Dietary phosphorus intake estimated by 4-day dietary records and two 24-hour urine collections and their associated factors in Japanese adults

Meta-analysis guided development of a standard artificial urine

In this study, we present the first meta-analysis of human urine reported in the literature, drawing data from a total of 35 articles with a combined participant count of 14,021. Through this analysis, we have developed an artificial urine (AU) composition that can be adjusted within typical physiological parameters for in vitro applications. Our findings demonstrate the utility of this AU in determining the solubility of nitrofurantoin, particularly in the context of crystalluria. Notably, we observe that in saline, nitrofurantoin solubility, within the framework of its urinary pharmacokinetics, suggests a risk of crystalluria. However, in AU, this risk is mitigated due to complexation with urea. More broadly, we anticipate that our developed formulation will serve as a foundation for translational studies across biomedical and pharmaceutical sciences.

Urinary Phosphorus Excretion and Cardiovascular Outcomes in Patients with Pre-Dialysis Chronic Kidney Disease: The KNOW-CKD Study

The relationship between 24-h urinary phosphorus excretion (24 h UPE) and cardiovascular disease in patients with pre-dialysis chronic kidney disease (CKD) has rarely been studied, despite the fact that the relationship between serum phosphorus level and the risk of a cardiovascular event is well established. A total of 1701 patients with pre-dialysis CKD were finally included for the analyses and were divided into tertiles by 24 h UPE (first tertile (T1, 349.557 (mean) ± 88.413 (standard deviation)), second tertile (T2, 557.530 ± 50.738), and third tertile (T3, 851.695 ± 171.593). The study outcome was a six-point major adverse cardiac event (MACE). The median follow-up duration was 7.992 years. Kaplan-Meier curve analysis visualized that the cumulative incidences of a six-point MACE (p = 0.029) significantly differed from 24 h UPE levels, as the incidence rate of the study outcomes was highest in T1 and lowest in T3. Cox proportional hazard models unveiled that, compared to T1, the risk of a six-point MACE was significantly decreased in T3 (adjusted hazard ratio (HR) 0.376, 95% confidence interval (CI) 0.207 to 0.683). The restricted cubic spline curve analysis visualized an inverted S-shaped association between 24 h UPE level and the risk of a six-point MACE, indicating a significantly increased risk of a six-point MACE in patients with a low 24 h UPE level. In conclusion, low 24 h UPE is associated with adverse cardiovascular outcomes in patients with CKD. Our finding emphasizes that low 24 h UPE should not be a reliable marker for dietary restriction of phosphorus that essentially leads to better outcomes in patients with CKD.

Modification and Validation of the Phosphate Removal Model: A Multicenter Study

BACKGROUND

Our research group has previously reported a noninvasive model that estimates phosphate removal within a 4-h hemodialysis (HD) treatment. The aim of this study was to modify the original model and validate the accuracy of the new model of phosphate removal for HD and hemodiafiltration (HDF) treatment.

METHODS

A total of 109 HD patients from 3 HD centers were enrolled. The actual phosphate removal amount was calculated using the area under the dialysate phosphate concentration time curve. Model modification was executed using second-order multivariable polynomial regression analysis to obtain a new parameter for dialyzer phosphate clearance. Bias, precision, and accuracy were measured in the internal and external validation to determine the performance of the modified model.

RESULTS

Mean age of the enrolled patients was 63 ± 12 years, and 67 (61.5%) were male. Phosphate removal was 19.06 ± 8.12 mmol and 17.38 ± 6.75 mmol in 4-h HD and HDF treatments, respectively, with no significant difference. The modified phosphate removal model was expressed as Tpo4 = 80.3 × C45 - 0.024 × age + 0.07 × weight + β × clearance - 8.14 (β = 6.231 × 10-3 × clearance - 1.886 × 10-5 × clearance2 - 0.467), where C45 was the phosphate concentration in the spent dialysate measured at the 45th minute of HD and clearance was the phosphate clearance of the dialyzer. Internal validation indicated that the new model was superior to the original model with a significantly smaller bias and higher accuracy. External validation showed that R2, bias, and accuracy were not significantly different than those of internal validation.

CONCLUSIONS

A new model was generated to quantify phosphate removal by 4-h HD and HDF with a dialyzer surface area of 1.3-1.8 m2. This modified model would contribute to the evaluation of phosphate balance and individualized therapy of hyperphosphatemia.

Weight Gain, Energy Intake, Energy Expenditure, and Immunosuppressive Therapy in Kidney Transplant Recipients

BACKGROUND

Weight gain after kidney transplantation is a common health problem. The factors in weight gain after kidney transplant include many factors such as age, ethnicity, gender, change in lifestyle (eg, kilocalorie intake and physical activity level), and immunosuppressive therapy.

RESEARCH QUESTIONS

This study aimed to evaluate the relationship between weight gain and energy intake in dietary, energy expenditure in physical activity, and immunosuppressive therapy in kidney transplant recipients.

DESIGN

This prospective, observational study included 51 participants who underwent kidney transplant, during 6 months from the start of the study. Anthropometric measurements were performed at first week, third- and sixth-month follow-ups of transplant recipients. Participants also completed 3-day "Dietary Record Form" and the "Physical Activity Record Form" at each follow-up. Simple frequency, analysis of variance analysis, and correlation analysis were used for data analysis.

RESULTS

Weight gain in sixth month follow-up compared to baseline value was positively related to energy intake in first week (r = 0.59), third month (r = 0.75), and sixth month (r = 0.67) follow-ups, and energy expenditure in first week (r = 0.35) and sixth month (r = 0.34) follow-ups. However, weight gain was negatively related to mycophenolate mofetil dose (mg/d) in sixth month (r = -0.31) follow-up (P < .05).

DISCUSSION

The results of this study provide an opportunity to reflect and discuss on modifiable risk factors such as energy intake and energy expenditure that affect weight gain posttransplantation in participants. It also examines the relationship between immunosuppressive therapy. Additionally, these results can be effective in designing interventions and managing risk factors to achieve weight management goals.

Validity of a dish composition database for estimating protein, sodium and potassium intakes against 24 h urinary excretion: comparison with a standard food composition database

OBJECTIVE

We assessed the validity of a recently developed dish composition database (DCD) against urinary biomarkers compared with a standard food composition database (FCD).

DESIGN

Intakes of protein, Na and K were estimated by 2 × 24 h urine collections and by 4 d dietary record data based on the DCD (including 128 dishes) or FCD (including 1878 foods).

SETTING

Japan.

PARTICIPANTS

A total of 161 men and 163 women aged 20-69 years.

RESULTS

Compared with the 24 h urine-based estimates, the median intakes estimated using the DCD and FCD differed significantly for protein and Na in men and for Na and K in women. Deattenuated Spearman correlation coefficients using 24 h urine-based estimates for the intakes of protein, Na and K were lower in the DCD (respectively: 0·26, 0·15 and 0·44 in men; 0·22, 0·27 and 0·22 in women) than those in the FCD (respectively: 0·43, 0·40 and 0·59 in men; 0·33, 0·45 and 0·42 in women). When data on dish portion size reported by participants were used for estimation instead of standard portion-size data based on the DCD, the accuracy of the estimated median intakes did not change notably, whereas the deattenuated correlation coefficients improved (for protein, Na and K respectively: 0·32, 0·31 and 0·56 in men; 0·31, 0·41 and 0·39 in women).

CONCLUSIONS

The DCD supported by individual-level information on dish portion size showed fair to moderate validity in ranking individuals according to their intakes of protein, Na and K, similar to the FCD.

The association of dietary phosphorus with blood pressure: results from a secondary analysis of the PREMIER trial

Inconsistent findings exist for the association between dietary phosphorus intake and blood pressure (BP). We examined the longitudinal association between urinary excretion and dietary intake of phosphorus (total, plant, animal, and added) with BP.

This is a secondary analysis of PREMIER, a randomized behavioral intervention study in adults (25–79y) with BP, measured at six months, as the primary outcome. We classified total phosphorus intake from dietary recalls into plant, animal, and added phosphorus. We modeled six month change of phosphorus intake (from 24h dietary recalls, N = 622) and excretion (from 24h urine collection, N = 564) on BP, using linear regression crude and adjusted for intervention, age, race, sex, income, education, study site, and change in energy intake (kcal/d), sodium intake (mg/d), fitness (heart rate, bpm), and DASH diet index.

Baseline phosphorus intake was 1154 mg/d (95%CI 1126, 1182) with 38%, 53%, and 10% from plant, animal, and added phosphorus, respectively. Total phosphorus intake was not associated with significant changes in BP. Increased urinary phosphorus excretion was associated with a significant increase in DBP [0.14 mmHg/100 mg (0.01, 0.28), adjusted]. In several analyses, phosphorus type (plant, animal, or added) significantly modified the association between phosphorus intake and BP. For example, added phosphorus (but not plant or animal) was associated with increases in SBP and DBP, 1.24 mmHg/100 mg (0.36, 2.12) and 0.83 mmHg/100 mg (0.22, 1.44), respectively, crude.

These findings suggest that the type of phosphorus may modify the association between phosphorus intake and BP. Trial registration (clinicaltrials.gov).

The Percentage of Dietary Phosphorus Excreted in the Urine Varies by Dietary Pattern in a Randomized Feeding Study in Adults

BACKGROUND

Urinary phosphorus excretion has been proposed as a recovery biomarker of dietary phosphorus intake. However, it is unclear whether phosphorus excretion is constant across a range of dietary and nondietary factors.

OBJECTIVE

We assessed whether percentage urinary phosphorus excretion is constant across 3 dietary patterns in the Dietary Approaches to Stop Hypertension (DASH) trial.

METHODS

DASH is a completed feeding study of 459 prehypertensive and stage 1 hypertensive adults (52% male, 56% black). After a 3-wk run-in on a typical American (control) diet, participants were randomly assigned to the control diet, a diet rich in fruits and vegetables (FV diet), or a diet rich in fruits, vegetables, and low-fat dairy with reduced saturated fat and cholesterol (DASH diet) for 8 wk. We estimated the percentage phosphorus excretion as urinary phosphorus excretion (from 24 h urine) divided by phosphorus intake (from analyzed food composites). Differences between group means for all 3 diets were compared by ANOVA followed by pairwise comparisons with Tukey's honest significant difference test.

RESULTS

At the end of the intervention, the mean phosphorus intake was 1176 mg/d (95% CI: 1119, 1233 mg/d), 1408 mg/d (1352, 1464 mg/d), and 2051 mg/d (1994, 2107 mg/d) in the control, FV, and DASH diet, respectively (P < 0.001, all comparisons). The mean phosphorus excretion was 734 mg/d (682, 787 mg/d), 705 mg/d (654, 756 mg/d), and 872 mg/d (820, 923 mg/d) in the control, FV, and DASH diet, respectively (P = 0.74 control vs. FV, P < 0.001 all other comparisons). The mean percentage phosphorus excretion was 63% (60%, 67%), 51% (48%, 54%), and 43% (39%, 46%) in the control, FV, and DASH diet, respectively (P < 0.001, all comparisons).

CONCLUSIONS

These findings in prehypertensive and stage 1 hypertensive adults strongly suggest that urinary phosphorus excretion should not be used as a recovery biomarker for dietary phosphorus intake, given the wide range of urinary phosphorus excretion across dietary patterns. This trial is registered at clinicaltrials.gov as NCT0000054.

Dietary phosphorus intake and blood pressure in adults: a systematic review of randomized trials and prospective observational studies

BACKGROUND

Elevated blood pressure (BP) is a major cause of preventable disease in the United States and around the world. It has been postulated that phosphorus intake may affect BP, with some studies suggesting a direct and others an inverse association.

OBJECTIVES

We systematically reviewed the literature on the association of dietary phosphorus with BP in adults and performed a qualitative synthesis.

METHODS

We included randomized and nonrandomized behavioral intervention and feeding studies (intervention studies) and prospective observational studies that measured dietary phosphorus intake or urinary phosphorus excretion and BP. We excluded studies of supplements, children, or individuals with major medical conditions. We searched PubMed, Embase, Cochrane Trials, and clinicaltrials.gov on 1 June, 2017 and 22 August, 2018. We assessed studies' risk of bias in their assessment of phosphorus exposure and BP.

RESULTS

We reviewed 4759 publications and included 14 intervention studies (2497 participants), 3 prospective observational cohorts (17,795 participants), and 2 ongoing trials. No included intervention studies were designed specifically to achieve a phosphorus contrast. Two studies found a significant positive association of dietary phosphorus with systolic BP, 4 a significant inverse association, and 8 no significant association. Four studies found a significant inverse association with diastolic BP and 10 no significant associations. Two cohorts found lower risk of incident hypertension comparing the highest with the lowest quintiles of phosphorus intake and 1 found no significant difference: HR: 0.86 (95% CI: 0.75, 0.98); HR: 0.83 (95% CI: 0.68, 1.02); and HR: 0.75 (95% CI: 0.45, 1.27), respectively.

CONCLUSIONS

We found no consistent association between total dietary phosphorus intake and BP in adults in the published literature nor any randomized trials designed to examine this association. This trial was registered at www.crd.york.ac.uk/prospero/ as CRD42017062489.

Influence of a physical exercise until exhaustion in normothermic and hyperthermic conditions on serum, erythrocyte and urinary concentrations of magnesium and phosphorus

AIM

The aim of this study was to evaluate the effect of the performance of a maximal exercise test until exhaustion in normothermic and hyperthermic conditions on body concentrations of magnesium (Mg) and phosphorus (P).

METHODS

19 adult males (age: 22.58 ± 1.05 years) performed two maximum incremental exercise tests on a cycloergometer separated by 48 h. The first was performed in normothermia (22 ± 2 °C) and the second in hyperthermic conditions induced with a sauna (42 ± 2 °C). Blood and urine samples were taken before and after each test.

RESULTS

The tests in hyperthermia did not produce ergospirometric alterations or a noticeable cardiovascular drift. Serum Mg concentrations underwent a reduction after the stress test in hyperthermia (p > 0.05) but not in normothermia. Nevertheless, urinary and erythrocyte concentrations of Mg, and urinary, erythrocyte and serum concentrations of P did not undergo alterations in either conditions.

CONCLUSIONS

It seems that exercise in hyperthermic conditions induces a tissue redistribution of Mg in the body, a fact which was not observed in normothermic conditions.

Dietary Phosphate and the Forgotten Kidney Patient: A Critical Need for FDA Regulatory Action

Careful dietary management that reduces high phosphate intake is recommended to slow the progression of chronic kidney disease (CKD) and prevent complications of CKD and may help reduce chronic disease risks such as incident CKD associated with high phosphate intake in the healthy general population. For patients treated with maintenance dialysis, control of serum phosphorus levels is considered a marker of good care and requires a coordinated plan that limits dietary phosphate intake, uses oral phosphate binders, and provides an adequate dialysis prescription. Even with traditional thrice-weekly hemodialysis or peritoneal dialysis, use of phosphate binders, and a concerted effort to limit dietary phosphate intake, adequately controlled serum phosphorus levels are not possible in all dialysis patients. Efforts to limit phosphate intake are thwarted by the underestimated and unquantified phosphate content of processed foods and some medications due to the hidden presence of phosphate additives or excipients added during processing or drug formulation. Effectively limiting phosphate intake could potentially be achieved through simple US Food and Drug Administration regulatory actions. Mandatory labeling of phosphate content on all packaged foods and drugs would enable identification of healthy low-phosphate foods and medications and permit critically important control of total phosphate intake. Simple changes in regulatory policy and labeling are warranted and would enable better management of dietary intake of phosphate at all stages of kidney disease, as well as potentially reduced health risks in the general population.