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Discussion

Public health effectiveness depends on both coverage and efficacy of treatment. This trial dealt with the latter. Fluid management of acute diarrhoea includes two stages. If possible, hydration should be properly maintained through adequate provision of fluid, to prevent fluid loss. If dehydration occurs, replacement therapy should be promptly initiated, and continuing losses should be maintained adequately to prevent further water and electrolyte imbalances [12, 21, 22, 38]. The main reason for conducting the clinical trial was to assess whether the RBG, prepared the way mothers do it in the village [26], could be considered safe as an oral hydration solution at the community level. The trial was an extreme test for a beverage intended to be used at the home level, where children with diarrhoea have no or only mild dehydration that is not severe enough for hospital admission. Based on the outcomes, RBG was not only as efficacious as the standard ORS currently in use by the Ministry of Health, but was actually more so. Mildly to moderately dehydrated children who were given RBG gained more weight, took less time to rehydrate, and had lower faecal output than children given ORS.

TABLE 3. Serum sodium on admission and discharge of RBG and WHO patients

RBG group p < .01; WHO group p = .09.

TABLE 4. Sodium in the faeces on admission and discharge in the RBG and WHO groups

NS = not significant.
a. t test.

The physiological mechanism that underlies the afficacy of rice-based beverages to rehydrate children is related to the continuous movement of water and electrolytes in and out of the gastrointestinal lumen, which responds to passive and active forces, the latter fueled basically by glucose. To give an idea of the magnitude of fluid flux, consider that, in a healthy adult, about 8 L fluid/day enters the small bowel and only 100 ml is normally excreted in stools. Only 25% of the fluid entering the small bowel is ingested; the remainder is secreted by the intestine [10]. An even greater proportion of fluid is secreted into the lumen during diarrhoea, which is caused more by an increased secretion of fluid into the gut than by reduced absorption of water [9].

Several studies show that the stool output is markedly reduced when cooked rice is given as part of an oral rehydration solution because of the slow liberation of glucose molecules from starch, the main carbohydrate present in rice [39, 40]. After ingestion, 50 g rice powder releases more than twice the amount of glucose present in standard ORS but contributes a considerably lower osmolar load to the solution [41 43]. The presence of glucose allows for greater reabsorption of sodium than would be possible with standard ORT, as the amount of glucose that can be added, keeping the equimolar ratio with sodium, is limited by the osmolar load of both elements. Thus, efficient reabsorption of electrolytes from fluid secreted into the intestinal lumen will prevent hyponatraemia over the short term, even in the face of increased losses during diarrhoea.

Our findings are in line with the results of clinical trials that used rice-based oral rehydration solutions with salts added according to WHO recommendations [31, 32, 39, 40, 44]. The almost complete lack of sodium in our test beverage (3 mEq/L) and the addition of a seemingly high amount of sugar (60 g/L) made these outcomes surprising to clinicians. The arguments were that a beverage lacking sodium would produce hyponatraemia, and that the amount of sugar added would make a hyperosmolar solution, which would worsen diarrhoea.

Actually, theoretical calculations showed that twice as much sugar would be required to produce a slightly hyperosmolar solution [26]. In fact, the added sucrose, as well as the natural starch present in the rice gruel, provides glucose, which enhances the carbohydrate sodium transport mechanism [45-47], thereby increasing the uptake of sodium and water secreted by the enterocyte to the intestinal lumen during diarrhoea [41]. We found that faecal sodium was 66% lower on discharge in the children fed RBG, despite similar faecal sodium concentrations on admission in both the RBG and the ORS groups, and only 2% difference in serum sodium levels at discharge.

On the other hand, serum sodium at discharge was significantly higher in the control group. Although no children had clinical signs of hypernatraemia, this finding was reported by other authors when rehydrating children with the standard WHO solution [48, 49]. The high levels of sodium in the formulation of the oral rehydration mixture proposed by WHO were based on experience in treating the most devastating of the secretory diarrhoeas, cholera, which causes heavy losses of sodium, leading to clinical hyponatraemia [4, 50 53]. However, where cholera is not endemic, such as in Mexico, most diarrhoeas, even the secretory ones due to rotavirus and E. coli, are not associated with heavy losses of sodium [54-56]. We identified a specific enteropathogen in only 14 patients (16% of the whole group), none associated with heavy loss of sodium.

Despite its relevance for only a small proportion of diarrhoeas [57 59], the utility of having a single solution for managing all cases of diarrhoea led to the widespread use of the WHO formula [38, 60]. Before our study, two trials of rice water-based beverages without added salts and with a very low sodium concentration, similar to the one that we tested, were conducted in Singapore and India, both reporting success [55, 61]. However, ours is the first trial to test a rice-powder solution with no added electrolytes but with added sugar.

Earlier findings regarding the widespread use and acceptability of the RBGs add significantly to the rationale for their inclusion in home-based strategies for the management of diarrhoea. An ethnographic study indicated that only 18% of mothers used standard ORS, but 80% used the rice-powder gruel in the home management of diarrhoea [26]. Similar findings were described in national surveys [62- 64] and worldwide [65]. Mothers commonly give their children rice-powder beverages to treat diarrhoea. They should now be taught that these beverages can also be given to prevent dehydration or to maintain hydration.

In summary, the rice-powder gruel, with added sugar but without added electrolytes, tested in this study, prepared according to mothers' practices, was effective in returning hydration status to normal without causing hypernatraemia in mildly to moderately dehydrated children with acute diarrhoea.

Acknowledgements

The authors acknowledge the support received for this study from the resident medical and nursing staff of the Oral Hydration Ward of the Hospital Infantil de México, as well as the participation of Drs. H. Viais, D. Bross, and L. Posadas in the care of the hospitalized patients. The contribution of Drs. M. Latham, R. Cash, J. Snyder, and J. Calva to the discussion of the study design and the interpretation of the results is also fully acknowledged.

This study was carried out in partial fulfillment for the Ph.D. degree in International Nutrition of one of the authors (H.M.).

Financial support for this research was provided in part by the Applied Diarrheal Disease Research Project of Harvard University by means of a cooperative agreement with the US Agency for Inter national Development. Financial and logistical support was also received from the Hospital Infantil de México and the Instituto Nacional de la Nutrición, Mexico.

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