Vitamin K: Health Benefits, Food List, Daily Dose & Supplements

Vitamin K is a nutrient that is essential for the body. It performs several functions, such as aiding in the blood clotting process and preventing bleeding. It also helps to strengthen the bones and prevent osteoporosis by ensuring calcium is absorbed into the bones.

The main form of vitamin K is vitamin K1, also referred to as phytoquinone. It is found mainly in dark green vegetables, such as broccoli, kale and spinach, as well as some fruits, such as kiwi, strawberries and grapes. Vitamin K2, known as menaquinone, is produced by the good bacteria in the intestines, and is present in some foods of animal origin.

In addition to being found in food, vitamin K can also be consumed in the form of supplements, which should be used as directed by your doctor or registered dietitian.

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Health benefits

Vitamin K is very important for the body, as it performs the following functions:

1. Aids in clotting

Vitamin K is necessary to synthesize the proteins that help control bleeding (clotting factors). These are important for blood clotting, for preventing bleeding and for promoting wound healing.

2. Maintains bone health

Vitamin K is necessary for the production of osteocalcin, a fundamental protein that is found in the bone matrix. Its function is to stimulate the absorption of calcium into the bones and teeth, which is needed for normal bone development and bone maintenance in adulthood. Adequate levels help to prevent the development of osteoporosis.

In order for vitamin K to impact bone mass positively, you should also consume plenty of calcium in your diet. 

3. Prevents bleeding in newborns

Newborns may be at a high risk for bleeding due to a vitamin K deficiency, as they are typically born with a very low supply of this vitamin. This occurs for the following reasons: 

  • Vitamin K does not easily cross the placenta 
  • Breast milk contains low levels of Vitamin K
  • The baby's intestine is not yet made up of bacteria capable of producing this vitamin in sufficient quantities.

Therefore, vitamin K is administered preventatively to newborns. Premature births, delivery complications and the use of some medications during pregnancy (such as anticonvulsants or anticoagulants) can all increase the risk of bleeding and the lack of vitamin K in the newborn.

4. Promotes cardiovascular health

Vitamin K is involved in the production of proteins that help prevent calcification or hardening of the heart arteries. This calcification can contribute to the development of heart diseases such as atherosclerosis and myocardial infarction.

Foods rich in vitamin K

The main foods rich in vitamin K are:

  • Dark green vegetables, such as broccoli, kale, watercress, arugula, lettuce and spinach;+
  • Turnip
  • Oil
  • Avocado
  • Boiled egg
  • Liver
  • Kiwi
  • Strawberry
  • Grape
  • Cabbage

In addition to these foods, vitamin K can also be found in nuts, chestnuts, pistachios, meat, cheese and soybeans. 

Daily dose

The recommended daily amount of vitamin K varies depending on age, and is outlined below:

  • 0 to 6 months: 2 mcg
  • 7 to 12 months: 2.5 mcg
  • 1 to 3 years: 30 mcg
  • 4 to 8 years: 55 mcg
  • 9 to 13 years: 60 mcg
  • 14 to 18 years: 75 mcg
  • Men over 19 years old: 120 mcg
  • Women over 19 years old: 90 mcg
  • Pregnant and breastfeeding women: 90 mcg

In general, these are easily achievable through a varied and balanced diet, with a diverse consumption of vegetables.

When to supplement

Vitamin K supplements should only be used under the guidance of a doctor or registered dietitian, and only when there is a deficiency of this vitamin in the blood. This can be confirmed through a blood tests.

In general, groups who are at a higher risk for low vitamin K include premature babies, people who have undergone bariatric surgery and people who take medications to reduce the absorption of fat in the intestine, as vitamin K is dissolved and absorbed into the body with fat from food.

Symptoms of a low vitamin K

Vitamin K deficiency is a rare condition, as this vitamin is present in several foods and is also produced by the gut (although the digestive tract should be in a healthy condition for adequate production). The main symptom of a lack of vitamin K is persistent bleeding that is difficult to stop, like a nosebleed, small wound, or in more severe cases, stomach ulcers. Patients with low vitamin K will also experience weakening of the bones.

Patients who have had bariatric surgery or who take medications to reduce fat absorption in the intestine also have a greater chance of being vitamin K deficient.

Excess vitamin K

Vitamin K in its natural form, which is obtained from food, has no toxic effects. However, when the supplement is taken in excessive amounts, it may have some side effects, such as irregular blood clotting, liver toxicity, hemolytic anemia or neurological problems, especially in newborns who receive injections of this vitamin.

Interaction with medications

It is important to highlight that people who are treated with anticoagulants, such as warfarin, should control their vitamin K intake, as increased consumption of this vitamin may interfere with the effects of this medication.

However, as it is an essential nutrient, it is not recommended to completely stop consuming foods rich in vitamin K. Instead, be sure to consume them in moderation and in appropriate serving sizes.

Furthermore, people who take antibiotics, cholesterol medications or weight loss medications may have problems absorbing this vitamin in the body and therefore develop a vitamin K deficiency. Patients on medications should be monitored by their doctor when supplementing with vitamin K.