There are two main forms of vitamin D used in supplements: vitamin D2 (ergocalciferol), of plant origin, and vitamin D3 (cholecalciferol), of animal origin or derived from lichen. Vitamin D3 is recognised as more effective than D2 at raising and maintaining blood levels of vitamin D (25-hydroxyvitamin D), making it the form favoured by most healthcare professionals. Cholecalciferol is identical to the form our skin naturally produces under UVB sunlight. Once ingested, vitamin D3 undergoes two conversions — first in the liver (into 25-hydroxyvitamin D, or calcidiol), then in the kidneys (into 1,25-dihydroxyvitamin D, or calcitriol, the biologically active form). Dr Jacob’s formula uses pharmaceutical-grade cholecalciferol, dosed at 2000 IU per tablet — the upper level recommended by many European health authorities for daily supplementation without specific medical supervision.

The choice of 2000 IU per tablet reflects the dose most commonly recommended by healthcare professionals to correct or prevent vitamin D insufficiency in adults, particularly in Northern Europe and regions with limited winter sunlight. In Paris, winter sunlight is insufficient to maintain adequate vitamin D levels: from November to March, the sun’s low angle means UVB rays rarely reach the skin with enough intensity to trigger vitamin D synthesis, an effect compounded by an urban lifestyle that limits sun exposure even in summer. Dietary sources of vitamin D (oily fish, egg yolk, some mushrooms) typically cover only 10–20% of daily needs, making a 2000 IU daily supplement a reasonable, well-documented approach to maintaining optimal vitamin D status year-round.

Vitamin D3 contributes to the maintenance of normal bones and teeth by supporting the intestinal absorption of calcium and phosphorus, the two main minerals in bone tissue. It also contributes to the normal function of the immune system — vitamin D receptors have been identified on most immune cells, underlining the importance of adequate intake, particularly during the colder months. Among its other roles recognised by the European Food Safety Authority (EFSA), vitamin D contributes to normal muscle function, normal cell division, and the maintenance of normal blood calcium levels, as well as to the normal absorption and utilisation of phosphorus.

Dr Jacob’s is a German brand specialising in high-quality food supplements, founded by Dr Ludwig Manfred Jacob, a physician and author of several works on nutrition. The brand is known for its rigorous scientific approach, formulations grounded in the medical literature, and high manufacturing standards in line with some of Europe’s strictest German regulations. Vitamin D3 FORTE is made in Germany in certified facilities, with full traceability and quality control at every stage; each batch is tested for exact cholecalciferol content and absence of contaminants. The formula is intentionally minimal — microcrystalline cellulose, hydroxypropyl cellulose, magnesium stearate and vitamin D3 — and the product is gluten- and lactose-free.

Follow the dose stated on the pack, generally 1 tablet a day. As vitamin D3 is fat-soluble, it’s best taken with a meal containing some fat (olive oil, avocado, butter, nuts) to optimise intestinal absorption — breakfast or lunch is often the most practical time. Supplementation is particularly recommended from October to March to offset reduced winter sunlight, though many healthcare professionals suggest year-round use, especially for people who work indoors, older adults, people with darker skin, and anyone with limited sun exposure — all groups at higher risk of vitamin D insufficiency, along with people living in cities like Paris, where limited time outdoors and air pollution further reduce UVB exposure.

Do not exceed the recommended daily dose. People on medical treatment — particularly anticonvulsants, long-term corticosteroids or cholesterol medication — should seek advice from their doctor before starting supplementation. Food supplement — does not replace a varied, balanced diet or a healthy lifestyle.

Where can I buy Vitamin D3 FORTE 2000 IU Dr Jacob’s in Paris?

Dr Jacob’s Vitamin D3 FORTE 2000 IU is available at Herba Barona, a food supplement shop in the 12th arrondissement of Paris. Our team can advise on the dosage and course length suited to your profile, with delivery available across Paris.

What’s the difference between vitamin D2 and vitamin D3?

Vitamin D2 (ergocalciferol) is plant-derived, while vitamin D3 (cholecalciferol) is identical to the form synthesised by the skin under sunlight. D3 is considered more effective at raising and maintaining blood vitamin D levels — Dr Jacob’s product uses the D3 form for optimal effectiveness.

Can I take 2000 IU of Vitamin D3 all year round?

Yes, continuous supplementation is possible and often recommended, particularly for people living in Paris where sunlight remains limited for much of the year. A blood test can help fine-tune the dose — ask our team at Herba Barona for guidance.

Is Dr Jacob’s Vitamin D3 FORTE suitable for people with gluten intolerance?

Yes, this product is formulated without gluten or lactose, making it suitable for people with coeliac disease or gluten intolerance.

Herba Barona is an independent specialist supplement shop in the heart of Paris — established in 2006. What you order is genuinely on our shelves: we ship from our own stock, with no dropshipping and no long waits.

Visit us at 10 rue Théophile Roussel, Paris 12 — or use Click & Collect and pick up your order in-store. We also deliver across France and Europe. Friendly, expert advice in English from our team.

Where is the shop?

Herba Barona is at 10 rue Théophile Roussel, 75012 Paris — a two-minute walk from Ledru-Rollin (line 8), close to Bastille. Open Tuesday to Saturday, 9:30 am–6:30 pm.

Can I order online or collect in store?

Yes. We ship across France and Europe under the same conditions as our French store, or choose Click & Collect to pick up your order for free at our Paris shop.