The term “biomarkers” is a shortened term for biological markers. Biomarkers are a broad category of medical signs that provide an objective measure -accurate and reproducible – of a person’s medical state [1]. While there are different ways to get biomarkers, the most common method is blood draws.
While we don’t entirely know all the biomarkers and what they can genuinely indicate, we have been able to develop baseline parameters for a wide variety of populations. These biomarkers can measure if nutrient deficiencies are present, resulting in the presentation of subtle symptoms that otherwise cannot be explained.
According to the American Dietetic Association, Dietitians of Canada, and the American College of Sports medicine, athletic performance and recovery can be enhanced through precise and individualized nutrition [2].
Impairments in performance and recovery can result from nutrient deficiency, measured via blood. In athletes, specific nutrient deficiencies have been identified, resulting in reduced work performance, muscle function, immune system, and recovery [3].
The idea is that we can optimize our nutrition using biomarkers to individualize dietary needs.
Below are seven critical vitamin and mineral status biomarkers that support physiological processes and impact performance.
Vitamin D
Studies have reported high rates of Vitamin D deficiency at speeds of 73% [4]. Rates were even higher for those that practiced Indoors, during winter months, with the addition of iron depletion.
Vitamin D is an essential, fat-soluble vitamin sourced from fatty fish, red meats, liver, egg yolks, and fortified food. Vitamin D is interesting because it is also obtained by being in sunlight.
Vitamin D plays a role in various physiological processes, including regulating the parathyroid hormone required for bone development, immune function, and Protein Synthesis. A vitamin D deficiency has been shown to impair muscle action and reduce muscle strength [5].
A systematic review identified that vitamin D supplementation (in those deficient) resulted in improvement in muscle strength and immune system in athletes [5]. Another study reported supplementation improvements in aerobic performance in combat sports athletes.
While vitamin D impacts performance, it is a fat-soluble vitamin stored in fat tissue. Before supplementation, vitamin D levels need to be established if a deficiency is present. It is recommended that athletes maintain 25(OH)D levels (a measure of vitamin D) to >40 ng/mL [6].
Iron
Iron status is the second most common nutrient deficiency in athletes; reported rates are 22-31% (mainly reported in female athletes) [7].
Iron plays a significant role in helping hemoglobin, a type of protein on red blood cells responsible for carrying oxygen to all body parts. Without enough iron, oxygen transportation is impaired, leading to fatigue.
Sources of iron include red meat, seafood, beans, dark leafy greens, and fortified foods.
Diagnostic levels of iron deficiency are ferritin levels below 15 ng/mL, but given the increased needs for athletes, a ferritin goal of 30 mg/mL or higher may be ideal [8]. An iron deficiency can be treated with nutrition counselling, oral supplementation, and severe causes by injection.
Calcium
Calcium is the primary mineral required to maintain strong bones and carry out other essential functions such as muscle contraction, blood clotting, and secretion of hormones. Sources of calcium include dairy products, green leafy vegetables, and soy products.
Due to high-intensity training and energy expenditure, athletes need to consume calcium-containing foods to prevent bone loss. Insufficient calcium status has been observed in female athletes and associated with injuries such as stress fractures [9].
The recommended calcium intake for adults is 1000-1500 mg of calcium per day.
B Vitamins
B vitamins include thiamin, riboflavin, niacin, pyridoxine, folate, biotin, pantothenic acid, and choline. B vitamins play a role in performance by playing a role in the energy metabolism of fats, carbs, proteins, and other bioactive compounds [3].
While defects in the B vitamins are not highly prevalent, female athletes are at a higher risk of folate and cobalamin deficiency, indicating anemia and impaired performance. There is an increased risk of vitamin B deficiencies in those who follow a diet that minimizes meat intake, as the primary source of b vitamins includes animal protein sources. Plant-based sources also have B-vitamins, but they may not be as easily absorbed.
While there is no specific measure of vitamin B status, the individual B-vitamins can be measured to identify a nutrient deficiency.
Vitamin E
Vitamin E is another fat-soluble vitamin required for the function of organs and is a powerful antioxidant. While vitamin E deficiency is not prevalent, diets low in fat can result in a vitamin E deficiency.
Sources of vitamin E include nuts and seeds (and oils), fatty fish, kiwi, mangos, and peppers.
While vitamin E has no direct implication on performance but can reduce cellular damage from intense training efforts. In a study of 30 elite cyclists, supplementation of 800 IU vitamin E significantly reduced markers of oxidative damage [10].
Another benefit of vitamin E supplementation may be in altitude, where oxidative stress is higher. Still, the study that demonstrated improvements included a small sample size of 6 mountain climbers [11].
The literature on vitamin E supplementation in athletes is sparse. Still, it is recommended that athletes consume various fruits and vegetables to increase dietary intake of vitamin E and other antioxidants.
Magnesium
Magnesium is a mineral that plays a role in 100s of metabolic reactions in the body, including muscle and nerve function. Magnesium can be found in legumes, dark leafy vegetables, nuts, seeds, whole grains, and fortified cereals.
Due to high levels of training, athletes lose magnesium via sweat and urine, those with suboptimal intake [12]. Low magnesium levels can contribute to muscle cramps, fatigue, and nausea. Magnesium is also an essential mineral for energy metabolism.
A study with 23 elite triathletes supplemented with four weeks of magnesium demonstrated increased power output than those without [13]. Endurance athletes may be at higher risk of magnesium deficiency and may need supplementation [12].
The broad reference range for serum magnesium is 1.5-2.5 mg/dL. However, athletes may need a higher reference range that is not yet determined [14].
Zinc
Zinc is a mineral that, as emerging evidence, may play a supporting role in athletes. Zinc is most notably known for its impact on the immune systems but plays a role in metabolism and energy (carbs, fats, and proteins).
Sources of zinc include whole grains, dairy products, oysters, red meat, poultry, beans, and legumes.
Long-term endurance athletes have been reported to have lower plasma zinc levels than less active controls [15], which is associated with impaired immune function and muscular fatigue, ultimately degrading performance. This appears to result from zinc being excreted in sweat and urine [16].
If an athlete presents a deficiency, it is recommended to increase dietary intake or supplement if dietary intake can not be maintained.
Take-A-Way
It is essential to understand that a single biomarker measurement does not allow for a precise explanation of an individual’s health status. While these biomarkers can provide value, it is a combination of various factors that should be integrated to help athletes practically interpret biomarker data.
Overall, monitoring nutrients biomarkers early can reduce the potential performance impairing impact of long-term nutrient deficiencies.
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References
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4. Constantini NW, Arieli R, Chodick G, Dubnov-Raz G: High prevalence of vitamin D insufficiency in athletes and dancers. Clin J Sports Med 2010, 20(5):368-371.
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16. Córdova A, Navas FJ: Effect of training on zinc metabolism: changes in serum and sweat zinc concentrations in sportsmen. Ann Nutr Metab 1998, 42(5):274-282.
