How Do I Start Understanding Vitamin K, Latest Research
Vitamin K, named after the German word “koagulation,” or blood clotting, is one of four fat-soluble vitamins, meaning that it requires fat to be fully digested and metabolized in your body. You may have not heard much about vitamin K outside of its blood-clotting capabilities or involvement in bone health, but there is a lot of research about whether vitamin K packs a punch for the alleviation of many unrelated health conditions.
Instead of focusing on vitamin K from dietary sources, although this will be discussed because it is important, I will be highlighting the research behind vitamin K supplements. Supplement advertisements often get ahead of themselves, meaning that conclusive science is lacking to make a definitive recommendation of intake prior to being marketed for specific functions or general health.
The Functions of Vitamin K
The functions of vitamin K that are most solidly identified include the following:
- Blood clotting (binds with calcium)
- Bone growth and development (osteocalcin, or protein that adds minerals to bones, is dependent on Vitamin K)
The functions of vitamin K that need more research include the following:
- Blood vessel health to prevent cardiovascular disease
- Cell growth (helping protect your body’s cells so that your body functions optimally)
- Protection for the nervous system (specifically as you age)
- Anti-cancer properties
- Increases insulin sensitivity
The Research Behind Vitamin K
A Recommend Dietary Allowances (RDA) does not exist for vitamin K due to insufficiency of evidence to develop a RDA. Because of this, an Adequate Intake (AI) has been established, which is the “level [that] is assumed to ensure nutritional adequacy.” For male adults, it is recommended to consume 120 micrograms (0.12 milligrams) of vitamin K per day; for female adults, it is recommended to consume 90 micrograms (0.09 milligrams) of vitamin K per day.
There are three forms of vitamin K:
- Vitamin K1
- Phylloquinone – found in green, leafy vegetables
- Vitamin K2
- Menaquinone – found in some animal products and fermented foods; also produced by bacteria in the human intestines
- Vitamin K3
- Menaphthone or menadione
In the United States, vitamin K1 and vitamin K2 are the forms used in dietary supplements. Vitamin K3 was utilized for a period of time in supplements, but was found to damage liver cells, so it was removed from the market. Vitamin K is often found in multivitamin and multi-mineral supplements but can also be found in isolated form in high doses. According to the National Institutes of Health, there are some vitamin K supplements that provide 4,050 mcg (4050% of AI average).
Many studies, especially in the early 2000’s, showed vitamin K to play a crucial role in the preservation of bone health. In combination with vitamin D3 and calcium, vitamin K2 (45 micrograms) has been shown to reduce your lifetime risk by 25 percent of having at minimum one fracture. A systematic review found that vitamin K2 reduced subjects’ risk of hip fractures, vertebra fractures and non-vertebral fractures up to 81 percent.
Vitamin K1 has not shown as much promise regarding the promotion of bone health and the prevention of bone degradation. According to this study in the elderly population, vitamin K1 (in combination with calcium and vitamin D) offered no benefit in bone mass density compared to the placebo group.
Like bone health, vitamin K2 has been shown to reduce human cardiovascular disease risk in some studies. For example, in a large study with over 4,800 subjects, results showed that those taking vitamin K2 supplements had a “significant risk reduction” in coronary heart disease. However, a 2015 systematic review concluded that there was a “lack of evidence currently available to determine the effectiveness of vitamin K supplementation for the primary prevention of cardiovascular disease.” In another analysis that included over 4,000 participants, no connection was found between vitamin K1 and vitamin K2 intake and cardiovascular incident rate.
In those with chronic kidney disease or are at a high-risk of vitamin K deficiency, there may be a higher risk of cardiovascular disease, implying that there may be an inverse relationship going on between vitamin K and cardiovascular disease risk.
Supplementation of Vitamin K2, specifically, has shown to improve insulin sensitivity and thus normalize blood glucose levels in those with Type 2 Diabetes. For example, supplementation of 30 micrograms of vitamin K2 daily in a placebo-controlled trial resulted in an increased insulin sensitivity in male participants. Another study found that increasing vitamin K1 intake could lower the risk of diabetes by 51 percent. Many of these studies involved men vs. women, and this is an important factor to consider when assessing the needs of the general population. More research needs to conducted.
Vitamin K supplementation has been shown to reduce the growth rate of cancerous cells in various types of cancers. A randomized controlled trial published in the International Journal of Cancer Research and Treatment found that vitamin K2 could suppress the reoccurring growth of liver cancer cells in conjunction with surgical removal of the cancer cells. In a laboratory setting, researchers tested vitamin K1 and vitamin K2 on the growth of pancreatic cancer cells. Vitamin K2 reduced cancer cell growth in the pancreas in more than 60 percent of the cell tested.
As you can see, the research is promising for vitamin K, specifically vitamin K2, in the alleviation of multiple common health conditions. However, some of the studies included an analysis of current vitamin K dietary intake and/or the initiation of vitamin K supplementation. It’s difficult to decipher whether vitamin K insufficiency or deficiency in participants contributes to health ailments, or if vitamin K supplementation (in addition to diet) will go the extra mile to alleviate some illnesses. More clinical trials involving supplementation in those that already consume an adequate amount of vitamin K daily are needed to clarify results.
As a side note, vitamin K does not have a toxicity level established due to low risk. This is different from other fat-soluble vitamins.
Are You at Risk for Vitamin K Deficiency?
Vitamin K deficiency is extraordinarily rare, as it is found in multiple food sources (spinach, collard greens, broccoli, soy beans, and chicken), and can be made in your intestines. However, there are a few instances that increase your risk of deficiency.
- Antibiotic use (kills intestinal bacteria)
- Blood thinner use like warfarin (Coumadin)
- Gallbladder disease, cystic fibrosis, celiac disease, liver disease or Crohn’s disease (can prevent absorption of vitamin K)
- Serious burns or long-term hemodialysis (typically used for chronic kidney disease)
The average American adult, according to the 2011-2012 National Health and Nutrition Examination Survey (NHANES), consumed 122 micrograms to 138 micrograms (women and men, respectively) of vitamin K from food alone. If you factor average supplement intake of vitamin K, those numbers increase to 164 micrograms for women and 182 micrograms for men. In other words, Americans are consuming (from foods only) 136 percent and 115 percent of the AI established for vitamin K among women and men, respectively.
It is important to be aware of current research ensuing about vitamins and minerals, as supplementation is a popular means to reduce and possibly alleviate negative symptoms from health ailments outside of traditional medication. However, it is also important to be cautious of the research you see and wait for conclusive research to arise. This can be difficult to determine as well, so ask your dietitian or physician for their knowledge on a particular subject.
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