Nutrition · Preventive Medicine
Vitamin D: the silent deficiency that slows your energy, bones, and immune system
Spain has more than 300 sunny days a year. And yet, between 40% and 80% of the adult population has insufficient vitamin D levels. It's not a paradox: it's the result of how we live.
Vitamin D is not exactly a vitamin. It is a prohormone that the body synthesizes from solar radiation and regulates more than 200 biological processes: from calcium absorption to the activation of the immune system, including muscle function, mood, and sleep quality.
When it's lacking, everything gets a little worse. The problem is that vitamin D deficiency rarely hurts or alarms. It manifests in diffuse ways that we tend to attribute to our lifestyle: fatigue, frequent mood swings, creaking bones, colds that won't go away. That's why we call it the silent deficiency.
Why we have a deficiency even though we live in Southern Europe
Cutaneous synthesis of vitamin D depends on several factors: the angle of solar incidence, the amount of exposed skin, the use of sunscreen, and pigmentation. In Spain, from October to March, the solar angle in most of the peninsular territory is too low for UVB to penetrate the atmosphere with sufficient intensity. In other words, even if you go for a walk at midday in December, your skin won't make vitamin D.
Added to this is the fact that the Western diet provides minimal amounts of vitamin D naturally. Only fatty blue fish, egg yolk, liver, and some fortified dairy products contain relevant doses. For a person who works indoors and eats a standard diet, supplementation is not a luxury: it's a necessity.
Signs that your vitamin D may be low
Moderate deficiency rarely produces dramatic symptoms. It slips in among the vague symptoms we tend to normalize:
If you recognize yourself in several of these — especially in the autumn and winter months — it makes sense to check your levels through a blood test (25-OH vitamin D). Optimal reference values are between 40 and 60 ng/ml; below 20 ng/ml is considered clinical deficiency.
What vitamin D is really for in the body
Bone health and calcium absorption
Without vitamin D, the intestine cannot absorb calcium efficiently. Even if you consume enough calcium in your diet, if vitamin D is scarce, a good part of it does not reach the bones. This is especially relevant for women over 40, when the drop in estrogen accelerates bone mass loss. Sustained vitamin D deficiency is one of the most direct risk factors for osteoporosis and fractures.
Immune system
Vitamin D activates specific receptors in T and B lymphocytes, the protagonists of the adaptive immune response. Its deficiency not only increases the frequency of respiratory infections but has also been associated with an increased risk of autoimmune diseases.
Muscle function and performance
There is a high concentration of vitamin D receptors in muscle tissue. Low levels translate into less strength, greater fatigue during exercise, and longer recovery times. For athletes, this is one of the deficiencies that most directly impacts physical performance.
Mental health and mood
Vitamin D is involved in serotonin synthesis. Its deficiency has been linked to a higher incidence of depressive symptoms, anxiety, and seasonal affective disorder (the slump many people notice in months with less light).
Medical Key
Vitamin D does not work alone. For it to function properly, it needs two essential cofactors: vitamin K2 (which directs calcium to the bones and away from the arteries) and magnesium (which activates the liver enzyme that converts inactive vitamin D into its active form). Taking vitamin D without these cofactors is like starting an engine without oil.
The D3 + K2 + Magnesium formula from tres60: why this combination
At tres60, we don't design single-ingredient supplements. The Vit D3 + K2 + Magnesium formula answers a specific medical question: how do we ensure that vitamin D is absorbed, activated, and gets where it needs to go?
| Ingredient | Why we include it | What you will notice |
|---|---|---|
| Vitamin D3 (2,000 IU) | The bioidentical form your skin produces. More potent and stable than D2. | Improved energy, more active defenses, stronger bones. |
| Vitamin K2 MK-7 | Activates osteocalcin, which takes calcium to the bone. Prevents arterial calcifications. | Calcium goes where it should. Long-term vascular safety. |
| Magnesium bisglycinate | Cofactor for liver 25-hydroxylase. Without magnesium, vitamin D is not activated. | Fewer cramps, better sleep, faster recovery. |
We use vitamin D3 (cholecalciferol), not D2 (ergocalciferol). The difference matters: D3 significantly raises blood levels more effectively and has a longer half-life. And we use K2 in MK-7 form, the most bioavailable and the one that remains active longer in circulation.
Who is this supplement for?
- People who work indoors most of the day.
- Women over 35–40 years old who want to preventively protect their bone mass.
- Athletes who experience muscle fatigue or long recovery times.
- People with frequent infections or a low immune system.
- Anyone during the autumn and winter months in peninsular latitudes.
How and when to take it
Vitamin D is fat-soluble, which means it is much better absorbed when taken with a meal containing fat. 1 capsule a day with the main meal is enough to maintain optimal levels in most adults.
The first noticeable changes usually appear between 6 and 12 weeks of continuous supplementation. Follow-up blood tests are the best way to confirm that levels are normalizing.
Vit D3 + K2 + Magnesium — tres60
Formulated by doctors. Produced in Spain under ISO 22.000 and GMPS standards. Suitable for vegans and coeliacs.
View product →Frequently asked questions
Can I take vitamin D all year round?
Yes. In latitudes like Spain, even in summer, many people do not reach optimal levels if they spend most of the day indoors or use high-protection sunscreen. Continuous supplementation is safe at the doses in the tres60 formula and allows stable levels to be maintained throughout the year.
What is vitamin K2 for with vitamin D?
Vitamin K2 activates the osteocalcin protein, which is responsible for "fixing" calcium in the bones instead of depositing it in the arteries. Taking vitamin D without K2 can increase blood calcium levels without ensuring that calcium reaches bone tissue. The D3+K2 combination is the most supported by current evidence.
How much magnesium do I need for vitamin D to work?
Magnesium acts as a cofactor for the liver's 25-hydroxylase enzyme, which converts inactive vitamin D into calcidiol (25-OH D3). Without enough magnesium, this conversion slows down, and the benefits of vitamin D are reduced even if blood levels rise. The tres60 formula incorporates magnesium bisglycinate, the most bioavailable form with better digestive tolerance.
Can it be taken with other tres60 products?
Yes, it is completely compatible with the entire line. In fact, it combines especially well with TriMagnesium (to increase magnesium intake if there is a pronounced deficiency) and with IMMUNE (direct synergy in strengthening the immune system).
This article is for informational purposes and has been written by the tres60 medical team. It does not replace the advice or diagnosis of a healthcare professional. For persistent symptoms or questions about your specific situation, consult your doctor.
