What Is Your Menaquinotype? The Effect of the Microbiome on Vitamin K
A not very well known fact is that we get vitamin K not only from the diet, but also from the bacteria that we co-exist with in our intestines. Vitamin K activity is provided by a group of compounds called vitamers. This is why newborns are given supplemental vitamin K: their digestive tract is sterile at birth and it takes time to acquire the microbes that make vitamin K. Until this time, they are at risk of vitamin K deficiency. Even though we have known since the 1950s that the gut microflora provide an important source of vitamin K (Gustaffson), the specifics are so complex that we have had to wait until developments in bioinformatics over the past few years to uncover how vitamin K is produced in the intestines. This may be important because the effect on health of vitamin K may go beyond the traditional role as a co-factor in blood coagulation to cardiovascular health, cognitive function, and cancer (see review by Booth).
Karl and co-workers have recently looked into detail about which bacteria are responsible for the production of the vitamin K, and whether there are links with cardiovascular risk factors. Fortunately for vitamin K researchers, the source of vitamin K (diet vs. microbes) is relatively easy to identify. The vitamin K forms phylloquinone and menaquinone MK4 are obtained from the diet, while the menaquinones MK5 to MK13 are produced by bacteria. The researchers could therefore correlate vitamer types with specific genera of bacteria. They obtained their samples from 77 overweight adults participating in a dietary intervention intended to modify the intestinal microflora of participants and induce modest weight loss.
The researchers found that only a few genera of bacteria seem to be mostly responsible for vitamin K production in the gut. Specifically, the bacterial taxa Ruminococcaceae, Bacteroides, Prevotella, Alistipes, Oscillibacter, Bilophila, Odoribacter and Barnesiella species were mostly responsible for the vitamin K content of the feces. Two “menaquinotypes” were found: for one, MK9 and MK10 predominated from the vitamers, and for the other, the vitamers MK5, MK11, MK12 and MK13 were the main types produced. It seems that Bacteroides were prevalent in the MK9/MK10 menaquinotype, while Prevotella were found more often in the MK5/MK11/MK12/MK13 menaquinotype. This is important as the different vitamers may have different health effects, and the relative abundance of each species of bacteria can be modified by the diet or the addition of certain prebiotics. For example, subjects with the MK9/MK10 menaquinotype had a more favorable diabetes risk profile and lower levels of IL-6, a marker of inflammation.
A weakness of the study is that the authors did not look at the vitamin K status of the subjects. It is entirely possible that each different vitamer is taken up and used differently by the body, therefore this would be an important step in working out whether changing the diet could affect the vitamin K production of intestinal microflora.
J Philip Karl, Xueyan Fu, Xiaoxin Wang, Yufeng Zhao, Jian Shen, Chenhong Zhang, Benjamin E Wolfe, Edward Saltzman, Liping Zhao, and Sarah L Booth. Fecal menaquinone profiles of overweight adults are associated with gut microbiota composition during a gut microbiota–targeted dietary intervention. Am J Clin Nutr ajcn109496; First published online May 27, 2015. doi:10.3945/ajcn.115.109496
Bird J. Vitamin K and Infant Bleeding: What Happens When Parents Refuse Preventive Measures? TalkingNutrition blog November 15, 2013. http://www.dsm.com/campaigns/talkingnutrition/en_US/talkingnutrition-dsm-com/2013/11/vitamin_k_deficiency_bleeding_CDC.html
Booth SL. Roles for vitamin K beyond coagulation. Annu Rev Nutr. 2009;29:89-110. doi: 10.1146/annurev-nutr-080508-141217. http://www.ncbi.nlm.nih.gov/pubmed/19400704
Gustafsson BE. Vitamin K deficiency in germfree rats. Ann N Y Acad Sci. 1959 May 8;78:166-74. http://www.ncbi.nlm.nih.gov/pubmed/13830426