The Many Names and Chemical Identity of Vitamin K3
For those asking "What is vitamin K3 also known as?", the primary answer is menadione. This synthetic compound is sometimes also referred to by its chemical name, 2-methyl-1,4-naphthoquinone, or the related term menaphthone. Its distinction from the natural forms of vitamin K, phylloquinone (K1) and menaquinone (K2), is critical for understanding its role and hazards. While K1 is made by plants and K2 by bacteria, menadione is a laboratory-produced substance that lacks the side chain present in its natural counterparts.
The Synthetic Origin of Menadione
Menadione's artificial origin sets it apart from the two naturally occurring families of vitamin K. Vitamin K1, or phylloquinone, is sourced from leafy green vegetables and is directly involved in photosynthesis. Vitamin K2, or menaquinone, is produced by bacteria in the human gut and fermented foods, and exists in several subtypes (e.g., MK-4, MK-7). Menadione, by contrast, is a simpler molecule that the body can convert into an active form of K2 in certain circumstances, but its synthesis is entirely external to natural food sources.
Why Vitamin K3 is No Longer for Human Consumption
Despite its potential biological activity as a precursor, menadione was withdrawn from the human supplement market decades ago due to its toxic effects. Unlike the natural K1 and K2, which have very low toxicity potential, menadione has been linked to significant adverse reactions in humans, particularly at high doses.
Adverse effects linked to menadione include:
- Hemolytic anemia: The destruction of red blood cells at a faster rate than they can be produced.
- Liver damage: Cytotoxicity in liver cells was observed in laboratory studies conducted in the 1980s and 1990s.
- Hyperbilirubinemia and kernicterus: This poses a particular risk to newborns, whose immature livers are unable to handle the excessive bilirubin load resulting from the destruction of red blood cells.
- Oxidative stress: Menadione can generate reactive oxygen species, which can cause cellular damage.
The Dangers for Newborns
The toxicity of synthetic menadione is so pronounced that it is never used in prophylactic vitamin K injections for newborns, which instead utilize the safer, natural phylloquinone (K1). In fact, cases of toxicity from synthetic K3 have been reported in formula-fed infants who were inadvertently exposed, highlighting the serious risks it poses.
The Use of Vitamin K3 in Animal Nutrition
In stark contrast to its status for human consumption, menadione is widely and safely used as a feed additive in the animal husbandry industry. Animals can efficiently convert the synthetic menadione into usable forms of vitamin K, making it a cost-effective way to prevent deficiencies. This is especially important for poultry and swine farming, where it ensures proper blood clotting and bone development. Given the regulated nature and controlled doses used in animal feed, menadione offers a reliable source of vitamin K activity for livestock.
Distinguishing Vitamin K3 from K1 and K2
Understanding the differences between the forms of vitamin K is essential for both health and nutrition. The most important distinction lies in their origin, their safety profile, and their current applications. K1 is natural and plant-based, K2 is natural and bacterially derived, and K3 is synthetic and associated with toxicity in humans, leading to its exclusive use in animal feed. For anyone seeking vitamin K supplementation, prioritizing the natural K1 and K2 forms is the safe and recommended path.
| Feature | Vitamin K1 (Phylloquinone) | Vitamin K2 (Menaquinone) | Vitamin K3 (Menadione) |
|---|---|---|---|
| Origin | Naturally synthesized by plants | Naturally synthesized by bacteria | Synthetically produced in laboratories |
| Natural Sources | Green leafy vegetables, vegetable oils | Fermented foods (e.g., natto), animal products | None; not found naturally |
| Human Supplementation | Yes, widely used and safe | Yes, widely used and safe | No, withdrawn due to toxicity concerns |
| Primary Function | Blood clotting activation in the liver | Bone metabolism and arterial health in peripheral tissues | Precursor to active vitamin K forms (in animals) |
| Toxicity Profile | Very low potential for toxicity | Very low potential for toxicity | High potential for toxicity in humans |
| Animal Feed | Yes, but K3 is more common due to cost | Less common due to cost | Yes, widely and safely used |
Conclusion
In summary, what is vitamin K3 also known as? It is known as menadione, a synthetic form of the vitamin that carries significant health risks for humans. Due to its demonstrated toxicity, especially liver damage and hemolytic anemia, it is no longer used in human supplements or fortified foods. Its use is now relegated to the animal feed industry, where animals can safely convert it into an active form of vitamin K. This critical distinction is essential for understanding the different types of vitamin K and making safe nutritional choices. For human health, the natural forms, K1 and K2, are the standard and safe alternatives.
For more information on the different forms of vitamin K, consult the Health Professional Fact Sheet from the NIH Office of Dietary Supplements: Vitamin K - Health Professional Fact Sheet
