The Difference Between K2 MK4 and K2 MK7
Vitamin K is a collective term for several fat-soluble nutrients, including Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinones). Vitamin K2 itself exists in various subtypes, with MK4 and MK7 being the most well-known. While both are forms of K2, their molecular structure, dietary sources, and behavior in the body differ significantly.
MK4 is found almost exclusively in animal products, including eggs, liver, and fatty meats. It has a much shorter half-life in the bloodstream, meaning it is cleared from the body relatively quickly. Due to its smaller structure, MK4 is rapidly used by the body, first for blood clotting and then for bone health once those needs are met. However, because of its poor bioavailability at nutritional doses, high or frequent intake is required to maintain its effect.
In contrast, MK7 is produced by bacteria during fermentation and is abundant in foods like natto (fermented soybeans) and some cheeses. MK7 has a longer half-life, allowing it to remain in the bloodstream for a longer period and accumulate in bodily tissues. This makes MK7 highly bioavailable and particularly effective for maintaining bone health over time with smaller, consistent doses.
Why Eggs Contain MK4, Not MK7
The presence of MK4 in eggs and other animal products is a result of the animal's metabolism. Animals that consume green plants containing Vitamin K1 are able to convert some of it into MK4 internally. This MK4 is then stored in fatty tissues and transferred to the egg yolk. Since MK7 is a product of bacterial fermentation, it is not produced or stored in the same way by chickens. Therefore, eggs naturally contain the MK4 variant, making them a source of K2 but not MK7.
How a Hen's Diet Affects K2 Content in Eggs
The amount of MK4 in an egg yolk is highly dependent on what the chicken eats. Pasture-raised hens that forage on grass, insects, and other green plants have a diet rich in K1. Their bodies efficiently convert this K1 into MK4, resulting in eggs with significantly higher K2 levels compared to conventionally raised hens fed a grain-based diet. In fact, some studies show that eggs from pasture-raised hens can have 20% more K2 than those from grain-fed chickens. For those seeking to maximize their dietary K2 from eggs, choosing eggs from pasture-raised or biofortified chickens is the best strategy.
Optimizing Your Intake of Egg K2
When consuming eggs for their K2 content, a few simple tips can help optimize your intake. Firstly, because K2 is a fat-soluble vitamin, the yolk is where the nutrient is concentrated, not the egg white. Consuming the entire yolk ensures you receive the full benefit. Secondly, the fat in the egg yolk itself aids in the absorption of the fat-soluble K2. Combining eggs with other nutrient-rich foods, such as leafy greens that contain K1, can also be beneficial, as the fat in the yolk helps your body absorb the K1 too.
Comparison: Egg Yolk (MK4) vs. Natto (MK7)
| Feature | Egg Yolk (MK4) | Natto (MK7) |
|---|---|---|
| Primary Source Type | Animal Products | Fermented Foods |
| Origin | Conversion from K1 in animals | Bacterial fermentation |
| Half-Life | Short (cleared in hours) | Long (circulates for days) |
| Bioavailability | Low at nutritional doses | High, accumulates in body |
| Main Food Examples | Pasture-raised eggs, goose liver, grass-fed butter | Natto (fermented soybeans), Gouda cheese |
| Best For | Consistent, daily intake required | Long-lasting availability in the body |
The Role of K2 from Eggs in Human Health
Despite being MK4 and not MK7, the K2 found in eggs plays a vital role in human health. It activates specific proteins, like osteocalcin and matrix GLA protein, which are responsible for directing calcium to the bones and teeth. This process is critical for maintaining strong bone density and preventing conditions like osteoporosis. Furthermore, by ensuring calcium is deposited in bone tissue, K2 helps prevent it from accumulating in soft tissues, such as arteries and kidneys, which is a key factor in cardiovascular disease. The fat content of the yolk also ensures efficient absorption of this crucial nutrient.
Other Dietary Sources of MK7
To complement the MK4 from eggs, you can incorporate other foods rich in MK7 into your diet. The richest source is natto, a traditional Japanese food made from fermented soybeans, which provides a high concentration of MK7. Other sources include certain cheeses, particularly hard and soft fermented cheeses like Gouda and Brie, and some cured or fermented meats. Smaller amounts may also be found in fermented vegetables like sauerkraut.
Conclusion: The Bottom Line on K2 in Eggs
In summary, do eggs have K2 MK7? No, eggs are not a source of MK7, but they are a valuable dietary source of the MK4 form of vitamin K2. The concentration of MK4 is directly influenced by the hen's diet, with pasture-raised eggs being a superior option for maximizing your intake. While MK4 and MK7 have different properties, both contribute to crucial bodily functions, particularly bone and cardiovascular health. Therefore, including pasture-raised eggs as part of a varied diet that also incorporates fermented foods can help ensure a balanced intake of both important K2 variants.
