Vitamins D, E, K and A are the body’s four fat-soluble vitamins. They share the same absorption pathway (dietary fat) and work in close synergy. Vitamin D3 (cholecalciferol) contributes to normal calcium and phosphorus absorption, normal immune function and normal muscle function — in France, 80% of the population has insufficient vitamin D status, especially in winter. Vitamin K2 (menaquinone MK-7) contributes to the maintenance of normal bone and helps fix calcium onto bones and teeth, complementing vitamin D’s action on calcium metabolism. Vitamin E (tocopherols) is a major lipid antioxidant, helping protect cells from oxidative stress. Vitamin A (retinol) is essential for vision, skin and mucous membrane health, and immune function, and works in synergy with D3 at the nuclear-receptor level.

Taken together, these four vitamins reinforce one another: D3 and K2 form an inseparable duo for calcium metabolism, E protects A and D3 from oxidation, and A and D3 share cellular receptors that jointly regulate immune gene expression.

Fat-soluble vitamins are better absorbed in liquid form than in dry tablets. The Dr Jacob’s drop format offers optimal bioavailability (already dissolved in oil, ready for absorption in the small intestine), customisable dosing (each drop delivers a precise amount of each vitamin, adjustable to season, age and diet), no capsule or tablet to swallow, and an economical use thanks to the small volume per dose. Drops can be taken directly under the tongue or mixed into a fatty food (yoghurt, avocado, dressing) to maximise absorption.

This formula is particularly suited to winter months (when sunlight is insufficient to synthesise vitamin D, roughly October to April in Paris), people who are sedentary or work indoors with limited sun exposure year-round, seniors (as skin synthesis of vitamin D decreases with age and K2 needs for bone health increase), vegans (as D3, K2 and A are mainly animal-derived in the diet), menopausal women (the D3+K2 duo contributes to maintaining normal bone), and growing children (all four vitamins are essential to bone and immune development, at an adapted dose).

Follow the manufacturer’s recommendations on the bottle. Take the drops with a meal containing fat to optimise absorption of the fat-soluble vitamins. Recommended pairings: magnesium bisglycinate (a cofactor of vitamin D — without enough magnesium, D3 cannot be activated in the liver and kidneys), zinc (supports immunity alongside vitamins D and A), and omega-3 (fatty acids improve absorption of fat-soluble vitamins).

Vitamin K2 is not recommended for people on vitamin K antagonist anticoagulants (warfarin, acenocoumarol) — consult your doctor. Do not exceed the recommended dose. Consult a doctor if pregnant.

Can DEKA be taken all year round?

Yes, though the dose can be adapted by season. In summer, with sufficient sun exposure, some people reduce the number of drops; in winter, the full dose is recommended.

Does DEKA replace a standalone vitamin D supplement?

Yes, and it does more: it provides D3 alongside its key cofactors (K2 to fix calcium, A for immunity, E for protection) — a more complete approach than an isolated vitamin D.

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.