Vitamin K: A lesser-known but notable nutrient

(Conversations are an independent, non-profit source of news, analysis, and commentary from academic experts.)

Tufts University Kyla Shea

(Conversation) When Danish scientist Henrik Dam fed a cholesterol-free diet to chick babies in his lab about 90 years ago, he noticed excessive bleeding in some of them. It didn’t stop after he replaced cholesterol. Dam finally concluded that bleeding was associated with “depletion of antihemorrhagic compounds.” This was what he called Vitamin K (short for “coagulation” in Danish). For his discovery, Dam was awarded the Nobel Prize in Physiology or Medicine in 1943.

Most people know about vitamins A, B, C, D and / or E, but vitamin K slips under nutrition radar. Still, it is essential to life because it is necessary for blood to coagulate normally. Scientists are now aware that they know more about this undervalued nutrient.

Today, Tufts University’s Janmeyer USDA Center for Human Nutrition on Aging has the only research team in the world dedicated to vitamin K nutrition. I am a research scientist on that team. We are studying how foods provide vitamin K to support healthy aging.

Why is Vitamin K important?

Over the past few decades, scientists have discovered vitamin K-dependent proteins in many tissues throughout the body. This suggests that vitamin K has a physiological role that goes far beyond blood coagulation. For example, in arterial tissue, vitamin K-dependent proteins help prevent calcification. This is important because calcification of the arteries can cause a heart attack.

Without Vitamin K, these proteins cannot prevent calcification. We are also studying how these vitamin K-dependent proteins are involved in osteoarthritis because these proteins are present in cartilage and bone.

Just as there are several forms of B vitamins, there are multiple forms of vitamin K. Scientists know at least 12. Phylloquinone, also known as vitamin K1, is synthesized by plants. Green leafy vegetables such as spinach and collard green, and vegetable oils such as soybeans and canola oil contain large amounts of phylloquinone.

Menaquinone, a class of vitamin K compounds also known as vitamin K2, is found in varying amounts in animal foods such as dairy products and some meats. Menaquinone is also produced by the intestinal flora, but its nutritional value is unknown.

In our lab, we measured the amount of vitamin K in thousands of foods commonly consumed in North America. In partnership with the United States Department of Agriculture, this information is published on USDA’s Food Data Central website, the world’s most comprehensive nutrition database. Over 350,000 foods are profiled.

What’s next?

The goal of our study is to establish a recommended dietary intake of vitamin K. In North America, the current dietary intake standard for vitamin K is called the “appropriate intake”, which is the amount expected to ensure nutritional sufficiency. If there is not enough scientific evidence to provide a more accurate recommended nutritional requirement, the appropriate intake will be set. For men over the age of 18, the proper intake of vitamin K is 120 micrograms daily. For women, 90 micrograms a day. One cup of raw spinach contains 145 micrograms of phylloquinone. Patients taking warfarin should consult with a healthcare professional for guidance on vitamin K intake.

Abnormal coagulation due to low dietary intake of vitamin K is extremely rare, as almost everyone consumes enough vitamin K in their diet to maintain normal coagulation. New evidence suggests that low vitamin K intake may affect health outcomes unrelated to coagulation, but at this time, even if they are on the market, this Evidence does not support the need to take vitamin K supplements. Menaquinone supplements are especially popular because they claim to have unique health benefits that phylloquinone does not have.

However, it is very difficult to isolate the effects of nutrients on health outcomes, and it is even more difficult to recommend the use of supplements based on previous studies. Large clinical trials should be designed to address the problem. These trials, which can cost millions, have not yet been conducted with vitamin K. The small trials conducted do not currently meet the scientific rigor standards required to promote vitamin K supplements.

[You’re too busy to read everything. We get it. That’s why we’ve got a weekly newsletter. Sign up for good Sunday reading. ]

As our research continues, we strive for a better understanding of the role of vitamin K in human health beyond coagulation. I want to know how much vitamin K is needed to protect against age-related diseases and disorders. However, it is safer and more enjoyable to take vitamin K from foods until there is more solid evidence that supplements are needed.

The opinions, findings, conclusions, or recommendations contained in this publication are those of the author and do not necessarily reflect the views of the USDA.

This article has been republished from Conversation under a Creative Commons license. Read the original article here: https://theconversation.com/vitamin-ka-little-known-but-noteworthy-nutrient-152161..