Test, Don’t Guess: Nutritional Tests You Need for Optimal Health And Performance

Taking care of your biggest asset—your body—can be simple with the right nutritional testing.


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Triathletes are an interesting breed. Despite accumulating a mass of measurements relating to bike weight, power output, RPM, running cadence, run shoe weight, heart rate, and RPE, they quite often have very little objective data relating to their health and nutrition. Given the amount of money invested in the sport to gain every little advantage, it is often beguiling why one of the biggest pieces of the puzzle is being overlooked: nutrition and nutritional tests. 

Athletes can spend thousands of dollars on their bikes to lose a few ounces for performance gains yet they could have low levels of iron that—if addressed and corrected—could drastically improve their performance (and their overall health). By testing, monitoring, and focusing on what an athlete consumes on a daily basis, significant improvements in performance can be made—and they don’t all cost as much as swanky carbon fiber bike frames. 

The Basics of Better Understanding Your Body and Health Through Nutritional Tests

Blood testing

In order to best understand how your body is working, you need to take a look at what’s going on inside—and that’s where blood testing comes in. The point of getting a blood test is to ensure your body’s biochemistry and complete blood count (CBC) is on point and that no deficiencies are evident. Triathlon is a demanding sport and you want and need to have a “full tank” before starting any training block. A standard blood test investigating biochemistry and CBC will assess some of the following markers:

  • Metabolic panel (sodium, potassium, blood urea, magnesium, glucose, creatinine, calcium)
  • Lipid profile (LDL, HDL, total chol, triglycerides, ratio)
  • White and red blood cells 
  • Iron panel (iron, ferritin, hemoglobin, hematocrit, transferrin saturation, TIBC, total iron-binding capacity, which is very important for female athletes and plant-based athletes)
  • Liver enzymes

A few other markers to consider are:

  • HBA1c – a better marker for insulin sensitivity and glucose control over 90 days
  • Vitamin D3 (also known as 25(OH)D)
  • B6 and B12 (especially if you are a vegetarian or vegan)
  • Omega 6:3 ratio (if possible)
  • TSH, T4 (especially for female athletes)

Blood tests should ideally be taken every six months or, at most, every 12 months if nothing of note is found in your initial blood draw. The logic here is to be proactive and for you to be functioning optimally rather than adequately. It’s also a good idea to get tested every six months in order to start building a picture of your longer-term health so you can track trends, as it is these trends that really matter. A blood test is a point in time, yet with multiple tests, you are able to see the direction in which you are headed—and also course-correct in a timely fashion if needed. 

Staying On Track

Tracking trends in your health markers really is key to long-term health, fitness, and wellbeing. I have been using the Inside Tracker system, for both myself and my clients, to help achieve this. It helps you better understand how what you do and what you eat on a daily basis can influence your health in the long term. Below you’ll see some screenshots from my Inside Tracker profile to show you how it works, but I’ve also highlighted some of the key areas which are important to focus on, namely:

  • Vitamin D3
  • Glucose
  • Sodium
  • Iron
  • Lipids

Deficiencies in any one of the above can lead to an impact in training and performance, which is why many of the professional sporting organizations I’ve worked with, such as the Toronto Maple Leafs, Leicester Tigers Rugby in the U.K., and the Oracle USA Sailing Team, all incorporate regular screening and blood tests for their athletes. All of these organizations view their athletes as high-value assets and, as a result, want to look after them with the highest level of care. At the Toronto Maple Leafs, for example, this kind of ongoing nutritional testing helped identify key issues such as vitamin D deficiency that had been present for a number of seasons, as well as sodium intolerance, cholesterol issues, and vitamin B12 insufficiencies. These are not uncommon findings among many of the triathletes I work with too. 

Next, we’ll do a deeper dive into some of these nutrients, why you want optimal levels of them, and how to correct them if they are sub-optimal. 

Vitamin D3

Nutritional Tests

Optimal levels of vitamin D are associated with improved bone density, mineral metabolism, muscle function, immunity, tendon integrity, mood, cardiovascular function, metabolic regulation, and total mortality. In short, it really is an impressive and important hormone. The Endocrine Society, National and International Osteoporosis Foundation, and American Geriatric Society define vitamin D deficiency as the level of 25-hydroxyvitamin [1,25(OH)D] of less than 30 ng/mL (nanograms per milliliter)1.

Adequate levels are considered to be above 40 ng/mL and optimal levels for the athletic population are 70 ng/mL. The body makes vitamin D in a chemical reaction that occurs when sunlight, in particular UVB rays, hits the skin. This reaction produces cholecalciferol, and the liver converts it to calcidiol. The kidneys then convert the substance to calcitriol, which is the active form of the hormone in the body and this is what is tested in the blood. It is entirely possible to achieve adequate levels (i.e. 40ng/mL) via 15-20 minutes of full skin exposure to the sun each day—no sunglasses, no sunscreen, and minimal clothing—which is relatively easy in summer, but not so much in winter. It is especially hard if you live in the Northern Hemisphere where sunlight rays from October to March are not even at the right wavelength to produce vitamin D by the body. In addition, if you are dark-skinned and stuck indoors all day, it is a recipe for deficiency or at least insufficiency. 

If sun exposure is not possible then supplementation is required. In order to get above the adequate level of 40 ng/mL, a recommended intake of at least 4000 IU/day is required. Before you consider taking a vitamin D3 supplement, it is highly recommended to have a blood test done as this is the only way to truly check your levels. You can see from my screenshot that my vitamin D was never terrible as I was conscious of supplementing 4000 IU/day. The large peak was as a result of taking 50,000 IU/week for eight weeks as part of the Maple Leafs supplementation regime I introduced over the winter in Toronto to improve team levels.

It had a drastic effect and, as a result, I reduced my intake to 20,000 IU/week and it came back to optimal. For the players in the team that were deficient, the 50,000 IU/week had a positive effect and brought more than 80% of the team into an optimal zone. It is recommended to consume 150 micrograms per day of vitamin K2 with the vitamin D3 as well as consuming it with some fat (e.g. yogurt or with a mixed macro meal). 

Other factors affecting vitamin D status include age, body weight, sun exposure, skin pigmentation, genetics, diet, and supplemental vitamin D (dose, form).2

Can too much vitamin D be bad for you? Yes, it can. Vitamin D will cause the resorption of calcium. Too much calcium could be deleterious to the arteries and cause deposits and hardening, which is obviously never a good thing.

Glucose

Glucose is the simplest form of carbohydrates and a very important part of a triathlete’s diet. Carbohydrates will form a major constituent of dietary intake during moderate to high-intensity training sessions, recovery, and loading meals. Glucose is often be ingested in the form of gels and fluids during bike and run sessions and, as a result, it is important to keep an eye on your blood glucose levels. One way of tracking this daily is through a continuous glucose monitor, such as Freestyle Libre, which is an innovative tool to track your response to food types on your blood glucose levels and ultimately your insulin sensitivity. The other method is by tracking your HbA1c, which is the amount of glucose bound to hemoglobin in your blood over the 90 days preceding your blood test. This will provide the best indication of whether you are managing your carbohydrate and glucose intake well. If it is outside the normal range, a review of your dietary habits to exclude simple sugars where possible and increase fiber intake would be prudent.

Sodium

Hydration is a constant concern for triathletes and the key to hydration is sodium. This is because sodium drives the osmolarity of fluid and results in the osmotic pressure being optimal for gastric emptying. As a result, electrolyte drinks are often recommended for athletes. These are usually required, yet the quantity of sodium being ingested can be an issue, especially if you don’t also consider the sodium content in food you’re consuming (e.g. whole foods, gels, chews, bars and other fluids) along with total sweat rates and sodium content in sweat. Having your sweat sodium content tested is one option to determine an indicator of your sodium content. For most people, an intake of around 600 mg/hour is going to be more than adequate, but if you have large sweat stains on your clothes after heavy sessions then more may be required. Electrolyte drinks such as SOS, SiS, Precision Hydration, and Nuun will often suffice.

It is well worth remembering that you do not have to replace all the sodium lost during exercise in order to function. Replacing around 80% of the amount of sodium lost is a good place to start, so do not feel like you have to consume liters of electrolytes every time you are exercising. The environment temperature and your sweat rate and thirst will guide you best. Excessive sodium or chronically elevated sodium levels can lead to high blood pressure, heart disease, and risk of stroke.3 It is worth checking your levels to ensure your hydration strategy is not causing longer-term health issues.

Hydration is a constant concern for triathletes and the key to hydration is sodium. This is because sodium drives the osmolarity of fluid and results in the osmotic pressure being optimal for gastric emptying. As a result, electrolyte drinks are often recommended for athletes. These are usually required, yet the quantity of sodium being ingested can be an issue, especially if you don’t also consider the sodium content in food you’re consuming (e.g. whole foods, gels, chews, bars, and other fluids) along with total sweat rates and sodium content in sweat. Having your sweat sodium content tested is one option to determine an indicator of your sodium content. For most people, an intake of around 600 mg/hour is going to be more than adequate, but if you have large sweat stains on your clothes after heavy sessions then more may be required. Electrolyte drinks such as SOS, SiS, Precision Hydration, and Nuun will often suffice.

It is well worth remembering that you do not have to replace all the sodium lost during exercise in order to function. Replacing around 80% of the amount of sodium lost is a good place to start, so do not feel like you have to consume litres of electrolytes every time you are exercising. The environment temperature and your sweat rate and thirst will guide you best. Excessive sodium or chronically elevated sodium levels can lead to high blood pressure, heart disease, and risk of stroke.3 It is worth checking your levels to ensure your hydration strategy is not causing longer-term health issues.

Iron

Iron is a hot topic for triathletes, especially for female athletes and those who are vegetarian or vegans. A lack of iron is called iron-deficiency anemia.5 Iron is required for the formation of hemoglobin and myoglobin, both are essential for endurance exercise. Hemoglobin is a protein found in red blood cells that carries oxygen from the lungs to your muscles, as well as the brain and digestive system. When assessing iron status, it is important to understand that serum (blood) iron levels are not always the best indicator of overall iron status. This is because these levels can fluctuate a fair amount on a daily basis. To gain a better understanding of iron status, ferritin status should be reviewed. Ferritin is a protein that stores iron in the muscle. It stores the excess iron in the body and then releases it into the blood when serum levels begin to reduce. If ferritin levels are optimized, your iron status is optimized. If not, then a review of an athlete’s diet and the forms of iron-rich foods being consumed is required. It is important to note that the form of food containing the iron will affect the absorption by the body, and it’s here we identify heme versus non-heme sources of iron and how they are absorbed very differently. Heme iron is found in animal sources, such as beef, poultry, seafood and offal and has a better bioavailability compared to non-heme iron. Non-heme iron is found in plant sources, such as whole grains, seeds, legumes, and leafy greens. Interestingly, non-heme iron is also found in animal sources (because these animals consume plant foods with non-heme). 

Examples of food containing the heme form of iron include: 

  • Liver pate
  • Beef heart
  • Kidneys
  • Steak
  • Ground beef 
  • Lamb steaks 
  • Oysters 
  • Eggs

Non-heme containing foods include: 

  • Fortified cereals 
  • Partially dried figs
  • Apricots 
  • Almonds 
  • Kidney beans
  • Peanut butter
  • Spinach

Some foods high in vitamin C can help improve the absorption of non-heme iron, such as kiwi fruit, strawberries, and oranges. And it’s also well worth remembering that caffeine consumption can inhibit iron absorption and should not be consumed during a meal that contains iron if you are attempting to maximize absorption.

If supplementation is required your prescribing physician will best direct you to the form that provides the optimal amount of iron for your requirements. Ferrous form is usually the first line of prescription although ferric forms can also be considered.

Nutritional Testing: Conclusion

When we think about health we often wait until a symptom raises its ugly head and then reactively begin trying to understand what can be done to resolve the problem. Perhaps a better way of viewing health is being proactive and taking the steps to better understand how your inner workings are firing and then implementing a structured program to rectify any issues that may exist before they materialize as signs and/or symptoms of a disease state. Think of it in the same way as you would preventative work in the gym or maintenance work on your bike—you undertake this work to ensure everything keeps working consistently and optimally, and your nutrition and health should be no different. 

References:

  1. Chauhan K, Shahrokhi M, Huecker MR. Vitamin D. [Updated 2020 May 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441912/
  2. Stokes, Caroline S, and Frank Lammert. “Vitamin D supplementation: less controversy, more guidance needed.” F1000Research vol. 5 F1000 Faculty Rev-2017. 17 Aug. 2016, doi:10.12688/f1000research.8863.1
  3. Dietary Reference Intakes for Sodium and Potassium. Washington (DC): National Academies Press (US); 2019 Mar.
  4. Soliman, Ghada A. “Dietary Cholesterol and the Lack of Evidence in Cardiovascular Disease.” Nutrients vol. 10,6 780. 16 Jun. 2018, doi:10.3390/nu10060780
  5. https://www.hsph.harvard.edu/nutritionsource/iron/