Do you miss vitamin D?

Vitamin D is one of the highly studied subjects (more than 74,200 studies referenced to date) and mediated in recent years. Well Named. This vitamin plays indeed essential roles for your health, well beyond the prevention of osteoporosis. But then, how to restore optimal status when you are deficient or deficient in vitamin D3? Let's see all this in details.

Why pay attention to its vitamin D status ?
The list of effects of a vitamin D deficiency could be the subject of a full article as the data are numerous. Recent scientific studies have revealed the existence of vitamin D3 deficiencies (rate below 10 ng / ml) in the context of many pathologies [1]. These include:

Osteomalacia (2), rickets (3), demineralization (4)
Decrease in muscle tone (5);
General susceptibility to infections, seasonal influenza (6);
Multiple sclerosis and rheumatoid arthritis;
Cröhn's disease and ulcerative colitis;
The increase in cognitive decline (7) and the risk of Alzheimer's disease (8),
Type 1 diabetes (10);
Cancers of the breast, colon, pancreas, uterus, kidneys, ovaries, leukemia (11);
Asthma and respiratory infections;
Cardio-vascular risks and high blood pressure;
Pulmonary tuberculosis.
What are the foods rich in vitamin D?
There are two forms of vitamin D: vitamin D2 (ergocalcif erol) produced by plants and vitamin D3 (cholecalciferol), produced by animals. In humans, what is commonly called vitamin D is actually 1,25-dihydroxyvitamin D, activated by UV rays from the sun from a cholesterol derivative (9). It is important to ensure (by a blood test) that you have a sufficient cholesterol status. The awareness of the relative risks of a high level of cholesterol is indeed frequent in the medical world, the deleterious effects of a lack unfortunately much less.

Vitamin D is a fat-soluble vitamin, which means that it is present mainly in foods rich in fats, especially of marine origin, but in quantities often insufficient to cover your needs. The diet brings on average 136 IU per day according to the SUVIMAX study. The richest foods are fatty fish containing between 400 and 800 IU per 100 g (salmon, mackerel, herring), shellfish (200 to 300 IU), canned sardines (100 IU) and to a lesser extent eggs .

Example of foods rich in vitamin D

vitamin D content

When we mention the vitamin D status, two units are used to quantify it: the international unit (IU) and the microgram (1 μg corresponds to 40 IU or 1 IU to 0.025 μg of calciferol).

You make your vitamin D a good part of the year ed
Your body makes some of the vitamin D it needs from a cholesterol precursor and in the presence of UVB. It is considered that sun exposure without sunscreen 15 to 30 min per day (12 min on average), from spring to fall, is necessary to cover the needs of most of the population. The wavelength of solar radiation for the synthesis of vitamin D3 must indeed be between 290 and 315 nanometers. The beginning of the afternoon is then opportune because it is the period during which these UVB predominate. Of course, be well protected from the sun the rest of the time through covering clothes or sunscreen.

Summer exposure, however, generally does not provide the necessary winter storage. It provides on average between 2,000 IU and 20,000 IU per day depending on the pigmentation of the skin, while the daily needs are about 5,000 IU. With the autumnal weeks advancing, the reserves dwindle, so it becomes necessary to check your status (12). According to the SUVIMAX study, 74% of men and 78% of women between 35 and 65 years old suffer from vitamin D deficiency, 14% of deficiency (13). More recent figures from 2007 confirm the prevalence of these deficits: 80% of adults lack vitamin D, of which 42% have a moderate to severe deficiency (14).

How do you know if you are missing vitamin D?
The threshold value defining a state of éficit for adults is 30 ng / mL (75 nmol / L). Some experts, however, recommend a minimum of 40 ng / mL or 60 ng / mL to prevent certain conditions including breast cancer (15) . The target value is therefore between 30 and 60 ng / mL. We are talking about vitamin D deficiency at a rate of less than 10 ng / mL.

You have all the more interest in checking your status if you do not expose yourself to the sun, if you do not do a lot of outside physical activity, if you do not take a summer vacation, if your skin is not white, if you do not live in a sunny area or if you are over 60 (the ability to make vitamin D3 decreases with age).

Which vitamin D to choose?
Vitamin D3 is the active form, so it is absolutely preferable to vitamin D2, less effective and reducing the other reserves vitamin D3 . You will find it in dietary supplements based on lanolin (derived from sheep's wool wax) or lichen (vegetable form). Vitamin D3 in the form of fish liver oil should be avoided because it contains vitamin A, blocking the activity of vitamin D and can be deleterious if you use large doses of supplementation (15) .

The oily form is the most int eres health, because it allows a better assimilation. If you use a tablet or capsule, it is best to consume it during a meal containing oil. The emulsified form is sometimes proposed but has not demonstrated any higher effects on the evolution of the blood level, if not an improvement in case of difficulties of digestion, intestinal inflammatory disease, malabsorption or in infants and the elderly.

Vitamin K2, especially the K2-MK7 form, can be proposed in synergy if the goal is to optimize bone status (it can activate osteocalcin) or in the context of cardiovascular prevention (16) .

How much vitamin D to consume?
To compensate for vitamin D deficiency, you can use two solutions:

A massive dose of vitamin D (about 100,000 IU) in one or more doses, as prescribed by your doctor based on your blood level. However, with this mode of administration, the blood level drops more after a few weeks.
Lower doses via dietary supplements over a longer period.
The recommended amount when dietary supplement consumption is 75 IU / kg body weight / day, a limit of 4000 IU / day according to the ' agency European ean for adults and children over 10 years, 2000 IU / d for children between 1 and 10 years old, 1,000 IU for infants (17). The American Academy of Medicine has set the risk of hypervitaminosis D from 10,000 IU / day for adults.

The duration of supplementation depends on the level of deficitbut it can last from 3 to 6 months, especially during the winter period, or even throughout the year in the elderly. The effects of this supplementation on blood levels of vitamin D can however vary greatly from one individual to another. In addition, the signs of deficits can be difficult to identify in isolation and appear late, once your reservations are well under way. Vitamin D is one of the vitamins with the advantage of being easily measurable by a blood test, so I recommend you seek advice from your doctor to analyze the benefits of performing a dosage and avoid any blind supplementation. Likewise, have your blood levels monitored and a few months later to evaluate the effectiveness of the supplementation.The blood level must not exceed 100 ng / m L , although such a value has not been associated with an increase in health risks.

Given the current scientific data, the French regulation deserves an upward revision . The recommended dose in food supplements is in fact 200 IU / day (5 μg) while the maximum tolerated dose can reach 1000 IU / day, which is a very insufficient quantity to respond to a deficiency state by supplement intake. food alone.

What are the contraindications to vitamin D supplementation?
I recommend that you seek advice from your doctor in case of lymphoma, calcium lithiasis, sarcoidosis, hyperparathyroidism or any doubt about the legitimacy of a supplementation.