-effects (35.1%), the adherence to a good diet (32.1%) and the good physical condition (32.8%) are the main reasons of DS non-use. Most participants adhered strongly the doctors’ (59.6%) and pharmacists’ (24.1%) recommendations, but followers of low in carbohydrates diet adhered mainly the coaches’ recommendations. Low in carbohydrates diet followers strongly believed that medical tests should preceded of any decision for DS intake (55.6%). However, vegetarian diet followers believe the opposite (58.4%). Respondents, especially those following vegetarian diet were convinced of their ability to evaluate DS importance for health (46.4%) and also any health risk from excessive DS intake (57.0%), but they were incapable to adequately evaluate DS ingredients’ authorization (mainly the free diet followers). The great majority of participants (especially the low in fat diet followers) considered seriously the recommended daily allowance.

Conclusions:
Data obtained on the use of DS among people following different diets could be very useful to formulate interventions aiming to maximize benefits from their use.