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Biomarkers

Important Biomarkers for Female Athletes 

We believe that when it comes to your health, there is strength and power in being your own advocate. To support this, our goal is to provide you with key information and knowledge about your body and what it needs to support your health in and out of sport. The more you know, the better you’ll feel and perform.

One way to stay informed is to be aware of vitamins and minerals that are important to support your health as a female athlete. Adequate fueling is closely linked to performance and recovery, and the food we eat provides us with a variety of essential vitamins, minerals, and nutrients. 

Blood Tests

One way to stay in tune with your body’s various nutrient, mineral, and hormone levels is by getting a blood test. These key identifiers, or biomarkers, can help to assess and evaluate different aspects of health and performance. A blood test can provide insight into these levels and what is happening inside of our bodies. It is important to remember that one biomarker does not determine the overall status of your health. Instead, these markers can be thought of as helpful tools to gain more knowledge and understanding of factors that may be affecting how you are feeling and performing. Getting your biomarkers tested periodically can be a helpful way to understand your baseline levels and notice trends over time. 

We have highlighted some of the blood biomarkers that may be important to female athlete health. If you are interested in learning more about your unique biomarkers, speak to a sports medicine physician and/or your primary care doctor about ordering a blood test. 

Iron is an essential mineral that makes up a portion of the hemoglobin molecule within red blood cells. Hemoglobin is responsible for transporting oxygen from the lungs to the rest of your  body. Iron is critical in this process, as well as for exercise performance. When your body does not have enough iron, it becomes harder for your body to efficiently transport oxygen, which can then have negative impacts on your health and performance. When your body does not have adequate iron to make enough healthy red blood cells, iron deficiency anemia can occur. Athletes can experience low levels of iron, or iron deficiency, while still having adequate levels of healthy red blood cells, so they may not meet the criteria for anemia. Note that low levels of iron with or without anemia can still have impacts on performance. Some signs of low iron or iron deficiency anemia include fatigue, shortness of breath, decreased performance, and negative mood states. Foods that are iron rich include red meat, lentils, tofu, and spinach. 

  • Risk Factors for Iron Deficiency
  • Ferritin
  • Complete Blood Count (CBC)

Low iron levels can be caused by several factors. Some potential causes of low iron levels include having a vegetarian or vegan diet, low overall energy intake (see previous blog posts on RED-S and Female Athlete Triad), heavy menstrual cycles, and endurance exercise.

Female Athletes tend to experience iron deficiency at a higher rate than male athletes. Because of this, it is particularly important to be aware of your iron levels as blood loss during menstruation can also affect iron levels. (Alaunyte et al, 2015).

One key blood biomarker to consider when assessing iron levels is ferritin. Ferritin is an indirect marker for the amount of iron stored in your body. A blood test can be a great way to check your ferritin levels. While it is important to have adequate ferritin levels, also be aware that inflammation within your body (fever, chronic inflammatory disorders, acute infections, etc) can also cause ferritin levels to increase. Optimal ferritin levels for athletes should be higher than 35 µg/L (Alaunyte et al, 2015).

A Complete Blood Count or “CBC” is a common blood test. It is a panel of numerous biomarkers that provide information about the production of your body’s blood cells. Blood values like hemoglobin and hematocrit are included in the CBC and help to provide insight on the oxygen-carrying capacity of your body. A CBC also can provide insight on the immune system by looking at the amount white blood cells in your body, and can help detect things like anemia, or iron deficiency, as well as number of other health concerns (George-Gay et al, 2003). 

Vitamin D is a nutrient female athletes should be conscious of, because it is crucial to bone health as well as immunity and injury prevention. Your body can get vitamin D from sun exposure, a number of food sources, and/or supplementation. Food sources of Vitamin D include salmon, tuna, mushrooms, cow and plant milk fortified with vitamin D, and fortified cheese. Several studies have shown that many female athletes tend to have low or abnormal levels of vitamin D. When your body does not have enough vitamin D, you may be at increased risk for bone injuries such as stress reactions or stress fractures and chronic musculoskeletal pain. According to research, it is reasonable to aim for your 25-OH-vitamin D levels to be greater than 50ng/mL to aid in the health and protection of your bones (Holtzman and Ackerman, 2021). 

  • Dream Team: Vitamin D & Calcium

Note that while it can be hard to measure calcium, it is still a very important nutrient, as our bones store large amounts of calcium. Vitamin D and calcium work in unison as vitamin D helps your body absorb calcium. This means that in order to maximize calcium levels in your body, you also need to get enough vitamin D. Athletes deemed as at risk for low calcium can supplement up to 1500 mg/day to support bone health. (Holtzman and Ackerman, 2021) Food sources of calcium include yogurt, cow milk, fortified plant milk, collard greens, and fortified orange juice.

Vitamin B12 is an important vitamin that supports cellular function and often comes from animal food sources. There are few plant based sources of vitamin B12, making it a common deficiency among vegetarians or vegans (Rizzo et al, 2016). Vegetarian or vegan sources of B12 include eggs, nutritional yeast, fortified cereals, or supplements.

  • Vitamin B12 & Folate

Folate, or folic acid, works together with vitamin B12 to produce healthy new red blood cells and aid in the proper function of iron in the body. This is particularly important when there is high demand for new tissue and cell growth in the body such as during adolescence and pregnancy. Maintaining healthy folate levels during pregnancy is important for healthy nervous system development of the infant. Sources of folate include leafy greens, fortified grains, legumes, and seeds. (Mikkelsen, K. and Apostolopoulos, V., 2019.)

There are a number of hormones that can be affected when an athlete is in a state of low energy availability (LEA). If a physician is concerned about LEA they may test for these biomarkers to aid in diagnosis.

  • Estradiol/FSH/LH
  • Thyroid Tests

Estradiol is essential to the menstrual cycle and is also thought to stimulate oxytocin release. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) also play an important role in maintaining a regular menstrual cycle. FSH and LH are responsible for promoting ovulation and stimulating the ovaries to release estrogen and progesterone. Individuals in states of low energy availability (LEA) may experience changes in levels of sex hormones such a estradiol, FSH and LH (Elliot-Sale et al). If you are concerned about LEA or amenorrheic (without a menstrual cycle), estradiol, FSH, LH may be a biomarker to talk to your doctor about. It’s important to note that estradiol will be suppressed when an athlete is on hormonal contraception and can be difficult to interpret if a eumenorrheic athlete (normal menstrual cycle) is unsure of her current menstrual cycle phase.

Thyroid function can be an indicator of low energy availability in both females and males as it can be a helpful warning sign of endocrine dysfunction. Two markers that are commonly assessed if LEA is a concern are total T3 and free T3. In females and males, both total T3 and free T3 decrease as energy availability decreases, with low values potentially being indicative of a state of LEA. This is especially true in amenorrheic athletes, but can also occur in eumenorrheic athletes in a state of LEA (Elliott-Sale, et al. 2018). However, there may be other causes of thyroid dysfunction so it’s important to work with your doctor to appropriately interpret your results and determine if additional workup is indicated.

Sources: 

Alaunyte I, Stojceska V, Plunkett A. Iron and the female athlete: a review of dietary treatment methods for improving iron status and exercise performance. J Int Soc Sports Nutr. 2015 Oct 6;12:38. doi: 10.1186/s12970-015-0099-2. PMID: 26448737; PMCID: PMC4596414.

Malczewska-Lenczowska J, Sitkowski D, Surała O, Orysiak J, Szczepańska B, Witek K. The Association between Iron and Vitamin D Status in Female Elite Athletes. Nutrients. 2018 Jan 31;10(2):167. doi: 10.3390/nu10020167. PMID: 29385099; PMCID: PMC5852743. 

Lee EC, Fragala MS, Kavouras SA, Queen RM, Pryor JL, Casa DJ. Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes. J Strength Cond Res. 2017 Oct;31(10):2920-2937. doi: 10.1519/JSC.0000000000002122. PMID: 28737585; PMCID: PMC5640004.

Holtzman B, Ackerman KE. Recommendations and Nutritional Considerations for Female Athletes: Health and Performance. Sports Med. 2021 Sep;51(Suppl 1):43-57. doi: 10.1007/s40279-021-01508-8. Epub 2021 Sep 13. PMID: 34515972; PMCID: PMC8566643.

George-Gay B, Parker K. Understanding the complete blood count with differential. J Perianesth Nurs. 2003 Apr;18(2):96-114; quiz 115-7. doi: 10.1053/jpan.2003.50013. PMID: 12710004.)

Elliott-Sale KJ, Tenforde AS, Parziale AL, Holtzman B, Ackerman KE. Endocrine Effects of Relative Energy Deficiency in Sport. Int J Sport Nutr Exerc Metab. 2018 Jul 1;28(4):335-349. doi: 10.1123/ijsnem.2018-0127. Epub 2018 Jul 14. PMID: 30008240.

https://www.ais.gov.au/__data/assets/pdf_file/0015/1033440/Vitamin-D-Infographic-FINAL.pdf

Rizzo G, Laganà AS, Rapisarda AM, La Ferrera GM, Buscema M, Rossetti P, Nigro A, Muscia V, Valenti G, Sapia F, Sarpietro G, Zigarelli M, Vitale SG. Vitamin B12 among Vegetarians: Status, Assessment and Supplementation. Nutrients. 2016 Nov 29;8(12):767. doi: 10.3390/nu8120767. PMID: 27916823; PMCID: PMC5188422.

Mikkelsen, K. and Apostolopoulos, V., 2019. Vitamin B12, folic acid, and the immune system. In Nutrition and immunity (pp. 103-114). Springer, Cham. 

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