This study investigates the use of social networks as a scientific tool for gathering medical data from young subjects while promoting healthier habits. Our first hypothesis is that social networks can facilitate epidemiological studies, reducing time and cost. The second question is whether social networks can enable the collection of data from young and healthy subjects who are otherwise beyond the reach of conventional social health polls. A Facebook application was created to collect data concerning adherence to the Mediterranean diet, considering the significant risk of cardiovascular and neurological degenerative diseases in subjects with poor adherence to a healthy diet. More than 1400 users were recruited in a short time without any promotional action. Collected data indicate that adherence to the Mediterranean diet is in general greater in older users vs young (p < 0.01) and Italian vs Other Countries (mainly participants from the US) (p < 0.03), while no statistical differences were found concerning gender. Results show that the proposed approach offers advantages in terms of reduced cost, faster data gathering and processing, and improved efficiency compared to a form-based epidemiology campaign. However, the initial network may influence the sample constitution in age and geographical location, especially if the spread does not become viral and autonomous. Based on the case study, we provide designers of Facebook apps with some simple guideline suggestions aimed at maximizing the heterogeneity of the sample, in order to collect significant data. The proposed scenario, suitable for collecting health data, can easily be extended to other fields.