Pulmonary arterial hypertension (PAH) is a chronic, progressive disease of the lung arteries, leading to heart failure and premature death. Symptoms of PAH include serious exercise intolerance, reducing the quality of life of patients. PAH patients are actively seeking nutritional advice, but evidence-based recommendations are scarce. In this thesis, the role of nutrition in PAH pathophysiology and the potential of nutritional treatment for PAH is being explored. The most important findings are that PAH patients often have iron and vitamin D deficiency, both at time of diagnosis as after 1,5 years of regular treatment. Iron deficiency is related to exercise intolerance, but the relevance of vitamin D deficiency remains unclear. Results of an in vivo mouse study show that a diet high in protein and anti-inflammatory components can reduce the development of disease symptoms in the heart and skeletal muscle in PAH.