Nutrition therapy is a critical component of treatment for patients with acute respiratory distress syndrome/acute lung injury. Underfeeding can cause cumulative caloric deficits, loss of lean body mass, and deteriorationof respiratory muscle strength, which can all lead to poor outcomes. However, overfeeding, on the other hand, is also harmful due to hypercapnia and hyperglycemia, which can increase the risk of infection. Therefore, an optimal nutrition therapy is very important. Although the importance of nutrition in this patient population is widely accepted, trophic enteral feeding during the acute phase is suggested in immunologic aspect to prevent nutrition-related complications. High-fat and low-carbohydrate enteral nutrition can decrease CO₂ production and help shorten the duration of mechanical ventilation in patients with acute respiratory distress syndrome. There are still areas of controversy regarding the role of omega-3 fatty acids and antioxidants, which are known to prevent oxidative cellular injury, modify the metabolic response, and modulate immunity and inflammation.

Lipids are structural components of cellular membrane and functional components exerting an important role in different metabolic pathways through regulation of cell signaling and metabolic homeostasis. Although the human body can synthesize some fatty acids, essential fatty acids (EFA) should be exogenously provided. Parenteral nutrition (PN) can be utilized to provide EFA for patients without normal gastrointestinal functions and those at risk of malnutrition. Parenteral lipids provide more energy-dense nutrition in a reduced volume and prevent EFA deficiency. However, prolonged PN with lipid emulsions is associated with metabolic complications including PN-associated liver disease. Currently available parenteral lipid emulsions provide various combinations of soybean oil, fish oil, olive oil and medium-chain triglycerides. The effects of parenteral lipid emulsions on the lipid nutrition status and PN-associated complications vary depending on the type and dosages of main oil sources used in parenteral lipid solutions. Therefore, understanding the composition, metabolism, and functional effects of lipids can be helpful in considering their clinical applications in PN.