Complément Alimentaire Vitamine D

Vitamin D plays a fundamental role in many bodily functions. However, many people struggle to get sufficient amounts of vitamin D through diet or sun exposure.

In this context, vitamin D supplements are becoming increasingly popular among consumers to increase the intake of this precious vitamin.

What is vitamin D?

Vitamin D is a fat-soluble vitamin that plays a role in several bodily functions essential to the body.

Unlike most vitamins, it can be synthesized by our body when exposed to sunlight, which distinguishes it from other vitamins that we primarily need to obtain through our diet or food supplements.

Types of vitamin D

Vitamin D primarily comes in two forms:

• Vitamin D2 (ergocalciferol): It comes mainly from plants and mushrooms.
• Vitamin D3 (cholecalciferol): This is the most common and active form of vitamin D, produced by the skin in response to sun exposure.
  It is also present in certain animal-based foods, such as cod liver and salmon. This form is the most common as a food supplement.

Vitamin D in the body

After being absorbed by the intestine or produced by the skin under the effect of UVB rays, vitamin D undergoes several steps to become functional in the body:

• Absorption and transformation: Vitamin D is absorbed in the intestine and enters the blood as vitamin D2 or D3, which must be transformed in the liver.
• Storage: Part of the vitamin D is stored in the liver and in fatty tissues, which serve as reservoirs.
• Regulation and elimination: The body regulates vitamin D levels to avoid excess. Excess vitamin D is slowly eliminated through feces and urine.

Daily vitamin D requirements

Vitamin D requirements vary depending on age, lifestyle, and sun exposure. According to ANSES (French Agency for Food, Environmental and Occupational Health & Safety), the satisfactory nutritional intakes (1) of vitamin D through diet are:

- Men and women aged 18 and over: 15µg per day.

What is vitamin D used for?

Vitamin D has several benefits in the body, particularly by contributing to:

• The maintenance of normal bones,
• The normal functioning of the immune system,
• The maintenance of normal muscle function,
• Normal blood calcium levels,
• The normal absorption and utilization of calcium and phosphorus,
• Contributes to the maintenance of normal teeth.

In addition, this vitamin plays a role in the process of cell division.

Where can you find vitamin D?

Our body is capable of producing vitamin D when exposed to sunlight, but this is not always enough, especially during winter or for people who spend little time outdoors. Here are the two main sources of vitamin D:

Synthesis by the sun

When exposed to the sun, UVB rays act on the skin and allow the production of vitamin D. This synthesis depends on several factors:

• Sun exposure: The duration of sun exposure, as well as the intensity of UVB rays, vary depending on the season, geography, and time of day.
• Individual factors: Age, skin type, use of sunscreen, and the amount of exposed skin can influence the amount of vitamin D produced.

Vitamin D foods, natural sources

Although sun exposure is an effective way to produce vitamin D, several foods can also be a source:

• Fatty fish:
  - Salmon,
  - Mackerel,
  - Sardines,
  - Herring,
  - Trout.
• Cod liver (and cod liver oil): Contains vitamin D, although it is often consumed as a food supplement.
• Fortified dairy products:
  - Milk,
  - Yogurt,
  - Cheese.
• Eggs, vitamin D is found mainly in the egg yolk.
• Mushrooms, some sun-exposed mushrooms, such as button mushrooms or shiitake, contain vitamin D2.
• Fortified cereals, some breakfast cereals are fortified with vitamin D.
• Tofu and other fortified soy products, some soy products are fortified with vitamin D.

These foods can be important sources of vitamin D, especially for those with little sun exposure.

Why take a vitamin D supplement?

Vitamin D is found in certain foods that are not compatible with all diets, which is why many people struggle to get enough of it through diet alone.

In this context, vitamin D supplements can be particularly useful for increasing the intake of this vitamin, especially for individuals such as:

• People living in areas with low sunshine.
• People with a sedentary lifestyle or who spend a lot of time indoors.
• People with restrictive diets.

Food supplements are a convenient way to increase vitamin D intake. It is essential to select a quality product, correctly dosed, that meets your specific needs, while following the recommended doses.

Vitamin D dosage: how to choose the right supplement?

The food supplement market offers a variety of forms and dosages of vitamin D. It is essential to choose the one that best suits your needs.

Vitamin D supplements come in different forms:

Capsules: Classic and practical form

• Advantages:
  - Easy to take and dose.
  - Allows for precise dosing.
  - Easy to transport.
  - Ideal for regular intake.
  
  
• Ideal for:
  - People who prefer a simple and quick intake, without preparation.

Drops and spray:

• Advantages:
  - Allow for flexible dosing, to adjust the quantity according to needs.
  
  
• Ideal for:
  - Those who prefer absorption without taking capsules.

Buying guide: how to choose the right vitamin D supplement?

When choosing a food supplement, several criteria must be taken into account to guarantee its quality and effectiveness.

Form of vitamin D: Formulation or isolated vitamin

• Vitamin D3

Vitamin D is most often found in its active form: D3.

• Vitamin D3 and K2

More and more food supplements combine vitamin D3 with vitamin K2 (D3K2), for their individual and complementary benefits.

Vitamin K contributes to normal blood clotting. It also contributes to the maintenance of normal bones, like vitamin D.

It is important to choose a good quality vitamin K with labels, for example (K2VITAL®).

Dosage

It is important to check the dosage in each food supplement to ensure a well-dosed quantity, such as 3000 IU, which is an ideal dosage in formulations. Always follow the dosage indicated by the manufacturer.

Quality of formulation

Prefer products without unnecessary excipients, without controversial additives, and ideally without artificial colors.

And opt for brands that are transparent about the composition of their supplement, which meet manufacturing standards such as ISO 22000 certification and HACCP standards.

Safety and precautions

It is important to respect the recommended daily doses: an excessive dosage is not more effective.

Vitamin D food supplement: in summary

Vitamin D has many benefits in the body. However, it is often difficult to obtain enough vitamin D solely through diet or sun exposure. Vitamin D food supplements help increase this essential vitamin.

When selecting a vitamin D supplement, it is essential to choose the form that matches your goals and lifestyle. To optimize the benefits of vitamin D, some supplements also combine vitamin K2.

Sources:

1. ANSES. "Nutritional references for vitamins and minerals." 2025. https://www.anses.fr/fr/content/les-references-nutritionnelles-en-vitamines-et-mineraux
2. ANSES. “Vitamin D: why and how to ensure sufficient intake?” 2022. https://www.anses.fr/fr/content/vitamine-d-pourquoi-et-comment-assurer-un-apport-suffisant