Blood chemistry analysis within a nutritional therapy context for athletic clients is a powerful tool. I am not just referring to standard GP panels to check iron status, vitamin D deficiency and TSH, but more comprehensive, privately run panels where you can gain insight into potential dysfunction in many areas.

Many competitive athletes have a wide range of unspecific symptoms, but are used to pushing through fatigue and niggles, putting a lot down to a hard training session, lack of sleep, or out entertaining clients. But what they forget is that day-by-day, week-by-week, this load builds up and can lead to dysfunction of different body systems. Assessing a wide array of markers and learning which ones to look at in conjunction with others, within the context of a client’s full case history, symptoms and training (historic and current), can be a powerful tool to know where interventions should be targeted.    

Examples of where insight can be gained are: 

  • Immune system – certain elevated/depressed markers, such as ferritin, serum iron, albumin, lymphocytes, neutrophils and total WBC’s, may indicate potential bacterial or viral infections. Looking at these in conjunction with other markers, may also help address the cause of symptoms, like hay-fever, caused by an imbalanced immune system and which is prevalent in runners and cyclists.
  • Gastrointestinal function – markers such as total protein, total globulin, total albumin, serum iron (plus others) may help indicate hypochloridria and/or the presence of inflammation, and provide useful information about athletes suffering from GI distress when training/racing.
  • Cardiovascular disease risk – can be assessed not only via lipid markers, but also ferritin, homocysteine, fibrinogen, vitamin D and blood glucose markers.
  • Thyroid – it is estimated that 90 per cent of hypothyroid dysfunction is attributable to Hashimoto’s disease. Markers such as TPO and thyroglobulin antibodies, along with T3, T4, rT3 and TSH to assess for full thyroid function, are useful. Thyroid hormones also help regulate gene transcription in relation to skeletal muscle.
  • Adrenal – low DHEA-S/DHEA in athletes is common when overtraining is an issue. Total cholesterol and sodium/potassium ratio can provide additional insight.
  • Liver and gallbladder – the load that an endurance athlete places on their liver is high, and additional detoxification/antioxidant support may be indicated to help target your nutritional intervention.
  • Acid-base balance – this is an area often impacted in athletes due to the build-up of lactic acid, aggravated by a diet that is insufficiently alkaline – anion gap and potassium/chloride levels can give a good indication of this.
  • Blood sugar regulation – some endurance athletes think they can eat what they want, but the incidence of insulin resistance in athletes is common. Reminding your clients that catching markers of insulin resistance early on is key to metabolic flexibility, a great attribute for endurance athletes. It is also a great tool if you need to discuss overtraining, lack of sleep and poor recovery. 

As always, data must be put into context and there are certain anomalies when looking at endurance athletes’ blood work, that need to be considered. For example:

  • Elevated liver enzymes – AST and GGT can be elevated after a hard/long workout, estimated to return to baseline after four to six days. There is debate as to whether to rest before testing because an athlete is always training, but does one not want to test to see what their typical levels are on a day-to-day basis? If significantly elevated, retesting might be a good idea and if constantly elevated, perhaps reassessing your approach is in order.
  • Haematocrit – while a greater haematocrit is associated with improved performance, a decreased level in endurance athletes, particularly runners, is not uncommon. This is possibly due to a dilutional effect resulting from an increased plasma volume, or to increased inflammation from factors such as the impact from a high foot strike. Look at this in conjunction with MCV and RDW to further differentiate from anaemia.
  • Protein markers – athletes need more protein for repair and recovery than your average individual. With a trend towards veganism, these are useful markers to see if your athlete is taking in enough protein, although gastric function and potential hypochloridria should also be considered.
  • Gastric inflammatory markers – besides the usual suspects, ask about NSAID use, which is highly prevalent in endurance athletes. With open-water triathletes, also consider if they have ever been bitten by a tick or what other parasites they may have picked up from their swimming.
  • Creatinine – this is not only a marker of kidney function, but also a proxy of muscle mass, and it can be elevated after a hard/long training session. Every time creatine is phosphorylated, creatinine is produced, so the more muscle you have and the more active you are, the more creatinine is produced. If kidney dysfunction is suspected, look at this with other markers of kidney function to gain a more comprehensive picture.

Athletes love hard data and blood chemistry analysis provides unequivocal evidence that is hard to ignore. Testing can therefore help improve client compliance, and is accepted by conventional medics when you need to work alongside them. Blood chemistry also provides easily repeatable data, allowing training progress and health to be assessed and monitored in the same way a coach will monitor TSS scores, FTP and race performance times. It is a powerful tool to help improve clinical outcomes and reach your client’s performance goals within a nutritional therapy context.  

Katherine is a degree-qualified nutritional therapist (mBANT, mCNHC) who specialises in working with clients who love their sport, but where either underlying health conditions are preventing them from reaching their goals and doing what they love, or who simply wish to be preventative. As a GB Age Group triathlete (European Middle and World Long Distance) and mother of two children, she understands the demands faced by her clients and practises what she preaches. Katherine has additional training in eating disorders and obesity, and practices in London and St Albans. Website: