Higher protein intake increases cardiac function parameters in healthy children: metabolic programming by infant nutrition-secondary analysis from a clinical trial

Protein Restriction in Metabolic Health: Lessons from Rodent Models

Consumption of protein-rich diets and supplements has been increasingly advocated by individuals seeking to optimize metabolic health and mitigate the effects of aging. Protein intake is postulated to support muscle mass retention and enhance longevity, underscoring its perceived benefits in age-related metabolic regulation. However, emerging evidence presents a paradox; while moderate protein consumption contributes to health maintenance, an excessive intake is associated with an elevated risk of chronic diseases, notably obesity and diabetes. Furthermore, recent studies suggest that reducing the ratio of protein intake to macronutrients improves metabolic parameters and extends lifespan. The aim of this study is to review the current evidence concerning the metabolic effects of protein-restricted diets and their potential mechanisms. Utilizing rodent models, investigations have revealed that protein-restricted diets exert a notable influence over food intake and energy consumption, ultimately leading to body weight loss, depending on the degree of dietary protein restriction. These phenotypic alterations are primarily mediated by the FGF21 signaling pathway, whose activation is likely regulated by ATF4 and the circadian clock. The evidence suggests that protein-restricted diets as an alternative approach to calorie-restricted regimes, particularly in overweight or obese adults. However, more research is needed to determine the optimal level of restriction, duration, and long-term effects of such interventions.

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.

A review of recent evidence of dietary protein intake and health

The Korea National Health and Nutrition Examination Survey of 2013 to 2017 reported that the average protein consumption of the Korean population is above the current recommended nutrient intake of protein proposed by the Dietary Reference Intakes for Koreans. Some health professionals and the media often advise consuming diets high in protein for promoting metabolic regulation, weight control, and muscle synthesis. However, due to lack of scientific evidence, the validity and safety of high protein consumption are yet to be fully ascertained. The present review assesses recent evidence published in 2014-2020 from human studies, focusing on adequate protein intake and protein sources for the prevention of chronic diseases, particularly metabolic disorders and sarcopenia.

Early-Life Predictors of Systolic Blood Pressure Trajectories From Infancy to Adolescence: Findings From Project Viva

Childhood blood pressure (BP) is a strong predictor of later risk of cardiovascular disease. However, few studies have assessed dynamic BP trajectories throughout the early-life period. We investigated the relationship between early-life factors and systolic BP (SBP) from infancy to adolescence using linear spline mixed-effects models among 1,370 children from Project Viva, a Boston, Massachusetts-area cohort recruited in 1999-2002. After adjusting for confounders and child height, we observed higher SBP in children exposed to gestational diabetes mellitus (vs. normoglycemia; age 3 years: β = 3.16 mm Hg (95% confidence interval (CI): 0.28, 6.04); age 6 years: β = 1.83 mm Hg (95% CI: 0.06, 3.60)), hypertensive disorders of pregnancy (vs. normal maternal BP; age 6 years: β = 1.39 mm Hg (95% CI: 0.10, 2.67); age 9 years: β = 1.84 mm Hg (95% CI: 0.34, 3.34); age 12 years: β = 1.70 mm Hg (95% CI: 0.48, 2.92)), higher neonatal SBP (per 10-mm Hg increase; age 3 years: β = 1.26 mm Hg (95% CI: 0.42, 2.09); age 6 years: β = 1.00 mm Hg (95% CI: 0.49, 1.51); age 9 years: β = 0.75 mm Hg (95% CI: 0.17, 1.33)), and formula milk in the first 6 months of life (vs. breast milk only; age 12 years: β = 2.10 mm Hg (95% CI: 0.46, 3.74); age 15 years: β = 3.52 mm Hg (95% CI: 1.40, 5.64); age 18 years: β = 4.94 mm Hg (95% CI: 1.88, 7.99)). Our findings provide evidence of programming of offspring SBP trajectories by gestational diabetes, hypertensive disorders of pregnancy, and formula milk intake and of neonatal BP being a potentially useful marker of childhood BP. These factors could be relevant in identifying children who are at risk of developing elevated BP.