Estrogen is a sex hormone that is primarily known for its role in female reproductive health. For menstruating individuals in their reproductive years, estrogen fluctuates throughout the menstrual cycle. Its rise mid-cycle stimulates the release of luteinizing hormone, which further signals ovulation to occur, and its fall at the end of the cycle triggers the onset of menstruation.
There are three types of estrogen with varying roles:
- Estrone: a weaker type of estrogen present in the largest amounts during menopause.
- Estradiol: the most common type of estrogen during reproductive years.
- Estriol: the type of estrogen that rises during pregnancy .
Men also produce estradiol, though in much smaller amounts compared to females. And despite its claim to fame as a reproductive hormone, estrogen’s job description cannot be limited only to reproductive health.
Next to reproduction, estrogen is most known for its role in bone health as it’s a major regulator of bone metabolism and has been found to both suppress bone resorption and stimulate bone formation . Notably, low estrogen has been found to predict fractures independent of age and body weight, which is important for athletes who wish to avoid injury 
Estrogen is also being researched for its role in cardiac health. Interestingly, the leading cause of death among females of any age is cardiovascular disease (CVD) . However, the important caveat to this is that studies have suggested that “premenopausal females have reduced incidence of cardiovascular disease (CVD) when compared to age-matched males, and the incidence and severity of CVD increases postmenopause,” which is when estrogen declines . It’s understood that estrogen mediates its cardioprotective actions by promoting the development of new blood vessels and vasodilation, which decreases blood pressure, while decreasing oxidative stress and fibrosis.
Further, estrogen is also believed to play a role in brain and immune health . It’s easy to imagine why estrogen is so important for female athletes!
Low energy availability contributes to low estrogen levels
For athletes, over-exercising combined with under-eating creates low energy availability and is a major contributing factor to low estrogen  . This can be accompanied by low body weight or low body fat percentage, but this is not a prerequisite!
While estrogen does fluctuate from high to low throughout the month in someone having a natural menstrual cycle (i.e. not taking hormonal contraceptives), it can create a variety of symptoms when not produced in sufficient amounts.
Low estrogen might show up as:
- Missing or irregular periods
- Hot flashes
- Increased UTI’s
- Weak bones or stress fractures
- Painful intercourse
- Increased abdominal fat
Missing periods are a red flag indicator that athletes should pay attention to - it’s better to catch a missing period than a bone fracture down the road! If someone is missing a period for more than three cycles (after having already begun menstruation), this is called secondary amenorrhea. It’s often due to an energy deficiency from under-eating and overtraining, but It’s important to explore this issue with a licensed physician to rule out other causes, such as a thyroid disorder .
Estrogen can also be experienced in excess, which may be an outright excess or a normal amount of estrogen unbalanced with its hormonal counterpart, progesterone (i.e. low progesterone). This may feel like heavy, painful periods, breast tenderness, weight gain, and mood swings. This is important for athletes, too, because it can cause emotional stress, discomfort, inconvenience, and training interruptions.
How to support estrogen with nutrition
As a foundation, an athlete must consume enough calories to support overall hormone production, including estrogen. This is a basic requirement that must be met for hormonal health. When energy is restricted, the body simply does not prioritize reproductive health, which carries other benefits as discussed, including bone and heart health.
Athletes tend to have extremely high energy needs that are often underestimated, making it easy to create an energy deficiency. If you’re low on energy, experiencing chronic injuries, or your periods are missing, it might be time to assess your energy intake!
Dietary fats are also important for hormonal health and can play an important role in closing large gaps in calories because of their energy density! In fact, fats have twice the amount of energy per gram compared to carbohydrates and protein.
Some healthy fats to include in your diet include:
- Extra virgin olive oil
- Nuts (e.g. walnuts, cashews, and almonds)
- Seeds (e.g. chia seeds, flax seeds, and sesame seeds)
- Grass-fed butter
- Egg yolks
- Fish (e.g. salmon, trout, and sardines)
Finally, estrogen wants support from both ends - it wants to be created in sufficient amounts, but it also wants to be metabolized in a healthy and efficient manner.
An important factor in this process is dietary fiber and regular, complete bowel movements (firm and at least once daily!) This is especially important if you relate more to signs of excess estrogen. Specific foods positively involved in estrogen metabolism include cruciferous vegetables such as kale, broccoli, arugula, and cauliflower; whole-food sources of soy such as tofu, tempeh, natto, and edamame; and flax seeds.
The good news is that estrogen is responsive to long-term and consistent dietary habits, and there’s much to be done with a food-first approach.
- Estrogen plays roles in reproductive, bone, cardiac, and cognitive health (therefore, always investigate missing periods!).
- Symptoms of low estrogen include missing or irregular periods, increased UTIs, hot flashes, and stress fractures.
- Low energy availability (i.e. not eating enough for your training load) can contribute to low estrogen.
- Sufficient calories are step one to achieving sufficient estrogen levels, and dietary fats can be helpful in closing large gaps in energy.