RESEARCH LETTER Effect of Fruit on Net Acid and Urinary Calcium Excretion in an Acute Feeding Trial of Women Janet Amy Bell, MSc, and Susan Joyce Whiting, PhD From the College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada OBJECTIVE: Consumption of fruits and vegetables has been implicated in lowering net acid excretion (NAE), but few studies have directly examined NAE and urinary calcium effects. Further, there is no evidence that only fresh fruits and vegetables must be consumed for a beneficial effect on bone. METHODS: A crossover, acute-load study was designed to investigate whether processed fruit was as effective as fresh fruit in reducing NAE and protein-induced hypercalciuria. Fifteen women completed three dietary treatments on three different mornings. A fasting urine sample was collected before consuming one of the following three isocaloric high-protein treatments: control, fresh apples, and processed applesauce. The serving size for the applesauce treatment was 2.5 times that for fresh apples. Urine was collected at baseline (0 h) and at 1.5, 3.0, and 4.5 h. RESULTS: Compared with baseline, NAE increased after control treatment but decreased after fresh or processed apple treatment (P = 0.041). Calcium excretion increased with all treatments by 3 h; however, the increase was less for fresh apple and applesauce (P = 0.024). CONCLUSIONS: In an acute feeding model, fruit intake reduced NAE and urinary calcium excretion. Processed fruit appears to be effective, although a larger serving size was needed than with fresh fruit. Nutrition 2004;20:492– 493. ©Elsevier Inc. 2004 KEY WORDS: fruit, calcium, net acid, urinary calcium INTRODUCTION Fruits and vegetables contain large amounts of base-producing organic acid salts, and the intake of these foods have shown benefits to bone health in epidemiologic studies. 1–3 Guidance to the public includes promotion of fresh fruits and vegetables and avoidance of processed foods 4 ; however, no one has determined whether processing fruit reduces its ability to be an alkalizing agent. Acute load studies have proved to be useful for determining urinary excretions of calcium, phosphate, net acid, sulfate, and potassium when subjects are given a single test meal. 5,6 Our two objectives were to determine whether 1) dietary treat- ment with fruit would lower net acid excretion (NAE) and urinary calcium excretion compared with a control treatment in an acute model and 2) dietary treatment with fresh fruit would reduce NAE and protein-induced hypercalciuria to a greater extent than pro- cessed fruit. MATERIALS AND METHODS The University of Saskatchewan Committee on Ethics in Human Experimentation approved the study procedures. Written informed consent was obtained from all subjects. The study design was a crossover one consisting of an acute load of one of three dietary treatments on 3 different days. Fifteen healthy female subjects ages 20 to 50 y participated. On test mornings, subjects fasted for 1.5 h. First morning urine was voided and discarded at home after which 250 mL of distilled water was consumed. A 0-h collection was made upon arrival, followed immediately by consumption of one of the three dietary treatments. Urine collections were made at 1.5, 3.0, and 4.5 h on site, during which subjects continued to fast, consuming only distilled water. Samples of each collection were frozen until analyzed for creatinine, sodium, potassium, sulfate, NAE, and calcium. 5,6 Subjects completed all three treatments with at least 1 d be- tween treatments, with order of treatments randomly assigned. The three isocaloric (500 kcal) treatments were the control (C), con- sisting of a meal of a protein drink and candy (108 g of jujubes); fresh apples (F), consisting of 311 g of peeled apple, a protein drink, and a small amount of candy (53 g) to equalize energy and carbohydrate content; and processed applesauce (P), consisting of 877.5 g of canned non-sweetened applesauce and a protein drink. Protein was added to the dietary treatments because the hypocal- ciuric effect of potassium salts has been shown to be evident when responding to protein-induced hypercalciuria. 4,5 This protein drink was made with distilled water and 32 g of whey protein drink mix (Prolab Nutrition, Bloomfield, CT, USA), which provided 22 g of whey protein, 2.1 g of fat, and 6.2 g of carbohydrate. The P treatment was equivalent to approximately seven servings of fruit and contained 17.6 mM of potassium (by analysis), and the F treatment was equivalent to slightly more than two servings and contained 7.4 mM of potassium (by analysis). Data are presented as mean  standard error. Because we expected fruit to lower urinary calcium and NAE, tests were run with one-side repeated measures analysis of variance followed by Fisher’s least significant difference test. Relations between NAE and calcium excretion were examined with Pearson’s correlation tests. Statistical significance was indicated at P  0.05. Analyses were performed with SPSS 11 (SPSS, Chicago, IL. USA). This study was supported by an Irwin Grant from the College of Pharmacy and Nutrition and a Graduate Student Award from the University of Saskatchewan. Correspondence to: Susan Joyce Whiting, PhD, College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon SK S7N 5C9, Canada. E-mail: susan.whiting@usask.ca 0899-9007/04/$30.00 Nutrition 20:492– 493, 2004 ©Elsevier Inc., 2004. Printed in the United States. All rights reserved. doi:10.1016/j.nut.2004.01.015