What Is Vitamin K
The Science Behind It
Vitamin K is a fat-soluble vitamin essential for blood clotting, bone mineralization, and calcium regulation. It comes in two main forms: K1 (phylloquinone) from leafy greens and K2 (menaquinone) from fermented foods and animal sources. K2 directs calcium into bones and teeth and away from arteries.
The Easygoing Edition
Vitamin K is the “traffic cop” of your calcium. It tells calcium where to go (your bones) and where not to go (your arteries). Without it, calcium gets confused and can cause buildup in the wrong places.
Type & Category
Fat-soluble vitamin.
Absorption Rate & Factors Affecting It
- Absorption Efficiency: Roughly 40–80%, depending on fat intake and gut health.
- Forms Matter:
- K1 (phylloquinone): Found in leafy greens, absorbed in the small intestine with dietary fat.
- K2 (menaquinone): Produced by gut bacteria and found in fermented and animal foods—better absorbed and longer-lasting in the body.
- Enhancers: Healthy bile flow, presence of fats (especially MCT or omega-3s), and a thriving gut microbiome.
- Inhibitors: Antibiotics (disrupt K2-producing gut flora), low-fat diets, gallbladder or pancreatic issues, and chronic gut inflammation.
Pro Tip: Vitamin K works best when taken with fat and vitamin D3—they’re metabolic partners in calcium management.
Function in the Body
- Activates clotting factors for wound healing.
- Supports bone formation by activating osteocalcin.
- Prevents arterial calcification.
- Works with Vitamin D to balance calcium.
Effects in the Body
- Blood Clotting: Activates clotting proteins, preventing excessive bleeding.
- Bone Health: Works with Vitamin D and magnesium to guide calcium into bones and teeth instead of soft tissues.
- Heart Protection: Prevents arterial calcification (plaque hardening) by regulating calcium transport.
- Cellular Growth: Supports mitochondrial energy production and helps prevent oxidative damage.
- Hormonal Regulation: Influences insulin sensitivity and sex hormone metabolism.
- Brain Function: K2 plays a role in sphingolipid metabolism, important for myelin sheath and cognitive health.
Organ & System Connection
Top Whole Food Sources
Animal-Based Sources (Rich in K2)
- Grass-fed butter and ghee
- Raw or aged cheeses (Gouda, Brie, Edam, Jarlsberg)
- Pasture-raised egg yolks
- Grass-fed beef liver
- Chicken thighs and liver
- Wild-caught salmon and sardines
- Fermented cod liver oil (trace amounts)
Note: Grass-finished and pastured animals yield much higher Vitamin K2 levels due to their chlorophyll-rich diets.
Plant-Based Sources (Rich in K1)
- Kale, spinach, collard greens, mustard greens
- Swiss chard, turnip greens, beet greens
- Broccoli, Brussels sprouts, asparagus
- Parsley, basil, cilantro
- Green peas and avocado
Tip: Steam or lightly sauté greens with olive oil or butter to improve absorption—raw greens alone provide poor K uptake.
Fermented & Specialty Foods (Richest in K2)
- Natto (fermented soybeans): The highest natural source of K2 (MK-7 form)
- Fermented sauerkraut and kimchi (contain small amounts depending on bacterial strains)
- Fermented dairy (kefir, yogurt, raw cultured cheese)
- Fermented meats (salami, traditional cured meats)
Fun Fact: The MK-4 form (from animal foods) acts quickly but has a short half-life; MK-7 (from natto/fermented foods) lasts up to 72 hours in the body.
Deficiency Signs
- Easy bruising or nosebleeds
- Weak bones or fractures
- Arterial stiffness
Quick Tips
Pair with Vitamin D for synergy.
Get both K1 and K2 through plants and fermented foods.
Eat with healthy fats for absorption.
Myth
Myth: “Vitamin K is just for blood clotting.”
Truth: It’s also vital for bone strength and cardiovascular health — one of the most underrated nutrients for longevity.