When the sun is lacking, as in winter, we can more easily lack vitamin D. Some people are particularly at risk of deficiency.
- 1 Vitamins D: what is the difference between D2 and D3?
- 2 What is vitamin D used for?
- 3 What are our daily vitamin D needs?
- 4 Where is vitamin D found?
- 5 What foods are rich in vitamin D?
- 6 In video: The top 5 foods rich in vitamin D
- 7 Do all skin types produce the same amount of vitamin D?
- 8 How long should you be exposed to the sun?
- 9 When should you supplement with vitamin D?
- 10 Do vegetarians and vegans need supplements?
Vitamins D: what is the difference between D2 and D3?
Vitamin D is a fat soluble vitamin which exists in two forms: the D2produced by plants, and the D3, by animals. In humans, these two forms exert the same biological activities since they are converted in the body into the same substance, commonly called vitamin D. However, D3 is better assimilated than D2. It has an action twice as important for an equivalent dose.
What is vitamin D used for?
By increasing the absorption of calcium and phosphorus and limiting their escape into the urine, it is essential for the mineralization of bones and teeth : a vitamin D deficiency promotes the risk of rickets in children, osteoporosis and fractures in adults. It also helps to better fight against stress, improve nerve transmission and ensure good muscle contraction. Finally, it constitutes a key factor of immunity.
What are our daily vitamin D needs?
Satisfactory intakess (AS) in vitamin D are estimated at 15 micrograms per day (µg/d)for men and women over 18 (source 1). The needs estimated by the National Agency for Food, Environmental and Occupational Health and Safety (ANSES) amount to:
- 10 µg/d for infants under one year old,
- 15 µg/d for children aged 1 to 10,
- 15 µg/d for adolescents aged 11 to 17,
- 15 µg/d for pregnant women,
- and 15 µg/d for breastfeeding women.
Where is vitamin D found?
This vitamin has a double origin.
- A part is synthesized by the organism, at the level of the skin, under theaction of ultraviolet raysthen put in reserve in the liver, muscles and adipose tissue to be used during winter periods.
- The other part (approximately 20%) is brought by foodespecially by products of animal origin and fats.
What foods are rich in vitamin D?
Foods richest in vitamin D are :
© Health Magazine
In video: The top 5 foods rich in vitamin D
Do all skin types produce the same amount of vitamin D?
No. The fair skin (phototypes I to III), produce more than dark skin (phototypes IV to VI) which contain more melanin, a pigment that blocks UVB rays.
Age also plays a role: as we age, the synthesis of vitamin D by the skin decreases.
How long should you be exposed to the sun?
If theregular sun exposure guarantees, in most people, a good reserve of vitamin D, it must of course remain reasonable, for reduce the risk of skin cancer. And we protect ourselves of course with a sunscreen of sufficient index.
The exposure time depends on many parameters. “In addition to age and phototype, you have to take into account the amount of UVB that reaches the ground. However, this depends on many factors,” explains Jean-François Doré, Emeritus Research Director at Inserm.
- First the season : there are on average five times more UVB in summer than in winter. Then the time of day: the higher the sun in the sky, the more there is.
- I’altitude: the UV index increases by around 10% for every 1,000 meters of elevation gain.
- The latitude: when it increases, the quantity of UVB decreases. The presence of clouds and the thickness of the stratospheric ozone layer also come into play.
- Another factor, the floor reverberation : grass, earth and water reflect on average 10% of UV radiation, sand 15% and fresh snow… 80%!
For Dr. Annie Sasco, epidemiologist for cancer prevention at the League Against Cancer, “exposure to the sun twice a week for 15 to 30 minutesenough to properly metabolize vitamin D » .For fair-skinned people, it is better not to exceed 5 to 10 minutes of exposure.
When should you supplement with vitamin D?
Supplementation is generally recommended for infantsthe Fpregnant womenand the the elderlyas well as for people of color and those suffering from pathologies inducing intestinal malabsorption . This supplementation can be extended to a good part of the population, especially in winter. In any case, it must be prescribed by the doctor. It can be done in one go (ampule) or daily (dropscapsules…)
Do vegetarians and vegans need supplements?
If you are vegetarian: Vitamin D intakes can be satisfactory when fish oils, eggs and dairy products are consumed.
If you are vegan: in the absence of animal products, supplementation is necessary because plants contain little vitamin D and do not provide sufficient needs.