Vitamin D: your immunity’s ally

[Article updated on 19/09/2023]

It received a lot of attention during the COVID19 pandemic following the publication of studies showing possible benefits for preventing infection by this virus. But, what is it for and where to find it?

Before reading on

I’m not an expert in this field, but I am passionate about nutrition and health.

The articles you’ll find on my site are the result of in-depth research that I’d like to share with you. However, I would like to stress that I am not a health professional and that my advice should in no way replace that of a qualified physician. I’m here to guide you, but it’s important that you consult a professional for specific questions or medical concerns. Your well-being is important. So be sure to consult the appropriate experts and take the best possible care of yourself.

Let’s take the time to talk about vitamin D.

Vitamin D: what is it?

This vitamin is part of the family of fat-soluble vitamins, that is to say soluble in lipids as is the case with vitamins A, E and K.

It exists in 2 forms:

  • Vitamin D3 or cholecalciferol produced in the animal world and by certain lichens. The human body also synthesizes this vitamin D3 in the skin under the effect of ultraviolet rays.
  • Vitamin D2 or ergocalciferol produced in the plant world.

Its roles in the body

Its roles in the organization are numerous:

  • It is involved in the absorption of calcium and phosphorus by the intestines as well as their reabsorption by the kidneys. However, calcium plays an essential role in our body because it ensures optimal mineralization of tissues (notably bones, cartilage and teeth), effective muscle contraction, good nerve transmission and adequate coagulation.
  • It is involved in hormonal regulation.
  • It plays an important role in our immune system and in the good health of our skin.
  • A lack of vitamin D prevents good pain management and therefore increases the perception of it.

Where can we find it in our diet?

Its food sources are diverse:

  • Fish liver oil, particularly cod liver oil and fatty fish such as herring, sardines, salmon, etc.
  • Foods rich in animal proteins such as meats, eggs, etc.
  • Semi-skimmed and full-fat dairy products. Since vitamin D is soluble in lipids, it is not present in 0% fat or skimmed products. You can find certain dairy products enriched with vitamin D on the market.
  • Butter…

Therefore, it is preferable for vegetarians and vegans to be vigilant about their vitamin D intake and to supplement, if necessary. The nutritional reference for the population (RNP) is 15 micrograms per day for adults.

For other populations, the RNPs are currently being evaluated and will be published in 2021. However, this reference only takes into account vitamin D intake through diet. However, the vast majority of vitamin D intake is due to the action of the sun on our skin. Indeed, the UV B rays of the sun will allow the formation of vitamin D3.

Therefore, it is advisable to expose yourself to the sun for 15-20 minutes at the end of the morning/early afternoon. However, this source varies greatly depending on the geographical area in which we live (more or less sunny place), the season, the thickness and pigmentation of our skin. The darker the pigmentation, the greater the risk of deficiency.

Is it sufficient ?

Vitamin D deficiency is one of the most widespread hypovitaminoses. According to the Suvimax report from 1997, 75% of the population is deficient in vitamin D and this does not seem to have improved over the years.

The signs of deficiencies are as follows:

  • Rickets in children, that is to say a growth disease which manifests itself by a deformation of the skeleton.
  • Muscle disorders in adults such as decreased muscle tone, tetany attacks, convulsions
  • Osteoporosis or even osteomalacia in adults, that is to say a generalized softening of the bones due to demineralization.

The body’s ability to absorb and synthesize vitamin D decreases with age. Elderly people are therefore particularly at risk of deficiency and this leads to a greater risk of osteoporosis. Newborns, infants and pregnant women are also populations at risk.

  • Supplementation necessary for children

Vitamin D supplementation is recommended from the first days of life. It is recommended that it be continued throughout the growth and bone mineralization phase, i.e. up to 18 years of age. To avoid the risk of overdose which may be linked to food supplements, it is important to respect the medication prescription from the doctor or pediatrician.

  • Supplementation sometimes recommended for adults:

Regular blood testing of your vitamin D is recommended several times a year, when sunlight is limited and your skin is more covered, i.e. in the fall and at the end of winter. . Your doctor will then be able to assess whether supplementation is necessary.

You can also find supplements in the form of drops in pharmacies to act as prevention. The recommended dose is often between 800 and 1000 IU/day (be sure to respect the dosages recommended by the manufacturers). However, if you opt for this type of product, be careful not to combine it with other supplements containing vitamin D.

Beware of the risk of overdose

Being little present in our diet, there is no known overdose of vitamin D for nutritional reasons. Cases of overdose have been recorded in infants following the taking of food supplements. It is therefore important to follow the doctor’s or pediatrician’s prescription for your children.

For adults, to avoid hypervitaminosis, be sure to respect the dosages indicated on the product and not to combine several supplements containing vitamin D.

To avoid this, it is better to seek the advice of your doctor or pharmacist.

An overdose of this vitamin can cause hypercalcemia, that is to say an excessively high level of calcium in the blood, leading to the calcification of certain tissues, and cardiological and renal consequences.

Excess vitamin D intake can cause other disorders such as headache, nausea, vomiting, weight loss or even one severe fatigue.