Influence of dietary energy intake on nephrolithiasis - A meta-analysis of observational studies

Objective: Obesity has been associated with an increased risk of kidney stone formation. The presence of obesity is due to an imbalance between energy intake and energy consumption resulting from physical activity and resting metabolic rate. The purpose of this meta-analysis was to assess the differences in dietary energy intake levels between patients developing urinary stones versus healthy individuals. Materials and methods: Medline/PubMed and EMBASE databases search was performed using the terms "urolithiasis", "kidney stones*", "calcul*", "energy", "calor*", "intake", "food", "kilojoule/kjoule", "Kilocal*/kcal" from January 1st, 2000, and were assessed as up to date on September 30th, 2019. Results: After having screened 1.782 records, four studies were included in the meta-analysis. The total population was 467.063, including 453.078 healthy men and/or women and 13.985 men and/or women affected by nephrolithiasis. When energy intake data were pooled irrespective of the sex of participants, mean calory intake values were significantly higher in nephrolithiasis patients, compared to healthy individuals. The mean difference (MD) was 39.16 kcal (95% CI 18.53 to 59.78, p = 0.0002, random-effects model, inverse-variance weighing). The odds ratio for this comparison - calculated from the standardized mean difference - is significant (OR = 1.946; 95% CI: 1.869 to 5.561). Conclusions: Patients affected by urolithiasis show a significantly higher energy intake in various patient populations (USA, China and Korea) including subjects of both sexes. The relevance of this finding should be confirmed by studies in populations showing different and diverse dietary patterns, and by evaluating energy consumption linked to physical activity and metabolic rate in renal stone formers.