Seaweeds are often seen as a healthy, component of future diets with low environmental impacts compared to other food ingredients. This study quantifies the environmental impact of the seaweed Saccharina latissima (S. latissima) cultivated in the North Sea and applied in food products using Life Cycle Assessment (LCA) The performance under current conditions and in future scenarios is evaluated, drawing on data provided by Dutch companies. The environmental benefits of inclusion of seaweed in diets, taking into account its nutritional value, are evaluated using Optimeal. Under the current cultivation conditions seaweed cultivation has a significant contribution to the environmental impact of the assessed food products, i.e., a burger with S. latissima (up to 60%), salt with 10% S. latissima (79–94%)and salt replacement based on 100% S. latissima (99%). Under current cultivation practices cultivation has an impact between 10 and 52 kg CO2 equivalent/kg wet weight S. latissima. The LCA results of current cultivation practices points towards a hotspot in the transport efforts (responsible for 74–80%) and a different means of installing the seaweed farms can directly reduce environmental impacts. Further reductions can be achieved by increasing yields and increasing the lifespan of materials used in the infrastructure leading to an impact of 0.2 kg CO2 equivalent/kg wet weight S. latissima. In the future cultivation scenario, which is a projection for 5 years from now with estimated yields and more efficient infrastructure design and transport, the impact of S. latissima to the total burger and salt product impacts diminished significantly to 1–4% for the burger, 15–40% for the salt, and 63–88% for the salt replacement. The analysis concludes that inclusion of seaweeds in future vegetarian burgers or as salt replacement can have a positive effect on the environmental impacts of diets.