Are Some Infants Consuming Too Much Protein?

Advances in Nutrition review finds higher intakes of total and animal protein during infancy are associated with higher BMI in childhood and adolescence

The media has been touting the benefits of increasing dietary protein for years, leading many to believe that consuming a greater percentage of total calories from protein is always better.  In many cases, such as for older adults, studies have shown that increasing protein intake may be beneficial, but studies have also shown that this strategy is not necessarily true for all population groups.

Published in Advances in Nutrition, “Protein Intake from Birth to 2 Years and Obesity Outcomes in Later Childhood and Adolescence: A Systematic Review of Prospective Cohort Studies,” for example, investigated the association of total protein intake during infancy with obesity outcomes in later childhood and adolescence.  Moreover, the authors examined the association of particular sources of protein, such as animal proteins and plant-based proteins, with obesity outcomes.  Authors Alexandra Stokes et al. found that “overall, higher intakes of total and animal protein during infancy were associated with higher BMI in childhood and adolescence.”

In order to complete their systematic review, the authors conducted a comprehensive search of the scientific literature for relevant prospective cohort studies, which tracked protein intake from birth to two years with obesity outcomes at up to 18 years of age.  Their search led them to 16 relevant studies that reported results from 9 cohorts, whose sample sizes ranged from 90 to 3,573 participants.  The studies were conducted mostly in Northern and Western Europe as well as in the United States.  The authors did therefore note that “the generalizability of the findings to low- or middle-income countries remains unclear.”

While the authors found an overall association between higher total protein intake from birth to two years with higher BMI in childhood and adolescence, they discovered that this association did not hold true for all individual sources of protein.  For example, higher intakes of animal protein, but not plant protein, were associated with a higher BMI in childhood and adolescence.  Within the category of animal protein, evidence linking dairy protein intake with a higher BMI appeared to be stronger than that for nondairy animal protein sources such as meat, fish, and eggs.  Studies linking specific protein sources with obesity were limited, however, prompting the authors to call for additional research.

Three of the 16 studies included in this review reported sex-specific associations between total protein intake and obesity.  Interestingly, two studies found significant associations between total protein intake and higher rates of obesity among girls, but not boys.  The third study found a significant positive association in boys only.

Today in the United States, some 18% of children are obese.  These children carry an increased risk of asthma, type 2 diabetes, and orthopedic disorders.  Moreover, obese children are more likely to become obese adults.  As obese adults, they will face a higher risk of coronary artery disease, hypertension, stroke, chronic kidney and liver disease as well as many types of cancer.  Strategies to prevent obesity early in life are therefore critical.

The authors of this systematic review believe that “future research with rigorously designed studies in wider population groups is needed” in order to further assess the long-term impact of protein intake in infancy and to better understand the mechanisms underlying the association between early protein consumption and obesity.  According to the authors, “such information is fundamental for informing future evaluation of infant feeding guidelines and protein nutrient recommended intakes.”

Reference

Alexandra Stokes, Karen J Campbell, Hong-Jie Yu, Ewa A Szymlek-Gay, Gavin Abbott, Qi-Qiang He, Miaobing Zheng. Protein Intake from Birth to 2 Years and Obesity Outcomes in Later Childhood and Adolescence: A Systematic Review of Prospective Cohort Studies. Advances in Nutrition, nmab034 (Epub ahead of print; DOI: https://doi.org/10.1093/advances/nmab034).

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