The importance of nutrition in Cancer has not been recognized sufficiently. Many believe that nutrition is not a priority once cancer is diagnosed or even that it can increase tumor growth, which is not founded on scientific evidence (Bossola, Pacelli, Rosa, Tortorelli, & Bastista, 2011). Proper nutrition can alleviate symptoms and even support cancer survivorship (Prado, Purcell, & Laviano, 2020). It is estimated that the deaths of 10-20% of Cancer patients can be attributed to malnutrition (Arends, et al., 2017).

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The primary nutritional problem, and likely also the most impactful on prognosis, is muscle wasting. It is an independent predictor of poor physical function, lower quality of life, surgical complications, cancer progression and even reduced survival. Muscle wasting leads eventually to low muscle mass. The prevalence of low muscle mass is >50% in people with newly diagnosed cancer. Interestingly, only 10% of the patients are underweight, showing that low muscle mass occurs independently of body weight or fat mass (Martin, et al., 2013). 

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Cancer patients are very heterogenous. The different types of cancer, the different stages and the different type of patients (obese, lean) make it difficult to generate a universal nutritional advice. Patients might suffer from sarcopenia (with or without obesity) or from cachexia. Cachexia is also characterized by involuntary weight loss and anorexia on top of muscle loss (Arends, et al., 2017).

Lots of studies have been done looking into the effect of nutrition in cancer patients. As mentioned, due to the heterogeneity, it is difficult to generate a universal advice for all patients. A group of experts published in 2017 a guideline for nutrition in cancer patients. This advice has been generated after an in depth screening of all the literature. (Arends, et al., 2017). They came to the conclusion that the total energy recommendation for cancer patients is 25-30 Kcal/kg body weight/day. On protein intake, they concluded that it should be between 1.2-1.5 g/kg body weight/day. This advice was, however, not based on the low muscle mass condition. 

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Among patients with cancer cachexia, it was shown that a protein intake >1.5 g/kg body weight/day could maintain or improve the muscle mass, and the effect might be more substantial when combined with exercise. This is also in line with a recent published position paper (Bauer, et al., 2019). It is still unknown whether 1.5 g protein/kg body weight/day is sufficient. 

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Cancer patients often have a lower intake of food due to anorexia, taste/smell alterations, dysphagia, nausea, vomiting which means that reaching a sufficient intake of nutrients becomes very challenging (Prado, Purcell, & Laviano, 2020). A high-quality ONS can be used to reach the required level of nutrients.