Vitamin K Supplements Review (Including Calcium,
Vitamin D, Magnesium & Boron)
Find the Best Vitamin K
Supplement. Tests and Reviews of Popular Vitamin K Supplements & CL's Top
Picks.
Medically reviewed and
edited by Tod Cooperman, M.D. 
Last Updated
: 10/23/2021 | Initially Posted:
11/23/2019Latest Update: Vitamin K and Coronary Artery Calcification
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Table of Contents
Summary
·
What is vitamin K? Vitamin K helps with proper blood
clotting as well as with calcium utilization in bones and the cardiovascular
system (See What It Does).
·
Do you need to take vitamin K as a supplement? Most people are not
deficient in vitamin K and symptomatic deficiency is rare, so unless you have a
malabsorption condition or are severely malnourished, you likely get sufficient
vitamin K from your diet (e.g., from green leafy vegetables, dairy, and
fermented foods -- see Vitamin K from food). Vitamin K supplements
have been clinically tested to increase bone density and reduce fractures, as
well as to improve cardiovascular function, but results have been mixed, so it
is not clear that supplementation will help (see What It Does).
·
Which form of vitamin K is best? There are several
forms of vitamin K. All are active, but one, the MK-7 form of vitamin K2, can
increase blood levels of vitamin K up to 8 times as much as other forms. It's
generally more expensive than the others, but it likely that you can take less
of it (see What It Is and What to Consider When Buying).
·
How much vitamin K should I take? For adults,
adequate daily intake of vitamin K 90 mcg for women and 120 mcg for men. It is
difficult to know what dose may be useful in bone health (or if any dose is
truly beneficial). However, studies involving supplements containing K1 or the
MK-4 form of K2 tend to use very high doses (e.g., 500 mcg to 45,000 mcg),
while studies with the MK-7 form of K2 have used more moderate dosing, e.g.,
180 mcg. (See What to Consider When Using).
·
How to take vitamin K: Vitamin K is fat soluble, so you'll
absorb more of it when you take it with a meal that has fats or oils. Other
fat-soluble vitamins, like vitamin D, can compete with its absorption, so take
them at least 3 hours apart. (See What to Consider When Using).
·
Best choice of vitamin K? Products vary in quality and cost
(See What CL Found). Among Approved products,
ConsumerLab.com identified several which represented its Top Picks.
·
Vitamin K safety and side effects: Vitamin K is fairly
safe. However it can interact with certain medications. If you have an allergy
to soy, be aware that most MK-7 forms of vitamin K are derived from soy,
(See Concerns and Cautions). One branded form of
MK-7 (MenaQ7) is derived from chickpeas and claims to be soy-free (See What It Does), although a product containing
this form did not pass testing (See What CL Found).
What It Is:
Vitamin
K is a group name for a number of structurally related, fat-soluble vitamins
including K1 (phylloquinone or phytonadione) and the K2 vitamin subgroup
(menaquinones). Vitamin K1 is the primary dietary source of vitamin K and is
found at high levels in green leafy vegetables and, in lower levels, in
vegetable oils. Vitamin K2 is found, typically in small amounts, in butter and
some cheeses and is produced by bacteria in the intestines from vitamin K1,
although it is unclear how much vitamin K this contributes to the body. There
are several forms of vitamin K2 (designated as menaquinones-1 through -10 or
MK-1 through MK-10). All forms of vitamin K are active in humans. Vitamin K1
(synthetically produced) was traditionally the most common form of vitamin K in
dietary supplements. However, vitamin K2 in the form of menaquinone-7 (MK-7) is
believed to have a longer half-life time than vitamin K1, resulting in much
more stable serum levels and accumulation of MK-7 to higher levels (7- to
8-fold) during prolonged intake (Schurgers, Blood 2007).
Consequently, K2 has become popular in supplements, despite higher cost as an
ingredient. MK-7 is typically obtained from natto, a popular Japanese food
product made from fermented soybean. In supplements, natto-derived MK-7 is
sometimes called "natural MK-7." New synthetic forms of MK-7 have
become available and also have a long half-life, although it is not clear if
these have the same bioactivity as MK-7 from natto. These new forms are
synthesized from flower extracts such as geraniol or famesol.
Another form of vitamin K2, known as menaquinone-4 (or MK-4), is produced in
certain animal tissues and can occur in small amounts in meats and egg yolk
and, when produced synthetically, is used in some supplements. MK-4 is absorbed
as well as MK-7 but it has a shorter half-life. Other forms of vitamin K exist
but are generally not sold as supplements.
For more information on how the forms of vitamin K are best used see ConsumerTips™.
(See separate reviews of Calcium and Vitamin D, which are
also used in bone health).
What It Does:
Vitamin K functions in the body to modify certain proteins that
ensure proper blood clotting and calcium utilization in the bones and
cardiovascular system. Bone
There is evidence that low vitamin K consumption or impaired vitamin K status
is associated with lower bone mass and higher risk of hip fracture among older
individuals (Kanai, Int J Gynaecol
Obstet 1997; Feskanich, Am J Clin Nutr 1999). There is mixed evidence as to
whether supplementation with vitamin K1 can help to prevent bone loss, although
it may help to prevent fractures. Supplementing with vitamin K2 as MK-4 has
shown some benefit in helping to prevent bone loss, but more research is
needed. Supplementing with vitamin K2 as MK-7 seems less promising.
Vitamin K1:
A study among 162 healthy, postmenopausal women in the Netherlands showed that
taking high dose (1,000 mcg) vitamin K1 along with calcium, vitamin D (320 IU)
and magnesium supplements for three years showed less bone loss when taking the
same supplements without vitamin K1 or taking only placebo (Braam, Calcif Tissue Int 2003).
Another large, 3-year study using a lower daily dose (500 mcg) of vitamin K1
per day plus calcium (600 mg) and vitamin D (400 IU) did not show
benefit for bone loss compared to taking the same amount of calcium and vitamin
D without vitamin K (Booth, J Clin Endocrinol Metab
2008).
A study of approximately 400 postmenopausal women in Canada (average age 59)
found that although supplementation with high dose vitamin K1 (5,000 mcg) daily
for two to four years did not prevent bone loss compared to placebo, it did reduce
the incidence of bone fractures. Over the course of the study, nine of the
women who took vitamin K experienced a bone fracture, while among those who
took a placebo, twenty women had a bone fracture. No adverse events were
reported (Cheung, PLoS
Med 2008).
Vitamin K deficiency can occur in people with Crohn's
disease, which can cause malabsorption, particular during active disease. Low
free and bone levels of vitamin K have been associated with low bone mineral
density in people with Crohn's, although one study found no improvement in bone
mass of the lumbar spine or the femur in people with Crohn's disease, vitamin K
deficiency and low bone mass who supplemented with vitamin K-1 (Weisshof, Curr Opin Clin Nutr Metab Care 2015).
Vitamin K2: Several clinical trials in Japan, Indonesia and
China have found that very high doses (45,000 mcg) of vitamin K2 as MK-4 (menaquinone-4)
taken for one to three years can improve bone mineral density and reduce
fracture risk in postmenopausal women with osteoporosis without toxic effects (Iwamoto, Nutrients 2014). One of these
studies, in Japan, showed that 45,000 mcg of MK-4 was the minimum dose required
to achieve this effect, with a lower dose of 15,000 mcg not showing a benefit (Orimo, J New Rem Clin 1992 — study abstract not
available).
A clinical trial in Japan reported that a very high dose (45,000 mcg) of the
menaquinone-4 form (MK-4) of vitamin K2 taken for two years improved bone
mineral density and reduced fracture risk in women (Shiomi, Am J
Gastroenterol 2002).
A three-year, placebo-controlled study using vitamin K2
as MK-7 (180 mcg per day) in healthy postmenopausal women in
the Netherlands found that MK-7 intake decreased the age-related decline in
bone mineral content and density at the lumbar spine and femoral neck, but not
for the total hip (Knapen, Osteoporo Int 2013).
Bone strength was also favorably affected by MK-7. Improvements were
statistically significant after 3 years, but not earlier. Calcium and vitamin D
supplements were not given as part of this study.
When taken in combination with calcium and vitamin D supplements, the effects
of MK-7 on measures of bone mineral density and fracture risk have not been
promising. A study in China among 311 older men and women that used a
lower dose (90 mcg per day) of MK-7 found no bone density benefit for men, nor
for men and women combined. Among women, there was no benefit at the lumbar
spine or hip, but, at the femoral neck, there was slightly less loss of
density than for those given a placebo. The study found no additional
benefit from adding vitamin D (400 IU) and calcium (500 mg) daily to the
vitamin K, nor a benefit from a lower daily dose (50 mcg) of vitamin K. A
weakness of the study was that it was only single-blind, i.e., the researchers
knew which treatment patients received (Zhang, Calcified Tissue Int 2020).
Similarly, a study in Demark among 142 postmenopausal women
with osteopenia (bone weakening that is less severe than osteoporosis) found
that taking 375 mcg of vitamin K2 as MK-7 along with 38 mcg of vitamin D3 and
800 mg of calcium daily for 3 years did not slow the decrease in bone mineral
density at the hip, femoral neck, or lumbar spine compared to taking only
vitamin D3 and calcium. Markers of bone turnover and bone microarchitecture
measured using high resolution peripheral quantitative computed tomography (HRpQCT) and dual energy X-ray absorptiometry (DXA) scans
were also similar between the vitamin K and placebo group after 3 years, suggesting
no significant benefit of supplementation with vitamin K2 as MK-7 (Rønn, Osteoporos Int 2020).
Clotting
Vitamin K1 is known to be effective in preventing and treating poor blood clotting
(hypoprothrombinemia) caused by vitamin K deficiency or induced by certain
medications. Vitamin K2 has also been shown to be effective and apparently,
more potent (Schurgers, Blood 2007). Symptomatic vitamin K
deficiency, however, is rare — resulting from severe malnutrition or
malabsorption, or prolonged therapy with some antibiotics.
In people treated with warfarin (a drug
that prevents blood clotting) who experience unexplained INR instability (i.e.,
large fluctuations in the amount of time needed for blood to clot), daily
low-dose oral vitamin K (100 to 200 mcg of K1) was previously recommended
to help improve clotting stability, provided it was used under medical supervision
(Ansell, Chest 2008). [Note: vitamin K2 in the
MK-7 form was not recommended due to its potential to interfere with warfarin
therapy. See Concerns and
Cautions for more details.] However, experts now
advise against low-dose vitamin K supplementation for people
taking warfarin. This change in recommendation was made after an analysis of
clinical trials showed that vitamin K did not reduce major bleeding events or
other complications related to blood clotting (Holbrook, Chest 2012; Witt, J Thromb Thrombolysis
2016).
While vitamin K supplements are now generally not recommended for people taking
warfarin, it is prudent to get an adequate intake of vitamin K from food
without large fluctuations. One study found that people who got less than 250
mcg of vitamin K daily from food were maintained on a dose of 4.4 mg of
warfarin, while those consuming more vitamin K required a dose of 5.8 mg of
warfarin (Dietary Reference Intakes Report, Natl Acad Press, 2001).
Heart disease
Low serum vitamin K levels have been associated with atherosclerosis. Higher
intake of vitamin K2 (particularly the MK-4 form) from the diet (mainly
from cheese) is associated with reduced risk of
coronary calcification and mortality from coronary heart disease (Geleijnse, J Nutr 2004; Beulens, Atherosclerosis 2009). These benefits have, so
far, not been proven with vitamin K2 supplements,
although one double-blind study found that 180 mcg of MK-7 (MenaQ7, NattoPharma ASA) taken daily for three years reduced
arterial stiffness in healthy postmenopausal women, especially in those with
high arterial stiffness. However, there was no effect on endothelial
dysfunction, which is closely associated with cardiovascular events such as
heart attack (Knapen, Thromb Haemost 2015).
A double-blind randomized study among 159 people with stage 3 or 4 chronic
kidney disease (average age 66) found that taking 400 mcg of MK-7 once daily
for 12 months did not reduce vascular stiffness or improve
blood pressure compared to placebo (Witham, J Am Soc Nephrol 2020). The people in
this study may have had adequate levels of vitamin K, so it remains uncertain
if vitamin K2 supplementation would benefit chronic kidney disease patients who
are vitamin K deficient.
Research suggests that vitamin K1 supplementation
does not have cardiovascular benefit in healthy people, but, in people with
existing coronary artery calcification, it may help slow progression. For
example, one study in Boston showed that people with pre-existing coronary
artery calcification who took a multivitamin including vitamin K1 for three
years had 6% less progression of calcification than those who received the
multivitamin without K1. However, among people without pre-existing
calcification, an equal percentage developed calcification regardless of
whether or not they received vitamin K1 (Shea, Am J Clin Nutr 2009). A study in Australia investigated the effects of
vitamin K1 supplementation in men and women (average age 66) with type 1 or
type 2 diabetes and moderate coronary artery calcification, half of whom were
also given the anti-inflammatory drug colchicine (which can reduce the risk of
heart attack and stroke in people with coronary artery disease). The study
found that 10 mg of vitamin K1 taken once daily for three months decreased the
risk of developing new calcified lesions in the coronary arteries and aorta,
respectively, by 65% and 73% compared to placebo. These decreases were similar
for those taking or not taking colchicine (Bellinge, Am J Clin Nutr 2021).
Cancer
A multi-year population study in Germany showed that people who consumed larger
amounts of foods (such as cheese) known to contain vitamin K2 had a
statistically lower risk of dying from cancer. Men (but not
women) also had a statistically significant decrease in the incidence of
cancer, particularly prostate and lung cancers (Nimptsch, Am J Clin Nutr 2010). While this study found no
association between vitamin K2 intake and risk of breast cancer in women, a
larger population study in the U.S. among 51,662 women who were followed for a
median of 13.6 years found that higher dietary intake of vitamin K2 was
associated with a 26% higher risk of breast cancer and 71% increased risk of
death from breast cancer (Wang, Clin Nutr
2020). In both studies, no such associations were found for the
consumption of foods (such as dark green leafy vegetables) containing vitamin
K1. Note that the studies above show only associations and do not establish
cause-and-effect relationships.
COVID-19 (SARS-CoV-2)
A blood marker of low vitamin K levels, known as Dp-ucMGP,
has been associated with having COVID-19 (the disease caused by the coronavirus
SARS-CoV-2) as well as unfavorable outcomes from the disease. The body's
increased use of vitamin K during severe illness may deplete vitamin K in
people with COVID-19, and it's been proposed that this could increase the risk
of abnormal blood clotting and venous thromboembolism (a type of blood clot) in
patients with COVID-19. Low levels of vitamin K may also increase the breakdown
of elastin, which occurs with lung damage. However, there is currently
no direct evidence that supplementation with vitamin K can prevent or treat
COVID-19.
Due to vitamin K's role in proper blood clotting, researchers in the
Netherlands investigated the relationship between vitamin K levels in the body
(as measured by Dp-ucMGP) and outcomes in patients
with COVID-19. They found that patients with COVID-19 had significantly higher
blood levels of Dp-ucMGP (indicating low levels of
vitamin K) compared to a control group of adults who did not have COVID-19, and
Dp-ucMGP levels were significantly higher in COVID-19
patients with unfavorable outcomes (i.e., ventilation and/or death) compared to
those with less severe disease who were discharged from the hospital without
ventilation. This was true even after factoring for age, gender, or use of
medications that may lower vitamin K levels, such as coumadin (Warfarin).
Reduced vitamin K status was also associated with accelerated breakdown of
elastin. The researchers warn that while "it might be tempting to
speculate that vitamin K administration" might improve vitamin K status in
severe COVID-19 patients, other conditions common in COVID-19 patients with
poor outcomes (such as type 2 diabetes and high blood pressure) are also
associated with reduced vitamin K levels, and whether vitamin K supplementation
would improve outcomes in COVID-19 has not yet been tested (Dofferhoff, Clin Infect Dis 2020).
Similarly, a study in Denmark found that
average blood levels of Dp-ucMGP were significantly
higher among people admitted to the hospital with COVID-19 (measured within
four days of admission) compared to a control group that did not have COVID-19
(1,022 pmol/L vs. 509 pmol/L,
respectively). Those who died from COVID-19 had Dp-ucMGP
levels that were significantly higher than in those who survived (1,445 pmol/L vs. 877 pmol/L,
respectively). Every doubling of the Dp-ucMGP level
increased the risk of death by 50%. However, the researchers cautioned that it
is not yet known if vitamin K supplementation would improve outcomes in people
with COVID (Linneberg, medRxiv 2020 --
preprint).
Quality Concerns and
Tests Performed:
Like
other supplements, neither the FDA nor any other federal or state agency
routinely tests vitamin K supplements for quality prior to sale. However,
quality issues can include the following:
·
Labeled Amount -- Does the product really contain the
labeled amount and form of vitamin K? Vitamin K, particularly the MK-7 form of
K2, can be an expensive ingredient, providing economic incentive for a
manufacturer to put in less (or a less expensive form) than what is claimed.
·
Purity -- Many vitamin K supplements include calcium which may
naturally be contaminated with heavy metals such as lead, cadmium or arsenic.
In children, infants, and fetuses, even low levels of lead can adversely affect
neurobehavioral development and cognitive function. In adults, lead at somewhat
higher levels can cause elevated blood pressure, anemia, and adversely affect
the nervous and reproductive systems. Lead is of particular concern during
pregnancy as the mother can deliver it to the fetus. Cadmium is a carcinogen
and kidney toxin. Arsenic is a carcinogen and can damage organs.
·
Ability to Break Apart for Absorption -- For a tablet to be
most useful, it must fully disintegrate prior to leaving the stomach,
delivering its contents for absorption in the gut. Some tablets are not
properly made and can pass through your body completely or partially intact,
depriving you of its ingredients. Remnants of such products are sometimes found
in the stool. This happens, for example, when a tablet is too tightly
compressed (too "hard") or is too thickly coated.
As part of its mission to
independently evaluate products that affect health, wellness, and nutrition,
ConsumerLab.com purchased vitamin K supplements (including those with calcium,
boron, vitamin D, and/or magnesium) sold in the U.S. These were tested to
determine whether they 1) possessed the claimed amounts of vitamin K, calcium,
boron, vitamin D, and magnesium, 2) were free from unacceptable levels of lead,
cadmium and arsenic, if containing 250 mg of minerals per daily dosage and/or
whole herbs and 3), if in tablet form, were able to break apart fully within an
expected period of time in disintegration testing (see Testing Methods and Passing Score).
What CL Found:
Among the eight vitamin K-containing supplements that
ConsumerLab.com selected for testing, quality evaluation, the following two
failed to meet CL's quality criteria for the following reasons which were
confirmed in a second, independent laboratory:
·
Relentless Improvement K2 Menatetrenone contained less
vitamin K than claimed, providing 88.1% (13,209.9 mcg) of the 15,000 mcg
vitamin K2 (MK-4) listed per capsule, although this is still a very large dose
of vitamin K.
·
Thorne Basic Bone Nutrients contained its claimed amounts of calcium
and magnesium, but only 69.7% of its claimed vitamin D (348.5 IU vs. 500 IU)
and just 2.2% of its vitamin K (1 mcg versus 45 mcg). These are major discrepancies,
particularly for vitamin K, indicating that one should not rely on this product
for either of these nutrients.
The six products that
passed testing are listed as Approved in the table below. Also listed as
Approved are three products that passed the same testing through CL's
voluntary Quality Certification Program.
Amounts of vitamin K in products
Be aware that there is an enormous range in the amount of vitamin K across
products. As shown below, among products tested this ranged from just a few
micrograms to over 13,000 micrograms (mcg) per pill.
Adequate daily intake of vitamin K for is 90 mcg for women and 120 mcg for men,
but this is based on K1 derived from food. So when judging products, be aware
that products made with K1 or the MK-4 form of K2 that contain about 100 mcg of
vitamin K provide approximately the amount you need per day from your total
diet. Due to its enhanced bioavailability, a 100 mcg dose of MK-7, such as from
a softgel of Health Origins Natural Vitamin
K2 as MK-7 or Innovix Labs
Vitamin K2 (which includes 500 mcg of MK-4), in actuality provide much
more than the daily requirement of vitamin K, as their 100 mcg dose of MK-7 may
be equivalent to getting 700 mcg to 800 mcg of vitamin K1.
Some products provide even higher doses of vitamin K, such as Relentless
Improvement K2 Menatetrenone (listing 15,000 mcg of MK-4 K2, but
actually containing about 12% less) and Life Extension Vitamin D and K
with Sea-Iodine (providing 1,000 mcg of K1, 1,000 mcg of MK-4 K2, and
100 mcg of MK-7 K2). The rationale for these extraordinarily high amounts are
likely rests with preliminary studies suggesting added benefit to bone health
from such doses, as discussed earlier.
Although there is no established upper limit for vitamin K, be aware that
taking too much vitamin K from supplements may interact with certain
medications (See Cautions and Concerns).
Cost
The cost to obtain a dose of 50 mcg of vitamin K ranged from less than one cent
to 26 cents among vitamin K-only products. Among formulas, it was as low as one
cent but, for most products, it ranged from 14 to 60 cents. Not surprisingly,
when calculated for the Thorne product that contained only
2.2% of its listed amount of vitamin K, the cost ballooned to more than $15.
Top Picks:
Vitamin K Only: Healthy Origins Natural Vitamin K2 as
MK-7 provides 100 mcg of vitamin K2 (as MK-7) in a single softgel for 21 cents. Similarly, Innovix
Labs Vitamin K2 provides 100 mcg of vitamin K2 (as MK-7) and, for just
3 cents more per softgel, includes 500 mcg of
MK-4. Both are our Top Picks for vitamin K
only, depending on whether you want just MK-7 or want a significant dose of
MK-4 as well. As discussed above, the amount of MK-7 in both products is
roughly equivalent to the adequate daily intake for vitamin K, but, due to the
enhanced bioavailability of MK-7, it is more like taking a much higher dose. Be
aware, however, that to help maintain bone density, evidence suggests that a
dose of 180 mcg of MK-7 per day may be preferable, although do not expect
short-term benefits nor dramatic long-term benefits (see What It Does - Vitamin K2). Dr.
Mercola Vitamin K2 has this higher dose, but, at 93 cents per 180 mcg
capsule, it is four times as expensive as Healthy Origins.
Vitamin D and Vitamin K: Although both of the products we tested in
this category (Life Extension Vitamin D and K With Sea-Iodine and Zhou
K2 + D3) passed testing, neither is a Top Pick for regular
use as they both provide 5,000 IU of vitamin D, a very large does that exceeds
the upper tolerable intake level of 4,000 IU per day. In addition, Life
Extension provides a very large amount of vitamin K — a total of 2,100
mcg, which is many times the daily 90 mcg to 120 mcg that is adequate for women
and men, respectively. The likely basis for this are studies suggesting that
very high-dose vitamin K over long periods of time may further strengthen
bones, as discussed earlier. Life Extension also contains a
very large amount of iodine — several times the daily requirement and
approaching the tolerable upper intake level for adults.
Although not tested this year, NOW Vitamin D-3 & K-2, a capsule
that provides 1,000 IU of vitamin D and 45 mcg of vitamin K (as MK-4 K2) for 7
cents passed our tests in 2017 and would be a reasonable choice if you are just
looking to boost your vitamin K intake to an adequate level while getting a bit
over the daily requirement of vitamin D.
Vitamin K, Calcium, Magnesium, and Vitamin D: Only one of two
products in this category passed our tests: New Chapter Bone Strength
Take Care. However, due to its high cost, it is not a Top Pick.
The suggested daily serving of 3 tablets provides 1,000 IU of vitamin D, 770 mg
of calcium, 80 mcg of vitamin K from K1 and K2, and a modest amount of
magnesium. It is best to break this into two or three servings to be taken with
meal during the day, as 770 mg of calcium is too much to take at one time. This
is a relatively expensive product at 96 cents per day and, considering that
there is no compelling research showing superiority of algae-based calcium or
magnesium, you can easily get these same ingredients for less by purchasing the
ingredients separately.
Vitamin K, Calcium, Magnesium, Boron & Vitamin D Both of the
products that we tested in this category, GNC Calcimate and Jarrow Formulas Bone Up, provide significant
amounts of calcium, vitamin K, and boron. What sets them apart is the amount of
magnesium they provide, with Jarrow providing
several times as much as GNC as well as a daily dose of
vitamin D (1,000 IU) that is closer to the adult requirement (600 IU to 800 IU)
than GNC's 2,000 IU. Although costs more (51 cents daily for 6
pills versus 25 cents daily for 4 pills), Jarrow
Formulas Bone Up is our Top Pick for this category.
With either product, consider cutting the suggest dose in half if you are just
trying to boost your intake of these nutrients and not trying to fulfill the
majority of the daily requirements from a supplement. By the way, Jarrow Formulas Bone-Up provides calcium
as StimuCal microcrystalline hydroxyapatite
(see What to Consider When Buying in the
Calcium Supplements Review for more about this ingredient).
Test Results by Product:
Listed
below are the test results for 11 supplements containing vitamin K. Products
are shown in groups: Those with vitamin K only and those with vitamin K in
combination with vitamin D, calcium, magnesium, and/or boron. Within each
group, products are listed alphabetically. ConsumerLab.com selected eight of
these products. Three other products (each indicated with a CL flask) were
tested at the request of their manufacturers/distributors through ConsumerLab.com's voluntary Quality Certification Program and
are included for having passed testing.
Shown for each product are the claimed amount and form of the tested
ingredient(s), serving size recommended on its label, pill size, price paid,
and cost per 50 mcg of vitamin K. Products listed as "Approved" met
their label claims and ConsumerLab.com's quality
criteria (see Passing Score). The full
list of ingredients (including special dietary designations) is shown for each
product in the last column.
Jump to results by ingredient:
·
Vitamins K, D, Calcium and Magnesium
·
Vitamins K, D, Calcium, Magnesium, and Boron
Results of
ConsumerLab.com Testing of VITAMIN K SUPPLEMENTS
(INCLUDING COMBINATIONS WITH CALCIUM, MAGNESIUM, BORON AND/OR
VITAMIN D)
(Click arrows or swipe left or right to see all columns)
Approval Statusⓘ
Product Name
Claimed Amount of and Form of Vitamin K,
Calcium, Magnesium, Boron & Vitamin D Per Servingⓘ
Heavy Metalsⓘ
Suggested Daily Serving on Label
Pill Sizeⓘ
Cost for Suggested Serving
[Price per 50 mcg Vitamin K]
Price
Notable Features
Full List of Ingredients Per Serving
APPROVED
Country Life Vegan K2
Dist. by Country Life, LLC
1 melt
500 mcg
(MK-4 & MK-7 K2)
✔
Heavy metals: NA
Adults take one (1) smooth melt daily and allow
it to melt on your tongue before swallowing.
Medium circular melt
1 melt
$0.30
[$0.03]
$18.06/60 melts
Stevia extract 2 mg
Certified gluten-free by GFCO.org; certified vegan by the AVA; no yeast or
wheat; no milk or salt; no preservatives; no artificial colors or flavors; no
magnesium stearate; no GMOs.
1 melt
Vitamin K (as menaquinone (K2) [MK-4 and MK-7]) 500 mcg, Stevia Extract (Stevia
rebaudiana) (leaf) 2 mg.
Other Ingredients: Glucose, cellulose, more...
APPROVED
Dr. Mercola® Vitamin K2
Dist. by NHP
1 capsule
180 mcg
(MK-7 K2)
✔
Heavy metals: NA
Adults, as a dietary supplement, take one (1)
capsule daily with a meal.
Large capsule
1 capsule
$0.93
[$0.26]
$27.97/30 capsules
Soy free.
1 capsule
Vitamin K2 (as Menaquinone-7 [MK-7, from Chickpea]) 180 mcg.
Other Ingredients: Microcrystalline cellulose, glycerol monostearate, more...
APPROVED
Top Pick
for vitamin K only
Healthy Origins® Natural Vitamin K2 as MK-7
Dist. by Healthy Origins®
1 softgel
100 mcg
(MK-7 K2)
✔
Heavy metals: NA
As a dietary supplement for adults, take one (1)
veggie softgel daily, or as recommended by a
physician.
Medium veggie softgel
1 softgel
$0.21
[$0.11]
$12.74/60 veggie softgels
Does not contain gluten, milk, eggs, fish,
shellfish, peanuts, wheat or soy. No preservatives or artificial flavors.
Suitable for vegetarians.
1 softgel
Vitamin K2 (from Natto) (as Menaquinone-7) 100 mcg.
Other Ingredients: Organic extract virgin olive oil, vegetarian softgel, more...
APPROVED
Top Pick
for vitamin K only
Innovix Labs Vitamin K2ⓘ
Dist. by Innovix Labs
- A Division of Innovix Pharma Inc.
1 softgel
500 mcg
(MK-4 K2)
100 mcg
(MK-7 K2)
✔
Heavy metals: NA
For general health: take one capsule per day.
For heart and arterial health: take two capsules per day.
Medium softgel
1 softgel
$0.24
[$0.02]
$21.99/90 softgels
Does not contain: dairy, eggs, corn, fish,
shellfish, tree nuts, peanuts, wheat/gluten, soy, sugar, GMO, yeast, artificial
colors or flavors.
1 softgel
Vitamin K2 MK-4 (as menatetrenone) 500 mcg, Vitamin K2 MK-7 (as menaquinone-7)
100 mcg.
Other Ingredients: Extra Virgin Olive Oil, Medium Chain Triglyceride Oil,
Gelatin, Glycerin, Purified Water, Carob Color.
NOT APPROVED
Relentless Improvement K2 Menatetrenone
Dist. by Relentless Improvement® LLC
1 capsule
15,000 mcg
(MK-4 K2)
Found
13,209.9 mcg vitamin K per serving (88.1% of listed amount)
Heavy metals: NA
Take 1 capsule daily or as recommended by your
health care professional.
Medium/large capsule
1 capsule
$0.41
[<$0.01 based on amount listed]
[<$0.01 based on amount found]
$36.96/90 capsules
Not manufactured with yeast, sugar, corn, wheat,
gluten. Soy, milk, egg, fish, shellfish, or tree nut ingredients.
1 capsule
Vitamin K2 (as menatetrenone, MK-4) [derived from orange jasmine (Murraya paniculata),
leaf geraniol extract] 15,000 mcg.
Other Ingredients: Microcrystalline cellulose, hypromellose
(vegecapsule).
APPROVED
Life Extension® Vitamin D and K With Sea-Iodine™
Dist. by Quality Supplements and Vitamins, Inc.
1 capsule
1,000 mcg
(K1)
1,000 mcg
(MK-4 K2)
100 mcg
(MK-7 K2)
2,100 mcg
(total vitamin K)
✔
5,000 IU (125 mcg)>UL(D3)
✔
Heavy metals: NA
Take one (1) capsule once daily with food, or as
recommended by a healthcare practitioner.
Medium/large capsule
1 capsule
$0.30
[$0.01]
$18.00/60 capsules
Non-GMO, Iodine™ complex blend 1,000 mcg>UL
1 capsule
Vitamin D3 (as cholecalciferol) 5,000 IU, Vitamin K activity from: [Vitamin K1
(phytonadione) 1,000 mcg, Vitamin K2 (as menaquinone-4) 1,000 mcg, Vitamin K2
(as all-trans menaquinone-7) 100 mcg] 2,100 mcg, more...
APPROVED
Zhou® K2 + D3
Dist. by Zhou Nutrition®
1 capsule
90 mcg
(MK-7 K2)
✔
5,000 IU (125 mcg)>UL
(D3)
✔
Heavy metals: NA
Take 1 vegetable capsule with food once daily or
as directed by your healthcare professional.
Large veggie capsule
1 capsule
$0.26
[$0.14]
$15.64/60 veggie capsules
Zero gluten, soy, milk, eggs, fish, shellfish,
tree nuts, peanuts & wheat. Made with non-GMO ingredients.
1 capsule
Vitamin D3 (as Cholecalciferol) 5,000 IU, Vitamin K2 (as Menaquinone) (MK-7) 90
mcg.
Other Ingredients: Rice flour, cellulose (vegetable capsule).
Vitamin K, Calcium,
Magnesium & Vitamin D:
APPROVED
New Chapter® Bone Strength Take Care™
Dist. by New Chapter, Inc.
3 tablets
35 mcg
(K1)
45 mcg
(MK-7 K2)
80 mcg
(total vitamin K)
✔
770 mg
(calcium from algae Lithothamnion calcareum & corallioides)
✔
58 mg
(magnesium from algae Lithothamnion calcareum & corallioides)
✔
1,000 IU (25 mcg)
(D3)
✔
Heavy metals: Pass
Also tested for disintegrationⓘ
Three tablets daily with food.
Large slim tablet
3 tablets
$0.96
[$0.60]
$38.37/120 slim tablets
Strontium 5 mg, silica 2 mg, vanadium 13 mcg
Kosher. Non GMO Project Verified seal. Gluten free; 100% vegetarian; no
artificial flavors or colors.
Precaution: Contains: Fermented soy.
3 tablets
Vitamin D3 (as cholecalciferol from ferment media) 1,000 IU, Vitamin K1 (as
phylloquinone from ferment media) 35 mcg, Vitamin K2 (as menaquinone-7 from
natto) 45 mcg, Calcium (from algae Lithothamnion
calcareum & corallioides)
770 mg, Magnesium (from algae Lithothamnion
calcareum & corallioides)
58 mg, Strontium (from algae Lithothamnion
calcareum & corallioides)
5 mg, Silica (from algae Lithothamnion
calcareum & corallioides)
2 mg, Vanadium (from algae Lithothamnion calcareum & corallioides) 13
mcg, more...
NOT APPROVED
Thorne® Basic Bone Nutrients
Mfd. by Thorne Research, Inc.
1 capsule
45 mcg
(MK-7 K2)
Found only
1 mcg vitamin K per serving (2.2% of listed amount)
200 mg
(DimaCal® DiCalcium Malate)
✔
50 mg
(Albion® DiMagnesium Malate)
✔
500 IU (12.5 mcg)
(D3)
Found only
348.5 IU vitamin D per serving (69.7% of listed amount)
Heavy metals: Pass
Take 1 capsule one to four times daily or as
recommended by a health-care practitioner.
Large capsule
1 capsule
$0.32
[$0.35 based on amount listed][$15.83 based on amount found]
$38.00/120 capsules
Gluten Free.
1 capsule
Vitamin D (as Vitamin D3) (500 IU) 12.5 mcg, Vitamin K (as K2 (MK-7)) 45 mcg,
Calcium (as DimaCal® DiCalcium
Malate) 200 mg, Magnesium (as Albion® DiMagnesium
Malate) 50 mg.
Other Ingredients: Hypromellose (derived from cellulose) capsule, calcium
laurate.
Vitamin K, Calcium,
Magnesium, Boron & Vitamin D:
APPROVED
GNC Calcimate
Complete™
Dist. by General Nutrition Corporation
4 caplets
50 mcg
(K2)
✔
800 mg
(calcium citrate malate)
✔
100 mg
(magnesium oxide)
✔
1,000 mcg
(boron hydrolyzed protein chelate)
✔
2,000 IU (50 mcg)
(D3)
✔
Heavy metals: Pass
Also tested for disintegrationⓘ
As a dietary supplement, take two caplets at
breakfast and two caplets at dinner for a total of four caplets daily.
Large caplet
4 caplets
$0.25
[$0.25]
$14.99/240 caplets
Zinc 7.5 mg, copper 1 mg, manganese 1 mg, MBP®
40 mg
No Artificial Colors, No Artificial Flavors, No Wheat, Gluten Free, Yeast
Free.
Precaution: Contains: Milk and Soybeans.
4 caplets
Vitamin D (as Cholecalciferol D-3) 2,000 IU, Vitamin K-2 (as Menaquinone) 50
mcg, Calcium (as Calcium Citrate Malate) 800 mg, Magnesium (as Magnesium Oxide)
100 mg, Zinc (as Zinc Oxide) 7.5 mg, Copper (as Copper Glycinate) 1 mg,
Manganese (as Manganese Gluconate) 1 mg, MBP® 40 mg, Boron (as Hydrolyzed
Protein Chelate) 1 mg.
Other Ingredients: Cellulose, titanium dioxide (natural mineral whitener),
vegetable acetoglycerides.
APPROVED
Top Pick
Jarrow Formulas® Bone-Up®
Dist. by Jarrow
Formulas®
6 capsules
45 mcg
(MK-7 K2)
✔
1,000 mg
(StimuCal™ microcrystalline hydroxyapatite)
✔
500 mg>UL
(magnesium oxide)
✔
3,000 mcg
(boron citrate)
✔
1,000 IU (25 mcg)
(D3)
✔
Heavy metals: Pass
Take 2 capsules 3 times per day (for a total of
6) with meals to facilitate maximum absorption, or as directed by your
qualified healthcare professional.
Large capsule
6 capsules
$0.51
[$0.57]
$20.37/240 capsules
Vitamin C 200 mg, zinc 10 mg, copper 1 mg,
manganese 1 mg, potassium 99 mg
No wheat, gluten, egg, fish/shellfish, or peanuts/tree nuts.
Precaution: Contains: Soy (in trace amounts).
6 capsules
Vitamin C (as Calcium Ascorbate) 200 mg, Vitamin D3 (Cholecalciferol) 25 mcg
(1,000 IU), Vitamin K2 (as Natural MK-7 [Menaquinone-7]) 45 mcg, Calcium
(Elemental) (from StimuCal™ Microcrystalline
Hydroxyapatite) 1,000 mg, Magnesium (as Magnesium Oxide) 500 mg, Zinc (L-OptiZinc®) (as Zinc L-Methionine Sulfate) 10 mg, Copper (as
Copper Gluconate) 1 mg, more...
Unless otherwise noted, information about the
products listed above is based on the samples purchased by ConsumerLab.com (CL)
for this Product Review. Manufacturers may change ingredients and label
information at any time, so be sure to check labels carefully when evaluating
the products you use or buy. If a product's ingredients differ from what is
listed above, it may not necessarily be of the same quality as what was tested.
The information contained in this report is
based on the compilation and review of information from product labeling and
analytic testing. CL applies what it believes to be the most appropriate
testing methods and standards. The information in this report does not reflect
the opinion or recommendation of CL, its officers or employees. CL cannot
assure the accuracy of information.
Copyright ConsumerLab.com, LLC, 2021 All
rights reserved. Not to be reproduced, excerpted, or cited in any fashion
without the express written permission of ConsumerLab.com LLC
ConsumerTips™:
What to
Consider When Buying:
Vitamin K from food
Increased intake of vitamin K from the diet is associated with
decreased risk of hip fractures but not an increase in bone density. This
decrease in fractures has been seen among elderly men and women consuming about
250 mcg per day of vitamin K. This can be easily obtained from a variety of
foods.
Vegetables — Vitamin K can be obtained in sufficient amounts from foods such as
green leafy vegetables, which contain vitamin K1. Kale and turnip greens are
the best food sources, providing about ten times the daily adult requirement in
a single serving. You can get 250 mcg of vitamin K from a half cup of broccoli
or a large salad of mixed greens. Oats, green peas, whole wheat, and green
beans, as well as watercress and asparagus can also provide good amounts of
vitamin K. The Japanese food natto (from fermented soy beans), can also provide
fairly high amounts of vitamin K2 — in fact, the MK-7 form of vitamin K2 which
is popular in supplements is often derived from natto.
Fruits — Among fruits, prunes are one of the better sources of vitamin K1,
providing 59.5 mcg per 100 gram serving (about 10 prunes) (USDA Nutrient Database).
Dairy — You can also get vitamin K (mostly as K2) from dairy
products, but not if they are fat-free. Remember, vitamin K is fat
soluble, and it's the fat in dairy from which you'll get the most vitamin K. A
recent analysis (Fu, Curr Develop Nutr 2017) found, for example, that a 100 gram
serving (just under 1/2 cup) of full-fat, 2%, 1% and fat-free milk contained 38
mcg, 19 mcg, 12 mcg and 5 mcg, respectively, of vitamin K. Full-fat versions of
yogurt contained about 27 mcg while non-fat versions contained no
detectable vitamin K. Low-fat kefir contained an average of 10.2 mcg per
100 gram serving (full-fat kefirs were not tested).
Cheeses can have very high concentrations of vitamin K. Soft cheeses such as
Brie, Camembert, crème fraiche, Limburger, and mascarpone contain about 506 mcg
of vitamin K per 100 grams (3.5 ounces), followed by blue cheese (440 mcg),
semi-soft cheeses such as Monterey Jack, Havarti, Fontina, Gouda, Swiss and
cream cheese (289 mcg), hard cheeses such as cheddar and parmesan (282 mcg) and
processed American cheese (98 mcg). Full-fat cheeses contain significantly more
vitamin K than reduced-fat cheese. For example, 100 grams of full-fat cheddar
cheese contains about 281 mcg total vitamin K, while reduced-fat cheddar
contains just 49 mcg. In general, reduced-fat or no-fat dairy products contain
just 5% to 22% of the vitamin K found in their full-fat counterparts.
While meat and egg yolks contain small amounts of K2, this is generally not
sufficient to meet an adequate intake of vitamin K.
Vitamin K from supplements
Both vitamin K1 and K2 (as menaquinone-4 (MK-4) and menaquinone-7 forms (MK-7))
are available in supplements and are active. However, as noted earlier, the
MK-7 form of vitamin K2 has a longer half-life than both vitamin K1 as well as
the MK-4 form of vitamin K2. When used over prolonged periods of time (days),
equal doses of the different forms can result in very different serum levels of
vitamin K, which may mean differences in potency. Consequently, dosages may
need to be adjusted when taking different types of vitamin K. In fact, a study
suggested that if taken on a daily basis, 25 mcg of the MK-7 form of K2 may be
more potent than 100 mcg of K1, as it stays in the body longer (Schurgers, Blood 2007). Be aware that the MK-7
form of vitamin K2 is a much more expensive raw material than vitamin K1, which
is reflected in the price of most supplements containing this ingredient.
What to Consider When Using:
True deficiency of vitamin K is rare. The AI (Adequate Intake) of vitamin K is
measured in micrograms (shown as mcg). The AI is 30 mcg for children ages 1 to
3, 55 mcg for children 4 to 8, 60 mcg for those ages 9 to 13, and 75 mcg for
those ages 14 to 18. For males 19 years and older, it is 120 mcg. For females
19 years and older, it is 90 mcg. There is no Upper Tolerable Intake Level (UL)
established for vitamin K.
As noted earlier, there is mixed evidence that vitamin K from supplements at
doses higher than nutritional needs may help fight osteoporosis and/or hip
fractures. Among studies which showed some benefit, a dose that was shown to
increase bone density is 1 milligram (1,000 mcg) of vitamin K1 per day. A much
higher dose of 45 milligrams (45,000 mcg) of the MK-4 form of K2 has also been
shown effective. A clinical study using the MK-7 form of vitamin K2, but at a
much lower dose (180 mcg per day taken with breakfast or dinner) also showed
some benefits but only after 3 years of supplementation (Knapen, Osteoporo Int 2013).
Large doses of vitamin E may antagonize vitamin K, making
it less effective (Traber, Nutr
Rev 2008), and there is potential concern about other fat-soluble
vitamins. A laboratory experiment using intestinal cells from mice found that
uptake of vitamin K was reduced by approximately half by vitamins A, D, and E —
likely due to competition for absorption among these fat-soluble vitamins (Goncalves, Food Chem 2015). Interestingly,
vitamin K did not significantly reduce uptake of the other fat-soluble
vitamins. While there do not appear to be studies demonstrating reduced vitamin
K absorption in people due to vitamin D, it may be best to take vitamin
K at least 3 hours apart from vitamin D and not from "bone health"
formulas (such as many in this review) which include vitamin D. Keep in
mind that such formulas are rarely clinically tested in people for ingredient
absorption, let alone for efficacy and safety.
Concerns and Cautions:
Vitamins
K1 and K2 are generally safe when used appropriately in healthy individuals;
vitamin K3 may cause toxicity
and is not sold as a supplement.
Because vitamin K
plays a role in coagulation, it may interfere with oral anticoagulant therapy,
reducing the effectiveness of warfarin (Coumadin and Jantoven).
This interference may occur with dosages as low as 10 mcg per day for the MK-7
form of vitamin K2 due to its long half-life (Schurgers, Blood 2007).
As a result, some experts suggest people taking warfarin should avoid MK-7
supplements (Theuwissen, J Thromb Haemost 2013).
Although supplements providing up to 100 mcg of vitamin K1 per day may not
cause clinically relevant disturbances of oral anticoagulant therapy, experts
now recommend against low-dose vitamin K supplementation for
people taking warfarin due to the limited evidence of benefit and potential for
interaction at the higher doses used in clinical research (100 to 200 mcg per
day) (Holbrook, Chest 2012; Witt, J Thromb Thrombolysis
2016). People taking warfarin should not begin supplementing with
vitamin K unless advised to do so by their doctor.
Newer blood thinning drugs, such as dabigatran (Pradaxa) and rivaroxaban
(Xarelto) are not thought to be affected by vitamin K intake (Pradaxa Prescribing Information
2015; Xarelto Prescribing Information
2015). Unlike warfarin, which inhibits the body's use of vitamin K
in the formation of clotting proteins, drugs such as aspirin and clopidogrel
(Plavix) work differently, by preventing platelets from sticking together to
form clots, and there is no evidence of vitamin K interacting with these drugs
nor mention of such an interaction in prescribing information for clopidogrel (Plavix Prescribing Information 2015).
People who are allergic to soy should be aware that the MK-7 form of Vitamin K2
is often derived from natto, which is made from soy. A branded form of
MK-7, MenaQ7 is derived from chickpeas and its manufacturer
claims it is soy free (although ConsumerLab tests in
2017 of a product containing this ingredient &dash Doctor's Best
Artery Prime With MenaQ7 &dash found it to contain just 80% of the
vitamin K claimed on the label). Be aware that a similar sounding
ingredient, MenaQ7 Natto MK-7 is derived from soy — so be sure
to read labels carefully. Although there is some concern that soy can affect
thyroid function (Messina, Thyroid 2006),
there does not appear to be evidence of a soy-based vitamin K supplement
affecting thyroid function.
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for Vitamin K Supplements
Vitamin K and Coronary Artery Calcification
10/23/2021
Can supplementing with
vitamin K1 slow coronary artery calcification? See what a new study among
people with diabetes found in the What It Does section of our Vitamin K
Supplements Review. Also see our Top Picks among vitamin K supplements.
Vitamin K & Risk of COVID Death
1/15/2021
A marker of low vitamin K
levels has been linked to a higher risk of death in people with COVID-19,
according to a new study. Get the details in the COVID-19 section of
our Vitamin K Supplements Review.
Vitamin K and Breast Cancer Risk
11/18/2020
Can eating foods high in
vitamin K affect the risk of breast cancer? Learn what a recent study showed in
the What It Does section
of our Vitamin K Supplements Review. Also see our Top Picks for vitamin K supplements.
Warfarin and Low-Dose Vitamin K
10/31/2020
Should people on warfarin
(Coumadin) take low-dose vitamin K to help stabilize fluctuations in INR? Learn
what experts say in the What It Does section
of our Vitamin K Supplements Review. Also, learn if other blood thinning drugs
are affected by vitamin K in the Concerns and Cautions section
of our review.
10/13/2020
Does supplementing with
vitamin K2 as MK-7 along with vitamin D and calcium improve bone density in
postmenopausal women with weak bones (osteopenia)? Find out what a recent study
showed in the What It Does section
of Vitamin K Supplements Review. Also, learn about other forms of vitamin K used
for increasing bone density and see our Top Picks for vitamin K.
Related CL Answers (19)