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Introduction: Reducing mean population sodium intake by ~1200 mg is projected to reduce thousands of deaths from heart disease and stroke and save billions of health care dollars annually. Twenty-four hour urine collection is recommended for assessing changes in mean population sodium intake, but can be difficult to implement. Predicting 24-hour urine sodium excretion using spot urines is not recommended due to diurnal variations in excretion. Further, sodium excretion patterns differ between black and white persons. We assessed the validity of previously published prediction equations for 24-hour sodium excretion in black and other young adults by timing of spot urine collection. Design: Of 481 adult volunteers aged 18-39 years (50% Blacks) asked to participate in a 2011 study in the Metropolitan DC area, 407 collected each urine void in a separate container for 24 hours. Four timed voids from the 24-h urine collection were selected (morning, afternoon, evening, and overnight) to use with previously published predictive equations. Predictive equations were based on one of two approaches; 1) an indirect approach using spot urine sodium-to-creatinine concentrations and predicted 24-hour creatinine excretion ( Tanaka, Kawasaki, Mage ), and 2) a direct approach using spot urine sodium, potassium, and creatinine concentrations, and age, and body mass index with separate equations by sex ( Brown ). We assessed mean differences between predicted and measured 24-hour sodium excretion (bias) and individual differences across levels of sodium excretion using Bland-Altman plots. Results: Among participants, mean measured 24-hour sodium excretion was ~3300 mg (SD ~1400 mg). Of the equations evaluated, mean bias in predicted 24-hour sodium excretion was least from Brown equations when using morning (-165 mg, 95% confidence interval [CI], -295, -36 mg), afternoon (-90 mg, 95% CI, -208, 28 mg) or evening ( -120 mg, 95% CI -230, -11 mg) spot urines. When using overnight spot urines, mean bias from Brown equations was greatest and statistically significant (-247 mg, 95% CI, -348, -151 mg). When using overnight spot urines, mean bias from Tanaka (-23 mg) or Mage (-145 mg) equations was not significant, however, when stratified by sex, mean biases were significant and in opposite directions. Among Blacks, mean biases from Brown were not significant (-167 to 122 mg) except using overnight specimens among Black females (-267 mg, 95% CI, -525, -47 mg). Across equations and time periods, Bland-Altman plots indicated significant bias at the individual level. Conclusions: Of the evaluated equations, predicted 24-hour urine sodium excretion using the Brown equations with morning, afternoon, or evening specimens may provide the least biased estimates of group mean sodium intake among young US adults. None of the equations adequately predicted individual 24-hour sodium excretion measured on the same day.

Use of dietary supplements is common among the U.S. adult population. Over 40% used supplements in 1988-1994, and over one-half in 2003-2006. Multivitamins/multiminerals are the most commonly used dietary supplements, with approximately 40% of men and women reporting use during 2003-2006. Use of supplemental calcium increased from 28% during 1988-1994 to 61% during 2003-2006 among women aged 60 and over. Use of supplements containing folic acid among women aged 20-39 did not increase since 1988-1994. In 2003-2006, 34% of women aged 20-39 used a dietary supplement containing folic acid. Use of dietary supplements containing vitamin D increased from 1988-1994 through 1999-2002 for men and women in most age groups. Dietary supplements can contain nutrients in amounts as high as or higher than the Institute of Medicine's Recommended Dietary Reference Intakes, therefore contributing substantially to total nutrient intake. Dietary supplements are widely available to U.S. consumers, and monitoring their use over time is an important component of the National Nutrition Monitoring System. Failure to include these nutrients when assessing the adequacy of diets and nutrition in the U.S. population may lead to inaccurate and misleading results. This report provides estimates of dietary supplement use for specific population groups over time. In addition to overall use of dietary supplements, this report focuses on estimates for specific nutrients consumed through dietary supplement use.

A randomized crossover trial on the effect of salt restriction on blood pressure was carried out involving 124 adolescents (mean age 16 years). Dietary sodium was reduced from approximately 110 to 45 mEq/24 h for a period of 24 days. Blood pressure was non-significantly lower at the end of the experimental diet for all participants. A slight (0.7 kg), yet statistically significant fall in weight was observed (P less than 0.05). Subgroup analysis demonstrated that participants whose body mass index was below the median had a statistically significant fall in systolic blood pressure (P less than 0.05); fall in weight and increase in heart rate were also more pronounced in the less obese individuals. It would appear that moderate sodium reduction does not have an overall short-term effect on blood pressure in normotensive adolescents. However, body size as reflected in body mass index may influence blood pressure response to sodium reduction.

A total of 417 individuals from all four major sex-race groups were examined for the rate of sodium flux via the countertransport pathway and the sodium concentration within red cells. The age span was from early adolescence to retirement. Males of both races had sizable higher countertransport rates than did women (p less than 0.01), and a slight increase in sodium concentration (p greater than 0.05). Contrariwise, while whites or both sexes had higher countertransport than their black counterparts, sodium concentration was higher in blacks than whites (p less than 0.01). This pattern is not consistent with a direct relationship between both countertransport or sodium concentration and blood pressure which applies across both racial groups. Sex-race differences must be taken into account in any group comparisons of these variables.

Differences in red cell sodium content and sodium-lithium countertransport were studied in black and white children with a mean age of 12 years. For both boys and girls red cell sodium content was higher in blacks and countertransport lower (P less than 0.05). For both ethnic groups red cell sodium was lower in girls than boys and a consistent positive relationship was noted between body mass index and countertransport. Despite the lower red cell Na-Li countertransport values in black compared to white children, a significant positive correlation with systolic blood pressure was found independent of adiposity. In contrast, no correlation was evident between Na-Li countertransport and blood pressure in the white children. If red cell cation transport is confirmed as a marker for hypertension, study of racial differences may help explain the twofold higher prevalence of this disease among blacks.

A total of 448 individuals ranging in age from 11 to 72 years were studied in a series of seven population-based surveys. Although the relationship was positive in all surveys, a significant correlation was noted between sodium-lithium countertransport and blood pressure in only three of the seven. Hypertensives as a group had significantly higher levels of countertransport than did those with a normal blood pressure. In stepwise regression analysis, however, entering weight into the equation eliminated a significant predictive effect of countertransport. Red cell sodium concentration and membrane leak did not bear any significant relationship to blood pressure. The association between countertransport and blood pressure appears to be weaker in the general population than previously reported for case-control studies.

High school students who had at least one parent with hypertension (n = 22) were compared to schoolmates of the same age with a negative family history of hypertension in the parents (n = 21). We investigated in both groups the maximal rate of the ouabain-sensitive Na pump and the Na-K cotransport in nystatin-loaded cells and the Lii-Nao countertransport in lithium-loaded cells. The two groups were significantly different only in the sum of net Na transport mediated by the Na-K pump and Na-K cotransport. The mean diastolic blood pressure in the positive family history group was significantly higher. With control for blood pressure the difference in the maximal rate of Na transport was no longer significant; it remains uncertain if control for blood pressure represents "over-adjustment'. The finding of a higher maximal rate of Na transport in these adolescents who are at increased risk of future hypertension, yet currently well within the normal range, suggests that abnormal sodium metabolism may be a useful marker and appears early in the pathogenesis of this disease.

A randomized, crossover trial was carried out on the effect of moderate sodium reduction on red-blood-cell sodium metabolism. The participants were healthy high school students (mean age = 16 years, n = 33). Changes in sodium-lithium countertransport and intracellular sodium concentration were evaluated 24 days after a decrease in dietary sodium from approximately 110 to 40 mEq per day. Dietary sodium restriction had no significant effect on either sodium-lithium countertransport or intracellular sodium concentration.