Do Menstruating Endurance Athletes Have Unique Sport Nutrition Needs?

Nutrition is one of the main cornerstones of my practice as a naturopathic doctor. It’s my “bread and butter” so to speak. Therefore I often get asked by my patients if there are any specific nutrition requirements for menstruating runners and endurance athletes. The short answer to this question is absolutely! For the long answer, keep reading.

A Quick Note on the Following Recommendations

For the context of this post I won’t be recommending dosages, forms of supplements, how much of each food to eat etc. This is because these types of details must be decided on a case by case basis. I suggest bringing these topics up with your health care provider, discuss if there is a need to test for any of these nutrients and changing your dietary choices and supplements based on your health practitioners’ recommendations for you! You are a unique individual who needs their own personalized care!

Protein Needs for Female Athletes

Protein intake is important in all endurance athletes for a number of reasons. For example, protein is important for cell and muscle recovery, immune function and hormone health.

Recent research suggests that previous protein recommendations for female (term used in the research) endurance athletes are actually too low. This may be because of the common school of thought in endurance sports that low body weight is needed for optimal performance. This sometimes leads to both male and female (again, terms used in the referenced studies) athletes reducing their food intake which in turn reduces the amount of protein athletes consume. This phenomenon is seen especially in female endurance athletes. It is so crucial to ensure you are eating enough to keep yourself properly fuelled with the guidance of a health care provider who is knowledgeable in sports nutrition. This will help you to avoid the negative health impacts that have the potential to occur when body weight and body fat percentage get too low. This brings up the added importance of cultivating love and acceptance of our bodies, a topic that needs a post all on its own.

In addition, progesterone, one of the hormones that peaks in the second half of our cycle (the luteal phase) has a catabolic effect on protein. This may translate into an added need for adequate protein intake during the luteal phase of the menstrual cycle to counteract progesterone’s catabolic, or breaking down, effects. I will be digging deeper into female hormones and performance in a future post!

Therefore, previous recommendations of 1.2 - 1.4 g of protein/kg of body weight/day have been raised to 1.6 g (or higher) of protein/kg of body weight per day for female endurance athletes. I know it can be challenging for a lot of athletes to get enough protein intake, I would love to work with you on this!

Iron Deficiency in Menstruating Athletes

It may not be a surprise that folks who have regular periods struggle with iron deficiency more than those athletes that do not. This is largely based on the fact that menstruation (having a period) leads to monthly iron loss. If you pair this with an overly heavy menstrual period then the odds that you are deficient in iron or even anemic (low number of red blood cells) increases.

Another reason athletes, especially runners, tend to have lower levels of iron has to do with the physical impact running has on the body. This impact of “pounding the pavement” can cause tiny microscopic traumas in the gut lining and hemolysis, also known as destruction of red blood cells.

Finally, an additional potential cause of iron deficiency that is emerging in the research in endurance athletes (runners in particular) is the amount of inflammation that is caused by strenuous physical activity. This is due to interleukin 6 (IL-6), an inflammatory marker that is part of the immune system, being elevated during exercise. IL-6 then causes hepcidin, a hormone regulator of iron homeostasis, to be secreted which then affects iron absorption and excretion.

Iron is one mineral I highly recommend all endurance athletes have tested since it is so common for this mineral to be deficient in this population. The range for what is a normal iron (typically tested as its storage form, ferritin) level is quite large. For athletes, I like to see ferritin at least around 60-80 ug/L. Signs you may have low iron include fatigue (despite having good sleep), shortness of breath, heart palpitations, hair loss among other signs and symptoms. That being said, I’ve seen many patients with low iron stores who don’t experience any of these symptoms. That’s why it’s best to get iron tested and this is a test that I run often with my athletes!

Finally, you should not supplement iron unless you are indeed deficient. When iron levels are too high this can cause negative health effects. Which brings me to the point that once your doctor has discovered you have iron deficiency, follow up bloodwork should be done in 3-4 months to make sure you are absorbing iron well and that you are not at a dangerous level of iron stores.

Vitamin D and Calcium Requirements

Most of us know the positive effects vitamin D and calcium have on our bone health which is especially important in athletes. However, vitamin D also plays a role in the immune system and muscle function among other areas of our health. Unfortunately, in the research female athletes tend to have lower levels of these 2 micronutrients when compared to male athletes.

Vitamin D can be found in fatty fish and sundried mushrooms however most of our vitamin D is obtained through sunlight (the quote “We need water and sunlight to function, we’re basically beautiful houseplants with more complicated emotions” is actually quite true!). Calcium can be found in collards, spinach, broccoli, dairy products, fortified dairy alternative products, sardines and tofu. Plant sources of calcium can be just as well absorbed if not better in some cases than dairy products. However, you often need to eat more of the plant sources to get the same amount of calcium that is found in dairy products, so be aware of this if you are a plant based athlete. Interestingly, as an aside, vitamin D, iron and calcium (among many other nutrients) play very important roles for folks who are trying to get pregnant and who are already pregnant. You should check in with your health care provider if you are planning to get pregnant or already are pregnant to make sure you are getting enough of all of these nutrients.

Athletes should be able to get their daily calcium needs from food but for folks living in more northern climates, it may be difficult to get their recommended daily intake of vitamin D in the colder months. Causes of lower than optimal calcium levels in female endurance athletes could be due to too low of caloric intake in this subset of the population as mentioned previously. In addition, calcium may also be lost in sweat in varying amounts depending on how much an athlete sweats.

Womxn athletes who do not menstruate may also have an increased requirement for calcium - especially if the lack of menstruation is due to menopause. This relates to estrogen’s role in bone health and calcium balance. Check with your health practitioner to see what your unique calcium and vitamin D needs are.

What about Menopause?

This is a unique topic that deserves a post all on its own! Stay tuned for a post focused on this group of athletes in my upcoming “Do Female Hormones Have an Impact on Sport Performance?” blog post in the coming weeks!

In Summary

Unfortunately in endurance sport, there is often an emphasis placed on having a low body weight and low body fat percentage which may result in all athletes fuelling inadequately. This can result in endurance athletes, especially seen in females, to be deficient in protein, vitamin D, calcium and iron. It is key to visit a knowledgeable health practitioner to get guidance and support for your particular activity level, hormone levels and sport of choice to make sure you are fuelling properly. You should not supplement these nutrients without testing your levels and medical supervision. Reducing these nutrient deficiencies could have a big impact on your performance and your overall health.

References:

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doi: 10.1080/17461391.2017.1416178

doi: 10.1016/s0002-9378(16)32480-2