Phenylalanine Requirements in the Menstrual Phases

Overview

Phenylalanine is an essential amino acid that must be obtained through food. Current adult phenylalanine recommendation is based on male-conducted studies and set the same for females. These recommendations may not be appropriate for females, as they do not take into consideration the hormonal changes over the menstrual cycle. The menstrual cycle is a rhythmic hormonal process split into two phases, with hormones regulating metabolism differently. The aim of this study is to find phenylalanine requirement for healthy, menstruating females. An innovative, non-invasive technique utilizing pre-determined diets, safe stable isotopes, and a simple breath collection method will be used. Previous work done by Elango Lab investigators has applied this method to investigate other amino acids in pregnant, non-pregnant, and lactating females as well as in children.

The objective of this study is to assess phenylalanine requirements in healthy, menstruating females, between the ages 20-35, during the luteal and follicular phases using the minimally invasive indicator amino acid oxidation method. In comprehending protein needs and achieving protein targets, it is imperative to establish individual amino acid requirements. This clinical study aims to determine the dietary phenylalanine requirement in females to help set nutrition guidelines for females that heavily consider the metabolic and hormonal effects of the differences between the menstrual cycle phases. The existing values, derived from guidelines designed for males, overlook the crucial impact of the menstrual cycle on energy and dietary intake. Relying on amino acid requirements derived from studies in males for females significantly heightens the risk of potential harm. It is crucial to identify the distinct amino acid requirements for females and grasp how these needs are affected by various phases of the menstrual cycle. A minimum of 15 healthy females (20-35 y) will be recruited and studied at two menstrual phases over a range of test phenylalanine intakes (2.5, 5, 7.5 10, 12.5 17.5, and 22.5 mg/kg/day). Subjects will be invited to participate in up to 7 study days/phase and randomized to a different intake at each study day. Participants' eligibility will be assessed during a pre-study day. The goal is to study a minimum of 7 participants at each intake, for a total of 49 study days in each stage.