Vitamin K and cancer: Is there a connection?

Vitamin K is one of the four fat-soluble vitamins our bodies need to function correctly. It’s important for both bone formation and blood clotting.

But can the precursors of this vitamin actually kill cancer cells or slow its growth? If so, which type? If you’ve heard talk or seen claims about this on social media, here’s what you need to know.

What is a vitamin K precursor?

A precursor is just something that comes before (or leads to) something else. In this instance, it’s a synthetic version of vitamin K called menadione — also known as K3. The body can convert K3 into a usable form called menaquinone, or K2.

Do vitamin K precursors really destroy cancer cells?

No. There has been no direct correlation established between a vitamin K precursor and the death of cancer cells. K3 (menadione) is not even something that’s available for human consumption. It’s primarily a component of animal feed.

Can vitamin K precursors actually slow the growth of cancer cells?

We don’t know yet. Researchers have been testing menadione (K3) on both liver cancer and prostate cancer cells.

But thus far, these studies only involve cells. They are not taking place in human subjects. So, we’re not talking about giving human patients a supplement and then noticing a decrease in cancer at the cellular level. We’re talking about scientists conducting studies in a lab to determine if there might be a connection.

As of today, no evidence exists to demonstrate a strong correlation between vitamin K precursors and the inhibition of tumor growth in humans.

Can the body make vitamin K itself or do we need to get it through our diet?

Your body can make small amounts of vitamin K on its own, but you do need to primarily obtain it through your diet.

Which foods are rich sources of vitamin K?

• Leafy green vegetables like spinach, kale and broccoli contain another usable form of vitamin K called phylloquinone (K1).
• Fermented products like kimchi, some cheeses and natto (a fermented soybean product that’s popular in Japan), contain menaquinone (K2).
• Eggs from chickens and other domesticated fowl contain roughly .03 mcg to 1.0 mcg of vitamin K each.

How much vitamin K do people need?

According to the National Institutes for Health, the recommended daily allowance (RDA) for adult men (19+) is 120 mcg. For adult women (19+), it’s 90 mcg.

Does vitamin K need to be taken with vitamin D?

Vitamin K and vitamin D can be taken together to help with the absorption of calcium, but vitamin D is not necessary for vitamin K to be absorbed properly. Taking vitamin K (or any fat-soluble vitamin) with a meal containing fat, on the other hand, can help with absorption.

Who might need a vitamin K supplement?

Vitamin K deficiencies are pretty unusual. But you might be deficient if you have:

• Liver disease
• Fat-malabsorption issues (Crohn’s disease, celiac disease)
• Had all or part of your pancreas removed.

What are the signs of vitamin K deficiency?

Again, vitamin K is not really one of the most common deficiencies doctors see. So, I’d only suggest getting tested for it if you’re at high risk due to one of the criteria I just mentioned.

Any signs that you might have a deficiency would be related to blood and bone health. So, you might notice that you’re bruising more easily, for instance. Or, you might experience prolonged bleeding episodes, even after something really minor, like a paper cut.

Is vitamin K the same thing as potassium?

No. The chemical symbol for potassium is “K,” but that is completely different from this vitamin.

What happens if I take a vitamin K supplement every day?

Most healthy individuals can take a vitamin K supplement daily with no issues.

Is there anyone who shouldn’t take a vitamin K supplement?

You should talk to a doctor before starting any new supplement. That’s especially true here.

Do not take vitamin K without consulting a doctor if you’re already on a blood thinner. Blood thinners like warfarin increase the amount of time it takes your blood to clot, while vitamin K does the exact opposite.

If you start taking both, they may cancel each other out. So, the effects of one or both might be negated. That could lead to dangerous blood clots. So, be very mindful of that and discuss any new supplements with your care team before starting them.

Request an appointment at UT MD Anderson online or call 1-877-632-6789.