Urinary excretion of calcium, phosphate, magnesium, and uric acid in healthy infants and young children. Influence of feeding practices in early infancy

BACKGROUND

Reference values for urinary calcium (Ca) and other solutes/creatinine (Cr) ratios in infants and young children are scarce. Its variation with type of lactation administered, breastfed (BF) or formula (F), is incompletely known.

METHODS

A total of 511 spot urine samples from 136 children, aged 6 days to < 5 years, was collected. Urine was collected no fasting in infants < 18 months and first morning fasting in children aged 2.5-4 years. Urinary osmolality, Cr, urea, Ca, phosphate (P), magnesium (Mg), and uric acid (UA) were determined. Values are expressed as solute-to-Cr ratio.

RESULTS

Urinary values were grouped according to the child's age: 6-17 days (G1), 1-5 months (G2), 6-12 months (G3), 13-18 months (G4), and 2.5-4 years (G5). G1 was excluded; Ca/Cr and UA/Cr (95th percentile) decreased with age (G2 vs. G5) from 1.64 to 0.39 and 2.33 to 0.83 mg/mg, respectively. The P/Cr median rises significantly with age from 0.31 (G2) to 1.66 mg/mg (G5). Mg/Cr was similar in all groups (median 0.20, 95th percentile 0.37 mg/mg). Ca/Cr (95th percentile) of BF infants was 1.80 mg/mg (< 3 months) and 1.63 mg/mg (3-5 months), much higher than F infants (0.93 and 0.90 mg/mg, respectively). P/Cr and P/Ca were lower in BF infants.

CONCLUSIONS

Values for urinary Ca/Cr, P/Cr, Mg/Cr, and UA/Cr in infants and children < 5 years were updated. BF infants < 6 months showed higher Ca/Cr and lower P/Cr than F infants. New cutoff values to diagnose hypercalciuria in infants < 6 months, according to the type of lactation, are proposed.

Higher versus lower protein intake in formula-fed term infants

BACKGROUND

Many infants are fed infant formulas to promote growth. Some formulas have a high protein content (≥ 2.5 g per 100 kcal) to accelerate weight gain during the first year of life. The risk-benefit balance of these formulas is unclear.

OBJECTIVES

To evaluate the benefits and harms of higher protein intake versus lower protein intake in healthy, formula-fed term infants.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, OpenGrey, clinical trial registries, and conference proceedings in October 2022.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of healthy formula-fed infants (those fed only formula and those given formula as a complementary food). We included infants of any sex or ethnicity who were fed infant formula for at least three consecutive months at any time from birth. We excluded quasi-randomized trials, observational studies, and infants with congenital malformations or serious underlying diseases. We defined high protein content as 2.5 g or more per 100 kcal, and low protein content as less than 1.8 g per 100 kcal (for exclusive formula feeding) or less than 1.7 g per 100 kcal (for complementary formula feeding).

DATA COLLECTION AND ANALYSIS

Four review authors independently assessed the risk of bias and extracted data from trials, and a fifth review author resolved discrepancies. We performed random-effects meta-analyses, calculating risk ratios (RRs) or Peto odds ratios (Peto ORs) with 95% confidence intervals (CIs) for dichotomous outcomes, and mean differences (MDs) with 95% CIs for continuous outcomes. We used the GRADE approach to evaluate the certainty of the evidence.

MAIN RESULTS

We included 11 RCTs (1185 infants) conducted in high-income countries. Seven trials (1629 infants) compared high-protein formula against standard-protein formula, and four trials (256 infants) compared standard-protein formula against low-protein formula. The longest follow-up was 11 years. High-protein formula versus standard-protein formula We found very low-certainty evidence that feeding healthy term infants high-protein formula compared to standard-protein formula has little or no effect on underweight (MD in weight-for-age z-score 0.05 SDs, 95% CI -0.09 to 0.19; P = 0.51, I2 = 61%; 7 studies, 1629 participants), stunting (MD in height-for-age z-score 0.15 SDs, 95% CI -0.05 to 0.35; P = 0.14, I2 = 73%; 7 studies, 1629 participants), and wasting (MD in weight-for-height z-score -0.12 SDs, 95% CI -0.31 to 0.07; P = 0.20, I2 = 94%; 7 studies, 1629 participants) in the first year of life. We found very low-certainty evidence that feeding healthy infants high-protein formula compared to standard-protein formula has little or no effect on the occurrence of overweight (RR 1.26, 95% CI 0.63 to 2.51; P = 0.51; 1 study, 1090 participants) or obesity (RR 1.96, 95% CI 0.59 to 6.48; P = 0.27; 1 study, 1090 participants) at five years of follow-up. No studies reported all-cause mortality. Feeding healthy infants high-protein formula compared to standard-protein formula may have little or no effect on the occurrence of adverse events such as diarrhea, vomiting, or milk hypersensitivity (RR 0.93, 95% CI 0.76 to 1.13; P = 0.44, I2 = 0%; 4 studies, 445 participants; low-certainty evidence) in the first year of life. Standard-protein formula versus low-protein formula We found very low-certainty evidence that feeding healthy infants standard-protein formula compared to low-protein formula has little or no effect on underweight (MD in weight-for-age z-score 0.0, 95% CI -0.43 to 0.43; P = 0.99, I2 = 81%; 4 studies, 256 participants), stunting (MD in height-for-age z-score -0.01, 95% CI -0.36 to 0.35; P = 0.96, I2 = 73%; 4 studies, 256 participants), and wasting (MD in weight-for-height z-score 0.13, 95% CI -0.29 to 0.56; P = 0.54, I2 = 95%; 4 studies, 256 participants) in the first year of life. No studies reported overweight, obesity, or all-cause mortality. Feeding healthy infants standard-protein formula compared to low-protein formula may have little or no effect on the occurrence of adverse events such as diarrhea, vomiting, or milk hypersensitivity (Peto OR 1.55, 95% CI 0.70 to 3.40; P = 0.28, I2 = 0%; 2 studies, 206 participants; low-certainty evidence) in the first four months of life.

AUTHORS' CONCLUSIONS

We are unsure if feeding healthy infants high-protein formula compared to standard-protein formula has an effect on undernutrition, overweight, or obesity. There may be little or no difference in the risk of adverse effects between infants fed with high-protein formula versus those fed with standard-protein formula. We are unsure if feeding healthy infants standard-protein formula compared to low-protein formula has any effect on undernutrition. There may be little or no difference in the risk of adverse effects between infants fed with standard-protein formula versus those fed with low-protein formula. The findings of six ongoing studies and two studies awaiting classification studies may change the conclusions of this review.

Protein quality and safety evaluation of sarcoplasmic protein derived from silver carp (Hypophthalmichthys molitrix) using a rat model

Consisting of 25 to 30% of protein in carp, water-soluble sarcoplasmic proteins lost in wash water, have been recovered and freeze-dried into a protein-rich powder. Study objectives were to evaluate protein quality and safety of a silver carp sarcoplasm derived protein powder (CSP) compared to commercial protein supplements, casein, and whey. In vivo protein quality assessment of CSP showed a lower (P < 0.05) protein digestibility corrected amino acid score compared to the commercial protein sources. Despite greater (P < 0.05) fecal amino acid excretion in casein-fed rats, there were no significant differences in liver and muscle amino acid profiles. All low (10% kcal) protein diets supported growth with the normal range. However, whey protein supplementation resulted in greater (P < 0.05) adiposity. CSP, casein, or whey-fed rats showed no differences in major organ weights, renal damage biomarkers, or bone indices. Collectively, results indicated CSP was safe with protein quality comparable to casein. PRACTICAL APPLICATION: As much as 40 percent of protein in fish can be lost due to sarcoplasmic protein solubilization in processing wash water. Silver carp sarcoplasm protein powder may have similar commercial potential as a sustainable and nutritious alternative to whey and casein proteins. This project aimed to verify the protein quality and safety of this economical protein source.