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Are You Getting Enough Vitamin K?

Research shows this lesser-known nutrient helps keep your heart healthy, your bones strong and more — yet many older adults fall short

Fresh fruits and vegetables containing vitamin K, with the letter K

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En español | If Vitamin K is not already on your radar, it probably should be.

The lesser-known nutrient has long been understood to play a key role in blood clotting. Now, a growing body of research suggests that getting adequate amounts can help ward off heart disease, cognitive problems, osteoarthritis and physical disability, making it especially important to healthy aging.

Yet many older Americans aren't getting enough of it.

About 60 percent of men and 40 percent of women ages 51 and older don't get the recommended amounts of vitamin K — 120 micrograms (mcg) for men and 90 mcg for women — according to an analysis by the Vitamin K Team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston.

Among men over age 70, two-thirds don't get enough vitamin K, the study found.

"You have to have some vitamin K in your diet for optimal health,” says study coauthor Sarah Booth, director of the Tufts lab. “If you eat a balanced diet with fruits and vegetables, you're probably getting adequate vitamin K. But as people get older, many of them don't.”

Vitamin K is an essential fat-soluble nutrient that can be found in many foods, including leafy greens, broccoli, liver, meats, peas and eggs.

Benefits go beyond being a blood thickener

Vitamin K was discovered by a Danish biochemist in the 1920s because of its role in preventing excessive bleeding after an injury. The “K” comes from the Danish and German word koagulation. People who take the blood thinner warfarin (Coumadin) are among those advised to keep their dietary intake of vitamin K steady; without it their medication can become less effective.

There are actually many forms of vitamin K, Booth says, but the two most studied are vitamin K1, which is mostly in plant-based foods, and vitamin K2, which seems to be mostly in animal products and fermented foods.


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Some researchers make distinctions between the two types, Booth says, “but right now I would argue that the data shows it doesn't matter what form vitamin K you eat in your diet; they all seem to have same effect."

Researchers have learned in recent years that vitamin K contributes to many types of molecular reactions in our bodies, says Keith R. Martin, a researcher at the Center for Nutraceutical and Dietary Supplement Research at the University of Memphis.

Perhaps most important, it appears to play a role in slowing calcification, the buildup of calcium in blood vessels, bone and other body tissue that happens as you age.

"Calcification is kind of like rust; it gunks things up over time,” Martin explains.

For example, calcification in your blood vessels or heart can lead to coronary heart disease. In the cartilage of your knee, it can lead to osteoarthritis.

A wide range of benefits

Largely because of how it fights calcification, research also shows these specific benefits with the vitamin:

Cardiovascular disease

Studies going back to the early 2000s have found that people who eat less vitamin K are more likely to have coronary heart disease, possibly because the blood vessels that feed the heart get stiffer and narrower without it. In one study, researchers looked at data on 7,216 people who were at high risk of cardiovascular disease and found that “an increase in dietary intake of vitamin K is associated with a reduced risk of cardiovascular, cancer or all-cause mortality.”

Cognition

At least six research studies have found a link between adequate vitamin K levels and cognition in older adults, according to a 2019 review in Frontiers in Neurology. In one study, healthy adults over age 70 with the highest average blood levels of the vitamin had better recall of specific past personal experiences than those with lower levels.

Osteoporosis/osteoarthritis

Several studies have found people who eat more vitamin-K-rich foods have stronger bones and are less likely to break a hip. In some parts of the world, vitamin K is prescribed as a treatment for osteoporosis. The European Food Safety Authority, for instance, allows companies to make the claim that foods with vitamin K help bone health, but the Food & Drug Administration has not authorized a health claim for the vitamin in the U.S.

Mobility

Booth and her researchers followed over 1,300 older adults and tracked their ability to walk a quarter-mile and climb 10 steps without resting. They found that those with low blood levels of vitamin K were twice as likely to have trouble with those tasks compared to those with sufficient levels.

Booth notes that while there have been a few small randomized double-blind studies of vitamin K, many of the larger ones have been observational, which means researchers found associations, but they don't necessarily prove cause and effect. More research is underway that will hopefully present a clearer picture of the benefits of vitamin K.

So should you take a supplement?

Although some nutraceutical companies already tout the benefits of vitamin K supplements, particularly vitamin K2, both Booth and Martin say they would not recommend taking one. (If you want some extra vitamin K, look for a multivitamin that contains it instead.)

"We don't have a lot of rigorous research around the safety and efficacy of vitamin K supplements,” Booth says. “Because vitamin K is involved in blood clotting, you don't want to play around with it."

She says it's not hard to get more vitamin K in your diet. If you don't like leafy greens (or you can't have them because you're on a blood thinner), try some of the other foods on the list below.

"You don't have to eat a big bowl of collards to get the benefits,” Booth says. “A small amount can make a difference.”

Foods High in Vitamin K

Mcg per serving Food
145 Spinach, raw, 1 cup
113 Kale, raw, 1 cup
110 Broccoli, chopped, boiled, ½ cup
43 Soy beans, roasted, ½ cup
25 Soy bean oil, 1 tablespoon
21 Edamame, frozen, ½ cup, prepared
20 Pumpkin, canned, ½ cup
19 Pomegranate juice, ¾ cup
16 Okra, raw, ½ cup
15 Salad dressing, Caesar, 1 tablespoon
15 Pine nuts, dried, 1 ounce
14 Blueberries, raw, ½ cup
14 Iceberg lettuce, raw, 1 cup
13 Chicken breast, rotisserie, 3 ounces (as MK-4)
11 Grapes, ½ cup
10 Vegetable juice cocktail, ¾ cup
10 Canola oil, 1 tablespoon
10 Cashews, dry roasted, 1 ounce
8 Carrots, raw, 1 medium
8 Olive oil, 1 tablespoon
6 Ground beef, broiled, 3 ounces (as MK-4)

Source: National Institutes of Health, Office of Dietary Supplements

Michelle Crouch is a contributing writer who has covered health and personal finance for some of the nation's top consumer publications. Her work has appeared in Reader's Digest, Real Simple, Prevention, The Washington Post and The New York Times.

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