Can a Simple Supplement Boost Muscle Power Blog Banner
When we think about what it takes to get stronger, faster and more powerful, we usually picture long training sessions, clean diets and maybe the occasional protein shake. What we don’t always think about is the quiet role of vitamins, especially vitamin D. But as it turns out, getting enough of this so-called “sunshine vitamin” could have a much bigger impact on athletic performance than many people realise, particularly when it comes to muscle power.
Athletes spend hours fine-tuning technique and building strength, but if their vitamin D levels aren’t up to scratch, they might be unknowingly holding themselves back. Even young athletes who are otherwise fit and healthy could be affected and a recent study on high school athletes in Japan has shone a light on just how important vitamin D could be for sports performance, particularly anaerobic power.
Vitamin D isn’t just about keeping bones strong. It’s deeply involved in muscle function too. Muscles have vitamin D receptors and when vitamin D levels are optimal, muscles are better at managing calcium, phosphate, and other elements that are crucial for powerful contractions. Essentially, vitamin D helps the machinery inside your muscles work properly, affecting how quickly and forcefully they can contract.
In the study, researchers looked at a group of 21 high school athletes and found that a staggering 71% of them were either vitamin D insufficient or deficient. This was despite training five days a week at a fairly intensive level. It shows that regular exercise and a generally healthy lifestyle aren’t always enough to guarantee good vitamin D status, especially when natural sunlight exposure is low or diets lack enough fortified foods.
To measure the athletes’ anaerobic power, the researchers used the Wingate Anaerobic Power Test. If you’re not familiar with it, imagine an all-out sprint on a cycle ergometer where you’re pedalling against heavy resistance for around 40 seconds. It’s brutal, short and one of the best ways to test an athlete’s ability to produce quick, explosive power. It’s exactly the kind of strength needed for sprinting, jumping, and many competitive sports.
What the study found was quite interesting. Athletes with better vitamin D levels performed better on the Wingate test even before supplementation started. They had higher peak power and could sustain that power more effectively. For example, before supplementation, athletes with vitamin D insufficiency had a median peak power output of 393 watts, compared to 440 watts in those with sufficient levels. After supplementing daily with 1,000 IU of vitamin D for six months, the athletes’ vitamin D levels improved significantly, rising from an average of 27.0 ng/mL to 37.9 ng/mL. Wingate anaerobic power scores also improved notably, with total power output increasing from a median of 580 watts to 598 watts.
The gains weren’t due to building bigger muscles; their muscle mass stayed roughly the same. Instead, it was about making their existing muscles function better. In other words, they became more powerful without necessarily getting bigger.
This is a crucial point for coaches and athletes to understand. Physical improvements aren’t always visible to the eye. We often associate progress with noticeable changes like bigger muscles or faster sprint times, but underlying biological factors like vitamin D status could be quietly influencing an athlete’s output. The takeaway here is that optimising performance isn’t just about pushing harder in training; it’s also about making sure the body has what it needs to respond effectively to that training.
It might be time for coaches and athletes to rethink their supplementation strategies. Traditionally, supplements like protein, creatine, and beta-alanine have dominated the conversation around boosting performance. Vitamin D on the other hand, has often been seen as something to worry about only in terms of bone health or in much older populations. But based on this study, ensuring that athletes maintain sufficient vitamin D levels could offer a simple, safe and inexpensive way to support better power output and by extension, better performance on the pitch, in the gym, or on the track.
For practical purposes, it might be worth considering vitamin D testing for athletes, particularly during the winter months when sunlight exposure drops. A simple blood test can reveal whether an athlete is deficient. If levels are low, supplementing with a daily dose of around 1,000 IU of vitamin D, which was used in the study and showed clear benefits, is generally considered safe for most people. Of course, it’s always wise to consult a healthcare professional before starting any new supplement routine.
Getting enough vitamin D through diet alone can be a challenge, particularly in countries like Japan or even here in the UK, where traditional foods may not naturally contain high amounts of it. Foods like oily fish (think salmon and mackerel), fortified milk and eggs can help, but they’re often not enough to fully bridge the gap, especially for busy teenagers who may have inconsistent eating habits.
Simple habits can make a difference. Encouraging safe sun exposure of around 10–20 minutes a day depending on the season and skin type, along with considering a modest vitamin D supplement, can go a long way. What’s appealing is that it’s not an extreme intervention. It’s a small daily habit that could quietly set an athlete up for better training results, better competition outcomes, and possibly even reduce the risk of injury down the line.
While training hard and eating well are undoubtedly important, athletes and coaches should also think about the “hidden” factors that could be influencing performance. Vitamin D might not grab headlines the way a new gym programme does, but this simple supplement has the potential to make a real difference.
As awareness of vitamin D’s role in sports performance grows, we may soon see regular vitamin D monitoring become as common as fitness testing in clients. For athletes chasing their personal bests and for the coaches guiding them, paying attention to vitamin D could be one of the smartest moves they make.
Want to become a personal trainer with a strong focus on nutrition? Our Nutrition & Exercise Specialist & Master Diplomas™ are the perfect place to start. And recent research makes it even more relevant. A 2025 study on high school athletes found that 71% were vitamin D deficient or insufficient, despite regular training. After just six months of 1,000 IU of daily vitamin D supplementation, athletes saw a notable improvement in anaerobic power, without gaining extra muscle mass, proving that nutrition directly affects performance. If you’re passionate about helping clients fuel their training and get the most out of every session, this course gives you the skills to coach both movement and meals. Learn how to apply real nutritional science to real results.
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