Benefits of Vitamin D3 and why we are deficient in this vitamin

Introduction

Vitamin D3 is one that plays a crucial role in the regulation of the immune system and bone metabolism. It can be obtained by sun exposure (90%) and through diet (10%).

Despite its importance, vitamin D3 deficiency is a growing problem in many populations. Various factors such as sunscreens with an SPF greater than 8, age, darker pigmentation, a north latitude greater than 40 degrees, and the winter season reduce vitamin D production in the skin. That is why it is so important to consume this vitamin through food supplements.

The impact of vitamin D3 on disease prevention has been extensively studied, leading to increased awareness of the need to maintain optimal levels. In this article, we will explore the function of Vitamin D in the body, how it is metabolized, and the keys to effective supplementation.

Vitamin D3 Benefits

Vitamin D is a fat-soluble vitamin with essential endocrine functions. Among its main benefits:

Strengthens bones and muscles

Vitamin D plays a critical role in bone metabolism by facilitating the absorption of calcium and phosphorus in the small intestine. These minerals are essential for the mineralization of the bone matrix, which ensures the strength and density of the bones. Without adequate levels of vitamin D, calcium in the diet cannot be absorbed efficiently, which can lead to diseases such as osteomalacia in adults and rickets in children.

Vitamin D is essential for athletes because it plays a key role in muscle health and performance. It helps regulate calcium, a fundamental mineral for muscles to contract and relax properly. This allows you to build force during movement and recover after physical activity.

In addition, vitamin D promotes the development of type II muscle fibers, responsible for strength and speed in intense movements, which is crucial both for sports performance and for preventing the loss of muscle mass with age. Maintaining optimal levels of this vitamin contributes to improving strength, coordination and endurance, helping to prevent injuries and promoting a better quality of life. https://doi.org/10.1210/edrv-10-1-3

Strengthens the immune system

Vitamin D is crucial for the activation of immune cells, including T cells and macrophages. These cells depend on the presence of vitamin D receptors to detect and respond appropriately to pathogens. In addition, this nutrient regulates the release of pro-inflammatory cytokines, promoting a balance between inflammation needed to fight infection and resolution of inflammation to prevent chronic tissue damage. Vitamin D deficiency has been associated with an increased risk of respiratory infections, such as the common cold and flu, as well as an increased incidence of autoimmune disorders, such as multiple sclerosis and systemic lupus erythematosus. https://doi.org/10.3390/nu15173842. In fact, this was the vitamin that became most popular during the COVID19 pandemic because of all the publications that were appearing of its importance in preventing infection and helping to make it less severe.

Protects the heart

This nutrient also has a significant impact on cardiovascular health by influencing several physiological mechanisms. Vitamin D regulates the function of the vascular endothelium, helping to maintain the flexibility and elasticity of blood vessels, which is crucial for blood pressure control. It also modulates levels of renin, an enzyme involved in the renin-angiotensin system, which plays a key role in regulating blood volume and blood pressure. In addition, adequate levels of Vitamin D have been linked to a reduction in arterial stiffness and a lower risk of left ventricular hypertrophy, contributing to the prevention of cardiovascular diseases such as hypertension and heart failure. https://doi.org/10.1155/2018/9276380

Vitamin D3 Deficiency

Numerous studies have shown that vitamin D deficiency is a widespread problem worldwide. It is estimated that between 40% and 70% of the adult population has insufficient levels of this vitamin, being even more common in older people, overweight individuals and those suffering from chronic diseases (Cashman et al., 2016). [Reference: https://doi.org/10.3389/fnut.2023.1070808]

Symptoms of deficiency include:

• Chronic fatigue
• Muscle and bone pain
• Weakened immune system
• Increased risk of osteoporosis and fractures
• Depression and mood disturbances

Diet provides insufficient amounts of Vitamin D3

We can provide vitamin D3 through the diet (10%). Some foods contain this vitamin. However, the amount present in the usual diet is minimal compared to the daily needs. The main food sources include:

• Fatty fish (salmon, tuna, sardines): 300 – 600 IU per serving
• Beef liver: 50 IU per 100 g
• Egg yolk: 40 IU per unit
• Fortified dairy: 100 – 150 IU per glass of milk

Given that the recommended daily intake of Vitamin D for adults ranges between 600 and 800 IU, and that many people require higher doses to reach optimal blood levels, relying exclusively on diet is often insufficient (Bouillon, 2017) https://doi.org/10.1024/0300-9831/a000733

Vitamin D3 and sun exposure

Vitamin D3, known as the “sunshine vitamin”, plays a fundamental role in the regulation of multiple biological functions. Although it occurs endogenously through sun exposure (90%), many people have deficiencies, especially in climates with less solar radiation. That is why, even if you sunbathe, you can be deficient in vitamin D.

While ultraviolet B (UVB) radiation stimulates the synthesis of vitamin D3 in the skin, this production is influenced by several factors:

• Season of the year and geographical latitude: During the autumn and winter months, in areas above 35° latitude (either north or south), the intensity of UVB radiation is insufficient to generate adequate amounts of vitamin D in the skin. This implies that many people have lower levels at certain times of the year (Holick, 2007) DOI: 10.1172/JCI29449.
• Use of sunscreen: Sunscreens with a protection factor (SPF) greater than 30 can reduce skin production of vitamin D by more than 95%, according to dermatological studies. https://doi.org/10.1111/j.1365-2133.2012.11004.x.
• Little direct sun exposure: Spending most of your time indoors, whether it’s due to lifestyle, work, or older age, limits the amount of UVB light that reaches your skin.
• Skin pigmentation: People with darker skin have higher levels of melanin, which decreases the skin’s ability to produce vitamin D in response to sunlight.

Many people face difficulty reaching optimal levels of vitamin D in their blood, even when they are exposed to the sun or take supplements.

The explanation lies in our genetics. Vitamin D does not act as a simple vitamin that is ingested and ready for its function. In reality, its activation process is complex and occurs in several stages, involving various enzymes and proteins, in which genes play a fundamental role.

The 4 Key Steps in Vitamin D Activation

• Synthesis in the skin: When the skin is exposed to the sun, particularly UVB radiation, a precursor molecule called 7-dehydrocholesterol is produced, which is converted into cholecalciferol (vitamin D3). Some people have variations in the DHCR7 gene, which affects the production of this precursor and reduces its ability to synthesize vitamin D.
• Transport in the blood: Once in the circulation, vitamin D3 must be transported. Vitamin D transporter protein (DBP) is involved in this process. Differences in this gene may cause some people to carry less vitamin D in their blood, reducing its availability.
• Conversion in the liver and kidneys: For vitamin D to be active, it needs to go through two conversion steps:
  • In the liver, the enzyme CYP2R1 converts vitamin D into 25-hydroxyvitamin D (25(OH)D), which is the form measured in blood tests. Variations in the CYP2R1 gene can cause some people to produce less 25(OH)D.
  • In the kidneys, another enzyme, CYP27B1, transforms 25(OH)D into its active form, 1,25-dihydroxyvitamin D (1,25(OH)₂D). Mutations in this gene can affect the final conversion of vitamin D to its active form.
• Action on cells: the vitamin D receptor (VDR): Finally, vitamin D must bind to its receptor on cells (VDR) to exert its effects. These receptors are found in the thyroid gland and bones. If this receptor does not work properly due to variations in the VDR gene, the active vitamin D will not be able to perform its function properly.

What does this mean in practice?
There are people who, due to their genetics, require greater sun exposure or higher doses of supplements to achieve optimal levels of vitamin D in the blood. Genetic testing may be helpful in identifying whether a person has difficulties in any of these processes.
The optimization of vitamin D is not limited to the amount, but also depends on how our body processes and uses it.

Major organs and tissues with vitamin D receptors (VDRs)

1. Bones (Osteoblasts and Osteoclasts)
   • It regulates bone mineralization and calcium and phosphorus metabolism.
   • It is involved in bone remodeling and in the prevention of diseases such as osteoporosis.
2. Small intestine (enterocytes)
   • Increases the absorption of calcium and phosphorus from food.
   • It is key to maintaining mineral homeostasis in the body.
3. Kidneys
   • It is involved in the reabsorption of calcium in the renal tubules to prevent its loss in the urine.
   • It regulates the production of the active form of vitamin D by the enzyme CYP27B1.
4. Parathyroid glands
   • It modulates the production of parathyroid hormone (PTH), reducing its secretion when there is enough calcium.
   • This prevents secondary hyperparathyroidism.
5. Immune system (Macrophages, T and B lymphocytes, Dendritic cells)
   • It regulates the immune response, reducing inflammation and promoting immune tolerance.
   • It can influence autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.
6. Skeletal muscle
   • It contributes to muscle function and prevents sarcopenia in older people.
   • Vitamin D deficiency has been associated with muscle weakness and risk of falls.
7. Brain and Central Nervous System
   • It influences neuronal function and the production of neurotransmitters.
   • Its role in neurodegenerative diseases such as Alzheimer’s is being studied.
8. Thyroid
   • Although not its primary function, vitamin D has been shown to modulate thyroid autoimmunity and thyroid hormone production.
9. Heart and cardiovascular system
   • It influences the health of blood vessels and the regulation of blood pressure.
   • It may have a role in preventing cardiovascular disease.
10. Pancreas (Beta Cells of the Pancreas)
    • It modulates insulin production, which can influence the prevention of type 2 diabetes.

Regular supplementation is key to avoiding fluctuations in blood levels

To maintain adequate values of Vitamin D3 in the blood throughout the year, experts recommend continuous supplementation with personalized adjustments according to individual needs. Regular monitoring by testing for 25-hydroxyvitamin D (25(OH)D) is critical to avoid both deficiency and toxicity.

The optimal range of vitamin D in the blood is between 40 and 60 ng/mL, although some studies suggest that levels of up to 70 ng/mL may be beneficial for bone and immune health. [Reference: https://doi.org/10.3390/nu14194148]

Frequently Asked Questions

How much vitamin D3 should you take?

The recommended amount of vitamin D3 varies depending on age, lifestyle, and individual health conditions, such as sun exposure. It is essential to consult with a healthcare professional to determine the proper dosage and avoid both deficiency and toxicity of this vitamin. However, general guidelines state the following daily doses:

• At general ranges: between 1000 and 5000 IU per day, depending on blood levels. Without knowing the values, it is not recommended to take more than 4000 IU/day.
• Adults with diagnosed impairment: 2,000 – 5,000 IU/day.
• Patients with specific pathologies (osteoporosis, autoimmune diseases, malabsorption, advanced age): 5,000 – 10,000 IU/day under medical supervision.

It is important, as mentioned above, to evaluate blood levels, since the amount needed depends on factors such as sun exposure, genetics and diet.

Is Vitamin D3 a temporary supplement or should it always be taken?

Vitamin D3 should be considered an essential nutrient that should be maintained consistently throughout the year for most people. Some professionals suggest taking 4000 IU in winter and 2000 IU in summer, and performing a blood test after a month to adjust the dose.

How do you know if the vitamin D we take is enough? What are the optimal values in blood and why measure 25(oh)D instead of 1.25(oh)₂D?

The most reliable test for vitamin D status is the measurement of 25-hydroxyvitamin D (25(OH)D) in the blood.

Reference values for 25(OH)D (according to most health experts):

• Severe deficiency: <20 ng/mL
• Insufficiency: 20 – 30 ng/mL
• Optimal: 40 – 60 ng/mL (some sources suggest up to 80 ng/mL for certain benefits)
• Possible toxicity: More than 100 ng/mL (rare and associated with excessive supplement intakes)

Levels below 20 ng/mL are associated with an increased risk of bone diseases, such as rickets in children and osteomalacia in adults. On the other hand, levels above 50 ng/mL do not provide additional benefits and may increase the risk of adverse effects, such as hypercalcemia.

How do you know if the vitamin D3 you take is enough through blood tests?

The only accurate way to assess whether vitamin D3 levels are adequate is through a blood test, measuring 25-hydroxyvitamin D (25(OH)D), the metabolite that reflects vitamin D deposits in the body.

Why measure 25(OH)D and not 1,25(OH)₂D?

1,25(OH)₂D is the active form of vitamin D, but its measurement does not adequately reflect the actual levels of vitamin D3 in the body due to the following reasons:

• 1,25(OH)₂D remains normal even in cases of vitamin D deficiency.
• Its production in the kidneys is regulated by parathormone (PTH), calcium and phosphorus.
• When vitamin D is low, the body compensates by increasing the conversion of 25(OH)D into its active form, which can result in normal or even elevated levels of 1,25(OH)₂D, masking the actual vitamin D deficiency.
• 1,25(OH)₂D has a very short half-life (about a few hours), while 25(OH)D can stay in the body for weeks.
• 25(OH)D is the best marker of vitamin D deposits in the body, as it is stored in the liver and other tissues.
• 1,25(OH)₂D can be elevated in inflammatory and kidney diseases, which can give an erroneous reading.

Is vitamin D necessary to be stopped before a test?

To obtain an accurate measurement of vitamin D levels, it is recommended to maintain uninterrupted supplementation until the day before the test, if taken daily. For higher doses given once a month, results may vary depending on when the test is performed, as levels may be higher immediately after taking the dose and lower after 15 days.

Conclusion

Vitamin D3 is an essential nutrient with extensive benefits for bone, cardiovascular and immune health. Its supplementation is essential to prevent deficiencies, improve quality of life and reduce the risk of various diseases.

Determining the appropriate dose requires considering individual factors, sun exposure and the values obtained in clinical analyses. Consulting with a healthcare professional is key to ensuring safe and effective supplementation.

Vitamin D acts as a multifunctional endocrine regulator with implications for both immunomodulation and bone and cardiovascular metabolism. Its ability to improve calcium and phosphorus absorption ensures the integrity of the skeletal system, while its influence on the renin-angiotensin system and blood pressure regulation underscores its impact on vascular health. In addition, it plays an essential role in activating immune cells, promoting an efficient adaptive response and reducing the risk of infections and chronic inflammatory diseases.

Recent studies have shown that the benefits of this vitamin, which acts as a hormone, depend on correct dosage, bioavailability, and interaction with other dietary and metabolic factors. Therefore, personalized supplementation is recommended, based on specific needs determined by health professionals.