Vitamin D plays an essential role in the quality of bone and muscle tissue and in strengthening our immune system. However, the majority of French people do not consume enough of it. What foods should we eat to ensure that we get enough? What are the health risks of vitamin D deficiency? Is the consumption of food supplements the solution to prevent these deficiencies? Do some populations need more vitamin D than others? Is there a risk in case of excess intake? The Anses answers all your questions.
Why is vitamin D important?
Vitamin D is essential for the proper functioning of our bodies. Its main function is to increase the levels of calcium and phosphorus in the blood.
Maintaining a sufficient level of calcium in the blood ensures :
- optimal mineralisation of tissues, particularly bones, cartilage and teeth
- efficient muscle contraction
- good nerve transmission;
- adequate coagulation.
Vitamin D is also involved in :
- hormonal regulation ;
- differentiation and activity of immune system cells
- differentiation of certain skin cells.
How can we ensure that our bodies receive sufficient vitamin D?
There are two ways of meeting daily vitamin D requirements:
Exposure to the sun: by exposing yourself to the sun for 15 to 20 minutes at the end of the morning or in the afternoon, you can ensure that your body has an adequate daily intake of vitamin D.
Eating foods rich in vitamin D such as :
- oily fish, such as herring, sardines, salmon and mackerel
- certain mushrooms, such as chanterelles, ceps and morels
- vitamin D fortified dairy products;
- egg yolk;
- dark chocolate;
- breakfast cereals fortified with vitamin D;
- butter and margarines;
- offal (especially liver);
- meat (to a lesser extent).
To ensure an adequate supply, it is advisable to balance and vary your diet throughout the year and to eat two portions of fish per week, including one portion of oily fish.
How much vitamin D should be consumed each day?
The population nutrient reference (PNR) is 15 micrograms per day for adults. For other populations, the NDRs are currently being evaluated and will be published during 2021.
It should be noted that the NNI for vitamin D has been defined by considering only dietary intake of vitamin D and not the contribution of sunlight exposure.
According to data from the Inca 3 study, the average vitamin D intake of the French population from food is
- 5.2 micrograms/day for children aged 1 to 3 years;
- 2.6 micrograms/day for children aged 4 to 10 years;
- 2.9 micrograms/day for children aged 11 to 17;
- 3.1 micrograms/day for adults aged 18-79.
These intakes are higher for men than for women.
What are the health risks of vitamin D deficiency?
The clinical signs of vitamin D deficiency are
- Muscle disorders: decreased muscle tone, tetany, convulsions;
- bone disorders: osteomalacia (in adults), rickets (in growing children) which can cause bone and muscle pain and bone deformities. Insufficient vitamin D intake can also lead to a decrease in bone mass and thus an increased risk of fracture. These risks are increased when physical activity is reduced.
In addition, more rarely, vitamin D deficiency can lead to anaemia.
Are some populations more susceptible to vitamin D deficiency than others?
As the body's ability to absorb or synthesise vitamin D decreases with age, the elderly are a particularly vulnerable population in whom low vitamin D intake can result in osteoporosis.
Other populations are also at risk: newborns, infants, pregnant women, post-menopausal women, whose hormonal upheaval leads to bone demineralisation, thus increasing the risk of fracture, and people with darker or dull skin, for whom the synthesis of this vitamin through exposure to the sun is less effective.
Finally, certain factors, such as specific diets that exclude meat, fish, eggs and dairy products, or pathologies that induce intestinal malabsorption, can aggravate the risks of deficiency.
Can taking supplements prevent vitamin D deficiency?
Satisfactory vitamin D status can be achieved through exposure to sunlight, through physical activity in the open air for example, and through diet, by ensuring that vitamin D-rich products are included in the diet.
However, for some populations such as newborns, or active person additional vitamin D supplements intake is needed to ensure satisfactory status.