Risk factors for development of decreased kidney function in a southeast Asian population: a 12-year cohort study

End-stage kidney disease has become an increasing burden in all regions of the world. However, limited epidemiologic data on chronic kidney disease in Southeast Asian populations are available. Therefore, a cohort study over a period of 12 yr (1985 to 1997) in 3499 employees of the Electric Generation Authority of Thailand, aged 35 to 55 yr, was conducted to determine the prevalence of decreased kidney function and risk factors associated with future development of decreased kidney function. The prevalence of decreased kidney function (GFR <60 ml/min) increased from 1.7% (95% confidence interval [CI], 1.3 to 2.1) in 1985 to 6.8% (95% CI, 5.7 to 7.9) in 1997, and the prevalence of elevated serum creatinine was 6.1% (95% CI, 5.3 to 6.9) and 16.9% (95% CI, 15.3 to 18.5) in 1985 and 1997 surveys, respectively. The adjusted odds ratio for future development of decreased kidney function was 2.57 (1.0 to 6.81) for systolic hypertension (>159 mmHg), 1.82 (1.12 to 2.98) for hyperuricemia (>6.29 mg/dl), 1.68 (1.02 to 2.77) for elevated body mass index (>24.9 kg/m(2)) compared with subjects with systolic BP <140 mmHg, serum uric acid <4.5 mg/dl, and body mass index 20.8 to 22.8 kg/m(2). The rising prevalence of decreased kidney function in this population resulted mainly from the increasing prevalence of the risk factors in the population. Screening to detect decreased kidney function and early intervention to modify the associated risk factors should be considered in otherwise healthy individuals. Future studies are also necessary to determine whether implementation of these measures results in a reduction of ESRD incidence in the population.     

Does zinc deficiency play a role in stunting among primary school children in NE Thailand?

Stunting in school-age years may result in a decrease in adult size, and thus reduced work capacity and adverse reproductive outcomes. We have compared the mean intakes of energy, protein and selected growth-limiting nutrients in fifty-eight stunted children and 172 non-stunted controls drawn from 567 children aged 6-13 years attending ten rural schools in NE Thailand. Control children were selected randomly after stratifying children by age in each school. Dietary data were calculated from 24-h recalls using nutrient values from Thai food composition data and chemical analysis. Inter-relationships between stunting and sociodemographic, anthropometric and biochemical variables were also examined. Biochemical variables investigated were serum albumin, zinc, ferritin, transferrin receptor and retinol, and iodine in casual urine samples. Significantly more males than females were stunted (males, n 38, 65.5% v. females, n 20. 34.5%: P=0.025). Stunted males had lower mean intakes of energy, protein, calcium, phosphorus and zinc, and a lower mean (95% CI) serum zinc (9.19 (8.53, 9.84) v. 9.70 (8.53, 9.29) micromol/1) than non-stunted males; no other biochemical differences were noted. Stunted males also had a lower mean arm muscle area (P= 0.015), after adjusting for age, than non-stunted males. In conclusion, the lower dietary intakes of the stunted males compared to their non-stunted counterparts may be associated with anorexia and hypogeusia induced by zinc deficiency. Hence, zinc deficiency may be a factor limiting linear growth, especially among boys in NE Thailand, but more research is needed to establish whether other factors also play a role.     

Low zinc,iron, and calcium intakes of Northeast Thai school children consuming glutinous rice-based diets are not exacerbated by high phytate

Phytate, a salt of phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate), is found in certain plant-based foods. It strongly chelates minerals, forming insoluble complexes in the small intestine that cannot be digested or absorbed. Information on the phytate content of rice-based diets of children in Northeast Thailand is limited. In this study 1-day weighed duplicate diet composites were collected from 40 Northeast Thai children (age 6–13 years) randomly selected from participants (n=567) of an efficacy trial in Ubon Ratchathani province. Diet composites were analyzed for zinc, iron, and calcium by atomic absorption spectrophotometry, and for phytate (as inositol penta-phosphate and hexa-phosphate) by high-performance liquid chromatography; the accuracy and precision were established using a certified reference material for the minerals and an inter-laboratory comparison for phytate. The median (1st, 3rd quartiles) zinc, iron, and calcium contents of the diet composites were 4.3 (3.7, 6.1), 4.3 (3.2, 6.5) and 130 (82, 216) mg/day, respectively. The inositol penta-phosphate and hexa-phosphate levels were so low they were below the detection limit, attributed in part to leaching of water-soluble potassium and magnesium phytate from glutinous rice after soaking overnight before cooking. Clearly, phytate will not compromise mineral absorption from these diets. Instead, low zinc intakes are probably primarily responsible for the low zinc status of these children. In contrast, although intakes of dietary iron appear low, the prevalence of biochemical iron deficiency was also low, suggesting that iron absorption may have been higher than previously assumed. Whether the low calcium intakes compromise optimal bone health in these growing Northeast Thai school children is unknown.     

Primary school children from northeast Thailand are not at risk of selenium deficiency

Selenium has important roles as an antioxidant, in thyroid hormone metabolism, redox reactions, reproduction and immune function, but information on the selenium status of Thai children is limited. We have assessed the selenium status of 515 northeast Thai children (259 males; 256 females) aged 6 to 13 years from 10 rural schools in Ubon Ratchthani province. Serum selenium (n=515) was analyzed by Graphite Furnace Atomic Absorption Spectrophotometry and dietary selenium intake by Hydride Generation Absorption Spectrophotometry from one-day duplicate diet composites, from 80 (40 females; 40 males) randomly selected children. Inter-relationships between serum selenium and selenium intakes, and other biochemical micronutrient indices were also examined. Mean (SD) serum selenium was 1.46 (0.24) micro mol/L. Concentrations were not affected by infection or haemoglobinopathies, but were dependent on school (P< 0.001), sex (P=0.038), and age group (P=0.003), with serum zinc as a significant covariate. None of the children had serum selenium concentrations indicative of clinical selenium deficiency (i.e. <0.1 micro mol/L). Significant correlations existed between serum selenium and serum zinc (r= 0.216; P < 0.001), serum retinol (r = 0.273; P < 0.001), urinary iodine (r = -0.110; P = 0.014), haemoglobin (r = 0.298; P <0.001), and haematocrit (r = 0.303; P< 0.001). Mean (SD) dietary selenium intake was 46 (22) micro g/d. Children with low serum selenium concentrations had a lower mean selenium intake than those with high serum selenium concentrations (38 +/- 17 vs.51 +/- 24 micro g/d; P< 0.010). In conclusion, there appears to be no risk of selenium deficiency among these northeast Thai children.     

Low zinc, iron, and calcium intakes of Northeast Thai school children consuming glutinous rice-based diets are not exacerbated by high phytate

Phytate, a salt of phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate), is found in certain plant-based foods. It strongly chelates minerals, forming insoluble complexes in the small intestine that cannot be digested or absorbed. Information on the phytate content of rice-based diets of children in Northeast Thailand is limited. In this study 1-day weighed duplicate diet composites were collected from 40 Northeast Thai children (age 6-13 years) randomly selected from participants (n=567) of an efficacy trial in Ubon Ratchathani province. Diet composites were analyzed for zinc, iron, and calcium by atomic absorption spectrophotometry, and for phytate (as inositol penta-phosphate and hexa-phosphate) by high-performance liquid chromatography; the accuracy and precision were established using a certified reference material for the minerals and an inter-laboratory comparison for phytate. The median (1st, 3rd quartiles) zinc, iron, and calcium contents of the diet composites were 4.3 (3.7, 6.1), 4.3 (3.2, 6.5) and 130 (82, 216) mg/day, respectively. The inositol penta-phosphate and hexa-phosphate levels were so low they were below the detection limit, attributed in part to leaching of water-soluble potassium and magnesium phytate from glutinous rice after soaking overnight before cooking. Clearly, phytate will not compromise mineral absorption from these diets. Instead, low zinc intakes are probably primarily responsible for the low zinc status of these children. In contrast, although intakes of dietary iron appear low, the prevalence of biochemical iron deficiency was also low, suggesting that iron absorption may have been higher than previously assumed. Whether the low calcium intakes compromise optimal bone health in these growing Northeast Thai school children is unknown.