Learn all about Vitamin K
What is Vitamin K?
Help calcium go to bones & support heart health with vitamin K2. Works closely with Vitamin D3. Strengthen your foundation!
Benefits of Vitamin K
- Essential for normal blood clotting by helping activate specific clotting proteins (factors II, VII, IX, X).[ref]
"Vitamin K shows how our understanding of nutrients grows. Once known only for blood clotting, we now see it as a key controller of how calcium is used everywhere in the body. Discovering that Vitamin K guides calcium into bones and away from arteries is huge for both bone and heart health. It's fascinating how the different K forms, especially the K2 types (menaquinones), seem to work in different body tissues. This new knowledge makes this once-overlooked vitamin seem crucial for healthy ageing."
- Dr Sarah Booth, PhD, Director of the Vitamin K Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University (source)
How to use Vitamin K
Dosage
Adults need about 90-120 micrograms (mcg) of K1 daily. Higher doses of K2 might be used for specific goals. There's no set upper limit for safety.
Timing
Best taken with meals containing some fat to help absorption. Once a day is usually fine.
Notes
Different forms (K1 vs. K2 types like MK-4 and MK-7) are absorbed differently and last longer in the body. MK-7 generally stays active longer and is absorbed better than K1.
Who should take Vitamin K?
- People who don't eat many green leafy vegetables.
- Those with conditions making it hard to absorb fat.
- Individuals taking antibiotics for a long time.
- Women after menopause concerned about bone health.
- People wanting to support their heart and blood vessel health.
- Newborn babies (receive a standard K shot to prevent bleeding issues).
- Those taking warfarin/coumadin blood thinners (need consistent K intake and doctor supervision).
How does Vitamin K work?
Vitamin K acts like a helper for an enzyme (gamma-glutamyl carboxylase) that 'switches on' certain proteins by modifying them. This change allows these proteins to grab onto calcium, which is key to how Vitamin K controls calcium use. For blood clotting, it activates proteins needed to form clots and others that help control clotting. In bones, it activates osteocalcin, a protein that helps minerals bind to the bone structure, making it stronger. For blood vessel health, it activates Matrix Gla protein (MGP), which stops calcium from building up in artery walls. The body recycles Vitamin K to reuse it; blood thinners like warfarin work by blocking this recycling process.
Frequently asked questions
Natural sources of Vitamin K
Vitamin K1 (phylloquinone) is rich in dark leafy greens like kale, spinach, collards, and Brussels sprouts. Broccoli and cabbage have some too. Some plant oils (soybean, canola) also contain K1. Vitamin K2 (menaquinones) is found in fermented foods (like natto - fermented soybeans, which is very high in MK-7) and animal products (cheese, egg yolks, meat, butter). Fermented foods like sauerkraut also contain K2 made by bacteria. Vitamin K levels in food can vary.
Potential side effects & risks
Warnings
If you take warfarin or similar blood thinners, keep your Vitamin K intake consistent and talk to your doctor before changing your diet or taking supplements, as it can affect how the medication works. High doses might make these drugs less effective. People with clotting problems should consult a doctor before taking extra K. Avoid synthetic K3 (menadione) due to safety concerns.
Side effects
Natural Vitamin K forms (K1, K2) are very safe, even at high doses. An old synthetic form (menadione/K3) can be toxic and isn't used anymore. Some people might get mild stomach upset from supplements.
Interactions
Vitamin K (especially K1) works against blood thinners like warfarin by competing for the same spots in the body's vitamin K recycling system. Some antibiotics can reduce gut bacteria that make Vitamin K. Certain cholesterol and weight loss drugs can lower Vitamin K absorption.