A lack of vitamin D is one of the most common vitamin deficiencies, with approximately 50% of the world’s population struggling to get enough.1 You’d be forgiven for thinking that your yearly trip to sunnier parts is all you need to top up your vitamin D requirements, but you actually need a lot more than this. In fact, Public Health England advises all adults to aid their intake with a 10mcg vitamin D supplement daily during autumn and winter months.2
Vitamin D deficiency can lead to a variety of conditions, such as rickets in children and osteomalacia (softening bones) in adults. Conversely, maintaining optimal levels can help to support energy levels, muscle repair, and exercise efficiency — all factors that can maximise the results you want to see at the gym.
How do you know if you’re deficient in vitamin D?
Vitamin D deficiency is incredibly common, but it can present itself in several ways. These are just a few examples:
- Fatigue: vitamin D can cause low energy levels and tiredness. Studies have shown it’s common for patients with fatigue to have low levels of vitamin D.3
- Bone pain: in part, since vitamin D helps regulate our body's calcium levels, low levels of the vitamin can lead to bone pain.4
- Muscle Weakness: a lack of vitamin D can cause a condition called myopathy, which causes the muscle fibers to not function properly, which in turn can lead to muscle weakness.5>
- Low moods: there are many different reasons for low moods, but some studies have suggested that those who are depressed are more likely to have low vitamin D levels.6
It’s important to note that these are fairly general symptoms. However, when you apply the context of exercise, it's clear to see how these symptoms can directly affect your workout. Let's take a closer look at how maintaining adequate vitamin D levels can help support your workout regime.
People with vitamin D deficiency might become used to life with low-energy levels; especially if the fatigue is only gradual.7
Vitamin D interacts with melatonin; an important mood regulator which helps with sleep by naturally winding down energy levels when you hit the pillow. However, when vitamin D is low melatonin increases, and that can leave you feeling sleepy, even when it's nowhere near your bedtime.8
Symptoms of vitamin D deficiency itself can impact our energy levels. For example, both osteomalacia, a disease caused by a deficiency which softens the bones, and myopathy, a disease also caused by deficiency, but which limits the functionality of the muscle fibers, can leave people feeling fatigued.9
Once a vitamin D shortfall has been made up you could notice a huge difference in your overall wellbeing. You may well find the energy boost can help you fit in extra training sessions or push yourself to reach milestones. On other occasions, the change might be more subtle, such as helping you to push out that extra rep — it entirely depends on the individual.
Supplementing vitamin D can play a critical role in supporting your muscles during a workout by helping them to recover from injury much more quickly, and even acting as a preventative altogether.
In 2015, a study investigated the nutrition status of 214 professional athletes in the National Football League (NFL). It found that low vitamin D levels were widespread amongst them, and that those players who had a reported history of muscle injury were more likely to have inadequate vitamin D levels — which could have contributed to their muscle strain.10
Vitamin D shortages could also cause future fitness setbacks, as those who had lower than adequate levels of the vitamin had higher odds of injuring their core muscles.
So why might this be? One of the most important functions of vitamin D is to help with the absorption of calcium: from both our bones and intestines. Vitamin D is needed to give the enzyme 1-alpha-hydroxylase a nudge to begin doing its job – and it’s this enzyme that’s involved in muscle contractions.11
Injury recovery also requires a strong immune system, with vitamin D helping to activate a special type of cell (called T cells), which can help us fight infections that might develop from injuries.12
One important part of going to the gym is performance. A study has shown that vitamin D supplementation helped athletes significantly increase 10 metre sprint times and vertical jumps, showing that this vitamin is especially important for avid gym goers and professional athletes.13
Of course, not everyone is a professional athlete, but the knowledge that this vitamin does have the potential to help you see performance results, no matter how small, is definitely something worth shouting about.
What should you do if you suspect your low in vitamin D?
If you have any of the symptoms of vitamin D deficiency, your GP can test whether you are deficient and advise you accordingly.
In any event, to maintain healthy vitamin D levels, ensure your diet contains oily fish and eggs (especially yolk). But bear in mind, while a healthy diet is incredibly beneficial, the main source of vitamin D comes from the sun’s rays triggering its synthesis on your bare skin. In the UK, however, the sun's UVB rays are not strong enough to allow this process to happen, which is why Public Health England advises everyone to take a supplement in the autumn and winter months.
For more information on how vitamin D can help support your overall health and wellbeing, head to our advice centre.
1 N. Rathish, A. Masheer, Vitmain D: The "Sunshine" vitamin, (2012) Journamal of Pharmacology & Pharmacotherapeutics, 3(2): 118–126.
2 Vitamin D and Health (2016), Science Advisory Committee on Nutrition,
3 S. Roy, A. Sherman, M.J Monari-Sparks, Olga Schweiker, K. Hunter, (2014), Correction of Low Vitamin D Improves Fatigue: Effect of Correction of Low Vitamin D in Fatigue Study (EViDiF Study), North American Journal of Medical Sciences 6(8).
4 E.Shipton, E. Shipton, Vitamin D and Pain: Vitamin D and Its Role in the Aetiology and Maintenance of Chronic Pain States and Associated Comorbidities,(2015), Pain Research and Treatment
5 B. Hamilton, Vitamin D and Human Skeletal Muscle, (2012), Scandinavian Journal of Medicine & Science in Sports 20(02)
6 S.Penckofer, PhD, RN, J.Kouba, PhD, RD, M.Byrn, BSN, RN, and C.Ferrans, PhD, RN, FAAN, Vitamin D and Depression: Where is all the Sunshine? (2011), HHS Public Access 353(1-2).
7 Amber Tovey(2014), New trial shows treating vitamin D deficiency significantly improves fatigue symptoms, Vitamin council
8 Damasceno A1, Moraes AS2, Farias A2, Damasceno BP3, dos Santos LM2, Cendes F3, Disruption of melatonin circadian rhythm production is related to multiple sclerosis severity: A preliminary study. J Neurol Sci.
9 B. Hamilton, Vitamin D and Human Skeletal Muscle, (2010), Scandinavian Journal of Medicine & Science in Sports
10 Brian J. Rebolledo, M.D.'Correspondence information about the author M.D. Brian J. RebolledoEmail the author M.D. Brian J. Rebolledo, Johnathan A. Bernard, M.D., Brian C. Werner, M.D., Andrea K. Finlay, Ph.D., Benedict U. Nwachukwu, M.D., M.B.A., David M. Dare, M.D., Russell F. Warren, M.D., Scott A. Rodeo, M.D.,(2018), The Association of Vitamin D Status in Lower Extremity Muscle Strains and Core Muscle Injuries at the National Football League Combine, Journal of Arthroscopic and Related Surgery, (Issue 4, Pgs 1280-1285).
11 Pojednic. R, Ceglia. L, The Emerging Biomolecular Role of Vitamin D in Skeletal Muscle, (2014), HHS Public Access, 42(2).
12 Bazian, Edited by NHS Website, Vitamin D immune system boost? (2010), NHS
13 Volpe, Stella Lucia Ph.D., R.D., L.D.N., FACSM, Vitamin D and Exercise Performance,(2014), ACSMs Health and Fitness Journal Volumne 18, Issue 3