Healthy Life

Fall, winter and vitamin D

by Uperform

en automne comme en hiver la vitamine D est indispensable pour la santé

In this fall-winter period, when the days are getting shorter, think about your vitamin D! It is a fat-soluble vitamin, it is vital, it acts like a hormone and it has been attributed with more than 300 biochemical functions in our body.

The variation in vitamin D in the body would partly explain why the flu is seasonal, with a peak in winter. Research epidemiologists and vitamin D specialists have gathered convincing evidence of the involvement of vitamin D in the seasonal nature of influenza, virulent in winter, absent or barely present in summer.


Foods are low in vitamin D and therefore should not be relied upon to correct these deficiencies. The 1997 SU.VI.MAX study found that food provides an average of 136 IU (international unit) of vitamin D per day, much less than the recommended 200 IU and the 1000 to 5000 IU now recommended by researchers. international.


Vitamin D is an organic substance necessary for the body’s metabolisms. A large part of our needs (80%) is synthesized from a derivative of cholesterol in our skin, under the action of UVB radiation from the sun, it is for this reason that it is also called “sunshine vitamin”. The rest must be taken from the diet but it contains only a little as we have seen.


In a report made public, the French Academy of Medicine (AMF) recommends considerably increasing the daily intake of vitamin D. According to it, nearly 80% of the Western population and almost all the elderly are deficient in vitamin D.


Start by doing a dosage with your doctor, to know your level.


Vitamin D is not simply a calcium absorption factor but a real hormone modulating genes of extreme importance for health and longevity

-> more than 900 genes capable of binding vitamin D have been identified.


It is involved in the absorption of calcium and phosphorus by the intestines, then in the reabsorption by the kidneys. Essential for growth during early childhood, it ensures the robustness of the human skeleton and prevents osteoporosis. It fixes calcium on the bone at a physiological dose, with vitamin K2. After a certain age, the body no longer synthesizes vitamin D as easily.


Taking vitamin D significantly improves:

• Muscle fiber composition: anti-atrophic effect
• Muscular strength, physical performance
• Reduces the risk of falls

It is necessary for the differentiation of lymphocytes and the production of antibacterial peptides.

Vit D has profound effects on innate immunity.

The more D there is in our body, the more it makes natural antibiotics, antimicrobial peptide AMPs.

It plays an essential role in the activity of telomerase (telomere growth hormone), it helps to slow down the shortening of telomeres (ends of our chromosomes). This activity is high in white blood cells which must be able to multiply themselves a large number of times to cope with an infection.


Vitamin D potentially contributes to healthy longevity because the shorter the telomeres, the greater the risk of cardiovascular disease, diabetes, cancers,… vitamin D deficient people have a greatly increased mortality!

The drop in D is associated with a markedly increased frequency of winter infections: colds, flu and high infectious mortality, particularly in seniors (also correlated with telomere shortening). But in winter there is less sun so more D is needed to fight infections.


Taking D supplements by pregnant women prevents respiratory syncytial virus bronchiolitis RSV in infants and also exhaustion and diabetes during pregnancy.

D deficiency is associated with a higher risk of cardiovascular disease.

The frequency of asthma is higher in people with low vitamin D levels, as well as most allergic, inflammatory and autoimmune pathologies.

Indispensable for the proper functioning of the brain, anti-inflammatory effect on the brain.

An improvement in symptoms is noted when the deficits are corrected.

The proper functioning of serotonin and oxytocin depends on D.

D2 (ergocalciferol) is of plant origin (fruits, vegetables)
D3 or cholecalciferol is of animal origin (fish liver oil, fish, milk, butter, cheese)
Few common foods provide an appreciable amount of vitamin D: fish liver oil, fish, liver, mushrooms.
In the skin, ultraviolet B (UVB) rays allow the formation of D3 from 7-dehydrocholesterol (derived from cholesterol). An exposure of about 20 minutes/day to the sun, on 50% of the skin, would be equivalent to an intake of 3000 IU per day, but only at the level of Spain in winter (October to April).


Are you SAD in winter? We speak of Seasonal Affective Disorder for mild seasonal depression that affects a large number of people in our regions, which are not very exposed to the sun in autumn-winter.

According to several studies (but not all), people who get enough vitamin D are less likely than others to have depression.


D would behave like a neurosteroid, just like DHEA, and therefore capable of performing important functions in the brain. There are vitamin D receptors in the central nervous system, especially for the brain in the prefrontal cortex, hippocampus, thalamus, hypothalamus, substantia nigra. It seems D activates the expression of genes that allow the synthesis of norepinephrine, a chemical messenger involved in mood. Vitamin D may also protect neurons that synthesize two other chemical messengers: dopamine and serotonin. It would also seem that a ‘dialogue’ exists between the vitamin D receptors in the hippocampus and the receptors for glucocorticoids, stress hormones.


Against seasonal depression also consider light therapy and chrono-nutrition.


Do not self-medicate, always consult a specialist.


Vincent Devalkeneer
Certified Nutrition Therapist