Question 1)
What form of Vitamin K does Shaklee use?

Answer: Vitamin K1.



Question 2)
Why does Shaklee use Vitamin K1, and not K2?

Answer: Vitamin K1 is the predominant form of Vitamin K found in green leafy vegetables such as spinach and broccoli. Vitamin K2 is a group of compounds occurring in animal-derived foods and certain fermented foods but also is produced in the human gut from vitamin K1. The preponderance of scientific evidence supports the benefits of dietary/supplemental Vitamin K1. While there is increasing interest in K2, there is not clear consensus on its mechanisms of action or daily requirements.

Further Explanation: There are 3 forms of Vitamin K: K1 (phylloquinone), K2 (menaquinone: MK), and K3 (menadione). Vitamin K1 is the plant-based form and can be found in green leafy vegetables and their oils; K2 is synthesized by bacteria and there are several forms of K2 (MK‐4 through MK‐10), which can be found in animal-based foods or in fermented foods such as soybeans (e.g., natto, a traditional Japanese food); K3 can be formed from vitamin K1 during absorption and also appears in low amounts in legumes or fermented soybeans.2‐4

All types of Vitamin K provide benefits on blood coagulation, bone health, and cardiovascular health.2 However, K1 is the primary dietary form, and both K2 and K3 can be synthesized from K1 by our gut bacteria or by an enzyme in our body when we consume K1.5,6 A study of lactating mothers taking phylloquinone (K1) supplements had higher concentrations of MK‐4 in their breast milk as compared to non-supplementing women, providing support of vitamin K1 conversion to K2.7 In addition, K1 is the only type among the Vitamin Ks that has been studied to fully understand its bioavailability and mechanism within the body.1



Question 3)
Can Vitamin K2 be listed as Vitamin K in the Nutrition Facts Label per FDA?

Answer: No. Vitamin K2 cannot be listed as Vitamin K in the Nutrition and Supplement Facts Label per Revision of the Nutrition and Supplement Facts Labels by FDA, but it can be included in the ingredient list as Menaquinone (scientific name of Vitamin K2).1

Further Explanations: Studies done on Vitamin K2 do not yet establish solid scientific evidence of its benefits or mechanism of action yet, and food source data for K2 are limited. Therefore, FDA ruled that K2 cannot be declared as Vitamin K in the Nutrition and Supplement Facts Label, but suggested that menaquinone (K2) can be included in the ingredient list to inform consumers that another variety of Vitamin K is a component of the product (Effective July 26, 2018).



Question 4)
Is Vitamin K2 supplementation necessary?

Answer: There is insufficient evidence at this time to support this idea.

Further Explanations: When one consumes sufficient Vitamin K1 from (space)your diet and supplementation, it appears that adequate Vitamin K2 can be synthesized from K1 in our intestinal tract. The contribution of K2 to the maintenance of Vitamin K status in human body has NOT been established because blood K1 level is used to determine Vitamin K status.1,2 Therefore, additional Vitamin K2 supplementation is not necessary, and it is unlikely for people to develop Vitamin K2 deficiency according to the current scientific evidence.

Due to several human studies showing beneficial effect of K2 supplementation on bone health, the necessity of supplemental Vitamin K2 has been proposed.8‐10 However, some of studies used a pharmacological dose (45 mg) of Vitamin K2, which is several hundred times higher than the daily recommended level for Vitamin K.1,2,8‐11 Despite the mega-dose of Vitamin K2 used in those studies, the evidence for Vitamin K2 on bone and other health benefits (e.g., cardiovascular health) to date is not conclusive.1,2,12,13 Also, numerous studies done on the effects of K1 demonstrated that higher K1 intake can benefit bone and cardiovascular health in addition to the effect on blood coagulation, and thus additional supplemental K2 is unlikely to be necessary.1,2,.14‐18



2020 Update

Vitamin K2 and Cardiovascular health

There is a recent study showing the association of higher intake of vitamin K2 with a lower risk of coronary heart disease CHD[1] but this is not a placebo-controlled randomized clinical study. Moreover, in this study, there is no measurement of any vitamin K biomarker and  vitamin intake was estimated through the use of a questionnaire.  No direct causality is established through this kind of study and in fact, there are some previous studies showing that vitamin K status is associated with overall mortality but not with cardiovascular (CVD) disease[2]. Low plasma phylloquinone (Vitamin K1) was associated with a higher CVD risk in older adults treated for hypertension[3]. VitK1 has also been shown to slow the progression of coronary arterial calcification (CAC) in healthy older adults with preexisting CAC[4].

As mentioned by the NIH website, at this time, the role of the different forms of vitamin K on arterial calcification and the risk of coronary heart disease is unclear, but it continues to be an active area of research in the general population and in patients with chronic kidney disease[5]




  1. Department of Health and Human Services. FDA. Food Labeling: Revision of the Nutrition and Supplement Facts Labels. Federal Register. 21CFR Part 101; 2016 May 27: pp. 33904‐05
  2. Booth, SL. Roles for Vitamin K Beyond Coagulation. Annu Rev Nutr 2009;29: 89‐110. doi: 10.1146/annurev‐nutr‐080508‐ 141217. Review. PubMed PMID:19400704.
  3. Shea MK, Booth SL. Concepts and Controversies in Evaluating Vitamin K Status in Population‐Based Studies. Nutrients. 2016 Jan 2;8(1). pii: E8. doi: 10.3390/nu8010008. Review. PubMed PMID: 26729160; PubMed Central PMCID:
  4. Walther B, Karl JP, Booth SL, Boyaval Menaquinones, bacteria, and the food supply: the relevance of dairy and fermented food products to vitamin K requirements. Adv Nutr. 2013 Jul 1;4(4):463‐73. doi: 10.3945/an.113.003855. Review. PubMed PMID: 23858094; PubMed Central PMCID: PMC3941825.
  5. Nakagawa K, Hirota Y, Sawada N, Yuge N, Watanabe M, Uchino Y, Okuda N,Shimomura Y, Suhara Y, Okano Identification of UBIAD1 as a novel human menaquinone‐4 biosynthetic enzyme. Nature. 2010 Nov 4;468(7320):117‐21. doi:10.1038/ nature09464. PubMed PMID: 20953171.
  6. Shearer MJ, Newman P. Recent trends in the metabolism and cell biology of vitamin K with special reference to vitamin K cycling and MK‐4 biosynthesis. J Lipid Res. 2014 Mar;55(3):345‐62. doi: 10.1194/jlr.R045559. Review. PubMed PMID: 24489112; PubMed Central PMCID:
  7. Thijssen HH, Drittij MJ, Vermeer C, Schoffelen E. Menaquinone‐4 in breast milk is derived from dietary phylloquinone. Br J Nutr. 2002 Mar;87(3):219‐26. PubMed PMID:
  8. Ikeda Y, Iki M, Morita A, Kajita E, Kagamimori S, Kagawa Y, Yoneshima H. Intake of fermented soybeans, natto, is associated with reduced bone loss in postmenopausal women: Japanese Population‐Based Osteoporosis (JPOS) Study. J Nutr. 2006 May;136(5):1323‐8. PubMed PMID:
  9. Miki T, Nakatsuka K, Naka H, Kitatani K, Saito S, Masaki H, Tomiyoshi Y, Morii H, Nishizawa Y. Vitamin K(2) (menaquinone 4) reduces serum undercarboxylated osteocalcin level as early as 2 weeks in elderly women with established osteoporosis. J Bone Miner Metab. 2003;21(3):161‐5. PubMed PMID:
  10. Iwamoto J. Vitamin K₂ therapy for postmenopausal osteoporosis. Nutrients. 2014 May 16;6(5):1971‐80. doi: 10.3390/ nu6051971. Review. PubMed PMID: 24841104; PubMed Central PMCID:
  11. Food and Nutrition Board, Institute of Medicine. Vitamin K. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National Academy Press; 2001:162‐196. PubMed PMID: 25057538. (Accessed Dec. 14, 2016)
  12. Binkley N, Harke J, Krueger D, Engelke J, Vallarta‐Ast N, Gemar D, Checovich M, Chappell R, Suttie J. Vitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American women. J Bone Miner Res. 2009 Jun;24(6):983‐91. doi: 10.1359/jbmr.081254. PubMed PMID: 19113922; PubMed Central PMCID:
  13. Hartley L, Clar C, Ghannam O, Flowers N, Stranges S, Rees K. Vitamin K for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2015 Sep 21;(9):CD011148. doi: 10.1002/14651858.CD011148.pub2. Review. PubMed PMID: 26389791.
  14. Booth SL, Broe KE, Gagnon DR, Tucker KL, Hannan MT, McLean RR, Dawson‐Hughes B, Wilson PW, Cupples LA, Kiel DP. Vitamin K intake and bone mineral density in women and Am J Clin Nutr. 2003 Feb;77(2):512‐6. PubMed PMID: 12540415.
  15. Tsugawa N, Shiraki M, Suhara Y, Kamao M, Ozaki R, Tanaka K, Okano T. Low plasma phylloquinone concentration is associated with high incidence of vertebral fracture in Japanese J Bone Miner Metab. 2008;26(1):79‐85. PubMed PMID: 18095068.
  16. Booth SL, Broe KE, Peterson JW, Cheng DM, Dawson‐Hughes B, Gundberg CM, Cupples LA, Wilson PW, Kiel DP. Associations between vitamin K biochemical measures and bone mineral density in men and women. J Clin Endocrinol Metab. 2004 Oct;89(10):4904‐9. PubMed PMID:
  17. Higdon, Jane. “Vitamin K.” Linus Pauling Institute, Oregon State University. 2000. (Reviewed by Booth, SL, 2014)‐K (Accessed Dec. 14, 2016)
  18. Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr 1999 Jan;69(1):74‐9. PubMed PMID: 9925126.
  19. Haugsgjerd, T.R., et al., Association of dietary vitamin K and risk of coronary heart disease in middle-age adults: the Hordaland Health Study Cohort. BMJ Open, 2020. 10(5): p. e035953.
  20. Shea, M.K., et al., Vitamin K status, cardiovascular disease, and all-cause mortality: a participant-level meta-analysis of 3 US cohorts. Am J Clin Nutr, 2020. 111(6): p. 1170-1177.
  21. Shea, M.K., et al., Circulating Vitamin K Is Inversely Associated with Incident Cardiovascular Disease Risk among Those Treated for Hypertension in the Health, Aging, and Body Composition Study (Health ABC). J Nutr, 2017. 147(5): p. 888-895.
  22. Shea, M.K., et al., Vitamin K supplementation and progression of coronary artery calcium in older men and women. Am J Clin Nutr, 2009. 89(6): p. 1799-807.
  23. Vitamin K: Fact Sheet for Health Professionals. Available from: