Health, Podcast

Blood tests and biomarkers for triathletes with Dr. Kush Joshi and Dr. Joel McCay | EP#249

 August 31, 2020

By  Mikael Eriksson


In this Episode you'll learn about:

  • What are the most important biomarkers that triathletes and endurance athletes should be aware of and keep track of?
  • When and how often to get a blood panel done
  • Reference ranges, and the differences between athletes and sedentary people
  • Health and injury risks associated with inadequacies in certain biomarkers
  • Specific discussion around serum iron, ferritin, vitamin D, thyroid hormones, sex hormones, vitamin B12, blood count, hemoglobin, etc.

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03:45 -

  • My name is Joel McCay and I am a doctor specialist in hematology, which is the medical field of diseases affecting the blood and bone marrow.
  • My name is Kush Joshi and I am a sport and exercise medical consultant working at a company called Melio health, which among other things offer blood tests to athletes and other consumers.

Benefits of keeping track of certain blood values

05:30 -

  • When it comes to elite or semi elite athletes, who are all looking to maximize their performance, a minor biochemical abnormality can be detected in different blood tests, which in turn could account for maybe a 1 % loss in performance.

    By detecting such an abnormality and consequently be able to correct it, could play a meaningful marginal gain in certain sports performance contexts.

    A good example of such a parameter would be Vitamin D, which we often see is low in individuals who is suffering performance declines and/or just had a stress fracture.
  • A good idea is to have a blood panel that you take quite regularly (at least twice a year), and one of these times should be during off season or when you don’t put too big of training load on your body, hence you will have your own ”base line” blood data to compare with when you need to check upon things due to symptoms, decline in performance and/or injuries.
  • Normally, you go and see your general practitioner when you start experiencing symptoms of more serious character and at this point, the injury and/or nonfunctional over reaching has already occurred.

    That is why we believe Melio health could play an important role for endurance athletes, as we are offering biochemical analysis in a preventive purpose.
  • What we also are trying to do at Melio is to give our customer a personalized statement in regards to your test results.

    Nowadays, there are many companies out there offering blood tests but no interpretations whatsoever of the results, we at Melio have the expertise to set the blood test results into contexts of what is normal and what is not normal in regards to high performing endurance athletes.

    For example, testosteron could fall below the reference range of what is considered normal, but if the blood test was taken immediately post a massively demanding three weeks training period, a value just below the reference range would then be considered to be expected, which we then will convey to the customer.

Most important blood markers for endurance athletes

17:00 -

  • Vitamin D is probably one of the most important blood markers for endurance athletes together with a full blood panel such as hemoglobin and iron levels.

    Low levels of Vitamin D is associated with development of stress fractures, poorer muscle remodeling capacity (that is basically the body’s ability to recovery and absorb training) and inferior immun response (higher incidence of respiratory tract infections etc.).
  • When it comes to a hematological panel, then hemoglobin together with different kind of iron blood markers are the most important.

    Athletes are in many cases more susceptible to suffer from anemia and/or iron deficiency due to a number of reasons, and that is why it is so important to check.

    Women are even more likely to suffer from anemia and/or iron deficiency due to the constant loss of blood and iron during menstruation, making this test even more important for female athletes.

    From hemoglobin and iron markers one can determine if the athlete is anemic (low hemoglobin) due to iron deficiency (most likely) or anemic from another (more uncommon reason) as well as discover if the athlete is not anemic but has low levels of iron (both in the blood stream and in stores).

    Anemia with iron deficiency should always be treated by taking iron tablets but it is more unclear how to approach iron deficiency without anemia.

    If the patient does not suffer any symptoms (tiredness, lethargic, coldness, shortness of breath etc.) whatsoever, as a first measure I use to recommend diet change in order to adjust iron deficiency without anemia.

Other interesting blood markets

32:00 -

  • Thyroid hormone is also a quite interesting market, where low levels also may be associated with iron deficiency and/or anemia.

    Thyroid hormone is also crucial for the bone structure and low circulating levels is hence also associated with stress fractures.

    When it comes to thyroid hormone and levels of T3, T4 and TSH it is highly beneficial to have ”baseline data” that you can compare the samples you take when you’re having symptoms with.

    For ambitious athletes, slightly surpassed levels of T3 and T4 may just be a consequence of high training load, why it is a bit difficult to say what the intervention would be if an athlete shows low level of thyroid hormones.

    The course of action would probably be on a case to case basis depending on hormone blood levels and symptoms, an endocrinologist (specialist in hormone diseases) may also be consulted.
  • Vitamin B12 is really important for the production of red blood cells and is hence also an interesting bio marker.

    I know one study (on mice) that found that the levels of B12 decreased following long aerobic endurance training, which may be something worth pointing out.

    Vegetarians and especially vegans suffer an extra large risk of B12 deficiency unless they are taking in any supplements.
  • Testosteron is an anabolic hormone and is hence essential for the body’s response and adaptions to training.

    Testosterone could also be highly affected and suppressed by RED-S and high training load, which makes this a very important blood marker to check.

Post-interview addition on testosterone in women from Dr. Joshi

Testosterone has many important features in women including maintaining lean mass and strength, bone density, brain function and overall well-being.

Similar to oestrogen, low levels of testosterone may result in reduced bone density and therefore may increase the risk of stress fractures. In conjunction with testosterone, sex hormone binding globulin (SHBG) may be tested. SHBG is a protein in the blood which a portion of circulating oestrogen and testosterone bind too. The remainder of these androgenic hormones remain free, which is regarded as the bioavailable portion. This is regarded as the portion that is available to act on the tissues of the bodies. If SHBG is high, this means that bioactive testosterone levels are less, and the benefits of testosterone will be limited. Such derangements can be due to a reduced energy state, and blood tests may identify the potential onset of a relative energy disorder. In women this may present as disturbance in menses. Similar to men however, in female endurance athletes, levels are likely to be at the lower end of normal, and longitudinal tests depending on levels of training should be done so to prevent any issues which may occur.

At the opposite end, testosterone levels which are at the higher end of normal, and sometimes elevated, have been seen in a number of athletes. This is seen more frequently in power athletes than in endurance athletes but is important to be aware off. This can also present with irregularities in menstrual function and may warrant investigation for conditions such as polycystic ovarian syndrome (PCOS).

”Over hyped” blood tests

52:15 -

  • I think that albumin as a marker of liver function is quite wasteful to take since many athletes do take in large amount of protein, which elevates the albumin levels without reflecting any pathology.

Practical aspects of blood testing

55:30 -

  • I think it is really wise to try and get a ”baseline value” during the off season period of the year to compare to when being in a very hard training period and/or starting to experience symptoms.

    I believe the cost for doing these tests are quite easy to overcome and gives a high value for the money in terms of potential health gains.

Rapid fire questions

1:04:40 -

  • What is your favorite book, blog or resource?
    Joel: A book called ”the Gene” by Siddhartha Mukherjee.
    Kush: I just finished Heroes by Stephen Fry (a very non-medical answer).
  • What is a personal habit that has helped you achieve success?
    Joel: I am a big Liverpool fan so I use to tell myself ”what would the Liverpool team do in a situation like this?” and act accordingly.
    Kush: Routine, I wake up at 5:30 every morning and exercise as the first thing I do every day, it sets me up for a good day.
  • What do you wish you had done differently at some point in your career?Joel: Getting engaged in research earlier.
    Kush: I think Joel’s point is really valid, but I don’t feel like I have any major regrets in my life, I am happy right where I am in my life.


Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode.

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