Fueling for Menstrual Cycles by Spring Energy's Jade Belzberg

Research currently shows that menstrual cycle stage does not relate to performance outcomes, but race day may go better if you know how to fuel your body. This is particularly important, as fueling needs for a race differ depending on which phase of a cycle an athlete is in. In her book Roar: How to match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life, Dr. Stacy Sims explains how carbohydrate needs are higher during the luteal phase; this need is further increased when performing endurance exercise—like running or cycling.

The menstrual cycle has three main phases: the follicular phase, the ovulatory phase, and the luteal phase. Energy needs differ depending on the hormone levels that characterize each phase. For example:

• During the follicular phase, also know as the low hormone phase, 30 to 40 grams of carbohydrates per hour are needed. 
• During the luteal phase, also known as the high hormone phase, carbohydrate requirements increase to about 50 grams per hour. Adding in higher amounts of fat and protein can also be helpful before and during workouts. 

What happens when you get to 60 grams of carbohydrates per hour? GI issues can result due to slower gut transit times in women.

Tracking your cycle is an important part of knowing how to fuel yourself. While some birth control options, like the Fertility Awareness Method, teach those with a cycle to track using basal temperature and cervical mucous, apps with or without accompanying basal temperature monitors have made this even easier. I’ve been using the Daysy Fertility Tracker for five years and appreciate how my period can be predicted based on my previous cycle information. There are numerous apps that can be used including Flo, Clue, and MyFlo.  Recording information about how you feel on any given day of your cycle can also be helpful for predicting and adjusting energy needs.

While the above information can be used for those using intrauterine devices (IUDs) or not on any form of hormonal contraceptives (and instead opting for the Fertility Awareness Method), some forms of hormonal contraception, like the pill, have different impacts. This is largely due to the pill creating phases that are different from a natural cycle. For example:

• The first five days of the active pill is equivalent to the mid-follicular phase.
• Following these five days, the body transitions to the equivalent of the high hormone phase. Note that these exogenous hormones are higher than what one would experience on a natural cycle.
• In the last week, when the placebo pill is taken, hormones are back to being equivalent to the mid-follicular phase. 

Since these phases are different, nutrition needs will be different, too. Athletes using oral contraceptives may find they require more carbohydrates, and increased gels (like Spring Energy Gels) during racing and training, during the middle 2-3 weeks of their 4-week cycle.  

While this information may seem like it pertains only to athletes who menstruate, those in the role of coach, spouse, training partner, and teammate should also understand how the menstrual cycle impacts menstruating athletes so they can offer support. We should all encourage athletes to fuel themselves as best as they can. 


References:
Folscher, L. L., Grant, C. C., Fletcher, L., & Janse van Rensberg, D. C. (2015). Ultra-Marathon Athletes at Risk for the Female Athlete Triad. Sports medicine - open, 1(1), 29. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4564455/

Sims, Stacy. (2016). Roar: How to match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life. Rodale Books. 

Sims, S. T., & Heather, A. K. (2018). Myths and Methodologies: Reducing scientific design ambiguity in studies comparing sexes and/or menstrual cycle phases. Experimental physiology, 103(10), 1309–1317. Retrieved from: https://physoc.onlinelibrary.wiley.com/doi/full/10.1113/EP086797

Sims, S. T., Ware, L., & Capodilupo, E. R. (2021). Patterns of endogenous and exogenous ovarian hormone modulation on recovery metrics across the menstrual cycle. BMJ open sport & exercise medicine, 7(3), e001047. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8291316/