The Important Role of Vitamin K in the Body

Vitamin K is an essential nutrient that plays a key role in several bodily processes. This article will discuss what vitamin K does, who is at risk for deficiency, signs of deficiency, dietary sources, and potential medication interactions. Recent research on vitamin K and cardiovascular health will also be summarized.

What Does Vitamin K Do?

Vitamin K is a group of fat-soluble vitamins that are important for:

• Blood clotting – Vitamin K is needed for the production of prothrombin and other clotting factors. Without adequate vitamin K, people can experience excessive bleeding from cuts or injuries. Newborns are given a vitamin K shot after birth to prevent life-threatening hemorrhages.
• Bone health – Research shows vitamin K is needed for bone mineralization and formation. It helps activate osteocalcin, a protein involved in bone building. Adequate vitamin K intake is associated with higher bone density, while low levels may increase osteoporosis risk.
• Possible cognitive benefits – Some studies suggest vitamin K may improve cognitive function in older adults. More research is still needed in this area.

There are several forms of vitamin K:

• Vitamin K1 (phylloquinone) – Found in plants and the primary dietary form.
• Vitamin K2 (menaquinone) – Produced by gut bacteria and also found in some animal-based foods. More absorbable than K1.
• Vitamin K3 – A synthetic form being researched for cancer treatments.

Vitamin K2 is considered the most bioavailable and active form in the body. It activates proteins involved in coagulation and bone metabolism.

Who is at Risk for Deficiency?

Vitamin K deficiency is uncommon in healthy adults eating balanced diets. Certain groups have increased risk:

• Those with fat malabsorption issues – Conditions like celiac, cystic fibrosis, liver disease can impair vitamin K absorption.
• People on antibiotics long-term – Antibiotics kill beneficial gut bacteria that produce K2.
• Individuals with poor nutritional status – Alcoholism, anorexia, malnutrition predispose people to deficiency.
• Hemodialysis patients – The dialysis process can deplete vitamin K.
• Newborns – Because vitamin K does not efficiently cross the placenta, babies are born with very limited stores.

Signs and Symptoms of Deficiency

Deficiency symptoms may include:

• Impaired blood clotting – Excessive or easy bruising, bleeding gums, heavy menstrual bleeding.
• Low bone mineral density – Increased fracture risk.
• Vascular calcification – Artery hardening.

Dietary Sources of Vitamin K

The recommended intake is 90 mcg/day for women and 120 mcg/day for men. Primary food sources include:

• Leafy greens like kale, spinach, collards, broccoli – These supply mostly K1.
• Soybean and canola oils.
• Liver, meat, eggs, dairy – Provide smaller amounts of K2.
• Fermented foods like natto, cheese, sauerkraut – Offer menaquinones.
• K1 is abundant in chlorophyll-rich plant foods. Cooking does not destroy vitamin K, but freezing may.

Supplements and Medication Interactions

While vitamin K deficiency is rare with a balanced diet, some people take K2 supplements for bone and heart health. Caution is warranted about interactions with these medications:

• Blood thinners (warfarin, Coumadin) – These medications work by blocking vitamin K. Suddenly increasing K intake can reduce effectiveness.
• Antibiotics – Long courses of broad-spectrum antibiotics can kill vitamin K-producing bacteria.
• Seizure medications (phenytoin) – The drug itself does not impact vitamin K levels, but patients taking it often have poor nutritional status.
• Cholesterol drugs (orlistat, Xenical) – May reduce absorption of fat-soluble vitamins like K.

For most people not on these medications, vitamin K supplements appear safe if taken as directed. However, talk to your doctor before starting any new supplement, especially if taking blood thinners.

Recent Study on Vitamin K and Cardiovascular Health

An interesting recent study looked at whether taking vitamin K2 (as MK-7) along with vitamin D could slow the progression of vascular calcification in older men.

The 2-year double-blind trial included over 200 men with coronary artery calcification. One group received daily vitamin D plus 720 mcg MK-7. The other group received placebo.

While there was no significant difference in calcification progression between groups, the vitamin K group had lower levels of inactive osteocalcin, a marker of poor vitamin K status. This indicates vitamin K supplementation improved vitamin K status. However, more research is still needed on K2 for cardiovascular benefits.

Key Takeaways – Vitamin K Essential Roles

• Vitamin K plays essential roles in blood clotting, bone metabolism, and potentially cardiovascular health. Inadequate intake over long periods can lead to bleeding risk and bone weakening.
• While deficiency is uncommon, certain medications and health conditions can increase risk by impairing vitamin K absorption or production by gut bacteria.
• Vitamin K1 is abundant in leafy greens and other plant foods. Vitamin K2 is found in some animal foods and fermented products.
• Supplements may provide benefit for some people with increased risk for deficiency. However, vitamin K can interact with common medications like blood thinners and antibiotics. Always talk to your healthcare provider before starting supplements.