I write a lot about lack of periods, which is known as amenorrhea, and nutrition strategies to restore the menstrual cycle (for more on that, click here), but how about nutrition for the female athlete with a regular menstrual cycle? Unlike males who have relatively stable levels of sex hormones, females have cyclical changes in sex hormones each month. This change in hormone levels impacts physiology and can in turn change the nutrition requirements or nutrition strategies implemented to optimize performance in the female athlete. In this blog, I cover nutrition across the menstrual cycle.
The menstrual cycle lasts 21 to 35 days and can be broken down into two phases: the follicular phase and the luteal phase (see image below). Day 1 of the menstrual cycle is the first day of bleeding, and marks the start of the follicular phase. During the early and middle of the follicular phase, levels of both estrogen and progesterone are low. Ovulation occurs half-way through the menstrual cycle and marks the start of the luteal phase. During the luteal phase, both estrogen and progesterone are high. In the image below you can see the changes in estrogen and progesterone levels throughout the menstrual cycle.
To determine the phase of your menstrual cycle you need to know when you ovulate. This can be determined with a urinary ovulation stick that can be purchased at most pharmacies. Divide the number of days of your menstrual cycle in half to estimate the day of ovulation and begin testing for ovulation 3 days prior to your estimated day of ovulation. For instance, if you have a 28-day cycle then ovulation would be estimated to occur on day 14 or if you have a 30-day cycle then ovulation would be estimated to occur on day 15. The number of days of your menstrual cycle should be fairly consistent from month to month, so if you know on what day of the menstrual cycle ovulation occurs then you can determine when you are in the follicular phase and when you are in the luteal phase of your menstrual cycle.
Notably, a unique hormonal phase of the menstrual cycle is during the late follicular phase, which is about 14-26 hours prior to ovulation. During this time estrogen levels are at their highest while progesterone levels remain low. This is unique as estrogen and progesterone are thought to have imposing effects, so this phase allows the examination of how estrogen impacts physiology without the presence of progesterone. Unfortunately, most research examining differences across menstrual cycle phase compare just the mid follicular phase and mid luteal phase, so I will just be discussing these two phases of the menstrual cycle.
Energy needs may fluctuate:
Resting metabolic rate, which is the calories required by the body at complete rest, is higher during the luteal phase of the menstrual cycle compared to the follicular phase . As such, calorie needs may be increased during the luteal phase, which is supported by research showing that females naturally increase their energy intake during the luteal phase of their menstrual cycle . You may notice that you have increased hunger during the luteal phase of your menstrual cycle because of this increase in resting metabolic rate. Don’t be surprised by this or try to ignore these hunger signals. If you’re feeling more hungry, trust your body, and eat more food.
Carb and protein requirements may change:
During the follicular phase of the menstrual cycle there is decreased levels of carbohydrate stores in muscles [3,4] and ability to re-synthesize these carbohydrate stores . Some research also shows that compared to the luteal phase of the menstrual cycle, more carbohydrate is used as an energy source during exercise during the follicular phase [6–10]. As a result, female athletes may benefit from increasing carbohydrate intake during the follicular phase of the menstrual cycle. Some examples of carbohydrate rich foods include: oats, rice, pasta, potatoes, fruit, milk, and yogurt.
While athletes may benefit from increasing their carbohydrate intake during the follicular phase of the menstrual cycle, during the luteal phase, protein needs may be greater [11,12] and female athletes could consider increasing consumption of protein during this time. When it comes to protein recommendations, it’s important to consider both the dosage and timing of protein intake. Across 4-5 equally spaced meals/snacks, aim for 0.3-0.5 grams of protein per kg of body weight. For instance, if you weigh 65 kg then you would aim for 20-35 grams of protein per meal .
Pre-cooling strategies may be become more important:
The high levels of progesterone during the luteal phase of the menstrual cycle causes an increase in body temperature . This increase in body temperature during the luteal phase may impact the ability to exercise optimally in hot and humid weather . Female athletes exercising in hot environments during the luteal phase of the menstrual cycle should be conscious of this and could consider implementing pre-cooling strategies to counteract this increase in body temperature, such as drinking an ice slushy pre-exercise . Alternatively, don’t be surprised if you find it harder to exercise in hot conditions during the luteal phase of your menstrual cycle. Be easy on yourself and slow down your pace accordingly.
Consider nutrition strategies aimed to alleviate menstrual cycle symptoms:
Most females experience menstrual symptoms in the days leading up to the onset of menses. There are a variety of different symptoms that are experienced and each female is unique. This may include stomach cramps, fluid retention/bloating, mood changes, and/or breast pain . While these symptoms don’t change nutrition requirements per se, targeted nutrition strategies could be implemented to help alleviate symptoms. For instance, if you struggle with stomach cramps and gas, reducing high fibre foods that are difficult to digest may be helpful. For those struggling with fluid retention and bloating, reducing sodium intake may help. Menstrual cycle symptoms may also require a change to the training plan such as reducing the intensity or volume of training.
Despite the well-known physiological changes across the menstrual cycle, much more research is needed on nutrition for the female athlete. The monthly changes in hormones that female athletes experience can have a profound effect on physiology, which may in turn influence nutrition recommendations.
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