What to remember :
- Vitamin D is fat-soluble and therefore can be absorbed by the body via fats.
- It is synthesized mainly by the skin thanks to the UVB rays of the sun and is provided in a minority by food.
- Supplementation is almost essential in winter due to low exposure to daylight.
- It is also essential for people at risk (infants, pregnant and breastfeeding women, elderly people, etc.).
- This vitamin contributes to bone, muscle, immune and nervous health, but also to the modulation of the intestinal microbiota and the regulation of certain hormones.
- It is found mainly in animal products.
What is vitamin D?
Vitamin D, also known as calciferol, is one of the vitamins partially synthesized by the body. The body synthesizes 80-90% of it through the skin, thanks to exposure to sunlight, particularly UVB rays. The remaining 10-20% comes from food.
Heat, light and oxidation can alter it. It is therefore stable if stored away from light and in the absence of oxygen.
It is a so-called fat-soluble vitamin, meaning it is soluble in fats. Therefore, it is assimilated by the body in the presence of these fats. In our bodies, it is stored in the liver, muscles, and adipose tissue. It is then released according to the needs of our cells.
However, excessive vitamin D stores, or hypervitaminosis D, can be dangerous and toxic to the body. This is why it is important not to supplement blindly, as there may not be a need.
What is vitamin D used for? Its different roles
Vitamin D is essential for the proper functioning of the body. Its main role is to maintain balanced calcium and phosphorus homeostasis. It does this by increasing the intestinal absorption of calcium and phosphorus.
A good blood calcium level helps ensure optimal mineralization of tissues (bones, cartilage and teeth), good muscle contraction, nerve transmission and blood clotting. Vitamin D therefore intervenes in these processes indirectly.
It also plays a role in hormonal regulation (particularly of thyroid hormones T3 and T4), the differentiation of immune system cells and the modulation of the intestinal microbiota (particularly in cases of chronic inflammatory bowel diseases).
It also appears that this vitamin, when taken as a supplement, is involved in the weight loss process in people who are obese or overweight.
Risks of deficit?
Vitamin D deficiency reduces the absorption of calcium, which is essential for bone health, leading to demineralization (osteomalacia in adults, rickets in children), increasing the risk of fractures and muscle disorders (weakness, tetany). It also weakens the immune system, causes general fatigue and low morale.
People at risk include: infants, children, pregnant women, breastfeeding women, postmenopausal women, women with amenorrhea, the elderly, those with sun intolerance, vegetarians without fish, vegans, individuals after intestinal surgery or obesity, those with osteoporosis, night workers, indoor athletes, residents of Nordic countries, and dark skin (dark skin acts as a UVB filter). Before taking a vitamin D supplement, it is essential to measure the baseline level, especially from September to October when sun exposure decreases. Since vitamin D is mainly produced by the skin under the influence of sunlight, winter supplementation is essential to avoid deficiency, despite daily dietary intake.
To correct a vitamin D deficiency, it is necessary to take prescription ampoules. However, these are highly dosed and some of them are not absorbed by the body. This is why it will then be essential to continue supplementation (with drops, for example) in order to maintain restored levels. The best solution, in any case, is to have daily dietary intake as well as exposure to the sun as soon as possible, alongside appropriate supplementation if necessary.
Sources of vitamin D
Vitamin D is found primarily in animal foods. Some plant foods also contain it to a lesser extent.
#1 - Cod liver oil
The richest food in vitamin D, with a content of 250 µg/100 g, or 25 µg per portion (= 1 tablespoon = 10 g), it is taken as a supplement in the form of a capsule, gel cap or oil directly. However, having a pronounced taste and smell, encapsulated forms are more appreciated.
This oil is also very rich in vitamin A, vitamin E and omega-3 , lipids essential for the body, particularly for the nervous and cardiovascular systems.
#2 - Cod liver
It is the second richest food in vitamin D with a content of 100 µg/100 g (when raw). It can be found fresh or canned, where it will have a content of 54.3 µg of vitamin D per 100 g.
Since vitamin D is a stored vitamin, eating one can of cod liver every week is more than enough to cover your needs, especially if your diet contains other sources of vitamin D.
#3 - Oily fish
The list of oily fish mainly includes salmon, trout, herring, sardines, mackerel and anchovies.
Here are the vitamin D contents of a serving of each fish:
Salmon: cooked: 8.7 µg/100 g - smoked: 5.5 µg/100 g
Trout: cooked: 15 µg/100 g - smoked: 5.2 µg/100 g
Herring: cooked: 11 µg/100 g - smoked: 22 µg/100 g
Sardine: raw: 14 µg/100 g - canned: between 7.5 and 12.5 µg/100 g
Mackerel: cooked: 7.7 µg/100 g - canned: between 2.4 and 7.3 µg/100 g
Anchovies: raw: 11 µg/100 g - salted: 4.6 µg/100 g
These fish are also very rich in omega-3.
It is recommended to consume 1 to 2 per week, favoring small oily fish (sardines, mackerel, herring, anchovies). Indeed, large fish like salmon and trout are rich in heavy metals/pollutants (mercury, PCBs, dioxins). Since toxins bind to fats, their consumption should be limited.
In concrete terms, a can of sardines or mackerel provides you with part of your daily needs.
#4 - Some lean fish
Some lean fish, such as sea bream, whiting, cod and tuna, have a good vitamin D content.
Here are the contents per 100g:
Sea bream: baked: 5.71 µg/100 g
Whiting: raw: 4.11 µg/100 g
Cod: salted, boiled: 1.25 µg/100 g
Tuna: raw: 7.8 µg/100 g - canned: 5.08 µg/100 g
It is recommended to eat 1 to 2 lean fish per week. However, sea bream and tuna should be limited due to their high toxin content (heavy metals/pollutants).
#5 - Certain mushrooms (chanterelles, porcini mushrooms, morels)
The only plant-based food sources that contain vitamin D are chanterelles (5.3 µg of vitamin D per 100 g), porcini mushrooms (3.1 µg/100 g) and morels (5.1 µg/100 g).
Consuming 100g of these 3 types of mushrooms regularly, in addition to the other sources mentioned here, allows you to easily meet your needs.
#6 - Offal (especially liver)
Calf liver, with a content of 2.52 µg of vitamin D per 100g, is worth consuming from time to time to benefit from this vitamin but also from the iron it contains. It is also often recommended in cases of iron deficiency.
#7 - Egg yolk
Considered the perfect protein source, eggs also contain high-quality fatty acids and a significant amount of vitamin D. In fact, 100g contains 2 µg of vitamin D. Eating two eggs (about 50g) daily, fried, soft-boiled, or boiled, will help supplement your daily needs.
#8 - Dairy products
Milk, yogurts, as well as cheeses and cottage cheeses, are well known for their calcium content. However, they also contain significant amounts of vitamin D. Consumed regularly as part of a balanced diet, they help cover your needs.
Boost your immune system with DIJO food supplements
At DIJO, we have developed a vitamin D drop suitable for an adult population. In combination with the Concrete Intestine Pack and Immunity Boost , it will be useful in winter in particular, to support bone health, immunity and many other processes as seen previously.
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Sources :[1] Anses, 02/03/2022, Vitamin D: why and how to ensure a sufficient intake?, consulted from: https://www.anses.fr/fr/content/vitamine-d-pourquoi-et-comment-assurer-un-apport-suffisant
[2] Battistini, C., Ballan, R., Herkenhoff, M.E., Saad, S.M.I., and Sun, J. (2020). Vitamin D modulates gut microbiota in inflammatory bowel disease. International Journal of Molecular Sciences, 22(1), 362. https://doi.org/10.3390/ijms22010362
[3] Khosravi, ZS, Kafeshani, M., Tavasoli, P., Zadeh, AH, & Entezari, MH (2018). Effect of Vitamin D Supplementation on Weight Loss, Glycemic Indices, and Lipid Profile in Obese and Overweight Women: A Clinical Trial Study. International journal of preventive medicine, 9, 63. https://doi.org/10.4103/ijpvm.IJPVM_329_15
