The benefits of vitamin K
While it may not be winning any popularity contests, vitamin K has big responsibilities in your body. “It is a group of fat-soluble vitamins that the body needs for blood clotting, helping wounds to heal, and the building of bones,” says Jaclyn Railsback, DO, internal medicine specialist with the Cleveland Clinic Weston Hospital in Florida. It's also good for "heart health and preventing the progression and development of vascular calcifications in the arteries.”
The vitamin’s role in blood clotting and bone health tends to get more attention than its dealings with the heart, but to better understand the relationship between vitamin K and your ticker, a group of researchers from New Edith Cowan University (ECU) in Australia looked at data for more than 50,000 people over a 23-year period. Their goal was to see if vitamin K consumption impacted the risk of plaque buildup in the arteries, known as atherosclerosis.
The study results, recently published in the Journal of the American Heart Association, suggest the people who consumed the highest levels of vitamin K were 35 percent less likely to develop atherosclerosis, especially in the narrow peripheral arteries that carry blood to other parts of the body. While the results provide more evidence that vitamin K is good for the heart, these findings also suggest we may benefit from consuming more than we currently do.
How much do you need
According to the National Institutes of Health Office of Dietary Supplements (ODS), the recommended daily intake for vitamin K is 90 micrograms (mcg) for women 19 and older and 120 mcg for men 19 and older. However, Nicola Bondonno, PhD, the senior author of the ECU research, says, “in our study, a lower risk of atherosclerotic cardiovascular disease was seen for people with even higher intakes.” The difference, according to Dr. Bondonno, is that the current guidelines are based on how much is needed to aid blood clotting. However, the ECU study suggests consuming more vitamin K could result in better protection against cardiovascular disease.
A vitamin that helps clot blood while preventing plaque from building up in arteries may sound counterintuitive, but it’s not. It’s all about protein. Matrix GLA protein in your heart tissue protects against plaque build-up, but you need vitamin K to do it, Dr. Bondonno says.
So how much vitamin K should you consume to max out the cardiovascular benefits? Unfortunately, the jury is still out on that. Dr. Bondonno says that because their study didn’t validate the vitamin K intake against biomarkers or food recalls, they can’t say for certain how much of the vitamin study participants actually consumed. Additional research is needed, but it looks like more might be better.
That doesn’t mean you should go buying vitamin K supplements though. “Since vitamin K is a fat-soluble vitamin, you can consume too much of it,” says Dr. Railsback. The ODS doesn’t provide clear daily limits, but the risk for overconsumption is possible, albeit low, Dr. Railsback says. She adds that too much can cause issues like anemia and jaundice. Additionally, the vitamin doesn’t play nicely with certain medications, which is why Dr. Railsback says you should always talk to your doctor before supplementing.
You do need to make sure you get enough of the vitamin, though. “Several observational studies have found that inadequate intake of vitamin K is linked to low bone density and increased risk for bone fractures,” says Dr. Railsback. People with certain gastrointestinal disorders (celiac disease, inflammatory bowel disease, short bowel syndrome) or a history of gastric bypass surgery might not absorb vitamin K properly and therefore may benefit from supplementation. The takeaway? You should always talk to your doctor before you supplement.
How to get enough from food
Chances are, you’re already getting enough vitamin K. According to the National Institutes of Health ODS, most people consume the recommended amount of vitamin K from their diet. But if you really want to be sure, you first need the whole story.
There are actually two main forms of vitamin K–vitamin K1 and vitamin K2. “Vitamin K1 is easy to incorporate into your diet since it’s widely distributed across our food supply,” says Rachel Dyckman, MS, RDN, CDN. “[It’s] found in green leafy vegetables including kale, collard greens, spinach, cabbage, arugula, broccoli, brussels sprouts, basil, and parsley.”
But remember, vitamin K is fat-soluble. “So in order to best absorb it, you’ll want to be sure that you’re eating K-rich foods with a fat source,” says Dyckman. She recommends drizzling olive oil on green leafy vegetables or adding in a handful of nuts to increase your body’s absorption of the vitamin.
Vitamin K2, on the other hand, is a little more complicated. “It is predominantly produced by gut bacteria and is further divided into other subgroups named MK4 to MK13,” explains Dr. Railsback. “These are found in some dairy products, pork, poultry, and fermented foods.” Dyckman suggests liver, cheese, fatty fish, and egg yolks as other good sources. And since most K2 sources already contain fat, you don’t need to add anything extra to ensure it's absorbed.
Now, to meet the official vitamin K requirement, you technically only need to worry about Vitamin K1. “A recommended dietary allowance for vitamin K2 has not yet been established, so the current vitamin K recommendation is based on our vitamin K1 needs alone,” says Dyckman. But if you’re going for the cardiovascular benefits, you shouldn’t count K2 out. Some studies have shown that vitamin K2 is better than K1 in preventing coronary heart disease. As for the ECU study, participants who consumed the most vitamin K1 were 21 percent less likely to go to the hospital for issues related to atherosclerosis, and those who ate vitamin K2 were 14 percent less likely.
It's also important to remember that vitamin K consumption isn't the largest factor in mitigating heart disease risk—quitting smoking, reducing alcohol intake, and regular exercise can also help keep your heart healthy.
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