Nutrition-related diseases can considerably contribute to many different health-related problems and can impact on several segments of the population. Promoting balanced diet plans is therefore pivotal; however, this is not a trivial task as it requires different stakeholders (nutrition experts, agro-industrial businesses and consumers) to cooperate. This work introduces a prototypical ontology-based decision support system to enable such a cooperation, allowing nutrition experts to rely on a support tool when developing diet plans, consumers to received tailored suggestions and to be informed regarding new food products that could have an effect on specific their health condition, and agro-industrial companies to divulge characteristics of novel food products and their expected effects. These stakeholders can also exchange comments, suggestions and observations. The decision support system relies on widely-adopted ontologies and its use is introduced by two scenarios.