- Specific forms of vitamin K called menaquinones are dubbed “MK” with numbers attached, such as MK-4 and MK-7, each one from specific food sources and exerting specific functions throughout your body
- Vitamin K1 is found in many dark green leafy vegetables and K2 is produced by bacteria in fermented foods like natto, a fermented soybean; MK-4 is found in animal foods such as free-range, organic eggs and chicken
- Vitamin K2 has two basic and crucial functions, having to do with cardiovascular health and bone restoration, helping to prevent osteoporosis and atherosclerosis. In fact, people who eat more K2 have the lowest risk of cardiovascular disease
By Dr. Mercola
There’s been a lot of discussion about certain essential nutrients, vitamins and minerals, such as vitamin D and omega-3 fatty acids. But lately, researchers are beginning to recognize that one often-misunderstood vitamin goes unnoticed.
In fact, a large percentage of the population is deficient in this essential nutrient. What is it? Vitamin K. Rather than being a single nutrient, vitamin K is a group of vitamins of similar composition; principally vitamin K1 (phylloquinone) and K2 (menaquinone).
One of the world’s leading authorities on vitamin K, Cees Vermeer, Ph.D., a renowned vitamin K2 scientist in the Netherlands, says inadequacy in this vitamin is the rule rather than the exception, especially one form, called menaquinone-7 (MK-7), a form of vitamin K2.
A number of studies in recent months have determined that vitamin K, a rather complex nutrient because it comes in so many parts, is responsible for some very important jobs in your body, especially your bones and your heart.
Forms of and Sources of Vitamin K
Vitamin K comes in several forms, and you get the most benefit when you eat healthy portions of each type of food that provides the different forms. The best source of vitamin K1 comes from plant-based foods, especially leafy greens. Better Bones1 lists the best foods to eat for vitamin K1, all of them cooked:
|Beet greens||Mustard greens||Turnip greens|
Vitamin K1 (phylloquinone) is involved in blood coagulation, which helps to stop bleeding. People who take blood thinners should know that forms of vitamin K1 can interfere with the drug’s effects.
MK-4 is found in animal foods such as free-range, organic eggs (particularly the yolk), dark chicken meat and goose liver. MK-7, MK-8 and MK-9 come from fermented foods, such as natto, a type of fermented soy, and hard cheeses such as Brie and Gouda.
When you eat vitamin K, your intestines parcel it out in portions known as chylomicrons, dispersing it through your lymphatic systeminto your blood.
In your arteries, MK-4 adheres to the outside edges where it’s most accessible to the areas that need it most, such as your kidneys, stomach and heart, and the remainder goes to your liver and bones.
From your liver, some MK-7 goes to your blood, where it’s taken to your tissues. MK-1, from leafy greens, degrades quicker, while MK-7 stays viable in your liver for a longer period. This means K1 is most effective for your liver; MK-7 most effectively supports your bones. MK-8 and -9 are similar to MK-7.
What’s so Special About Vitamin K2?
One of the simplest ways to explain the importance of vitamin K2 is to say it has two basic and crucial functions, again, having to do with cardiovascular health and bone restoration. It helps prevent osteoporosis and hardening of the arteries, or atherosclerosis,2 and several other valuable things, including:
- Directing calcium to places like your bones, making them stronger, and your teeth to help prevent cavities. It also prevents calcium from going to the wrong areas, such as to your kidneys, where it could lead to kidney stones, or your blood vessels, where it could trigger heart disease.
- Optimizing sexual function by increasing testosterone and fertility in men, and decreasing androgens, the male hormones, in women with polycystic ovarian syndrome (PCOS)
- Creating insulin to stabilize your blood sugar (keeping your system sensitive to maintaining correct amounts), protecting against diabetes and helping to prevent metabolic problems associated with obesity
- Suppressing genes that can promote cancer while strengthening genes that promote healthy cells
- Enhancing your ability to utilize energy as you exercise improving overall performance
A study in Rotterdam involving 4,809 Dutch adults determined that those with the highest vitamin K2 intake had fewer heart attacks, a lower aortic calcification risk and the lowest death rate, altogether. That’s one reason why naturopathic doctor and author Tal Friedman recommends taking vitamin K2 supplements, particularly MK-7.3
More About Vitamin K2
As mentioned, vitamin K2 refers to a collection of MKs that are found in a variety of different foods, namely animal foods and fermented foods. MK-4 is most abundant in animal foods while you can find MK-7, MK-8 and MK-9 in fermented foods.
If you don’t typically eat these foods, getting enough K2 may be difficult. Grass-fed organic animal products (i.e., eggs, raw butter and raw dairy) are good sources, as are certain fermented foods such as natto or vegetables fermented at home using a starter culture of vitamin K2-producing bacteria.
Certain cheeses such as Brie and Gouda, as mentioned, are particularly high in K2, containing about 75 micrograms (mcg) per ounce.
Here’s why it’s important to consume vitamin K2: Think how much you rely on the optimum function of your heart, which pumps just over one time every second, perpetuating the flow of blood throughout your whole body. That takes a lot of energy, not to mention flexible blood vessels and arteries.
Vitamin K2, working with coenzyme-Q10, or CoQ10, can help. According to a Dutch study, matrix Gla Protein (MGP), a protein that relies on vitamin K2, is the most potent natural inhibitor of calcification there is,4 but it requires activation. Vitamin K2.org explains:
“When the body has adequate vitamin K2 (specifically as menaquinone-7, or MK-7, as it is the most biologically active and available form of vitamin K2), MGP repels calcium from depositing in the arteries and blood vessels, returning it to the bloodstream so it can be utilized by other systems, such as building strong, dense bones.”5
“The longer the side chain [the number following MK reveals its number of side chains], the more lipophilic — and bioavailable — K2 becomes, generally at MK-7 and above,” Friedman noted.6
Friedman added that vitamin K is “a generic term for a collection of fat-soluble nutrients widely known for their role in healthy blood coagulation.” K1 (phylloquinone) is the most common, and K2 (menaquinone) is made up of a number of compounds with varying side chain lengths, known as MK-4 through MK-13. Better Bones notes:
“K2 as MK-7 significantly reduces bone loss during menopausal transition, which is especially important when you consider the average woman loses up to 10 [percent] of her bone mass during this time.
Vitamin K2 as MK-7 not only protects bone, but it has been found to reduce the incidence of both heart disease and cancer.”7
Age has a tendency to impede human heart function, especially when calcium reduces your blood flow. Additionally, vitamin K2 helps relieve varicose veins, as K2 helps prevent an accumulation of calcium from settling in the walls of your veins.8
MK-4 Regulates Gene Expression
No other form of vitamin K affects gene expression the way MK-4 does. As Chris Masterjohn, Ph.D., explains in his Ultimate Vitamin K2 Resource:
“While we tend to think of our genes as the destiny we inherited from our parents, it’s actually how they are expressed — meaning, what our cells do with the information carried by those genes — that determines our health. MK-4 turns on some genes and turns others off.
For example, in our sex organs, it turns on the genes involved in sex hormone production. In a wide variety of cells, it turns on the genes that keep cells healthy and turns off the genes that make cells become cancerous. Thus, MK-4 plays an exclusive role in cancer protection and sexual health.”9
A clue that MK-4 is so important is that all animals (including humans) are able to synthesize it from other forms of vitamin K. It’s still important to obtain MK-4 from animal foods, however, because the conversion process is inefficient and likely varies depending on your health status and genetic factors.
Additionally, it’s important to know that certain drugs, such as statins to lower your cholesterol, and some osteoporosis drugs, inhibit the vitamin K conversion to MK-4.
A Last Word on the Importance of Vitamin K2
Problems with heart disease, diabetes and osteoporosis are all signs that you may not be getting enough K2. People with a low K2 intake have significantly lower bone mineral density compared to those with the highest intake.10
Poor diet may affect your vitamin K status in multiple ways, even beyond not consuming vitamin-K-rich foods. For instance, research shows that hydrogenation of plant oils (i.e., trans fats) appears to decrease the absorption and biological effect of vitamin K in bone.11
So, even though trans fats are finally being removed from the food supply, if you ate a lot of these unhealthy fats in the past, it could have influenced vitamin K’s role in your body.
If you think you may not be ingesting enough vitamin K, increase your intake of green leafy vegetables (for K1) and grass-fed raw dairy products and fermented foods (for K2). As for how much you need, as a general guideline I recommend getting around 150 mcg of vitamin K2 per day. Others recommend slightly higher amounts — upwards of 180 to 200 mcg.
You can obtain healthy amounts (about 200 mcg) of K2 by eating 15 grams (half an ounce) of natto or fermented vegetables each day. If you fermented them at home using a starter culture designed with vitamin K2-producing bacteria, 1 ounce will give you about 200 to 250 mcgs.
If you opt for a vitamin K2 supplement, make sure it’s MK-7. Also remember to take it with fat since it’s fat-soluble and won’t be absorbed otherwise. Fortunately, you don’t need to worry about overdosing on K2, as it appears to be virtually non-toxic. That said, people who are taking vitamin K antagonists, i.e., drugs that reduce blood clotting by reducing the action of vitamin K, are advised to avoid MK-7 supplements.