Everything you need to know about vitamin D

According to ANSES, more than 70% of the French adult population in 2019 had vitamin D insufficiency and a deficiency in almost 7% of cases. The symptoms can be very violent, this vitamin being essential for the proper functioning of the human body. We explain the importance of this vitamin, its actions on the body and how to prevent vitamin D deficiency.

Vitamin D: What is it?

Vitamin D is 90% made by the human body. It brings together five different molecules (D2, D3, D5, D6 and D7) but they all look very similar chemically.

Vitamin D3 behaves like a hormone that is activated by reaction to sunlight. It is a fat-soluble vitamin, in other words, it dissolves and is stored in fat. It can therefore be released slowly according to the body's needs.

What is the role of vitamin D in the body?

Vitamin D contributes to many functions within the body, such as:

• Bone mineralization (cartilage and teeth) and tissues, particularly in children. A deficiency of this vitamin can cause rickets in young people.
• Muscle contraction: vitamin D protects against atrophy of muscle fibers.
• Hormonal and mood regulation: it increases the production of serotonin and wards off the symptoms of depression.
• Prevention of certain diseases and cancers. Thanks to its immunomodulatory action, vitamin D could slow the development of autoimmune diseases such as multiple sclerosis, rheumatoid arthritis or even inflammatory bowel diseases.
• Prevention of fractures and osteoporosis, a bone disease that deteriorates tissue and makes bones thin and fragile.

According to a study* carried out in 2012, vitamin D supplementation reduces the risk of falls because muscle strength and postural balance are improved. Athletes and seniors have less risk of falls and potential injuries.

In addition, vitamin D plays a role in sports performance and tends to improve it by protecting bones from fractures and promoting recovery (according to a study by the University of Newcastle in 2013).

What is the difference between vitamin D2 and D3?

Among the different forms of vitamin D, we find vitamins D2 and D3 in the form of food supplements. These are also the most well-known variants.

Vitamin D2, also called ergocalciferol, comes from plants and mushrooms.

Vitamin D3, or cholecalciferol, is found in animal products, but also in lichen. Also called the “sunshine vitamin”, it is the one closest to vitamin D synthesized by the body exposed to the sun and fat.

These two vitamins are metabolized in the liver in the form of calcifediol, which allows the release of calcitriol, the active form of vitamin D. However, vitamin D3 is better assimilated by the body and generates a higher level of calcitriol. than vitamin D2.

How to recognize a vitamin D deficiency?

Lack of vitamin D is common, especially in Nordic countries during winter. People living or working indoors are also very affected, along with the elderly, infants and pregnant women.

The withdrawal manifests itself by fatigue, cramps or bone pain, but also a depression of mood. It can also harm the cardiovascular system through the onset of certain diseases, in the most serious cases.

You may also feel muscle weakness in addition to general fatigue. Diseases develop more easily because the immune system is weakened.

Low vitamin D levels promote the development of insulin resistance and therefore diabetes. In addition to monitoring your vitamin D levels, it is important to fight against a sedentary lifestyle and move regularly.

Vitamin D deficiency in athletes

According to a study by Constantini, 63% of participating athletes had insufficient vitamin D levels, particularly for indoor athletes (80% have deficiencies, compared to 48% of outdoor athletes). This vitamin D deficiency increases the risk of fracture and makes healing slower.

We can therefore deduce that vitamin D improves sports performance by protecting bone tissue, preventing fractures, and protecting against cardiovascular disorders.

Contrary to what one might believe, high-level athletes are also subject to vitamin D deficiency and are encouraged to take supplements, always with the advice of a doctor. If this deficiency affects indoor athletes more (sneakers, dancers, etc.), outdoor athletes are not protected from it.

Click here to learn more about vitamin D deficiency.

Excess vitamin D

Overdose is not very risky through diet and exposure to sunlight. Food intakes are below the recommended intake, with foods containing only a small quantity of vitamin D. Food supplements are suggested, particularly for young children or people at risk. It is this vitamin supplementation that must be controlled because it can lead to an overdose and be toxic to the body.

Excess vitamin D3 leads to high levels of calcium in the blood, can lead to headaches, vomiting and severe fatigue. It is therefore important to monitor it during regular blood tests and consult your doctor before any supplementation.

Where is vitamin D found?

According to ANSES, exposure to the sun for 15 to 20 minutes per day is enough to provide a sufficient daily intake of vitamin D (15 μg/day in adults). In cold periods, be on the lookout for the slightest ray of sunshine to avoid winter depressions for as long as possible. Exposure to the sun must be adapted according to the season, the UV index (< 3 without sunscreen) and the melanin level of the person exposed.

Certain foods are rich in vitamin D, including:

• Oily fish (salmon, sardines, trout) which should be consumed once or twice a week
• The egg yolk
• Milk or certain cheeses whose consumption must be limited
• Dark chocolate
• Certain mushrooms, such as chanterelles, porcini mushrooms and morels
• Butter and margarine.

It was customary to take cod liver oil to benefit from its vitamin D levels.

When to take vitamin D?

It is particularly in winter that vitamin D levels should be monitored. The cures are particularly effective when taken over the duration of a sports program or to get through the winter. A treatment of a few weeks is not enough to benefit from the effects of the vitamin.

The recommended daily allowance is generally not met, which is why so many people are deficient in vitamin D3 in France. Before any supplementation, ask your doctor for advice. If it is important to compensate for shortages, it is just as important to protect yourself from overdoses.

Nutrimuscle has chosen to partner with the supplier Quali®-D to offer high quality and traceable vitamin D. Take a vitamin D capsule during breakfast with a glass of water.

*Bischoff-Ferrari, HA Relevance of vitamin D in muscle health. Rev Endocr Metab Disord 13, 71–77 (2012