Study links vegetable protein to delayed puberty through gut microbiome changes

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Jul 2 2024

In a recent letter to Signal Transduction and Targeted Therapy, researchers report the results of a large Chinese study on the impact of dietary protein on the gut microbiome and puberty timing.

Study: Dietary protein sources, gut microbiome, and puberty timing in children: findings from a cohort study. Image Credit: CrispyPork / Shutterstock.com

The impact of different proteins on gut microbiota

The current prospective study included children between six and eight years of age who participated in the Chinese Adolescent Cohort (CAC) study. A total of 1,826 children were stratified into tertiles of dietary protein intake, with children in the highest tertile exceeding the recommended daily allowance (RDA) for animal protein at 59.4 g/day.

When accounting for other factors, children consuming higher levels of vegetable protein had a greater abundance of Butyricicoccus, Enterococcus, Dorea, and Romboutsia bacteria. Each of these bacteria genera produces short-chain fatty acids (SCFAs) like butyrate, which have immunoregulatory, anti-inflammatory, anti-obesity, anti-tumor, cardioprotective activity, and various other essential physiologic functions.

Higher animal protein intake was associated with enriched levels of unidentified_Saccharimonad. These findings suggest that SCFAs may be involved in the different metabolic processes that digest vegetable and animal proteins.

Protein intake, microbiome, and puberty

Total protein-microbial index (TPMI), animal protein-microbial index (APMI), and vegetable protein-microbial index (VPMI) were also calculated from dietary protein-associated gut microbiome characteristics.  

The highest APMI tertile was associated with earlier menarche in girls and voice breaking in boys as compared to those in the lowest tertile. Conversely, the highest VPMI tertile was associated with later menarche or voice break relative to the lowest VPMI tertile.

These findings indicate that dietary protein intake likely impacts the timing of puberty and that the gut microbiome mediates this effect. In fact, 15% of the association between animal protein intake and puberty timing could be explained by the APMI. Comparatively, about 40% of the effect of vegetable protein intake on puberty timing was attributed to the VPMI.

Protein intake and metabolites vs puberty timing

Digestive enzymes break down a significantly greater amount of animal protein, with little protein available for digestion by bacteria within the gastrointestinal tract. Comparatively, vegetable protein is primarily digested by the gut microbiota, thus demonstrating that vegetable protein digestibility is directly dependent on the composition of the gut microbiome.

The gut microbiome in children who consumed more vegetable protein exhibited a significantly different metabolic profile than those who consumed more animal protein. Likewise, several urine metabolites, including 2,5-furan dicarboxylic acid, citric acid, alpha-ketoglutaric acid, and butyric acid in the feces, rose in proportion to vegetable protein consumption. In contrast, both butyric acid in feces and 2,5-furan dicarboxylic acid in urine were less abundant with increased animal protein intake.

When compared against puberty timing, the presence of these metabolites showed a positive association. Both citric acid and alpha-ketoglutaric acid were present at higher levels in metabolic pathways related to releasing hormone secretion, such as gonadotropin hormone-releasing hormone and endocrine function.

Butyric acid improves blood sugar control and may support the regulation of pubertal changes. In general, puberty is associated with higher insulin resistance, thus making more glucose available to the cells. As a result, metabolic shifts affect adolescent physiology to a greater extent than those of healthy adults.

Soy protein and puberty

In China, dietary soy protein is the primary source of vegetable protein and, as a result, may be responsible for later puberty timing in this country. To test this hypothesis, the study participants were classified by soy intake, demonstrating that VPMI was associated with later puberty timing with higher dietary soy intake.

The mechanism by which soy protein affects puberty timing remains unknown. However, the identification of this association supports dietary recommendations to include more soy in the total vegetable protein intake. 

Conclusions

Habitual intake of animal protein and vegetable protein has the potential to influence puberty timing by reshaping the gut microbiome in different directions.”

Some of the strengths of the current study include its large and representative sample and comparatively long follow-up period.

Early puberty is significantly more common in the highest tertiles of animal protein intake, which exceeds dietary recommendations. Thus, the overall relevance of animal protein intake on puberty timing may not be evident when a balanced diet is consumed.

The study findings suggest that dietary recommendations for the transitional years of childhood should promote vegetable protein intake while emphasizing the importance of avoiding excessive animal protein consumption.