What is vitamin D for?

During the summer it is easier to get enough vitamin D during the day, also known as the “sunshine vitamin”. But when winter comes, the daylight hours are shorter and the rides get gloomier. It is possible that we are considering whether to add supplements or foods with this mineral.

The body produces vitamin D naturally when exposed to direct sunlight. We can also get vitamin D from certain foods and supplements to ensure adequate levels of the vitamin in the blood. Vitamin D has several important functions. Getting enough is important for normal growth and development of bones and teeth, as well as improving resistance to certain diseases.

What is vitamin D?

This type is a fat- soluble vitamin that performs many functions in the body, including vitamins D1, D2, and D3. You may know it for its regulation of bone structure, and while strong bones are important for athletes, vitamin D is also necessary for calcium absorption and fast-twitch muscle fiber function . It also modulates more than 2,000 genes involved in cell growth, immune function, and protein synthesis.

If we look for foods with large doses of this mineral, you can consume:

  • fatty fish, such as salmon
  • Rainbow trout
  • fortified milk
  • fortified cereal
  • Eggs with yolks
  • Raw white mushrooms exposed to ultraviolet light
  • Dairy products such as yogurt and cheese.
  • Fortified orange juice

Recommended dose

The recommended daily intake of vitamin D is 600 IU/day for children and adults up to 70 years of age. However, many experts question whether this amount is adequate, especially for functions other than bone health and athletic performance.

Between 1,500 and 2,000 IU per day is recommended for people who do not get adequate exposure to the sun without protection, which is equivalent to five (for people with fair or fair skin) to 30 (for those with dark skin) minutes of sunlight at noon on arms, legs and back two or three times a week without sunscreen.

We know that sunbathing in the winter months can be difficult, especially in the northern half of Spain, because there is less sunlight and people wear multiple clothes to keep warm. It’s not that you need to increase IUs in the winter either, but we do need to recognize that it will be difficult to get adequate vitamin D from sunlight alone.

Athletes who do not get regular sun exposure should have a plan in place for this supplemental vitamin or a combination of dietary and supplemental vitamin D. Eating fortified foods or a regular multivitamin alone probably won’t be enough to maintain a sufficient level of vitamin D.

Eating a balanced diet , containing the necessary portions of oily fish, is enough to meet the vitamin D needs that are met through food. In addition to this, sunbathing 15 minutes a day will ensure that we meet the necessary level. Keep in mind that this exposure is in the morning or late in the afternoon, since the ideal is that you do it without sunscreen, in order to acquire the benefits. Keep in mind that the amount of said vitamin that you are contributing to your body comes directly from sun exposure. And, secondarily, you will do it through food.

dosis vitamina d


Vitamin D has many benefits, the best known being its participation in bone formation. However, below, we will explain other important functions in which it participates.

strengthens the bones

Perhaps one of the most outstanding benefits of this vitamin will be the prevention of osteoporosis . This vitamin is responsible for the intestinal absorption of calcium and phosphorus. This absorption will be decisive for the calcium to reach the bones correctly.

In addition, vitamin D is responsible for preventing, through the kidney, the elimination of excess calcium.

insulin resistance

According to a study, vitamin D deficiency is associated with a higher probability of diabetes. This study, when analyzing organisms from people who had diabetes, found lower levels of vitamin D than compared to organisms that had normal glucose levels.

Therefore, vitamin D can influence the metabolism of blood glucose. In turn, deficient levels of vitamin D are associated with greater resistance to insulin.

muscle function

In recent studies, vitamin D has been studied for its involvement in skeletal muscle function. It has been concluded that an adequate amount is linked to the improvement of muscle quality. In addition, the implication of vitamin D in the activation of protein synthesis has been studied.

Although getting enough vitamin D is important for maintaining healthy bones, mechanical loading is also an important factor. The loads generated by walking and running are important because they play an important role in the cellular processes that regulate bone maintenance.

Although exercise routine (running and strength training, for example) can help protect against bone loss, diet can also contribute. To get enough vitamin D in your diet, look for foods like swordfish, salmon, tuna, milk, yogurt, eggs, and cheese. It is not necessary to consume more vitamin D than recommended (600 IU per day).

Cardiovascular health

Vitamin D has been studied for its importance in cardiovascular health. Its deficiency has been linked to an increased risk of cardiovascular diseases.

Among the data obtained in some studies, we can see that the deficiency of this substance increases the risk of cardiovascular diseases by 42%, and the risk of heart attacks by 49-60%.

Reduces depression

Research has shown that vitamin D may play an important role in regulating mood and lowering the risk of depression.

One study found that those experiencing negative emotions who were given vitamin D supplements saw an improvement in symptoms. Vitamin D supplementation may help people with depression who also have a vitamin D deficiency. Another study identified low vitamin D levels as a risk factor for more severe symptoms of fibromyalgia, anxiety, and depression.


People with higher body weights are more likely to have low vitamin D levels. In one study, people with obesity who received vitamin D supplements in addition to following a weight-loss diet plan lost more weight and fat mass than the members of the placebo group, who only followed the diet plan.

In an earlier study, people who took daily calcium and vitamin D supplements lost more weight than subjects who took a placebo supplement. The researchers suggest that the extra calcium and vitamin D may have had an appetite-suppressing effect.

Current research does not support the idea that this vitamin causes weight loss, but there does appear to be a relationship between vitamin D and weight.

cítricos con vitamina D

Vitamin D deficiency

Although the consumption of foods rich in vitamin D is probably not enough, this vitamin can also be synthesized in the skin after exposure to sunlight. But in the winter months, people often spend less time outdoors and wear more clothing, making it difficult to get adequate exposure.

Some are also at higher risk of deficiency, including the elderly, people with dark complexions (due to the pigment melanin), and athletes who train and compete indoors.

It’s a good idea to test vitamin D levels during the summer or early fall to find out if we’re deficient, even when we can get more sun exposure, in order to plan for the winter months. It is important to have good habits throughout the year, not just take excessive care of ourselves in winter to avoid falling ill.

Although there does not seem to be a universal consensus for vitamin D deficiency, low levels may be related to an increased risk of acute illness, inflammatory lesions, stress fractures, muscle pain and weakness, and suboptimal muscle performance.

In addition to bone and skeletal health, it also helps regulate inflammation in the immune system and affects hormones , so it has the potential to influence mood. The former is important for staying healthy when training hard, and the latter can affect motivation and excitement for the sport.

And yes, low vitamin D levels will affect your workouts. Impairments can affect lung function, VO2 max. and can even affect the maintenance of fast-twitch muscle fibers.