For athletes, nutrition is a crucial element of health and performance.
But how does women's sports nutrition compare to men's?
There are several studies on micro- and macronutrients related to an athlete's body, but these studies seldom respect the specific physiological features of the female body.
Women are generally smaller than men, and their body composition and hormonal picture are different. This reflects in their nutritional requirements.
In this blog, we talk about the female body, its metabolism, and nutrition for female athletes.
Influence of hormones on female athletes
The influence of hormones on physiology and metabolism is similar in women and men. But women have to account for hormonal fluctuations, which affect their metabolism.
Problems with studies
Due to its hormonal complexity, the female body is a lot more difficult to study than the male body.
During the menstrual cycle, complex changes to the hormonal conditions occur. Since these conditions affect many physiological processes in the body, one can only compare measurements from the same hormonal condition or menstrual period.
But it is difficult to find a representative number of female athletes in the same hormonal condition, as no two menstrual cycles are exactly the same.
Studying female athletes is expensive and complex, that's why high-quality studies on women's sports nutrition are scarce.
Because you need a much higher number of female athletes participating in a study to get tangible results, hormonal factors increase the cost and complexity of any high-quality study.
Estrogen and progesterone
Estrogen and progesterone are the two main female hormones.
Both have agonistic and antagonistic effects on nutrient metabolism — agonists activate receptor function, and antagonists prevent it.
The ratio and the quantity of these two hormones influence nutrient metabolism (carbohydrate, protein, and fat) during exercise or rest.
Estrogen and progesterone are the two main female hormones, which among other things affect nutrient metabolism and athletic performance.
Estrogen regulates appetite, energy, and distribution of white fat. It also affects insulin sensitivity in the skeletal muscles, liver, adipose tissue, and the immune system cells, preventing accumulation of fat. Estrogen also affects pancreatic beta cells, regulating insulin secretion and blood sugar levels.
Progesterone indirectly affects energy consumption by increasing metabolism and oxidation of amino acids and reducing muscle protein synthesis.
The female menstrual cycle lasts 28 days on average.
It can be divided into two phases.
- The follicular phase, which lasts from day 1 to day 14 of the cycle.
- The luteal phase, which lasts from day 14 to day 28 of the cycle.
The cycle begins on the first day of the period. That's when estrogen and progesterone levels are low.
During the follicular phase, the level of estrogen gradually increases, while the level of progesterone remains low.
On the contrary, the luteal phase is characterized by higher levels of progesterone and lower levels of estrogen.
The menstrual cycle strongly affects female athletes' nutritional requirements and performance.
Energy intake is crucial for female athletes
To preserve your long-term health and performance, you must intake sufficient quantities of energy for exercise and other daily tasks.
The term energy availability means the amount of energy available in the body after exercise to perform body functions, such as breathing, blood circulation, thermoregulation, growth, and movement.
The optimal energy availability to enable optimal physiological function — essential for your health — is around 45 kcal/kg of lean body mass per day.
If your energy availability is too low, it can lead to the relative energy deficiency in sport (RED-S).
The symptoms of RED-S are disturbances in:
- metabolic function,
- immune system,
- bone metabolism,
- menstrual cycle,
- protein synthesis,
But early symptoms of RED-S may be deceptive and easily attributed to other causes not related to energy deficiency.
Intaking sufficient amounts of energy, i.e. carbohydrates, is crucial for female athletes to avoid health complications, such as RED-S.
The results of the study by Ackerman et al. (2019), which involved 1000 female athletes aged 15-30 years, are worrying.
Compared to athletes with sufficient energy availability, athletes with low energy availability experienced:
- increased risk of menstrual dysfunction,
- deteriorated bone health,
- metabolic disorders,
- hematologic disorders,
- psychological disorders,
- heart disorders,
- and gastrointestinal problems.
Low energy availability also negatively impacted:
- and endurance.
Carbohydrates represent the main source of energy, especially when the intensity of your physical activity is high.
To fill their glycogen stores, same as men, women need 8 to 12 grams of carbohydrates per kilogram of body mass. Studies show that female athletes are equally capable of tolerating high doses of carbohydrates without experiencing digestive issues.
Keep in mind that during the follicular phase, women's ability to store muscle glycogen is reduced. But provided you intake a sufficient amount of carbohydrates, you can still manage to fill your glycogen stores.
Low levels of estrogen in the follicular phase increase glycogen depletion. Be sure to consume sufficient amounts of carbohydrates in this phase.
In terms of muscle glycogen recovery after exercise, the recommendations are the same as for men.
Female athletes who compete in multi-day sports events or have more training sessions in a day must refill their glycogen stores — we recommend that after exercise you consume 1.2 grams of carbohydrates per kilogram of body mass.
Dietary protein provides important building blocks for growth and muscle recovery, which is crucial after exercise.
Female athletes on a predominantly plant-based diet or who want to lose body mass are often subject to protein deficiency.
The recommended protein intake depends on several factors, including the type of your physical activity, its duration, and its intensity.
In the follicular phase, estrogen reduces protein metabolism due to a higher proportion of fat oxidation. Conversely, in the luteal phase, a low estrogen to progesterone ratio increases protein breakdown and amino acid oxidation.
Protein is an essential macronutrient in a female athlete's diet, and you should daily consume at least 1.2 gram of protein per kilogram of body mass.
A widely-accepted recommendation is that an average active person should consume about 0.8 grams of protein per kilogram of body mass. For athletes, these requirements are higher, and the recommendations range from 1.2 to 2.2 grams of protein per kilogram of body mass.
To allow your body to efficiently use dietary protein, we recommend spreading their daily intake over several meals. Each meal should contain about 0.3 grams of protein per kilogram of body mass. In case a female athlete weighs 65 kg, this amounts to about 20 grams of protein per meal.
Dietary fats are the third macronutrient, and they are equally important for the health of female athletes as carbohydrates and protein.
Fats perform many important functions in your body — they are the building blocks of cells, they regulate metabolism, absorption, and transport of fat-soluble vitamins A, D, E, and K, they perform the task of insulation, and they are essential in hormone production.
While they are crucial for your health, sometimes fats are not desired in an athlete's diet, as they do not provide an immediate source of energy and needlessly burden your digestion before, during, and after physical activity.
Daily, you should get about 30% of energy from fats, but also important is their type. Saturated fats should represent no more than 10% of your energy intake, while about 20% should be unsaturated fats.
Limiting fats in the diet of female athletes below 20% of their daily energy intake should be limited to acute scenarios, such as nutrition before race or intense training session when you are filling your glycogen stores.
Chronic fat restriction below the recommended threshold may lead to vitamin A, D, E, and K deficiencies and hormonal disorders, which leads to a variety of undesired health issues.
While you should avoid fat before, during, and after races or intense training sessions, chronic fat restriction is detrimental to your health.
Women versus men
In many sports, men are better than women.
In a marathon, this difference is estimated at about 10%. But this difference gets smaller in ultra endurance sports, such as ultramarathon (4%), or in extreme ultra endurance events where the difference is negligible.
It seems that the longer the event is, the smaller the success margin between men and women gets.
Fats and carbohydrates are the main sources of energy in endurance and ultra endurance exercise. Since glycogen stores are limited, higher fat oxidation rates during prolonged exercise slow down glycogen consumption.
This is also one of the reasons why the margin between men and women gets closer as the length of the endurance exercise increases.
Due to increased fat oxidation, women close the gap between men in ultra-distance endurance events.
Usually, women get more energy from fats than man during physical activity. During prolonged and moderate intense exercise, the breakdown of fats in the body, which includes the release of fatty acids from the fat stores into the bloodstream, is higher in women. This is due to the presence of estrogen, which increases fat oxidation during exercise.
Studies have also shown that female athletes have increased fat oxidation rates during exercise irrespectively of the amount of glycogen stored in the body.
Compared to sedentary women, female athletes need to pay more attention to proper hydration.
This is especially important in hot and humid conditions and during prolonged or high-intensity exercise. If the amount of fluid lost during exercise is high, you also need to replace the depleted electrolytes.
Estrogen and progesterone receptors are also found in the hypothalamus, the cardiovascular system, and in the kidneys — all organs involved in establishing fluid balance in the body.
These organs are susceptible to hormonal changes, but it seems that the hormonal fluctuations during the menstrual cycle have a minimal influence on sodium and fluid balance.
Hydration is fundamental for all body functions, so be sure to consume sufficient amounts of water and minerals aka electrolytes.
The most common cause of micronutrient deficiency in female athletes is low energy availability.
Once the basic needs for a sufficient energy intake of macronutrients are met, it's time to focus on the optimization of the micronutrient intake.
Female athletes often experience iron, vitamin D, and calcium deficiencies.
Iron is crucial to provide enough oxygen to your muscles, which is why it's extremely important for athletes.
Iron deficiency is very unpleasant. Its symptoms are general fatigue, poor results, reduced performance, poor concentration, etc.
Compared to men, women have increased iron requirements due to the fact they lose iron during their period.
Some female athletes have an increased risk of iron deficiency. This includes female athletes on a predominantly plant-based diet, as the absorption of non-heme iron is lower compared to heme iron found in animal-origin foods.
Another group of female athletes who have an increased risk of iron deficiency are those who practice sports with a high frequency of repetitive movements (e.g., running) and endurance sports (e.g., cycling) and those who experience strong menstrual bleedings.
Iron is a crucial mineral for women, especially during their period when they experience increased blood loss.
Vitamin D is one of the micronutrients that performs several important functions in your body, including those that support good physical performance.
Among other things, vitamin D is involved in:
- bone health,
- muscle function,
- immune system,
- and hormonal balance.
That's why it's important that female athletes take care of a sufficient intake of vitamin D — either through food or sun exposure. Especially in winter time, we recommend supplementing this crucial vitamin.
Calcium is another mineral crucial for the health and strength of your bones.
Calcium is also essential for normal muscle function, as it is involved in muscle contraction and muscle relaxation, which in turn are crucial to preserve muscle strength and mobility and to prevent muscle cramps.
Some studies show that an adequate calcium intake helps reducing the symptoms of the premenstrual syndrome (PMS), which allows female athletes to better perform their training sessions.
Female athletes should intake sufficient amounts of calcium with food, which includes dairy products, nuts, legumes, and green leafy vegetables.
In some cases, especially if your diet is limited to a certain group of foods, you should consider supplementing calcium.
Despite all health benefits of physical activity, it can also be harmful.
Studies show that women are more susceptible to the risks of developing different health issues due to improper nutrition during physical activity.
Women must be aware of their special nutritional requirements, which are different to men's. This allows your body to function at its best and achieve good results in sports.