Maternal obesity does not influence human milk protein ¹⁵N natural isotope abundance

ABSTRACT

Obesity increases protein metabolism with a potential effect on nitrogen isotope fractionation. The aim of this study was to test the influence of obesity on human milk extracted protein ¹⁵N natural isotope abundance (NIA) at one month post-partum and to compare human milk extracted protein ¹⁵N NIA and bulk infant hair ¹⁵N NIA. This cross-sectional observational study involved 16 obese mothers (body mass index (BMI) ≥ 30 kg m⁻² before pregnancy) matched with 16 normal-weight mothers (18.5 kg m⁻² ≤ BMI < 25 kg m⁻²) for age and pregnancy characteristics. Human milk extracted protein and bulk infant hair ¹⁵N NIA were determined by isotope ratio monitoring by mass spectrometry interfaced to an elemental analyser (IRM-EA/MS). No significant difference was found in human milk protein ¹⁵N NIA values between obese and normal-weight mothers (8.93 ± 0.48 ‰ vs. 8.95 ± 0.27 ‰). However, human milk protein ¹⁵N NIA was significantly lower than bulk infant hair ¹⁵N NIA: 8.94 ± 0.38 ‰ vs. 9.66 ± 0.69 ‰, respectively. On the basis of these results, it is concluded that human milk protein ¹⁵N NIA measured at one month post-partum is not influenced by maternal obesity. These findings suggest that ¹⁵N NIA may be exploited to study metabolism without considering maternal obesity as a confounder.

KEYWORDS:

• Breastfeeding
• infant nutrition
• nitrogen-15; natural isotope abundance
• human milk
• protein metabolism
• obesity

Acknowledgements

Special thanks to Sonia Leroux, Elodie Rogeon and Dr. Pierre-Jean Saulnier from INSERM CIC1402, to Prof. Fabrice Pierre and Dr. Emmanuelle Descombes from the Maternity Ward of the Poitiers University Hospital, to Drs. Alain Godard and Florence Compain from the Maternity Ward of the Chatellerault General Hospital, and to all the participating families.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Arnaud De Luca http://orcid.org/0000-0003-1704-8599

Additional information

Funding

This work was funded by a grant from French Ministry of Health (Programme Hospitalier de Recherche Clinique Interregional Grand-Ouest) [grant number B91049-20] and in part by core funding from the Centre National de la Recherche Scientifique.