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Persistent fatigue, lack of energy, or low motivation? Before blaming stress or lack of sleep, it might be useful to take a closer look at your vitamin D levels. This essential nutrient plays a crucial role in many bodily functions, and a vitamin deficiency can quickly impact vitality.
Vitamin D: much more than just a bone vitamin
Vitamin D, also known as the sunshine vitamin, is a fat-soluble vitamin synthesized by the body under the effect of UVB rays.
It exists in two main forms: vitamin D2 (ergocalciferol), found in certain plants, and vitamin D3 (cholecalciferol), found in animal products and produced by our skin when exposed to the sun.
It plays a key role in:
- the absorption of calcium and phosphorus, essential for bone health
- the immune system
- the regulation of mood and daily vitality
Vitamin D levels below 30 ng/mL (the limit set for optimal status) can lead to symptoms such as chronic fatigue, muscle weakness, or even an increased risk of fractures in the long term [1].
How can vitamin D deficiency cause fatigue?
Vitamin D deficiency can disrupt energy metabolism, alter the production of certain hormones, and affect the balance of the nervous system. Several studies suggest that insufficient vitamin D intake is associated with daytime fatigue, lack of motivation, and slower muscle recovery after exercise [2].
This is partly due to its role in neuromediator regulation and its ability to support immune defenses, which are often compromised during periods of prolonged fatigue.
Moreover, low 25-hydroxyvitamin D in the blood can be the first marker of a latent deficiency, even without visible symptoms. This type of deficiency is particularly common in winter, among people with little sun exposure, or those following a diet low in vitamin D-rich foods.
What foods ensure a good vitamin D intake?
To avoid fatigue linked to vitamin D deficiency, it is essential to ensure a regular intake, via diet or food supplements, especially in case of lack of sun.
Here are some foods rich in vitamin D:
- Fatty fish (salmon, mackerel, sardine)
- Cod liver and its oil
- Egg yolk
- Dairy products fortified with vitamin D
- Mushrooms (exposed to UV)
However, these intakes often remain insufficient to meet the RNIs (Reference Nutrient Intakes), which set the requirements at 15 μg/day (or 600 IU) for an adult. Hence the importance of supplementation, especially in autumn and winter.
What to do in case of persistent fatigue and low levels?
If you experience lasting fatigue, muscle pain, or low mood, a blood test can confirm a possible vitamin D deficiency. In case of levels below 30 ng/mL, vitamin D3 supplementation is often recommended by health professionals.
Food supplements are available in different forms (capsules, ampoules, oils) and dosages. It is preferable to choose a D3 form, which is better absorbed than D2, and to respect the dosages to avoid overdose.
The final word
Unexplained fatigue can sometimes be a sign of vitamin D deficiency. This essential vitamin, still too often neglected, conditions our energy, mood, and physical resilience. 15 to 20 minutes of sun exposure per day, a rich diet, and appropriate supplementation are the pillars of an effective strategy against chronic fatigue.
Scientific references
【1】Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266–281. doi: 10.1056/NEJMra070553
【2】Nowak A, Boesch L, Andres E, et al. Effect of vitamin D3 on self-perceived fatigue: a double-blind randomized placebo-controlled trial. Medicine (Baltimore). 2016;95(52):e5353. doi: 10.1097/MD.0000000000005353