Eating Habits among Lithiasic Patients in Kinshasa, the Democratic Republic of Congo

Introduction: Worldwide, the incidence of kidney stones has been progressively increasing. Various factors can influence the risk of stone formation, including lifestyle and eating habits. The dietary investigation is a standard of care in patients with urolithiasis. The objectives of this study were to determine the dietary habits of lithiasis patients in the city of Kinshasa and to investigate the association between dietary habits and the composition of the stones. Material and methods: From January 2017 to September 2019, 85 patients attending 8 hospitals participated in the nutrition survey. Various foods commonly consumed in the Democratic Republic of Congo were categorized based on their composition: foods rich in animal proteins, foods rich in calcium, foods high in sugar, foods high in oxalate, and various vegetables and fruits. We also investigated daily water intake. The composition of the collected stones was analyzed by infrared spectrophotometry. Results: The mean (SD) age of patients was 47.1 (14.0) years, 63.5% of patients were males, 75.3% of the patients had stones located in the upper urinary tract, and 7.1% were undernourished. Most of patients consumed vegetables (77.6%), animal proteins (62.4%), and foods rich in oxalate (58.8%). The daily water intake was less than 1500 mL in more than half of the patients (68.2%). Major anhydrous uric acid stones were associated with a high body mass index (p = 0.025). Male patients with a high oxalate diet had more calcium oxalate stones (64.3%) compared to other types of stones (p = 0.041). Conclusion: High consumptions of vegetables and low water intake were linked to the formation of calHow to cite this paper: Diangienda, P.K.D., Moningo, D.M., Mayindu, A.N., Makulo, J.-R.R., Sumaili, E.K., Mafuta, E.M., Loposso, M.N., Punga-Maole, A.M.L., Lufuma, S.L.N., Haymann, J.-P. and Daudon, M. (2021) Eating Habits among Lithiasic Patients in Kinshasa, the Democratic Republic of Congo. Open Journal of Urology, 11, 200-213. https://doi.org/10.4236/oju.2021.116018 Received: April 25, 2021 Accepted: June 13, 2021 Published: June 16, 2021 Copyright © 2021 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access P. D. K. Diangienda et al. DOI: 10.4236/oju.2021.116018 201 Open Journal of Urology cium oxalate monohydrate stones. More data are needed to confirm these findings.


Introduction
Urolithiasis is a common health problem with a multifactorial etiology arising from the interaction of various factors including metabolic, genetic, and environmental [1]. Calcium oxalate accounts for the majority of kidney stones [2].
Over the last decades, urolithiasis incidence has been increasing worldwide at an alarming rate [3]. Several factors such as age, gender, race, nutrition, daily water intake, climate, geography, physical activity and Body Mass Index (BMI) play a key role in urolithiasis pathogenesis [4]. Early studies showed that nutrition contributes substantively to kidney stone formation [5] [6]. Prior evidence reported that high dietary calorie, animal protein and oxalate intake and low daily water intake, calcium and potassium consumption correlated with higher incidence of calcium oxalate stone formation, thus representing important risk factors in kidney stone formation [7] [8]. Therefore, dietary investigation represents an important step in the etiological investigation of urolithiasis [9]. Despite a wealth of studies investigating the association between kidney stone formation and nutrition habits, data on the nutritional status and dietary habits of patients afflicted with kidney stones in the Democratic Republic of Congo (DRC) are lacking. To fill this gap, the present study was designed to determine the dietary habits of patients who followed for urolithiasis in the city of Kinshasa and to evaluate the association between dietary habits and the composition of the stones.

Study Design and Setting
This was a dietary survey conducted from January 2017 to September 2019 among lithiasic patients attending 8 hospitals in the city of Kinshasa. In this case study, the sample size was not predetermined in its initial phase and the study focused on lithiasic patients for the most part easily accessible in hospitals that agreed to collaborate in this study. Thus, 85 patients had taken part in the study. Only the patients followed in these hospitals for urolithiasis who agreed to freely answer the questionnaire for this survey had taken part in this study.

Dietary Survey
The final report of the study on the identification and evaluation of the nutritional quality of food supplements in use in the DRC carried out by the non-governmental We then established a scale from 1 to 4 according to the frequency of consumption of these foods: occasional consumption of a food was rated 1, consumption once a week was rated 2, while consumption 2 to 3 times a week was rated 3, and a daily consumption was rated 4. Ratings 3 and 4 were categorized as heavy consumers of a given food.
We also evaluated daily water intake. This frequency was qualified as "a lot" when the patient took water several times during the day (quantity estimated at more than 1500 mL/d), "Not much" when the patient took water twice during the day (quantity estimated at 1000 to 1500 mL/day), finally "hardly" when there was only one dose during the day (quantity estimated at less than 1000 mL per day).

Infrared Analysis of Stones and Study Parameters
The different layers of stones were analyzed by Fourier transform infrared spectrophotometry (Vector 22 FT-IR spectrophotometer, Bruker Optics, Champssur-Marne, France) in absorbance mode by accumulation of 32 spectra between 4000 and 400 cm −1 , with a resolution of 4 cm −1 . Stones were classified according to their main component (chemical or crystalline body representing the large proportion in a stone).
Patient demographic and clinical data were obtained from medical records and during the medical appointment, including age, sex, place of residence, weight and height to calculate the body mass index (BMI), occupation, site of stones, existence of a urinary tract infection, comorbidities, and serum creatinine. Age was divided into 4 categories: <20 years, 20 -39 years, 40 -59 years, and ≥60 years. The profession was categorized in 3 groups: civil servant, liberal, and student/pupil and unemployed.

Statistical Analysis
Continuous variables were expressed as means and medians. Categorical variables were summarized into proportions. Differences in categorical variables between groups were assessed using Chi square test or the chi-square likelihood-ratio as appropriate. Differences in means were assessed by the student's t test. p values less or equal to 0.05 were interpreted as statistically significant. Statistical analysis was performed using SPSS Statistics software version 22 (IBM, Armonk, USA). This study was approved by the ethics committee of the School

Results
A total of 85 lithiasis patients attending various hospitals in Kinshasa participated in this survey. Demographics are summarized in Table 1. The mean (SD) age of patients was 47.1 (14.0) years. Most participants were males (63.5%, n = 54). Sixty-four patients (75.3%) had stones located in the upper urinary tract.
While 6 (7.1%) patients were undernourished, 46 (54.1%) were overweight or obese. Just over a quarter of patients (25.9%) had a urinary tract infection and Escherichia coli was the most frequently isolated bacteria. Twenty patients (23.5%) had hypertension and 9 (10.6%) had impaired renal function ( Table 2).       animal proteins, consumptions of foods rich in oxalate, refined sugars, calcium, and consumptions of foods high in salt. Also, men with a diet high in oxalate had more calcium oxalate stones compared to other main stones.

Eating Habits and Chemical Composition of Stones
Most of patients in this study (77.6%) had a diet rich in vegetables and fruits. Several studies have demonstrated the protective role of a diet rich in vegetables and fruits [11] [12]. Likewise, a Dietary Approaches to Stop Hypertension (DASH) diet, rich in fruits, vegetables, whole grains, and low-fat dairy products, has been shown to significantly reduce the risk of kidney stone formation [13]. However, it is worth mentioning that the protective effect of a diet rich in vegetables and fruits is only observed in people who rarely consume them [12]. Indeed, Meschi et al. [12] found that urinary citrate excretion was significantly reduced and calcium excretion was significantly increased after a two-week diet of vegetables in a normal population [12]. Furthermore, Daudon et al. [14] revealed that a vegetable diet is often rich in oxalic acid and poor in calcium, which would promote hyperoxaluria and the formation of calcium oxalate stones observed in developing countries. In this study, whewellite (73.8%) was the most frequent component and less than half of patients (40%) consumed foods rich in calcium. Thus, the need to examine the oxalate content in various green leaves and vegetables regularly consumed in the DRC.
In this study, 58.8% of patients had a diet rich in oxalate and a statistically significant association was found between a diet rich in oxalate and calcium oxalate stones in men. Higher consumptions of oxalate increase the risk of stone forma-tion [15]. Oxalate, a terminal acid in metabolism whose primary route of excretion is the kidney, binds to calcium to form calcium oxalate which is an important lithogenic complex [9] [16]. Three potential sources of oxalate intake are known: foods rich in oxalate (represents 10% to 20% urinary oxalate) [9] [16], hyperoxaluria may be secondary to intestinal malabsorption [16] [17] [18] [19] and hepatic oxalate synthesis which depends on lean body mass (represents 80% to 90% of oxalate). However, a diet very low in oxalate can reduce urinary oxalate excretion by half [9] and only 100 -1000 mg of free oxalate which is absorbed per day [9] [14].
Besides higher consumptions of vegetables, we also found that 62.4% of patients had a diet rich in animal proteins and 58.8% consumed refined sugars contained in juices and other soft drinks. Ferraro et al. [20] found that higher consumption of sugary drinks was one of the modifiable risk factors associated with urinary stones. There is also evidence that sugary and carbonated drinks increase the risk of urinary stone formation [21]. Zhuo et al. [11] reported that animal protein intake was significantly associated with the occurrence of urolithiasis. Short-term restriction of animal protein significantly reduces the excretion of calcium, phosphate, hydroxyproline, uric acid and oxalate and increases the excretion of citrate in the urine, reducing the risk of stone formation [22].
Therefore, patients with recurrent calcium oxalate urate stones should decrease consumptions of animal proteins and avoid foods high in purines. It is known that calciuria is an important determinant of calcium lithogenicity because hypercalciuria is found in 30% to 60% of lithiasis patients. Calciuria is influenced by nutritional factors such as excessive salt, calcium, and proteins intake [9] [14] [16] [23] [24]. In this study higher intake of salt, calcium and proteins were found in 34.1%, 40%, and 62.4% of cases, respectively.
Milk, dairy products, and drinking water are the main sources of dietary calcium [9] [16]. Digestive absorption of calcium represents 20% of the amount ingested, or 5 mmoL/d (200 mg), and the kidney is the only way out of calcium. Any excess sodium intake in food leads to increased urinary calcium excretion. It is also known that the consumption of animal proteins is associated with the increased incidence of calcium urolithiasis. The multifactorial effects of excess animal proteins include: lowering of urinary pH, increased excretion of calcium, uric acid, oxalate and a decrease in citrate excretion. [14] [25] [26] [27] [28]. Thus, sodium intake must be maintained around 6 and 7 g/d; whereas protein intakes should be normalized to 1 g/kg/day in adults [29] [30].
This dietary survey revealed that 68.2% of patients drank less than 1500 mL of water per 24 hours. High fluid intake has been shown to increase urine volume, reduce the concentration of calcium oxalate in urine, and reduce the risk of stone formation by 50% and the recurrence rate from 60% to 80% [31] [32]. Indeed, Zhuo et al. [11] demonstrated that fluid intake was significantly associated with the occurrence of urolithiasis. We believe that lower water intake in our study is due, at least partially, by limited access to clean drinking water. Water intake should be harmoniously distributed throughout the day and adjusted ac-  [31]. Remember that there are three categories of water; prepackaged natural mineral waters, prepackaged spring waters and water for public distribution (tap water), rainwater and well water; the latter being generally very low in calcium. Mineral and spring waters are the only ones that can take advantage of properties favorable to health, benefiting from an original nature and purity, coming from underground water free from any pollution, stable in their composition [9].
Finally, the small sample size of this hospital series is a limiting factor that must be taken into account in interpreting these results. But, beyond this possible limit, this study made it possible for the first time to describe the eating habits of lithic patients in the DRC.

Conclusion
In this study, high consumptions of vegetables and low water intake were linked to the formation of calcium oxalate monohydrate stones. More data are needed to confirm these findings.