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Soy Consumption Has No Influence on Risk of Precocious Puberty, Early Menarche

A systematic review and meta-analysis provide insight into the risks of precocious puberty and early menarche based on consumption of a soy-based infant diet.

New research from investigators at Sao Paulo State University details the impact of a soy-based infant diet on the onset of puberty.

The study, which was a systematic review and meta-analysis designed to evaluate associations between soy-based infant diets and onset of puberty in girls, boys, and both, concluded there were no statistically significant associations between soy-based infant diets and onset of puberty in boys or girls.

“We did not observe any association between a soy-based infant diet and the onset of puberty in boys or girls. The meta-analyses did not show any significant differences between groups in the risk of precocious puberty and menarche age,” wrote investigators.

Citing conflicting evidence from previous studies, a team of 6 investigators from Sao Paulo State University sought to assess the associations between a soy-based infant diet and the onset of puberty. To do so, investigators designed a systematic review and meta-analysis with the intent of examining the associations in a contemporary cohort of observational and randomized clinical trials.

Performing a search of the Embase, Medline, LILACS, Cochrane, Trip database, SCOPUS, and Web of Science databases, investigators identified 962 references for possible inclusion in their systematic review and meta-analysis. The search terms used by investigators were “Soy Foods,” “Soy Milk,” “Soybeans,” “Soybeans Protein,” “Soybean oil,” “Puberty,” “Puberty, precocious,” “Sexual Maturation,” and “Menstruation Disturbances”. Of the 962 references, 16 were selected for final examination and 8 met all eligibility criteria for the systematic review and meta-analysis. Investigators noted, of the 8 studies excluded, 1 was a literature review, 1 was a case report, 2 presented only laboratory outcomes, 1 was an animal study, 1 did not describe clinical outcomes related to puberty, and in 2 studies the time of follow-up was insufficient to evaluate the health outcomes.

Of the 8 studies included, 7 were observational studies and 1 was a randomized clinical trial. Within these 8 studies, investigators identified a cohort of 598 children who consumed a soy-based diet and 2957 who did not. Primary outcomes of interest for the study were the onset of puberty in girls, boys, and both. Puberty outcomes in girls included thelarche, pubarche, and menarche age. For boys, puberty outcomes included pubarche, voice change, and testicular and penis enlargement age. When assessing both, the puberty outcome of interest was risk of delayed precocious puberty.

In their analyses, investigators hoped to calculate the odds ratio and mean difference as a measure of the association between soy consumption and outcomes. Investigators pointed out random-effects model was used to pool results across studies and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to evaluate the certainty of evidence.

Upon analysis, investigators found the only primary outcomes of interest that could be plotted within the meta-analysis were the risk of precocious puberty and age at menarche. In their analyses, investigators observed no statistical difference between groups for precocious puberty based on soy consumption (OR, 0.51 [95% CI, 0.09 to 2.94]; 3 studies, 206 participants, low certainty of evidence. Further analysis revealed no between-group difference for menarche age (MD, 0.14 [95% CI, -0.16 to 0.45]; 3 studies, 605 children, low certainty of evidence).

Investigators noted a single study reported the outcome of menarche age in terms of median and interquartile range. In this study, the onset of menarche was increased in girls who received a soy-based diet, but the reported age was within the normal age range for menarche.

Investigators underlined the need for more research to further evaluate potential associations between soy-based infant diets and the onset of puberty in boys and girls.

“Cohort studies with large sample sizes and appropriate methodology are required to evaluate whether the lack of an association between a soy-based infant diet and the onset of puberty remains when the results are compared considering the length of exposure, amount of soy consumption, and assessment of pubertal development through self-report or physical examination,” wrote investigators.

This study, “Association between a soy-based infant diet and the onset of puberty: A systematic review and meta-analysis,” was published in PLOS ONE.