A large body of evidence exists, which demonstrates the importance of nutritional support in cancer. The nutritional needs of patients with cancer may differ from those of the healthy population due to hypermetabolism, impaired organ function, increased nutrient losses and therapy-related malnutrition. Patients with cancer often have increased requirements for both macro- and micronutrients due to long periods of undernutrition prior to diagnosis. The aim of nutritional support should be the prevention or reversal of malnutrition, and this should be initiated as early as possible to improve outcomes. Oral supplementation is a simple, non-invasive method of increasing the nutrient intake of those patients who are unable to meet nutritional requirements, despite dietary counselling. Enteral tube feeding is indicated for patients who are unable to meet their nutritional needs by oral intake alone, and has been shown to improve clinical outcomes. Novel approaches in oral supplementation include the use of eicosapentaenoic acid (EPA), a compound under investigation for its role in preventing and treating cancer-associated malnutrition. Individual studies suggest that EPA attenuates cancer-associated wasting and improves immune function. In addition, it has been shown to have anti-tumour effects and improve clinical outcomes. However, results are not consistent for all patient groups and further research is required.