Synthesized by the skin under the action of UVB from the sun and stored in muscles and fatty tissue, vitamin D plays a crucial role in the absorption and fixation of calcium and phosphorus, contributing to the healthy bones and teeth. It also has an important role for muscle and immune functions.
“There seems to be an association between a vitamin D deficiency and the onset of diabetes, depression, cardiovascular disease or even certain cancers”, indicates Dr Pascal Douek, micronutritionist doctor.
Who should take vitamin D as a supplement?
- It can be prescribed to children who do not drink milk enriched with vitamin D, as well as to pregnant women and the elderly living in institutions, for its role in bone mineralization.
- It is interesting in case ofrecurrent respiratory infections. A recent meta-analysis shows that vitamin D3 supplementation reduces the risk of getting sick by 40 to 60%. “The patients to whom I prescribe it, after dosing to check that they lack vitamin D, generally note less fatigue and infections in the months which follow”, observes Dr. Charles Henry Guez, general practitioner.
- She is helpful after 60 years, because the natural capacities of synthesis and metabolism of vitamin D decrease.
- It is essential for people with osteoporosis or those at risk: menopause and premenopause if there is a history of fractures. Vitamin D supplementation, combined with calcium, reduces the risk of non-vertebral fractures after 65 years. “In addition, basic treatments for osteoporosis such as bisphosphonates are less effective if they are given to patients with vitamin D deficiency,” adds Jean-Claude Souberbielle, biologist.
The rare contraindications to vitamin D supplementation are kidney failure or sarcoidosis.
When to take vitamin D
We are more likely to lack vitamin D during winter due to low sunshine. This is also the time when we need her to fight viral infections. It is therefore from October to March that it is interesting to do a cure of at least three months.
Vitamin D could have a protective role against severe forms of Covid-19, a new infectious disease linked to the SARS-CoV-2 coronavirus. As such, it can be taken as a preventive treatment. According to’National Academy of Medicine : vitamin D “plays a role in the regulation and suppression of the inflammatory cytokine response at the origin of the acute respiratory distress syndrome which characterizes the severe and often lethal forms of Covid-19”.
Should we do a dosage before?
The dosage of vitamin D is recommended by the High Health Authority and reimbursed, only if there is suspected rickets or osteomalacia (bone disease), after obesity surgery, for kidney transplant recipients and the elderly with repeated falls. The rheumatologist can also prescribe one before starting treatment for osteoporosis in order to adjust the dose of medication.
“It is not necessarily necessary since the risk of toxicity from supplementation is extremely low,” says Dr. Douek.
How much to take vitamin D?
It is expressed in IU (International units). In osteoporosis, studies show that vitamin D supplementation reduces the risk of fractures at doses ofat least 800 IU per day. “In people over 60, we even recommend 1,000 to 1,500 IU per day,” notes Dr Souberbielle.
For more effectiveness on the bone, vitamin D must be associated with calcium (ideally from the diet).
In what form ?
Vitamin D is available in different forms and in different doses. Drops allow you to take a little every day while the lightbulbs offer a high dose more spaced.
The first option is preferable because it helps to maintain a more stable level of vitamin D in the blood. “With the blisters every 3 or 6 months, there is a peak with a high blood level at the beginning, then this level gradually decreases”, explains Dr. Douek. And if they remain beneficial to the bone, monthly or quarterly doses do not prevent respiratory infections. Their big advantage: being less restrictive, which is why doctors continue to prescribe ampoules.
“I rather recommend drugs, which guarantee reproducibility of dosages and are inexpensive, less than € 2 for a month of treatment,” says Dr Douek.
Take vitamin D2 or D3?
There are two D vitamins: vitamin D3 of animal origin, and vitamin D2 of plant origin. D3 is closer to our natural vitamin D and above all has a longer half-life (time required for its concentration in the blood to decrease by half).
“When we prescribe spaced doses, vitamin D3 is superior to vitamin D2, because it is eliminated more quickly and makes it possible to maintain a satisfactory level longer,” explains Dr. Souberbielle. In daily doses, no study shows the superiority of one over the other.
Our selection of vitamin D supplements
You can buy these drugs in pharmacies without prescription, but they are reimbursed at 65% if prescribed by the doctor.
- Zymad 10,000 IU / ml vitamin D3, 300 IU / drop, 10 ml dropper bottle (333 drops), € 2.07.
- Sterogyl 2,000,000 IU / 100 ml of vitamin D2, 400 IU / drop, 20 ml dropper bottle, € 1.89.
Other products available in pharmacies and drugstores allow you to fill up with vitamin D:
- In liquid form: Vitamin D3 of Phyto-Active, 2 drops (400 IU per drop) per day, € 9.90 per 15 ml bottle.
- In effervescent form: Calcium-Vitamin D3, of Fleurance Nature, 1 to 2 tablets per day (= 800 mg of calcium + 5 μg of vit. D), € 4.30 for 20 tablets.
- For vegans: Vitamin D3 1000 IU vegan, of Orfito, ultra-concentrated, 1 drop each day, € 21.50 per 20 ml bottle.