Low plant protein intake may cause PMS-induced impairment of athletic performance: Japan study

Premenstrual syndrome (PMS) is a psychosomatic disorder involving physical discomfort or dysphoria, such as irritability, tension, depressed moods, tearfulness, and mood swings, occurring in the weeks prior to menstruation.

It has been said to compromise athletic performance, although evidence surrounding the relationship between dietary habits and PMS has been limited.

Performance-enhancing plants?

For this reason, researchers at Japan's Kindai University conducted a study to determine the link between proportions of dietary animal and plant protein and PMS-related impairment of athletic performance.

They assessed 135 female athletes between the ages of 18 and 23 years old, all of whom were members of authorised Kindai University clubs that ranked highly among Japanese university sports.

They had to complete self-administered questionnaires on diet history, demographic details, and PMS-related athletic performance impairment. Their total, animal and plant protein consumption was measured, and each participant’s proportion of dietary plant protein was calculated.

They were then divided into two groups: 18 athletes with PMS-related athletic performance impairment in one group, and in the other group, 117 without.

The researchers then compared the mean values and multivariable-adjusted mean values between the two groups; adjustment variables included BMI, energy intake, and daily training duration.

They found little difference in total protein intake between the two groups, but observed that those whose performance was affected by PMS had reported a higher intake of animal protein (mean 50.6g) and lower intake of plant protein (mean 25.4g) than those whose performance was unaffected by PMS (mean 34.9g of animal protein and 26.9g of plant protein).

This meant a lower proportion of dietary plant protein among those affected by PMS-related performance impairment (39.3%) than those who were unaffected (45.9%).

Limitations and beliefs

The researchers stated that athletes in general often consume large amounts of animal protein as they believe doing so will improve their performance.

However, based on the study's findings, insufficient dietary plant protein may induce PMS-related athletic performance impairment.

As the sample size was small, the researchers could not analyse the components of the plant proteins the participants had consumed, and stated that they may not be "truly representative of female athletes in general"​.

The study’s cross-sectional design also prevented clear causality from being established, and the physical demands of training might have differed between the two groups; the latter could have influenced the severity of PMS.

They concluded: "These limitations notwithstanding, our results suggest that a low proportion of dietary plant protein may cause PMS-related athletic impairment in female athletes."​

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Source: The Tohoku Journal of Experimental Medicine​

https://doi.org/10.1620/tjem.244.119​

"Low Proportion of Dietary Plant Protein among Athletes with Premenstrual Syndrome-Related Performance Impairment"​

Authors: Keiko Yamada, Takashi Takeda