Optimisation of the carbohydrate intake during the menstrual cycle
Because it makes a difference

There is no doubt that the female and male physiology is different. Therefore, certain considerations must be taken into account when planning a nutritional strategy for female athletes. Energy and nutrient requirements can be explained by many variables, such as our physical activity, non-exercise activity, the phase of the training cycle, but also the phase of the menstrual cycle. A detailed tracking of the menstrual cycle and nutritional period around the menstrual cycle and training cycle leads to optimal performance and health. In this article you will find basic guidelines for structuring nutrition for female athletes.

The ingested carbohydrates (sugars) are stored in liver and muscle glycogen. The latter is intended solely for the purpose of muscular work and is expended during an exercise. Carbohydrate requirements are determined by the type of physical activity (endurance-based activities require more carbohydrates), the intensity (the higher the intensity, the greater the need), the duration of the training session, environmental conditions and, above all, the physical abilities of an athlete.

Roughly speaking, medium to high intensity workouts require about 5-7 grams of carbohydrates per kg of body mass per day, while extremely strenuous activities that take more hours/days can require even more than 10 g/kg of carbohydrates per day.

Unfortunately, female athletes often fail to consume enough energy-dense, carbohydrate-rich food. A study of the female football team that investigated carbohydrate intake found that female athletes consumed less than 5 g/kg of carbohydrates per day. Insufficient carbohydrate intake leads not only to reduced performance but also to impaired recovery and medical problems associated with relative energy deficiency (RED S).

Influence of hormones on carbohydrate metabolism

The hormones oestrogen and progesterone act directly and indirectly on tissues and organs involved in energy metabolism. They are produced in the female body, but can also be ingested in synthetic form as part of a hormone replacement therapy or as oral contraceptives. The effect on menstrual loss (amenorrhoea) or during menopause must not be neglected.

Compared to their male counterparts, women show a greater reliance on fat oxidation to support energy demands and less dependence on carbohydrates, which can be partly explained by the activity of the above-mentioned hormones.

Due to the monthly fluctuation of oestrogen and progesterone during the menstrual cycle, differences in substrate metabolism are expected. In studies in which men and women are treated with oestrogen, they found greater fat oxidation and greater reliance on the energy derived from fat. In the luteal phase, where the concentrations of both oestrogen and progesterone are high, greater fat oxidation rates are observed at the same absolute intensity. Consequently, the muscles begin to spare the glycogen, but there is also more efficient storage of the glycogen.

Oestrogen reduces the breakdown of liver glycogen, which could lead to lower blood sugar levels. This can impair performance, especially during high-intensity exercise where carbohydrates are the main source of energy. To avoid such inconveniences, increased carbohydrate intake before and during intensive luteal phase exercise is crucial. Increased carbohydrate intake, and therefore increased availability of sugar from the blood, solves problems caused by the reduced breakdown of glycogen in the liver.

While the glycogen storage capacity is increased in the luteal phase, the opposite can be observed in the follicular phase. For the same amount of stored glycogen, more carbohydrates are needed due to the lower storage capacity, which must be ingested in the follicular phase.

Here you can find some practical recommendations:

Rehrer N.J. et al 2017

To conclude, fluctuations of female sex hormones influence the metabolism of substrates and thus energy availability during training. Optimally structured nutrition according to the training plan and menstrual cycle leads to well-executed training sessions and consequently optimal results. Coaches and nutritionists at the Human Performance Centre monitor your cycle and adapt training and nutrition according to your specific needs.

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