To be completely honest, life as a dietitian involves a bit of guesswork, some trial and error and plenty of ‘let’s give it a try and see how it goes’. 

Which actually makes complete sense given humans are complex beings and there’s a whole lot about the brain, body and emotions of humans that we just don’t, and probably never will, have a really solid grasp on. 

Similarly, while we know a great deal about food, and the contents of food – science continues to evolve and that’s both the beauty and the challenge of nutrition – especially when it comes to performance, as we learn more we can continue to tweak and refine performance (and health) focused strategies. 

But there are lots of things that we can rely on to guide us in better understanding and taking steps to optimise nutritional strategies. 

One of these is a simple blood test. Giving dietitians a lot of clues as to the individual requirements of any athlete.

You can request a blood test from your doctor, but if they aren’t a sports doc or aware of your level of activity, you may want to specifically request iron studies, and even cortisol and testosterone in addition to the basics. 

It’s important that results are compared appropriately, an active elite athlete will have vastly different requirements and levels of ‘acceptable’ compared to their sedentary counterparts. 

Some of the key markers I look for in blood tests that give insight as to nutritional interventions are: vitamin D, red blood cell count, magnesium, B12, folate, and full iron studies including ferritin. 

These can indicate deficiencies that might mean a focus on certain foods, supplementing appropriately or a simple tweak in the timing of intake.

For instance, vitamin D deficiency is common, even in sunny Australia and even in active, outdoor athletes. There aren’t many foods that add to vitamin D status (aside from fatty fish and mushrooms), but a quality supplement can help address this and better support immune function, bone and muscle health and reduce inflammation. 

Markers like insulin and c-reactive protein tell a story of carbohydrate metabolism and excessive inflammation. These tests are sensitive to timing so interpretation is key before changes are recommended. 

Cholesterol, triglycerides, LDL (low density lipoprotein), VLDL (very low density lipoprotein) are also key parts of the overall picture of health and performance and help guide a sports dietitian’s recommendations around food composition and timing for best results. 

A one off blood test can give you a bit of a profile, but they can also be used as monitoring tools. Identification of vitamin deficiencies, iron status, red blood cell numbers, oxidative stress and inflammation – can all help guide not only nutrition interventions, but also training load and adaptations. 

Used properly these markers can help athletes avoid overtraining, illness and injury. 

As always be guided by an experienced professional, but don’t be afraid to ask for tests and don’t wait for something to feel ‘off’ or for health or performance to decline to start getting some testing done. Like any data, several monitoring points provide a much better picture than a one off snapshot.