Protein Supplementation During Luteal Phase

The physiologic effects of the female menstrual cycle have been shown to cause many changes to metabolic processes throughout the body depending on the phase of the cycle. For example, during the follicular phase, increase in estrogen aids in arterial vasodilation, lipid metabolism, neuroprotection, and maintaining bone density (Gruber et al. 2002). During the luteal phase, the increase in progesterone aids in thermoregulation, increased respiration, and basal insulin levels (Taraborrelli 2015). However, there is conflicting evidence regarding net progesterone effects on skeletal muscle. Some studies state that progesterone has an anabolic effect while others suggest the contrary. Despite the discrepancies with current literature, Sims et al. recommends female athletes increase their protein intake by 12% during the luteal phase of their menstrual cycle to potentially counteract the protein catabolic effects of progesterone on skeletal muscle (2023). The basis of this conclusion was based on invitro and in vivo studies showing decreases amino acids during the luteal phase (Faustmann et al. 2018 & Draper et al. 2018)

To our knowledge, no study exists that analyzes protein degradation with protein supplementation increase during the luteal phase. The purpose of this research is to determine if increasing 12% of daily protein intake during the luteal phase mitigates the potential catabolic effects of progesterone on skeletal muscle. This research could help determine if millions of women would benefit from additional protein supplementation during the luteal phase, which may lead to decreased skeletal muscle atrophy over time. We anticipate there will be an advantageous, decreased catabolic effect with increasing protein intake during the luteal phase.