Why is vitamin D important?
Vitamin D is essential for our bodies to function effectively. Its main function is to increase blood concentrations of calcium and phosphorus.
Maintaining adequate calcium levels in the blood helps ensure:
- optimal mineralisation of tissue, mainly bones, cartilage and teeth;
- effective muscle contraction;
- proper 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 I ensure that my body gets enough vitamin D?
We meet our daily vitamin D needs in two ways:
- exposure to the sun: by exposing your skin to the sun for 15 to 20 minutes in late morning or in the afternoon, you ensure that your body has an adequate daily intake of vitamin D;
- consumption of foods that are rich in vitamin D, including:
- oily fish, such as herring, sardines, salmon and mackerel;
- certain mushrooms, such as chanterelles, ceps and morels;
- dairy products fortified with vitamin D;
- egg yolk;
- dark (plain) chocolate;
- breakfast cereals fortified with vitamin D;
- butter and margarine;
- offal (particularly liver);
- meat (to a lesser extent).
To ensure that your body has an adequate intake, you are advised to eat a varied, balanced diet all year round, and to have two servings of fish per week, including one of oily fish.
Did you know?
In France, the main foods that contribute to vitamin D intakes in the population are fish and dairy products (yoghurt, fromage blanc, cheese, milk), which respectively account for 19% and 25% of vitamin D intakes in adults, and 12% and 40% of intakes in children between the ages of 11 and 17. For children under 10 years old, dairy products are the main contributors, meeting 63% of their vitamin D needs.
How much vitamin D do I need every day?
The population reference intake (PRI) is 15 micrograms per day for adults. For other population groups, PRIs are currently being assessed and will be published in 2021.
It should be noted that the PRI for vitamin D was defined considering only the vitamin D intake from food and not the contribution from exposure to the sun.
According to data from the INCA 3 study, the average vitamin D intake in the French population through food is:
- 5.2 micrograms/day for children between the ages of 1 and 3 years;
- 2.6 micrograms/day for children between the ages of 4 and 10 years;
- 2.9 micrograms/day for children between the ages of 11 and 17 years;
- 3.1 micrograms/day for adults between the ages of 18-79 years.
These intakes are higher for men than for women.
What are the health risks in the event of vitamin D deficiency?
The clinical signs of vitamin D deficiency are:
- muscular disorders: loss of muscle tone, tetany, seizures;
- bone disorders: osteomalacia (in adults), rickets (in young, growing people), which can cause bone and muscle pain and bone deformities. Inadequate vitamin D intake can also lead to a reduction in bone mass and therefore a greater risk of fractures. These risks are particularly high where the level of physical activity is low.
More rarely, a vitamin D deficiency can lead to anaemia.
Are some populations more susceptible than others to vitamin D deficiency?
Because the body’s ability to absorb or synthesise vitamin D decreases with age, elderly people are particularly vulnerable to osteoporosis, in the event of low vitamin D intake.
Other population groups are also at risk, i.e. newborns, infants, pregnant women, postmenopausal women, for whom hormonal disruption leads to greater bone demineralisation, increasing the risk of fractures, and people with olive or dark skin, who synthesise vitamin D less efficiently when exposed to the sun.
Lastly, certain factors – such as specific diets that exclude meat, fish, eggs and dairy products, or diseases that cause intestinal malabsorption – may aggravate the risk of deficiency.
Can taking food supplements prevent the risk of vitamin D deficiency?
It is possible to ensure an adequate vitamin D status through exposure to sunlight, for example through outdoor physical activity, and through food, by ensuring that products rich in vitamin D are included in the diet.
Nevertheless, for some populations such as newborns, vitamin D supplementation is necessary to ensure an adequate status. To prevent any risks of overdose, medicinal products should be used in preference to food supplements, as they guarantee readable information on doses, precautions for use, risk of adverse effects and overdose. In any case, this supplementary intake should only be on dietary or medical advice.
What are the health risks in the event of excess vitamin D intake?
As mentioned above, taking food supplements containing vitamin D may increase intake to excessive levels leading to hypercalcaemia, a build-up of calcium in the blood. This can result in tissue calcification, with consequences for the heart and kidneys.
Besides hypercalcaemia, excess vitamin D intake can cause other problems such as headaches, nausea, vomiting, weight loss and fatigue.