Vitamin K is a crucial fat-soluble vitamin necessary for a variety of bodily functions. Its different forms have distinct names and characteristics, impacting how the body absorbs and uses them. While often referred to as simply "vitamin K," understanding the specific names helps to clarify its complex roles in human health.
Phylloquinone (Vitamin K1)
The most prominent and common form of vitamin K found in the average diet is phylloquinone, also known as vitamin K1. It is synthesized by plants and is the primary form the body uses for its critical function in blood clotting.
Functions and Sources of Phylloquinone
- Essential for Blood Clotting: Phylloquinone is transported to the liver where it is a required cofactor for the activation of blood clotting factors like prothrombin. Without sufficient K1, the blood's ability to clot effectively is impaired, which can lead to excessive bleeding.
- Dietary Sources: Phylloquinone is abundant in a wide range of leafy green vegetables, as well as some vegetable oils. The bioavailability from leafy greens is generally low unless consumed with fat.
- Plant-Based Foods High in Vitamin K1:
- Kale
- Spinach
- Broccoli
- Brussels sprouts
- Collard greens
- Soybean and canola oils
Menaquinones (Vitamin K2)
Menaquinones, or MKs, are another family of vitamin K compounds known collectively as vitamin K2. These are predominantly produced by bacteria, both in fermented foods and within the gut microbiota. The various subtypes (e.g., MK-4, MK-7) are named based on the length of their side chain.
Functions and Sources of Menaquinones
- Bone and Heart Health: K2 plays a key role in bone metabolism and cardiovascular health by activating proteins that help bind calcium. For instance, it activates Matrix Gla Protein (MGP), which prevents calcium from depositing in arteries, reducing vascular calcification.
- Higher Bioavailability: Some forms of K2, particularly MK-7, are believed to be more effectively absorbed and circulate longer in the blood compared to K1.
- Bacterial Conversion: While gut bacteria can produce K2, the amount and absorption are not always sufficient, making dietary intake important. MK-4 is an exception, as it is converted from K1 or menadione in animal tissues.
- Fermented and Animal Sources High in Vitamin K2:
- Natto (fermented soybeans), which is particularly rich in MK-7
- Cheeses (especially hard and semi-soft varieties)
- Certain meats and egg yolks
- Fermented vegetables like sauerkraut
Menadione (Vitamin K3)
Menadione is a synthetic form of vitamin K and is also known as vitamin K3. However, its use is restricted due to safety concerns. Research from the 1980s and 1990s linked it to liver damage and the destruction of red blood cells in humans, and it is no longer used in human supplements. It is still sometimes used in animal feed.
Comparison of Vitamin K Forms
| Feature | Vitamin K1 (Phylloquinone) | Vitamin K2 (Menaquinone) | Vitamin K3 (Menadione) |
|---|---|---|---|
| Primary Source | Plant-based foods (leafy greens) | Bacteria (fermented foods, gut) and animal products | Synthetic |
| Key Functions | Blood clotting | Bone and heart health | Formerly blood clotting; now obsolete for humans |
| Absorption | Can be low unless consumed with fat | Generally considered better absorbed, especially MK-7 | Absorbed efficiently, but safety concerns limit use |
| Storage | Primarily accumulates in the liver | Found in extrahepatic tissues like bone, kidneys, and pancreas | Converted to K2 in the body |
| Safety for Humans | Very safe, low toxicity potential | Very safe, low toxicity potential | Associated with liver damage and hemolytic anemia; not for human consumption |
Why is Knowing the Other Names Important?
Because K1 and K2 have different origins, bioavailability, and primary target tissues, knowing their specific names is important for nutrition and health. While K1 is crucial for proper blood clotting, K2 plays a more prominent role in directing calcium to the bones and away from the arteries. A balanced diet should include both forms for optimal health. Consuming K1 from leafy greens along with a source of dietary fat can enhance absorption. Incorporating fermented foods and some animal products can increase K2 intake.
Conclusion
There is no single other name for vitamin K, but rather a family of compounds identified as phylloquinone (K1), menaquinone (K2), and menadione (K3). While K1 is vital for blood coagulation and found in plants, K2 supports bone and cardiovascular health and is found in fermented foods and animal products. Menadione, the synthetic K3, is no longer used in human nutrition due to toxicity. A diverse diet rich in both plant-based K1 and fermented or animal-based K2 is the best way to ensure optimal vitamin K intake. For more information, consult the National Institutes of Health [https://ods.od.nih.gov/factsheets/VitaminK-Consumer/].
Note: This information is for educational purposes only and is not a substitute for professional medical advice. Always consult a healthcare provider for any health concerns or before making dietary changes.
