Wasting, but not malnutrition, predicts cardiovascular mortality in end-stage renal disease

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Abstract
Beddhu et al. [1] recently have reported that there were no positive associations of malnutrition with documented acute coronary syndromes requiring hospitalization in a large incident Medicare dialysis population. The authors state that their findings do not support our suggestion [2] of an association between malnutrition, inflammation and atherosclerosis (MIA hypothesis) in patients with end-stage renal disease (ESRD). No doubt the study by Beddhu et al. [1] is a well performed study conducted in a large group of dialysis patients. However, we feel that some fundamental issues regarding the nomenclature and definition of ‘malnutrition’ need to be discussed. First, as discussed by Mitch [3], the use of the word ‘malnutrition’ has often been used incorrectly in the renal literature, and, according to Mitch, ‘malnutrition’ should be used to describe a deficient nutritional status caused by insufficient nutritient intake. However, literally, the word ‘malnutrition’ (derived from the latin word ‘malus’) means, ‘not correctly nourished’. Thus, both under- and over-nourished (obese) patients could be considered to be ‘malnourished’. Secondly, whereas malnutrition is usually defined as a consequence of insufficient food intake and low serum protein levels, the loss of muscle mass (i.e. cachexia or wasting) in the ESRD patients is usually the consequence of a number of catabolic mechanisms stimulated by renal insufficiency. Indeed, the aetiology of loss of lean body mass in ESRD is very complex and may include numerous factors apart from poor food intake (i.e. true malnutrition), such as delayed gastric emptying, hormonal derangements, inadequate control of acidosis, co-morbidity and inflammation [3].