Vitamin K and Childhood Bone Health
Since I began working at a family nutrition program, I’ve become quite interested in childhood nutrition. I work with low-income clients and I commonly see issues that affect bone mineral density such as iron deficiency anemia and Vitamin D inadequacy. Sadly, several of the kids I've counseled already have crowns on their teeth to cover up cavities. At a pediatric nutrition conference I attended this spring, I learned from 1969 to 1999, there was a 40% jump in forearm fractures in kids! (1) Clearly steps need to be taken to reverse this trend.
Vitamin K2 has become a hot topic in holistic health approaches to improving bone health, and I’ve become especially curious about the relationship between Vitamin K2 and children’s bone health.
What I wanted to find out is:
Does Vitamin K2 supplementation actually improve bone health markers?
Would it be recommended for children? If so, in what amount?
Vitamin K plays a role in blood clotting and activating calcium binding proteins, so it’s thought there's also a role in improving bone mineral density. Chris Kresser has written more on other health properties of K2 and food sources here. Neither of the studies address food quality, but I do think it's important to note that not all sources of K2 are equal: grass-fed dairy is a superior K2 source to conventional, grain fed dairy (see here), and Stephan Guyenet at Whole Health Source has more about this here.
The first paper I read was a review article published in 2008 about the role of Vitamin K in skeletal health. Vitamin K is named so because the word “coagulation” in German begins with the letter “k” (see here). The difference between Vitamin K1 and K2 is that K1 is the primary form in our diet and is found primarily in leafy green veggies. K2 is synthesized in the gut of humans and animals - we find K2 mostly in animal products like cheese and butter.
The recommendations for Vitamin K are 90µg/day for women and 120µg/day for men, which, weirdly, during my research I discovered kale provides just over 1000µg in a 1 cup serving (see here). However this paper comments the daily recommendations: “may not be adequate to maintain optimal vitamin K status, based on full [activation] of all Vitamin K-dependent proteins”, suggesting the research is still inconclusive on what the daily intake of Vitamin K should be (Shea and Booth, 2008). In addition, with people eating fewer and fewer veggies, the population's K1 intakes are dropping.
The most common way of measuring Vitamin K status is to measure the ratio of uncarboxylated (“not yet activated by Vitamin K) to carboxylated (“activated by Vitamin K”) proteins found in bone. To be more specific, the protein being measured is osteocalcin and produces the osteoblasts needed for bone formation! Cool, huh B)
Since the field of Vitamin K/bone health is so new, most of the data out there is from observational studies, so results are somewhat mixed. These studies are in adult populations.
The Nurses Health Study found an association between K1 intake and a decreased risk of hip fractures in women between 30 and 88 years old. The Framingham Heart Study found results supporting this with an association between lowered K1 intake and an increased risk for hip fractures in men and women of on average 75 years of age, however the relationship specifically between K1 intake and bone mineral density was inconclusive. As of this article there were only four clinical trials on Vitamin K and bone health and results were also inconclusive. These studies and more dosed at 200µg to 10mg/d.
It appears K2 may be more influential on bone health than K1. Interestingly, K2 is used as a pharmaceutical to treat osteoporosis in Japan and is dosed at 45mg/d – WAY more than used in the observational and clinical studies. It’s suggested the combination of K2, Vitamin D and calcium may have a stronger effect than K2 alone, and certainly more than K1.
The study I read regarding K2 and kid’s bone health suggested K2 may have a stronger role in bone health since it has a longer half-life than K1. This was a double-blind, randomized, placebo-controlled intervention study whose subjects were kids from 6-10 years old. The intervention group took one 45µg supplement of K2 per day for eight weeks at their evening meal; the other group took a placebo.
This study also measured the uncarboxylation:carboxylation ratio and the primary goals were to measure how much this ratio changed and to measure changes in biometrics like K2 concentration in the body.
The study concluded that after the intervention, the test group had an improved ratio (therefore participants were more in the bone "formation" phase) and “no increase of procoagulant activity was noted in the treatment group, indicating that supplementation with [K2] is safe” (Khosla et al 2009)..
Overall it seems that there's strong research to link K2 and bone health in the elderly, and hopefully there'll be more clinical trials with K2 and kids in the future.
Khosla S, Melton III L, Dekutoski MB, Achenbach SJ, Oberg AL, Riggs B. Incidence of Childhood Distal Forearm Fractures Over 30 Years: A Population-Based Study. JAMA. 2003;290(11):1479-1485.
Marieke J. H. van Summeren, Lavienja A. J. L. M. Braam, Marc R. Lilien, Leon J. Schurgers, Wietse Kuis and Cees Vermeer (2009). The effect of menaquinone-7 (vitamin K2) supplementation on osteocalcin carboxylation in healthy prepubertal children. British Journal of Nutrition, 102, pp 1171-1178.
Shea, M Kyla and Booth, Sarah L. Update on the role of vitamin K in skeletal health. Nutr Rev. 2008;66(10):549-57.