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5 Micronutrient Deficiencies to Look for in Athletes

BY Phil White

Even if your athletes seem to be eating well, they may still not be getting everything they need. Here are five common micronutrient deficiencies that can affect athletes, and how to spot them.

Nutrition coaching for endurance athletes often centers on obsessing about the intake of the macros – protein, carbs and fat. Perhaps it also addresses under-fueling and consuming too many calories at the other end of the spectrum. But even though many of your athletes might get these big rocks in place, they could still struggle with their micronutrient intake. In this post, we’ll zero in on five vitamins and minerals that athletes are often low in, explain the adverse effects of deficiency in each, and then suggest how they can increase their intake — first through foods and then, if needed, via supplementation.


This mighty mineral plays a part in more than 300 processes throughout the body and brain. While your athletes need to keep their sodium and potassium levels topped up during training and racing, it’s magnesium that helps modulate the balance between the two — more on this in a moment. Magnesium also aids in the utilization of carbohydrates, helps regulate cardiovascular output and promotes adequate rest and sleep.

Magnesium is in short supply for some athletes for two different reasons. First, because their muscles contract more often and with greater force than sedentary folks, athletes use more ATP, which uses magnesium. Nutritionist Dan Garner stated that athletes require around 20% more magnesium than the general population “due to the increased need for magnesium during muscular repair and increased magnesium loss through sweat and urine.” Second, when your clients place extra stressors on their bodies, their rate of magnesium usage increases because their allostatic load is higher. These can include sports-specific factors like pre-race anxiety, travel to events, the combined effects of training and competing and lifestyle factors such as relationship issues.

A study published in The American Journal of Clinical Nutrition stated that 79% of adults don’t consume enough magnesium. Some athletes take standalone magnesium supplements or natural sleep aids that contain it, like Doc Parsley’s Sleep Remedy or ZMA, to up their consumption. But it’s best to start with trying to increase your athletes’ dietary intake. Good portable snack sources include Brazil nuts, almonds and pumpkin seeds. Whole grains like brown rice and sprouted bread are good magnesium choices for main meals.

B Vitamins

OK, this is technically cheating as the B vitamins constitute an entire family of micronutrients. But bear with me, as they’re all essential to your athletes’ ability to produce energy, repair muscle tissue and form red blood cells. Thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (b5), pyridoxine (B6) and biotin (B7) can all be depleted by excessive sweating in hot and humid conditions and too many bathroom breaks. Suppose any of your clients are regularly taking ibuprofen or other NSAIDs, eating a lot of processed foods instead of whole ones or struggling with chronic inflammation. In that case, this can also negatively impact their vitamin B levels.

In his compelling book Peak, Dr. Marc Bubbs wrote, “A simple heuristic for correcting low levels of B-vitamins is to increase animal protein intake and eat more raw, leafy greens. For vegans, think about supplementation during periods of intense training.” He went on to recommend that if any of your athletes are comparing B vitamin complexes, they should look for the term “activated” on the labels. As with all supplements, those vetted by NSF Certified for Sport®, Informed Sport or Labdoor are more likely to be pure and free of banned substances and contaminants.


Vitamin C gets most of the attention when it comes to immune system function, but zinc also plays a crucial role in warding off viruses and pathogens. If any of your clients frequently struggle with cold and flu-like symptoms, this could indicate that they’re not getting enough zinc to support optimal immunity. It might also impact their utilization of vitamin A – an antioxidant that reduces free radical damage, is involved in regulating immunity and is needed for cell, bone and muscle growth – and vitamin D.

Zinc deficiency can compromise all of these processes. The authors of a study published in Sports Medicine noted that “In athletes, zinc deficiency can lead to anorexia, significant loss in bodyweight, latent fatigue with decreased endurance and a risk of osteoporosis.” In trying to pinpoint why zinc levels might be too low, they suggested that “Endurance athletes often adopt an unusual diet in an attempt to enhance performance: an excessive increase in carbohydrates and low intake of proteins and fat may lead to suboptimal zinc intake in 90% of athletes.”

An easy win is to assess your clients’ macronutrient intake and have them tip the scales in favor of fewer carbs and more fat and protein if they’re following a high-carb approach. Red meat, cheese, shellfish and oysters are all rich animal sources of zinc, while for those on plant-based diets, legumes, seeds, and nuts are solid choices.

Vitamin D

It might seem like your endurance athletes would be the least likely group to be deficient in vitamin D. After all, they’re training outside multiple times a week and sometimes every day. Yet, the weak winter sun makes it difficult for anyone to get enough during frosty months in the Northern Hemisphere. Even in spring, summer and fall, if someone’s covering up with long sleeves or putting on sunscreen before heading out for a run or ride, they might not be getting anywhere near the kind of sun on skin that would promote sufficient D synthesis. And as a result, their bone health, sleep, and immune function could be compromised.

The solution? Supplementing with between 2,000 and 5,000 milligrams in the winter and getting at least 20 to 30 minutes of direct sunlight on as much skin as possible per day before applying sunblock throughout the rest of the year can boost vitamin D levels. A study conducted by British and Australian exercise scientists concluded that such supplementation in vitamin D deficient athletes improved their muscle regeneration and increased their speed, strength and power, demonstrating vitamin D’s unheralded role in muscle function. It’s important that your athletes don’t consider their vitamin D status in isolation. The paper in The American Journal of Clinical Nutrition mentioned earlier concluded that even if they’re consuming sufficient vitamin D or prompting its production through sunlight exposure, this won’t be expressed in their bodies unless they are also getting enough magnesium.


Most adults in the general population get enough calcium, but a surprisingly high number of athletes aren’t. A study of cross-country runners found that 40% of female participants and 35% of males had suffered at least one stress fracture during their competitive careers. “All of these did not meet the recommended daily energy intake or adequate intakes for calcium or 25(OH)D required for their amount of training,” the researchers wrote.

We’ve already addressed the vitamin D component of their findings. When it comes to calcium, one reason for the increasing rates of stress fractures might be related to more athletes switching to non-dairy alternatives. In a previous article, I stated that per Wolff’s Law, the body will make bones thicker, denser, and more resistant to injury when regularly exposed to resistance training. But this is only possible when your clients are intaking enough of the building blocks, of which calcium is the cornerstone. It’s also involved in nerve conduction and muscle contraction.

The simplest solution to calcium is the most obvious: your athletes should get more from their diets via dairy, seafood and leafy greens. If they still suspect a shortfall, a supplement could be used to get their total intake up to between 1,000 and 1,500 mg per day.

As a coach, it is important to be aware of the signs and symptoms of micronutrient deficiencies in your athletes. A lack of these essential nutrients can hurt performance and overall health. So if you notice any problems with your athletes’ performance or overall health, consider looking for a deficiency in one of these five micronutrients.


Qi Dai et al, (2018, December). Magnesium Status and Supplementation Influence Vitamin D Status and Metabolism: Results from a Randomized Trial.Retrieved from https://pubmed.ncbi.nlm.nih.gov/30541089.

Bubbs, Marc. (2019)pg. 170. athletes’ New Science of Athletic Performance that is Revolutionizing

Micheletti, A. et al. (2001). Zinc Status in Athletes: Relation to Diet and Exercise. Retrieved from https://pubmed.ncbi.nlm.nih.gov/11475319.

Close, GL. et al, (2016, September). New Strategies in Sport Nutrition to Increase Exercise Performance. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0891584916000307.

Knechtle, Beat, et al (2021, March). Vitamin D and Stress Fractures in Sport: Preventive and Therapeutic Measures—A Narrative Review. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7999420.

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About Phil White
Phil White is an Emmy-nominated writer and the co-author of The 17 Hour Fast with Dr. Frank Merritt, Waterman 2.0 with Kelly Starrettand Unplugged with Andy Galpin and Brian Mackenzie. Learn more at www.philwhitebooks.com and follow Phil on Instagram @philwhitebooks.

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