Vitamin K new research shows that this ‘forgotten’ vitamin may be good for your bone health

food items with vitamin K
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Eating vitamin K-rich foods such as leafy green vegetables, parsley, prunes, avocados or kiwi can help you get your daily dose of this neglected nutrient.

Unlike the other more ‘popular’ vitamins, most people aren’t aware of the benefits of vitamin K. Doctors have long known that it helps the body make proteins that are needed for normal blood clotting. In fact, it is so important that people who take anticoagulants (such as warfarin) must be careful to keep their vitamin K intake stable. However, more recently, an increasing number of studies indicate that vitamin K has a role to play  in bone health too.

Improving bone health

Although vitamin K is not as significant to bone health as are calcium and vitamin D, low levels of circulating vitamin K have been linked with low bone density. As well, several studies have shown that supplementation with vitamin K results in improvements in bone health1. In fact, new evidence points towards the potential role of this vitamin in:

  • Slowing down bone loss after menopause in women
  • Increasing bone strength and decreasing and/or limiting the risk of fractures in people suffering from osteoporosis

One study (Nurses’ Health Study) suggests that women who get at least 110 micrograms of vitamin K a day are 30% less likely to break a hip than women who get less than that2. Eating a serving of green leafy vegetable a day cut the risk of hip fracture in half when compared with eating one serving a week. Another study showed that eating 100 g of prunes (8-10 pieces) daily for one year, was associated with increased bone mineral density (BMD) at the spine and forearm in young osteopenic postmenopausal women compared to those who were eating 75 g of dried apple3. Data from yet another study showed that low vitamin K levels were associated with low BMD in women but not in men4.

Which foods contain vitamin K?

The two main groups of vitamin K that occur naturally are vitamin K1 and K2. Different foods contain different kinds of vitamin K, and we also get some vitamin K from the bacteria that normally live in our large intestine. Although the recommended dietary allowance (RDA) has not been established for vitamin K, the adequate intake is considered to be 120 μg /day for men aged 19+ and 90 μg /day for women aged 19+.

Vitamin K is present in a range of foods that includes:

  • Green leafy vegetables, e.g. kale, spinach, turnip greens, collards, parsley, romaine, and green leaf lettuce
  • Vegetables such as Brussels sprouts, broccoli, cauliflower, and cabbage
  • Prunes, kiwi, avocado, blackberries, figs, rhubarb
  • Fish, liver, meat, eggs, and cereals (K2)
  • Natto (a Japanese dish made of fermented soybean) (K2)
Plant foods high in vitamin K
VegetablesVitamin K (μg/serving)
Kale, cooked, 130 g/ 1 cup, chopped1062
Collards, cooked, 190 g/ 1 cup, chopped772
Swiss chard, cooked, 175 g/ 1 cup, chopped572
Broccoli, cooked, 156 g/ 1 cup, chopped 110
Parsley, fresh, 15 g/, 1/4 cup chopped246
Cabbage, cooked, 75 g/ 1/2 cup, shredded81
Fruits 
Prunes (dried plums, uncooked, pitted), 174 g/ 1 cup103
Kiwi, green, raw 180 g/ 1 cup sliced72
Avocado, raw 150 g/ 1cup, cubed31
Nutrient data from USDA National Nutrient Database for Standard Reference Releases 27

In comparison to the high-vitamin K1 containing foods listed above, many vegetables (e.g. carrots and potatoes) and most fruits (e.g. apples, melon, oranges) contain negligible, or practically no, vitamin K. However, if you add a regular serving of green leafy vegetables to your daily diet it’s not difficult to get an adequate amount of vitamin K1. For example, even one serving of broccoli (or a handful of prunes or a kiwi) will give your body the vitamin K boost it needs for the day.

It should be noted that most people would find it more difficult to get vitamin K2 as opposed to K1 from foods and there is therefore more concern about vitamin K2 as opposed to K1 deficiency. As the results of more ongoing research become available we can expect to learn more about how the different kinds of vitamin K impact on our bone health.

In the meantime, do keep eating regular helpings of vitamin K rich vegetables and fruits - for the benefit of both your bone and overall health.

LYB logoThis article appeared in our monthly Love Your Bones newsletter sent to IOF members.

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References

1.Weber P. Vitamin K and bone health. Nutrition. 2001; 17:880–7. Facts about Vitamin K1 
2. Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr. 1999; 69:74–9.
3. Hooshmand S Brisco JRY, Arjmandi BH. (2014) The effect of dried plum on serum levels of receptor activator of NF-kB ligand, osteoprotegerin and sclerostin in osteopenic postmenopausal women: a randomised controlled trial. Br. J. Nutr. 112; 55-60.
4. Booth SL, Broe KE, Gagnon DR, et al. Vitamin K intake and bone mineral density in women and men. Am J Clin Nutr. 2003; 77:512–6.

Further reading

> Harvard School of Public Health – Vitamin K 
> Facts about vitamin K1 – (UF IFAS Extension, University of Florida) 
> Vitamin K2 — A Little-Known Nutrient Can Make a Big Difference in Heart and Bone Health

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