Seasonal variation of water and electrolyte in serum with respect to homeostasis

Total Water Intake from Beverages and Foods Is Associated with Energy Intake and Eating Behaviors in Korean Adults

Water is essential for the proper functioning of the body. Even though a recommendation exists for adequate water intake for Koreans, studies identifying actual water intake from all beverages and foods consumed daily in the Korean population are limited. Thus, we estimated total water intake from both beverages and foods and its association with energy intake and eating behaviors in Korean adults. We used a nationally representative sample of 25,122 Korean adults aged ≥19 years, from the Korean National Health and Nutrition Examination Survey 2008–2012. We performed multiple regression analyses, adjusting for sociodemographic and health-related variables to investigate the contribution of overall energy and dietary intakes and eating behaviors to total water intake. The mean total water intake excluding plain water was 1071 g (398 g from beverages and 673 g from foods) and the estimated plain water intake was 1.3 L. Among Korean adults, 82% consumed beverages (excluding plain water) and these beverages contributed to 10% of daily energy intake and 32% of total water intake from beverages and foods. For every 100 kcal/day in energy intake, water intake consumed through beverages and foods increased by 18 g and 31 g, respectively. Water intake from beverages and foods was positively associated with energy from fat and dietary calcium, but inversely associated with energy density and energy from carbohydrates. When there was a 5% increase in energy intake from snacks and eating outside the home, there was an increase in water intake from beverages of 13 g and 2 g, respectively. Increased daily energy intake, the number of eating episodes, and energy intake from snacks and eating outside the home predicted higher water intake from beverages and foods. Our results provide evidence suggesting that various factors, including sociodemographic status, dietary intakes, and eating behaviors, could be important contributors to the water intake of Korean adults. Findings from this cross-sectional analysis may provide insight into strategies for promoting adequate water intake among Koreans.

Decline in the prevalence of anaemia among children of pre-school age after implementation of wheat flour fortification with multiple micronutrients in Jordan

Objective

To examine changes in the prevalence of anaemia and its correlates among children of pre-school age after implementation of wheat flour fortification with multiple micronutrients in Jordan.

Design

Retrospective analysis of the data from two repeated national cross-sectional panels of pre-school children.

Setting

The two surveys were conducted in 2007 and 2009, 16–20 months and 34–36 months, respectively, after implementation of wheat flour fortification with multiple micronutrients in Jordan. Anaemia was considered if Hb level was <11 g/dl. An anaemia prevalence of ≥40 % was considered a severe public health problem, while that of 20–39·9 % was considered a moderate public health problem.

Subjects

A total of 3789 and 3447 children aged 6–59 months tested in 2007 and 2009, respectively.

Results

The prevalence of anaemia in pre-school children declined from 40·4 % in 2007 to 33·9 % in 2009 (adjusted OR=0·74; P<0·001). The decline in the prevalence in 2009 as compared with 2007 was more pronounced among children aged >24 months (−13·7 points), children living in urban areas (−8·0 points), children from rich households (−9·0 points), children who had never been breast-fed (−17·0 points) and well-nourished children (−6·8 points). In both surveys, presence of childhood anaemia was strongly associated with child age ≤24 months, living in poor households, breast-feeding for ≥6 months, malnourishment, poor maternal education and maternal anaemia.

Conclusions

The public health problem of childhood anaemia declined from severe in 2007 to moderate in 2009, after the implementation of wheat flour fortification with multiple micronutrients in Jordan.

Seasonal influence over serum and urine metabolic markers in submariners during prolonged patrols

Within the framework of earlier publications, we have consistently dedicated our investigations to eliciting the effects of both seasonal vitamin D deficiency and submarine-induced hypercapnia on serum parameters for acid–base balance and bone metabolism in submariners over a 2-month winter (WP) or summer (SP) patrols. The latest findings reported herein, contribute further evidence with regard to overall physiological regulations in the same submariner populations that underwent past scrutiny. Hence, urine and blood samples were collected in WP and SP submariners at control prepatrol time as well as on submarine patrol days 20, 41, and 58. Several urine and serum metabolic markers were quantified, namely, deoxypyridinoline (DPD), lactate, albumin, creatinine, nonesterified fatty acids (NEFA), and ionized sodium (Na⁺) or potassium (K⁺), with a view to assessing bone, muscle, liver, or kidney metabolisms. We evidenced bone metabolism alteration (urine DPD, calcium, and phosphorus) previously recorded in submarine crewmembers under prolonged patrols. We also highlighted transitory modifications in liver metabolism (serum albumin) occurring within the first 20 days of submersion. We further evidenced changes in submariners’ renal physiology (serum creatinine) throughout the entire patrol time span. Measurements of ionic homeostasis (serum Na⁺ and K⁺) displayed potential seasonal impact over active ionic pumps in submariners. Finally, there is some evidence that submersion provides beneficial conditions prone to fend off seasonal lactic acidosis (serum lactate) detected in WP submariners.

Water balance and body weight: Studies in a tropical climate

Total body weight, water balance and energy balance were estimated in young adult men in a hot climate, over three 6-day periods. The aim was to determine the relative contributions to body weight changes of fluctuations in water and energy stores. In these subjects, the small observed body weight changes were due almost entirely to water balance changes. Water balance was regulated to within +/- 1% of body weight from day-to-day.

Seasonal variation of pretransfusion hemoglobin levels in patients with thalassemia major

Patients with thalassemia major often report that they do not maintain their usual pretransfusion hemoglobin concentration during the summer season. We collected 3977 pretransfusion hemoglobin values, amount of blood transfused, and intertransfusion intervals for 94 patients with thalassemia major from 4 centers worldwide. We also assessed the hematocrits of blood donors, the hemoglobin content of units transfused in one center, and the local mean monthly temperatures during the periods of data collection. Pretransfusion hemoglobin levels were significantly lower during the summer in all centers except the one center where monthly temperatures have the least variation throughout the year. A similar relationship to temperature was observed for the hematocrits of blood donors and the hemoglobin content of donor units. This study confirms that pretransfusion hemoglobin levels in patients with thalassemia major are lower in the summertime. Possible mechanisms include expansion of plasma volume with resultant hemodilution in the patient and lower hemoglobin content in donor blood.

Haematocrit: within-subject and seasonal variation

This review was undertaken, concerning within-subject biological variation and seasonal variation of haematocrit in normal healthy adults and athletes, to find the limits for natural, intra-individual variation in haematocrit values. The terminology and calculations followed well defined theories, from the field of laboratory medicine, about biological variation. Based on results from 12 studies of 638 normal healthy adults, and which used a sampling interval of 1 day to 1-2 months, the coefficient of within-subject biological variation of haematocrit is 3%. The normal within-subject biological variation (3%) and analytical variation (3%) may explain a relative change of approximately 12% (95% level) [e.g. a change from 0.42-0.47] between two successive haematocrit values, measured with a time interval between 1 day and 1-2 months, in a normal healthy adult. Partly due to haemodilution in warm weather, haematocrit often has a seasonal variation in normal healthy adults; based on results from 18 studies of 24 793 participants, the population mean is approximately 3% lower in summer than winter. Population mean values that are 7% lower in summer than winter have been found in some studies, although no seasonal effect may also be seen, especially in temperate climates. If haematocrit values are sampled at yearly peak and trough time points, with intervals of up to 6 months, a 15% relative change (95% level) can be seen in a normal healthy adult; e.g. a change from 0.42-0.48. Published values for haematocrit in athletes are scarce. It is known that the haematocrit value is influenced by training, especially in the first weeks before a new steady-state is reached. Theoretically, the biological variation in athletes could therefore be greater than in normal individuals. Based on two references addressing the biological variation of haematocrit in athletes, however, the above results are also valid for athletes. Further studies, both in the short term and throughout the seasons, are recommended about the natural variation of haematocrit in athletes.

Changes in blood volume and vascular compliance during body heating in rats

The effects of hyperthermia on blood volume and effective vascular compliance were studied in control and heat acclimated rats (three weeks at 32 degrees C and 50% R.H.). Experiments were performed on conscious rats whose abdominal aorta and both jugular veins were cannulated. Continuous changes in blood volume (BV) were monitored by measuring 51Cr tagged erythrocyte dilution, using an arterio-venous extracorporeal shunt passing through a gamma counter. Total vascular compliance was calculated from the relation between changes in BV and central venous pressure during 10 min of infusion of saline at a rate of 1.6% body wt/10 min. Hyperthermia induced a significant blood volume expansion. This expansion was more pronounced in non-acclimated rats. Effective vascular compliance was similar in the normothermic, both non-acclimated and acclimated rats. However, while hyperthermia did not affect the vascular compliance of non-acclimated rats, it was decreased significantly in the acclimated hyperthermic rats. The data suggest that changes in vascular compliance play a role when rapid blood volume changes take place, especially in acclimated hyperthermic animals. The relations between changes in vascular compliance and heat induced redistribution of cardiac output are discussed.

[Seasonal variation of blood components important for diagnosis (author's transl)]

In a comparative study, the differences between the values measured for 26 blood and serum components in both winter and summer were determined in 78 healthy subjects. Comparable conditions during the preparation of test persons, sampling, processing of specimens, and measurement were strictly observed. The term "season" is defined more precisely by meterological data. In the summer season, significantly higher values were found for leukocytes (9%), lactate dehydrogenase and MCHC (7% each), creatinine (7%, in women only), and MCH (1%) whereas significantly lower values were exhibited by aspartate aminotransferase (18%), alanine aminotransferase (14%), alkaline phosphatase (11%), glucose and packed cell volume (7% each), MCV (6%), total protein (2%), erythrocytes, albumin, sodium and chloride (1% each). These partly considerable alterations should be taken into account in the establishment of reference values and evaluation of laboratory findings (above all, when intraindividual comparison is involved). There were no significant alterations of the following parameters: hemoglobin, gamma-glutamyl transferase, urea, uric acid, creatinine (men only), bilirubin, cholesterol, total glycerol, potassium, calcium, and inorganic phosphate. In another series of experiments involving 32 test persons, the influence of different ambient temperatures during blood sampling on the above mentioned blood components was studied. Within the 18-30 degrees C range, no significant alterations were detected.

Seasonal variations in vasopressin secretion in rats

Plasma vasopressin concentrations and vasopressin content in neurohypophysis in rats show seasonal variations; namely, high in summer and low in winter.