*Nutritional Reference Values

Ingredients : Virgin rapeseed oik*, vegetable Vitamin D3 from lichen, antioxidant : Vitamin E. *ingredients from organic farming. Contains 96% ingredients from organic farming, FR-BIO-01

Vitamin D, which is ?

Vitamin D is vital for bone health by stimulating the absorption and metabolism of calcium and phosphorus. The earliest established role of vitamin D was in the absorption of calcium from the intestine and therefore in the mineralisation and remodelling of bone. During the years of research on vitamin D, its functions have been greatly expanded to include the regulation of metabolism, cell proliferation and differentiation. This vitamin belongs to the class of fat-soluble vitamins and has a hormonal action. There are two forms of vitamin D: vitamin D2 or ergocalciferol and vitamin D3 or cholecalciferol. Vitamin D3 is synthesised in the skin after exposure to sunlight and can be consumed via (mainly) animal food sources, while the D2 form is the synthetic form often found in vitamin D-fortified food products and is derived from plants [1,2]. In summary :

• Natural vitamin D2 of plant origin is synthesised from ergosterol (provitamin D): ergocalciferol is therefore of exogenous origin only,
• Natural vitamin D3, mainly of animal origin, is synthesised in the epidermis and dermis under the action of the sun: cholecalciferol is therefore of endogenous and exogenous origin.

The highest amounts of vitamin D are found in foods of animal origin and specifically in marine products (see table on the amount of vitamin D (μg) per 100g of food consumed; the nutritional composition of foods can be consulted on the website of the ANSES - Agence nationale de sécurité sanitaire de l'alimentation, l'environnement et du travail :https://www.anses.fr/fr/content/la-table-de-composition-nutritionnelle-du-ciqual).

The market for vitamin D food supplements is substantial: oily capsules, drops, capsules, gummies... The most widespread origin is lanolin: a fat (sometimes called "wax") derived from sheep's wool. Today, even if sources are rare, there are also alternative sources, of vegetable origin and in the form of vitamin D3.

Why vitamin D is essential to our health ?

As mentioned above, vitamin D is essential for bone health. But its roles go beyond that [3-6]:

• Involvement in the expression of numerous genes of our metabolism,
• Participation in the activity of our immune system,
• Primordial to growth and development during life in utero and childhood,
• Protection against the risk of developing chronic diseases (obesity, type II diabetes, cancer...). A meta-analysis has reported that vitamin D supplementation reduces the risk of mortality [7],
• Implication in physical performance. Recent evidence suggests that vitamin D supplementation to ensure coverage may be beneficial in improving physical performance [8,9].

The literature on supplementation has increased steadily over the last 10 years. It is thanks to this work that the importance of vitamin D and the coverage of its needs in populations has been demonstrated, particularly in terms of its beneficial role in extra bone-related health [10].

While supplementation is needed as a comprehensive health prevention strategy for the general population, for some populations more susceptible to impairment it seems to be absolutely essential. For example, it would significantly prevent the risk of falls and fractures in people with osteoporosis [11]. Finally, it ensures optimal child growth during pregnancy and childhood to combat developmental delays and disturbances [12].

Where to find vitamin D ?

As stated above, vitamin D in humans comes mainly from exposure to sunlight. After exposure to the sun, UVB radiation photolyses (decomposition by light) the "7-dehydrocholesterol" (7-DHC) stored in the epidermis as pre-vitamin D3. Once the latter has been formed, it undergoes a thermal transformation to form vitamin D3, which joins the bloodstream. On the other hand, when exposure to sunlight is too great, pre-vitamin D3 is transformed into inactive vitamin D products. When we consume vitamin D, in the form of D2 or D3, it reaches the intestinal tract and joins the bloodstream. These two forms of vitamin D, D3 (from sunlight and food) and D2 (from food) are converted in the liver to a form of vitamin D3: calcidiol (25(OH)D). And it is in this form that vitamin D is referred to as a prohormone (which is an inactive hormonal form). It is then in the kidneys that calcidiol is transformed into calcitriol (1,25(OH)2D). It is in this form of calcitriol that vitamin D becomes an active hormone, known as steroid hormone. In this form, it exerts its best known role on bone metabolism. It has what is known as hypercalcemic and hyperphosphatemic activity. That is to say, it stimulates the absorption of calcium and phosphorus in the intestine, contributing to the bone mineralisation mechanism (synthesis of bone compounds, particularly collagen). Calcitriol works in conjunction with a hormone with the same activity that you may be familiar with, parathormone [6,13,14].

(Adapted from [1])
Image digestive anatomy: "Servier medical art"

Why supplement with vitamin D? ?

Despite the solar and dietary origin of vitamin D, many populations have a deficiency status. In women, as bone status is highly engaged over time due to the hormonal variations that take place, vitamin D status via a plasma calcidiol (25(OH)D) assay is achieved more automatically. Vitamin D deficiency can indeed be measured by a blood test. Reference values vary between different health authorities in different countries to determine deficiency or insufficiency status [15]. The reported reference values for plasma vitamin D status are as follows [8,16]:

The reasons for vitamin D deficiency are diverse and additional [5,13] :

• As we have seen, very few foods naturally contain significant amounts of vitamin D,
• Sunshine varies significantly according to the season (the winter season would represent a period of zero synthesis of vitamin D via the epidermis) which also implies variations according to the geographical area,
• Although vitamin D can be stored in fat (++) and muscle (+), stocks are limited and cannot meet the needs during periods of no sunshine,
• Our lifestyles (sedentary, no consumption of vitamin D containing products, immediate protection from the sun's rays...), health status (significantly overweight, ageing, ...), ethnicity...

For these reasons we understand why vitamin D deficiency is common in the general population and therefore there are several reasons for taking a vitamin D supplement.

In addition, the European Food Safety Authority (EFSA) has set Nutrient Reference Values (NRVs) for vitamin D for different age groups as assessed at 15μg/day or 600 IU/day for an adult [17]. On the other hand, the analysis of several studies shows that these NRVs do not cover all needs and, above all, do not take into account the variability that exists according to an individual's lifestyle and state of health. The conclusions of this analysis of 8 clinical studies on subjects over 40 years of age showed that the coverage of needs could be equivalent to approximately 50 μg per day, i.e. 2000 IU per day [18,19]. It has also been reported that the bio-effectiveness of vitamin D3 is much greater than D2 and therefore vitamin D3 should only be offered as a D3 form of supplementation [20].

Publications

1. Zhang, R.; Naughton, D.P. Vitamin D in health and disease: Current perspectives. Nutr. J. 2010, 9, 65, doi:10.1186/1475-2891-9-65.
2. Souberbielle, J.-C.; Maruani, G.; Courbebaisse, M. Vitamine D : métabolisme et évaluation des réserves. Presse Médicale 2013, 42, 1343–1350, doi:10.1016/j.lpm.2013.07.010.
3. Wang, S. Epidemiology of vitamin D in health and disease. Nutr. Res. Rev. 2009, 22, 188–203, doi:10.1017/S0954422409990151.
4. Hossein-nezhad, A.; Holick, M.F. Vitamin D for Health: A Global Perspective. Mayo Clin. Proc. 2013, 88, 720–755, doi:10.1016/j.mayocp.2013.05.011.
5. Meehan, M.; Penckofer, S. The Role of Vitamin D in the Aging Adult. J. Aging Gerontol. 2014, 2, 60–71, doi:10.12974/2309-6128.2014.02.02.1.
6. Jorge, C. Vitamin D – new insights into an old molecule. Port. J. Nephrol. Hypertens. 2019, 33, doi:10.32932/pjnh.2019.10.033.
7. Autier, P.; Gandini, S. Vitamin D Supplementation and Total Mortality. ARCH INTERN MED 2007, 167, 8.
8. de la Puente Yagüe, M.; Collado Yurrita, L.; Ciudad Cabañas, M.J.; Cuadrado Cenzual, M.A. Role of Vitamin D in Athletes and Their Performance: Current Concepts and New Trends. Nutrients 2020, 12, 579, doi:10.3390/nu12020579.
9. Wiciński, M.; Adamkiewicz, D.; Adamkiewicz, M.; Śniegocki, M.; Podhorecka, M.; Szychta, P.; Malinowski, B. Impact of Vitamin D on Physical Efficiency and Exercise Performance—A Review. Nutrients 2019, 11, 2826, doi:10.3390/nu11112826.
10. Scragg, R. Emerging Evidence of Thresholds for Beneficial Effects from Vitamin D Supplementation. Nutrients 2018, 10, 561, doi:10.3390/nu10050561.
11. van den Bergh, J.P.W.; Bours, S.P.G.; van Geel, T.A.C.M.; Geusens, P.P. Optimal Use of Vitamin D When Treating Osteoporosis. Curr. Osteoporos. Rep. 2011, 9, 36–42, doi:10.1007/s11914-010-0041-0.
12. Hollis, B.W.; Wagner, C.L. New insights into the vitamin D requirements during pregnancy. Bone Res. 2017, 5, 17030, doi:10.1038/boneres.2017.30.
13. Holick, M.F. Vitamin D Deficiency. N ENG J MED 2007, 357, 266–277.
14. Landrier, J.-F. Vitamine D : sources, métabolisme et mécanismes d’action. Cah. Nutr. Diététique 2014, 49, 245–251, doi:10.1016/j.cnd.2014.07.008.
15. HAS Vitamine D_Note de cadrage_Utilité clinique du dosage de la vitamine D; 2013; p. 42;.
16. Basit, S. Vitamin D in health and disease: a literature review. Br. J. Biomed. Sci. 2013, 70, 161–172, doi:10.1080/09674845.2013.11669951.
17. EFSA Dietary reference values for vitamin D; 2016; p. 145;.
18. Heaney, R.P.; Armas, L.A.G.; French, C. All-Source Basal Vitamin D Inputs Are Greater Than Previously Thought and Cutaneous Inputs Are Smaller. J. Nutr. 2013, 143, 571–575, doi:10.3945/jn.112.168641.
19. Holick, M.F.; Binkley, N.C.; Bischoff-Ferrari, H.A.; Gordon, C.M.; Hanley, D.A.; Heaney, R.P.; Murad, M.H.; Weaver, C.M. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J. Clin. Endocrinol. Metab. 2011, 96, 1911–1930, doi:10.1210/jc.2011-0385.
20. Mistretta, V.I.; Delanaye, P.; Chapelle, J.-P.; Souberbielle, J.-C.; Cavalier, É. Vitamine D2 ou vitamine D3 ? Rev. Médecine Interne 2008, 29, 815–820, doi:10.1016/j.revmed.2008.03.003.