How much vitamin D should I take?

In addition to sunlight, you should consider a vitamin D intake range to train hard and feel healthy.

As an athlete, reducing the likelihood of conditions and injuries while pushing your body to its limits is crucial for achieving success; therefore, adding vitamin D, among other micronutrients, is essential for your well-being and performance.

Well, due to its many benefits, numerous athletic research studies have been conducted on the optimal level of this vitamin for athletes.

Vitamin D is particularly important because:

• Boosts immune defenses.
• Helps the body fight injuries.
• Protects the joints and bones.
• Optimizes physical performance.
• Stimulates protein synthesis.
• Increases testosterone.
• Reduces inflammation.

In addition, its deficiency is associated with an increased risk of cardiovascular disease.

What does the scientific literature say?

Many studies indicate how much vitamin D to take and what the optimal amount is. Around 4,000 IU daily is often discussed, with an additional 6,000 IU in winter

It is also not recommended to take more than 10,000 IU per day without medical supervision, as toxicity symptoms may develop. Overdose symptoms may include mental confusion, nausea, and vomiting, but they are rarely seen.

A high-quality 5,000 IU dose of a supplement is an excellent investment in your health and a safe level for athletes; however, one thing should be kept in mind [2].

There are two forms of vitamin D available as supplements;

• Vitamin D3 is the over-the-counter supplement, while vitamin D2 is the prescription form.
• Surprisingly, research consistently indicates that the over-the-counter form (vitamin D3) is more readily absorbed by the body and is the best form to take.

Why do athletes require more vitamin D?

Vitamin D plays an important role in supporting many of the body’s systems, including the muscles, nervous system, and immune system, making it particularly important for athletes [3].

This micronutrient also plays a critical role in calcium absorption, which is important for developing strong bones. Scientific research indicates that adequate vitamin intake throughout life helps prevent stress fractures, muscle injuries, and long-term diseases [4]

However, athletes who are vitamin D deficient and participate in a training program have a high risk of skeletal injuries, autoimmune diseases, and arthritis.

In this case, a slightly higher intake is recommended, especially in cold climates or if you have darker skin. Remember that the body can produce it from ultraviolet B rays, which in the Northern Hemisphere are likely to occur only in summer.

In sports, peak performance requires the best nutritional support, and this micronutrient is a fundamental pillar, as it can also help you build muscle and reduce body fat while you control your hormone levels.

Does vitamin D have an anabolic effect?

To determine whether vitamin D3 can actually have an anabolic effect, the researchers conducted an in vitro study with muscle cells, insulin, and leucine [5].

• The focus of this study was the anabolic mTOR signaling pathway in muscle cells.
• The results showed that, in the presence of insulin and leucine, the vitamin significantly improved mTOR pathway activity and protein synthesis.

This means that vitamin D has the potential to directly alter protein synthesis in muscle cells and promote muscle growth.

Can it increase testosterone?

Getting out in the sun can be about more than relaxing and getting some color; it could actually be anabolic because vitamin D  can increase testosterone.

A study found that when a group of fitness athletes took 3332 IU per day for one year, their testosterone levels increased by an average of 25% [6].

Another study found that men with sufficient vitamin D levels had significantly higher testosterone levels and lower SHBG levels than men who had insufficient amounts of the vitamin in their blood serum [7].

Does it increase muscle strength?

Vitamin D affects muscle histochemistry and therefore has a positive effect on muscle strength.

This was confirmed in a meta-analysis of controlled trials investigating the effect of supplementation with this vitamin on muscle strength in young athletes who received vitamin D3 daily.

• The participants underwent upper- and lower-limb strength exercises.
• They performed handgrip dynamometer strength exercises, one-repetition maximum bench press, one-repetition maximum leg press, free-weight squats, an isokinetic dynamometer test of gastrocnemius–soleus strength, and isometric quadriceps contraction.

Researchers found that vitamin D supplementation had a significant positive effect on strength indices in the upper and lower limbs; therefore, taking this vitamin daily is an effective way to increase muscle strength.

How is it linked to athletic performance?

Although vitamin D is not considered a direct enhancer of athletic performance, having optimal blood levels reduces the risk of debilitating stress fractures, which indirectly affects performance through prevention.

Therefore, by preventing injuries that could keep you away from the gym and the weights, this micronutrient is crucial for helping you perform at your best, because it protects your osteoarticular system and boosts your immune system.

A review by Von Hurst identified only two studies that showed a beneficial effect on muscle strength after supplementation in deficient athletes, associated with improved jumping performance, VO2 max, and running ability [8].

It actually has a positive effect on VO2 max, indicating that elite athletes can or should take advantage of its ability to increase performance.

How does vitamin D act in the muscles?

Vitamin D is not technically a vitamin; it is actually a prohormone produced photochemically in the skin when exposed to sunlight, and unlike traditional vitamins, it has its own hormone receptor (VDR).

Through VDR receptors, it is found throughout the body, including skeletal muscle, where it activates pathways that regulate multiple processes, such as the proliferation and growth of myocytes or muscle cells.

In addition to regulating calcium homeostasis in the bones, it affects skeletal muscle through these VDR markers, which are present in muscle cells.

A series of studies detected this:

• When muscles do not have functional VDRs, the result is smaller and more variable muscle fiber size, as well as lower body weight, size, and coordination levels, indicating that vitamin D has a direct effect on muscle fibers.
• Furthermore, this vitamin promotes the proliferation and differentiation of muscle cells through membrane signaling, which improves myosin movement over actin within the sarcomere through increased calcium release from the sarcoplasmic reticulum, resulting in greater contractile force in the muscle unit.

In addition, this calcium influx also plays a role in muscle cell differentiation.

Above all, vitamin D has a direct effect on skeletal muscle through the VDR receptor and plays an important role in muscle function, strength, and recovery.

Can it influence body composition?

Using innovative technology, the researchers studied the impact of active and inactive vitamin D levels on body composition through a study conducted by the University of Birmingham in the United Kingdom [9].

• The team examined vitamin D levels in 116 healthy people between 20 and 74 years of age, measuring the participants’ body fat and lean body mass.
• The researchers found that women with a healthy body composition and lower levels of body fat were less likely to have high levels of inactive vitamin D, a common marker of vitamin D deficiency.
• In contrast, women with more body fat had lower levels of inactive vitamin D, suggesting that greater lean mass and muscle mass translate into higher levels of active vitamin D, which helps optimize muscle strength.

What role does it play in bones?

On the other hand, it plays an important role in calcium synthesis and maintaining phosphorus levels in the blood, vital factors for keeping bones and teeth healthy.

This role in bone growth and maintenance is well known; however, additional functions have been discovered, suggesting that it may also contribute to the overall health and recovery of a competitive athlete.

Due to prolonged exposure to training and high levels of physical activity, the physiological demands for vitamin D increase in the athletic population.

What athletes may not realize is that even with normal levels of the micronutrient, they may have suboptimal bone health.

Preliminary results from a study of middle- and long-distance runners who suffered stress fractures found that those with higher vitamin D levels returned to sport more quickly.

In this way, vitamin D helps prevent stress fractures, arthritis, and osteoarticular injuries, thereby strengthening your skeletal system.

How does your immunity participate?

Intense training and the constant stress your body experiences while training can make you prone to skeletal injuries, autoimmune diseases, and arthritis, as well as infections that your immune system cannot fight.

In this context, vitamin D  has numerous effects on your immune system, as immune cells (B cells, T cells, monocytes, DCs) respond positively to its immunomodulatory effects when they interact with it, strengthening your body's natural defenses.

Recent evidence supports that certain amounts of the micronutrient circulating in the blood—around 75 nmol/L—help prevent and improve innate and mucosal immunity and generate anti-inflammatory actions through the induction of regulatory T cells, in addition to inhibiting the production of pro-inflammatory cytokines [10].

Insufficient exposure to sunlight (UVB) is the most likely reason for suboptimal vitamin D status in athletes.

Most concerningly, several studies demonstrated that only 5%–15% of recreational athletes meet the minimum requirements for this vitamin.

The anti-inflammatory function of vitamin D

Low-grade chronic inflammation accompanies obesity and its related chronic conditions.

Both peripheral blood mononuclear cells (PBMCs) and cell lines have been used to study whether vitamin D has immunomodulatory effects.

A group of researchers conducted a systematic review on the effect of vitamin D on protein expression and the secretion of inflammatory markers.

The inclusion criteria for study selection consisted of human-derived immune cell lines or cell studies in which PBMCs were obtained from humans between 2000 and 2015 [11].

The selection protocol was mapped according to the PRISMA guidelines. Twenty-three studies (7 cell-line studies and 16 PBMC studies) met our criteria.

• All but one of the selected studies used the active metabolite 1,25(OH).
• The selection protocol was mapped according to the PRISMA guidelines. Twenty-three studies (7 cell-line studies and 16 PBMC studies) met the search criteria.
• Four of the seven cell-line studies showed an anti-inflammatory effect, with suppression of key markers such as macrophage chemoattractant protein 1, interleukin 6, and interleukin 8 being observed.
• Fourteen of sixteen PBMC studies also showed a similar anti-inflammatory effect based on common inflammatory endpoints.

Mechanisms for these effects included decreased expression of toll-like receptor 2 and toll-like receptor 4 proteins; lower levels of phosphorylated p38 and p42/42; reduced expression of phosphorylated signal transducer and activator of transcription 5; and decreased reactive oxygen species.

This review demonstrates that an anti-inflammatory effect of vitamin D is a consistent finding in studies of cell lines and human-derived PBMCs.

And what about cardiovascular health?

Vitamin D is essential for the proper functioning of the endothelial cells lining the blood vessels.

Without sufficient levels of the vitamin, these endothelial cells become more susceptible to damage and dysfunction, which can ultimately lead to the development of atherosclerosis and arterial calcification.

The benefits of supplementing with this micronutrient for cardiovascular disease have not been confirmed in recent randomized controlled trials.

Although several mechanisms linking vitamin deficiency to these factors have been proposed:

• Cardiovascular risk factors.
• Activation of the renin-angiotensin-aldosterone system.
• Abnormal regulation of nitric oxide.
• Oxidative stress or altered inflammatory pathways.

How can you get enough vitamin D?

Vitamin D is obtained from a small number of foods, including oily fish such as salmon, mackerel, herring, and sardines, as well as red meat and eggs.

It is also added to infant formula, as well as some breakfast cereals, spreads, and non-dairy milk alternatives.

Most people can produce enough of this vitamin by spending brief periods in the sun every day.

When sunbathing, expose the uncovered forearms, hands, or lower legs without sunscreen from late April through late September, especially during nap times.

The alternative is supplements; they are generally taken with water. Depending on the product and dosage, the amount may range from 1 to 2 servings daily, preferably with meals.

What are the vitamin D supplements?

Vitamin D3 (CHOLECALCIFEROL) delivery formats range from tablets, caplets, gummy capsules, and softgels.

Liquid supplements with isolated or combined formulas for various uses are also available.

• Combined with minerals such as calcium, magnesium, and zinc to maintain bone density and energy metabolism.
• In multivitamins as nutritional support.

Conclusions

We are currently experiencing a major deficiency of this micronutrient, not only because of viruses or a pandemic, but also because of deficiencies of our own making.

Athletes, including fitness athletes and bodybuilders, have the same predisposition to low vitamin D levels, and even more so because of the amount of effort involved both in their diet and in training with weights or any type of resistance.

According to statistics, most athletes maintain concentrations below 20 ng/mL across a wide range of sports, especially during the winter months.

Vitamin D is important for bone health, but recent research also highlights its essential role in extra-skeletal functions.

• These functions include skeletal muscle growth and immune and cardiopulmonary function.
• In addition to inflammatory modulation, which together influence athletic performance.
• On the other hand, it can also interact with extra-skeletal tissues, regulating injury recovery.
• It can also affect the risk of infections.

Once the question of how much vitamin D to take is clear, you can consider adding foods rich in vitamin D, going out in the sun occasionally while protecting your skin and eyes, and, depending on blood test monitoring, adding 1,500–2,000 IU through supplementation to maintain a sufficient range.

However, despite the high demand for effort during an intense season in the colder months, 4,000–5,000 IU may be required, especially in a high-performance training program.

To conclude, keep in mind the balance of vitamins and minerals not only for your performance, but also to maintain your health and well-being and support longevity.