Vitamin D3 spray with MK-4 vs pills with MK-7: why we made it the way we did

Why vitamin D deficiency is everywhere

Vitamin D is one of the only vitamins the body produces itself — through skin exposure to UVB light. In theory, an outdoor lifestyle in a sunny climate should keep levels topped up. In practice, that's stopped being true for several converging reasons.

Indoor living. Most people are awake-and-indoors during peak UVB hours. Office work, school, screens, AC. The skin barely sees direct sunlight on a typical workday.

Sun avoidance. The same UVB that synthesizes vitamin D also damages DNA and increases skin cancer risk. Public health messaging — correctly — has pushed sunscreen, hats, shade. The trade-off is that vitamin D production drops dramatically.

Latitude. Above ~40° latitude^[3], the sun's angle in winter months produces almost no UVB regardless of how long you stand outside. Most of Europe, the northern US, Canada, Russia falls into this category for several months each year.

Skin pigmentation, age, body composition. Darker skin produces less vitamin D for the same UV exposure. Older skin produces less. Body fat sequesters vitamin D, making circulating levels lower at the same dose in higher-BMI individuals^[7].

The result: I have, over ten years, tested thousands of people across multiple climates. The number whose vitamin D came back at a comfortable level without supplementation is so small I can barely remember any. A 2014 systematic review of 103 studies confirms low vitamin D status across all age groups globally^[2], with major clinical guidelines recommending supplementation for individuals with documented deficiency or limited sun exposure.

Why the form matters: spray vs tablet

Vitamin D as a tablet works. It's been the default for decades. But the moment you start asking what's actually inside the tablet, the case for a spray gets stronger.

What's in a tablet

• Vitamin D3 itself — usually a small amount of oil-based active ingredient.
• Bulking agents — microcrystalline cellulose, dicalcium phosphate.
• Binders — magnesium stearate, stearic acid.
• Coatings — gelatin (from animal sources) or hypromellose (vegetarian) plus plasticizers.
• Flow agents, anti-caking agents, sometimes synthetic colorants.

None of these are dangerous. Most are inert. But none of them are helpful either. They exist because pressing a tablet requires them. They are the cost of using a tablet format.

What's in a spray

• Vitamin D3 dissolved in MCT (medium-chain triglyceride) oil.
• K2 (MK-4 form) dissolved in the same oil.
• Nothing else.

The MCT oil base provides a clean fat carrier; vitamin D3 is fat-soluble and absorbs better in the presence of dietary lipids. The spray is the active ingredients plus their carrier. No fillers, no binders, no coatings. Every spray is signal, no noise.

The other practical advantage

Vitamin D needs to be taken consistently — daily, indefinitely. The format that actually gets taken every day is the format that wins. A tablet requires water. A spray needs nothing. You can use it in a car, at a desk, in transit, while putting on shoes. That removed friction is the difference between "I supplement" and "I forgot to supplement again".

And the dose is adjustable. Each spray delivers a fixed amount. A child needs three sprays. An adult with deficiency needs fifteen. The same bottle handles the whole family at different doses. With a tablet you'd need three different SKUs.

Why MK-4 specifically (not MK-7)

K2 has multiple natural forms — primarily MK-4 and MK-7. Both are biologically active. They differ in pharmacokinetics:

• MK-4 — endogenously converted form found in animal tissue, with rapid clearance from the bloodstream^[4]. Mucosal/buccal delivery routes may suit its kinetic profile, though head-to-head sublingual research is limited.
• MK-7 — bacterial fermentation form with longer half-life (~3 days), achieving steady-state plasma levels with oral dosing^[4].

For a spray that delivers vitamin D and K2 in droplet form, comparable to capsule absorption in healthy adults^[6], MK-4 is the form that matches the delivery route. The molecule absorbs fast through the same tissue the spray contacts. MK-7 in a spray would partly waste its longer half-life advantage by being absorbed too quickly anyway.

For an oral tablet that releases in the gut, MK-7 is often the better choice. So the answer to "MK-4 vs MK-7" depends on the format. A spray pairs with MK-4. A tablet pairs with MK-7. Both are correct — for their format.

Why D3 needs K2 alongside

D3 increases calcium absorption from food. That's its primary mechanism for bone support. The catch: increased absorbed calcium has to go somewhere. The body's destination of choice is bone tissue. Without proper signaling, however, some of that calcium can deposit in vascular tissue instead — calcification of arteries, calcified plaque buildup.

K2 is the molecule that activates the proteins (osteocalcin, MGP) that direct calcium into bone and away from arteries. With both D3 and K2 in the system, calcium goes where it should. Without K2, you're absorbing more calcium than the body's logistics layer is set up to handle correctly.

Vitamin K2 activates matrix Gla protein and osteocalcin — proteins that direct calcium toward bone tissue and away from arterial walls^[5]. Pairing D3 with K2 — especially at the higher D3 doses needed for deficiency correction. The two work as a system. Putting them in the same bottle isn't a marketing combo; it's the form that gives the body what it actually needs to use the D3 safely.

Why glass

Oils interact with plastic. Plasticizers can migrate. The oil itself can oxidize faster in plastic packaging. For a fat-soluble vitamin dissolved in MCT oil and used daily, packaging quality is part of the product.

Glass is inert. The oil that arrives in the bottle is the same oil that leaves it after eight months of daily use. For a daily product where lipid stability matters, plastic is a hidden compromise — invisible to the consumer, but present in the chemistry.

Side-by-side: tablet vs NAN spray

How much, and how often

Maintenance dose for adults with normal levels: 2000–4000 IU per day (~6–8 sprays). This keeps blood levels in the optimal range (50–80 ng/mL) once corrected.

Correction dose for documented deficiency: 5000–10000 IU per day (~15–20 sprays) for 8–12 weeks, then retest. Higher doses for severe deficiency should be supervised by a clinician.

Children: 1000–2000 IU per day (~3–4 sprays), depending on age and exposure.

Timing: Morning is convenient. With food slightly improves absorption (D3 is fat-soluble, MCT helps), but the spray works without it.

Testing: Get a 25(OH)D blood test before starting if you're correcting a deficiency. Retest after 8–12 weeks to see what dose actually moved your level. Individual response varies more than dose-response charts suggest.

This article is educational and reflects 10 years of nutritional practice. It does not replace medical advice. If you have hyperparathyroidism, granulomatous disease, take blood thinners or anticonvulsants, or are pregnant, consult your physician before starting D3 supplementation, especially at correction-level doses.