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Different types of drinking water are available in Makka including Zamzam water. Zamzam water is characterized by a high mineral content. Thus, some urologists recommend that kidney patients not drink this water because it could worsen their health status. This study included 91 apparently healthy adult males with a long-standing pattern of drinking water and living in Makka. They were classified into four groups according to their water intake pattern as follows: GI (n=24) Zamzam water, GII (n=25) desalinated purified water, GIII (n=25) mineralized water and GIV (n=17) of mixed pattern. Serum levels of electrolytes and minerals, including sodium, potassium, chloride, calcium, magnesium, phosphorus, and iron were evaluated. Kidney functions including serum levels of urea, creatinine, and uric acid, as well as correlations to the type of water intake were determined. In comparison with GI, there was a significant decrease in serum levels of calcium (P<0.05) in GII, while a significant increase in sodium (P<0.001) and chloride (P<0.05) in GIII was observed. In respect to renal function tests, people who are entirely dependent on Zamzam (GI) have a similar pattern with the other groups, except a significant decrease in serum urea (P<0.05) in GIII when compared to other groups. Significant correlations between the parameters in the serum of all subjects were observed. This study suggests that the higher mineral content of Zamzam did not change the serum levels of minerals and electrolytes in people whom primarily drink Zamzam and it has no negative effect on their kidney function.
Key words: Zamzam water, electrolytes, water minerals, kidney function.
Drinking water is considered as an important source of mineral intake because waterborne minerals (ionic form) are easily absorbed by the gastrointestinal tract (Heaney and Dowell, 1994). It has been established that deficiencies in mineral elements are the basis of immune systems defense impairment, decreased physical and mental development, and thus increased rate of morbidity and mortality. The water intake pattern is varies among people living in Makka, Saudi Arabia; some drink Zamzam water only, others are dependent on mineralized water and a few are dependent on well water. This variation in the water intake pattern may be reflected in their serum mineral content, because the different types of drinking water differ in their mineral content. The Zamzam well is present in Makka and it is characterized by high mineral content such as Ca2+, Mg2+, S2+, Fe2+, Mn2+, and Cu2+ (Shomar, 2012). The increase of calcium and magnesium in the drinking-water has a positive impact on the gastrointestinal absorption of minerals and decreases dietary intake of toxic metals (Kozisek, 2005). This is very important in hot weather such as that found in Makka because it would the key be replacing minerals lost through sweating and diuresis.
The pH of Zamzam water is alkaline, which might be because it is relatively high Ca2+, K+, and HCO3â€’ contents, which could explain its healing properties (Shomar, 2012). The beneficial role of the consumption of more alkaline water in several diseases has been reported in many studies (Ayne, 2008; Bertoni et al., 2002; Kellas et al., 1996; Koufman and Johnston, 2012; Whang, 1994; Wynn et al., 2009). Furthermore, the relationship between the quality and composition of water supplied to health has long been recognized. For example the inverse relation between water hardness and cardiovascular death has been reported in many previous studies (Catling et al., 2008; Derry et al., 1990; Ferrandiz et al., 2004; Monarca et al., 2009). However, water hardness was reported as risk factor for kidney stones in patients with renal disease (Bellizzi et al., 1999).
In humans, the catabolism of proteins and creatine produces urea and creatinine, respectively. While, uric acid is considered a major product from the catabolism of purine nucleosides (adenosine and guanosine). The majority of these nitrogen metabolites are eliminated through the kidneys. So, serum levels of creatinine, urea, and uric acid have been found to be fairly reliable indicators of kidney function. Their elevation signifies impaired kidney function or kidney disease, such as urolithiasis (formation of urinary calculi or stones in the urinary tract or bladder). The quantity and quality of water intake has a key role in urinary stone formation. Furthermore, the amount of mineral consumption depends on the volume of water ingested per day. Arid climates with relatively high temperatures such as in Mekka, lead to increased physical exertion and thus increased water requirements. Therefore, insufficient intake of water leads to permanent dehydration (even if slight) and thus increases the risk for urolithiasis.
On the other hand, the mineral content of water, especially magnesium and calcium, also plays an important role in stone formation. Many studies report that increases in the intake of water hardness (especially, calcium and magnesium) correlates with higher incidences of urolithiasis (Bellizzi et al., 1999). On the other hand, other reports state that excessively drinking soft water is associated with an increased risk of urolithiasis and kidney diseases (Buridi et al., 1998; Caudarella et al., 1998; Fink et al., 2009; Liao et al., 2012). However, epidemiological studies explain these conflicting results via various experimental designs, elucidating that the hardness value of drinking water in the commonly reported range is a non-significant factor in urolithiasis (Kellas et al., 1996; Kohri et al., 1993; Kohri et al., 1989; Ripa, 1993; Schwartz et al., 2002; Singh and Kiran, 1993). Therefore, our study aimed to evaluate the effects of four different types of drinking water in Makka (Zamzam, desalinated, mineralized, and mixed pattern) on the serum levels of minerals and kidney functions parameters. The possibility of Zamzam water to alter the kidney functions or serum levels of minerals, especially those that have a role in urinary stone formation such as Ca2+ and Mg2+, was studied.
Materials and methods
More than 150 healthy volunteers from Makka city were involved in this study from October 2009 to July 2010. After exclusion of subjects, the study included 91 volunteers. No one had a history of a pathological condition, such as primary hyperparathyroidism, kidney diseases, urinary tract infection, or hypercalcemia. Moreover, at the time of the study none was receiving prescription drugs, such as vitamin D, calcium supplements, or diuretics.
Venous fasting blood samples (10 ml) of the volunteers were drawn, and serum samples were collected after centrifugation (2500â€’3500 rpm for 5 min). Each serum sample was kept frozen at âˆ’20 °C in capped 10 ml serial plastic tube until analysis. Glassware and pipettes with metallic bodies were not used.
In each blood sample, serum levels of sodium (Na+), potassium (K+), and chloride (Clâ€’) were determined by ion-selective electrode (Annan et al., 1980).
Calcium (Ca2+) was evaluated by the o-cresolphthalein complexone method (Schwarzenbach, 1955). Ca2+ formed violet color complex with o-cresolphthalein complexone in alkaline conditions. The change in absorbance at 552 nm was proportional to the Ca2+ concentration in the serum sample.
Magnesium (Mg2+) was measured by the colorimetric method with chlorophophonazo III (Ferguson et al., 1964). Chlorophophonazo III reacted with Mg+ to form a colored complex (659 nm). Nonspecific absorbance interferences were reduced by EDTA. The difference in absorbance between the Mg-chlorophophonazo complex and the EDTA treated complex was calculated as the absorbance of magnesium alone.
Iron (Fe2+) was assayed by the iron guanidine/ferrozine® method (Stookey, 1970). Ascorbate and hydroxylamine reduced Fe3+ (which was released from transferrin by guanidine hydrochloride) to Fe2+. Ferrozine chelated ferrous ions and formed a red-colored complex, which was detected at 552 nm. The increase of absorbance is proportional to the iron concentration in samples.
Phosphate (PO42-) levels were determined by the direct phosphomolybdate method, according to Daly and Ertingshausen (Henry, 1964). Inorganic phosphate reacted with ammonium molybdate in an acidic solution to from non-reduced phosphomolybdate, which was measured as colorimetric at 340 nm. The increase of absorbance was proportional to the inorganic phosphate concentration.
Kidney function was assessed by determining the serum levels of urea, uric acid, and creatinine. Serum urea was evaluated using the kinetic test with urease glutamate dehydrogenase method (Sampson et al., 1980). Urease enzyme hydrolyzed urea to carbon dioxide and ammonia. Ammonium ion and 2-oxoglutarate were converted into glutamate and water by the catalyzing action of glutamate dehydrogenase. Simultaneously to this conversion, nicotiamide adenine dinucleotide (NADH) was oxidized into NAD. The decrease of absorbance by the glutamate dehydrogenase reaction was recorded at 340 nm.
The enzymatic colorimetric test by uricase-peroxidase method was used to measure uric acid (Fossati et al., 1980). Uricase enzyme oxidized uric acid to allantoin and hydrogen peroxide. Peroxidase catalyzed the reaction mixture of hydrogen peroxide, 4 -aminoantipyrine (4-AAP), and 3,5-dichloro-2-hydroxybenzene sulfonate (DCHBS) to produce a colored product, which measured at 520 nm. The change in absorbance was proportional to the concentration of uric acid in the serum samples.
Creatinine was assessed using the buffered kinetic Jaffe reaction (Jaffe, 1886). The creatinine was changed into a creatinine-picrate complex by picrate in an alkaline solution. The concentration of creatinine in the sample was proportional to the change in absorbance at 520 nm.
All parameters were analyzed using the fully automated, computerized chemistry analyzer (COBAS INTEGRA 400 plus, Roche Diagnostics GmbH, Switzerland).
The data were represented as mean ± SD. The obtained results were statistically analyzed using IPM SPSS statistics version 21. Statistical analyses between the different variables were calculated according to one-way ANOVA analysis of variance with Tukey's multiple comparison tests. The statistical significance of the correlation coefficient was determined using the Pearson correlation coefficient. Statistical significance (P<0.05) was indicated.
In this study, the volunteers were selected in the age range of 18â€’25 years because the men in this age stratum are relatively healthy and have no kidney diseases. They were classified into four groups, according to their long standing pattern of drinking water (3 years or more) (Table 1).
Serum levels of minerals and electrolytes
The levels of each parameter in serum from volunteer subjects are shown in Figure 1. The mean Na+ level for the 24 subjects whose daily maximum intake pattern is Zamzam water (GI) is 138.42±1.64 mmol/dl (Fig. 1A). While, it is slightly elevated in two other groups (GIII and GIV) reaching to 140.84 ± 1.46 mmol/dl in the group which drinks mineralized water (GIII) with highly significant difference (P<0.001). The mean K+ level of GI is 4.31±0.37 mmol/dl, and the lowest value between groups is observed in the mixed pattern group (GIV), where it is 4.04±0.34 mmol/dl (Fig. 1B).
Among those whose intake was mineralized (GIII) there was a significant increase in the serum levels of Clâˆ’ (104.72 mmol/dl) in comparison with its levels in GI (P<0.05) and GII (P<0.05). Serum Ca2+ recorded the lower levels in desalted water group (GII) with a significant difference in comparison to GI (P<0.05) and GIII (P<0.01) (Fig. 1D). The serum levels of phosphorous, magnesium, and iron are shown in Figure 1Câ€’G, and the differences between the four groups are not significant.
Serum levels of kidney functions parameters
The parameters of renal function are summarized in Figure 1Hâ€’J. Our results show that the mean urea levels of the mineralized group (GIII) were slightly lower than other groups (26.88±3.8 mg/dl), with a significant difference with GI (P<0.05) (Fig. 1H). However, the differences between the four groups are not significant in uric acid and creatinine (Fig. 1Iâ€’J).
Comparison and relationships of all parameters
Figure 2 shows a scatter plot of the most significant correlated parameters in the serum of all subjects in the study. Serum sodium has a significant positive Pearson correlation coefficient with potassium (r=0.26, P<0.01) and chloride (r=0.56, P<0.001) Fig. 2Aâ€’B. A positive correlation between calcium and potassium (r=0.36, P<0.001) and magnesium (r=0.31, P<0.01) was observed (Fig. 3C and G). However, chloride showed a negative correlation with calcium (r=âˆ’0.21, P<0.05), magnesium (r=0.26, P<0.01), and phosphorus (r=0.35, P<0.001) Fig. 3 Dâ€’F. There is a significant correlation found between the serum levels of creatinine and uric acid (r=0.34, P<0.01) (Fig. 3I).
WHO Guidelines define safe drinking-water as "does not represent any significant risk to health over a lifetime of consumption" (World Health Organization., 2011). The drinking of Zamzam water for centuries by natives and visitors of Makka without any risk to human health authenticates that it is the safe drinking-water by this definition. Additionally, many studies have investigated the potability of Zamzam water and described its purity and mineral contents (Al-Ansi et al., 2011; Alfadul and Khan, 2011; Naeem et al., 1983; Shomar, 2012). Collectively, these studies report that Zamzam water contains 34 elements with relatively high levels of calcium (Ca), magnesium (Mg), sodium (Na), and chloride (Cl). It also has wonderful physicochemical properties that give it advantage over other drinkable liquids because it is naturally pure and sterile. However, the effect of Zamzam water on the serum levels of these minerals has never been studied. We, therefore, urge more biochemical studies to determine the effect of Zamzam water drinking on the serum levels of minerals and electrolytes and whether there are adverse effects of Zamzam water on kidney functions for some Makka populations.
Furthermore, the chemical composition of drinking water varies widely depending on the source of water. Some types of drinking water are characterized by high mineral contents, others are moderate and a few are nearly mineral deficient. Mineral content of water may affect the serum and urine electrolyte and mineral levels, and in the long term may affect their kidney functions (Coen et al., 2001). Health outcomes of those living in Saudia Arabia, especially in Makka, may be affected by the specific type of water available to them. Previous studies suggest that increases in drinking water hardness may have an adverse health effects and may increase urinary stone incidence on long term consumption (Coen et al., 2001). The study was conducted to show the effect of different water intake patterns on the health of the people of Makka.
In this study, serum levels of Na+ and Clâˆ’ were significantly elevated in the group with a mineralized water intake pattern as compared to all groups, while there was no significant difference between the mean Na+ levels between the group of Zamam and desalinated or mixed pattern (Fig. 1A and 1C). This may be due to the high content of sodium chloride in mineralized water. Previous clinical studies reported that increased levels of sodium and chloride led to an increase in mean arterial pressure and systolic blood pressure and changed parameters for glucose and lipid metabolism in individuals drinking mineral water (Schorr et al., 1996). Therefore, increased serum levels of sodium and chloride is a contraindication for patients with hypertension, heart, kidney, and circulatory diseases. The results of increased levels of Na+ and Clâˆ’ in the serum of people in GIII may be an issue of health interest because of their disability to maintain the desired body balance of sodium (Beers and Berkow, 2004). Moreover, we could explain the decrease the Clâˆ’ levels in the Zamzam group in comparison to GIII by its high calcium content and pH. Calcium forms complexes with other anions in water, especially chlorides as well as with nitrates, bicarbonates, sulfates and hydroxides. This complex prevents absorption of Ca2+ and Clâˆ’, and thus decreases their bioavailability readings. Above pH 8.0 such as Zamzam water, the possibility of complex formation increases, and thus decreasing the amounts of absorbed calcium (World Health Organization., 2009).
Calcium levels decreased significantly in the desalinated water intake pattern comparing to the Zamzam (P<0.05) or mineralized (P<0.01) groups. This is in agreement with a previous study (Kozisek, 2005) and could be explained by the replacement of calcium (as a source of hardness) by sodium in desalinated water. This data shows a need to consider the addition of calcium ions to desalinated water as part of the stabilization process to be used as a drinking-water. Adverse effects are unacceptable, while positive benefits are practicable. However, the serum levels of magnesium show no significant difference between the studied groups, in spite of the difference in hardness between the three types of water.
The correlation between the studied parameters (Fig. 3) indicate that the presence of several inorganic elements could be a source of the interaction between others, either synergistically or antagonistically, and the high content of one may enhance or reduce the absorption or bioavailability of another (World Health Organization., 2009).
In respect to renal function tests, people who are entirely dependent on Zamzam water have a similar pattern with the 3 other groups, except a significant decrease (P <0.05) in serum urea in GIII (those persons whom their daily maximum water intake is mineralized water) (Fig. 1H). This slight decrease in urea level with normal creatinine levels (Fig 1I), is mostly seen in subject with an increased plasma volume, simply due to increased water intake/day. This may be a behavior for those people entirely dependent on mineralized water.
In conclusion, regarding persons whose daily maximum water intake is Zamzam water, the characteristic high mineral content of Zamzam water did not change their mineral and electrolyte levels upon long term consumption in comparison to other groups, also their kidney function tests are within the range of other groups. Additionally, the elevated sodium level found in persons whose daily maximum water intake is mineralized water suggests that this pattern of water drinking is not suitable for hypertensive patients as it may have a share in keeping their blood pressure high. This study also concludes that serum minerals and electrolytes, as well as urea, creatinine and uric acid are within the normal ranges in people using the different types of drinking water available in Makka city. These findings should be confirmed by a study on a larger scale, as the small sample size of our study is a limitation, but we think that the results obtained are reliable.
We thank Dr. Ahmad Ashi, Department of Laboratory Medicine UQU for his valuable support to this study. We would also like to thank our students: Mohammed Ali Al-Zahrani, Abdulla Salem Al-Matrafi, Ayman Mohammed Al-Saadi and Faisal Khalid Al-Malki, for their valuable participation in this work.