Recommended daily intake of vitamin K
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Recommended Daily Intake of Vitamin K: Guidelines and Key Insights
Vitamin K Daily Intake Recommendations for Adults
Most health authorities recommend an adequate intake (AI) of vitamin K at 1 microgram per kilogram of body weight per day for adults, which typically translates to about 70–80 micrograms per day for a healthy adult, regardless of sex or age group 136. Some guidelines specify 45 micrograms per day for men and 35 micrograms per day for women, based on maintaining normal blood clotting function . For adults, intakes of around 100 micrograms per day are commonly cited as sufficient to maintain hemostasis and prevent deficiency .
Vitamin K Intake for Special Populations
- Infants and Children: The recommended intake is lower, with 10 micrograms per day for infants aged 7–11 months, and increasing from 12 micrograms per day for children aged 1–3 years up to 65 micrograms per day for those aged 15–17 years .
- Pregnancy and Lactation: The same AI of 1 microgram per kilogram of body weight per day is recommended for pregnant and lactating women .
- Newborns: Supplementation is strongly advised due to low vitamin K content in breast milk and immature gut flora .
Vitamin K1 (Phylloquinone) vs. Vitamin K2 (Menaquinones)
Most recommendations focus on vitamin K1 (phylloquinone), as there is insufficient evidence to set dietary reference values for vitamin K2 (menaquinones) 36. However, some research suggests that vitamin K2, especially at higher intakes (up to 180 micrograms per day), may offer additional benefits for bone and cardiovascular health, and that current recommendations may be too low for optimal health in adults 47.
Typical Dietary Intakes and Food Sources
- Average Intake: Studies show that young adults typically consume about 80 micrograms of vitamin K per day, while older adults may consume up to 150 micrograms per day 18.
- Food Sources: The main sources of vitamin K1 are leafy green vegetables and certain vegetable oils, while vitamin K2 is found in eggs, meat, and fermented foods 158.
- Bioavailability: Vitamin K from food sources is not always well absorbed, and the majority of vitamin K in the diet comes from a limited number of foods 14.
Safety and Upper Limits
There is no established tolerable upper intake level for vitamin K, as no adverse effects have been reported from high intakes of natural forms of the vitamin in healthy individuals 69. Guidance levels for supplements suggest that up to 1,000 micrograms per day of phylloquinone is considered safe for adults .
Regional and Population-Specific Recommendations
- China: For healthy middle-aged and elderly people, suggested adequate intakes are 90 micrograms per day for total vitamin K, with 80 micrograms from vitamin K1 and 10 micrograms from vitamin K2 .
- Nordic Countries and Europe: Average intakes are around 100–150 micrograms per day, with recommendations aligning closely with the 1 microgram per kilogram body weight guideline 368.
Conclusion
The recommended daily intake of vitamin K for adults is generally set at 1 microgram per kilogram of body weight per day, or about 70–80 micrograms daily, with higher intakes potentially beneficial for certain health outcomes. Most guidelines focus on vitamin K1, but emerging evidence suggests vitamin K2 may also be important, especially for bone and cardiovascular health. There is no known risk of toxicity from natural dietary sources, and maintaining a consistent intake is especially important for individuals on anticoagulant therapy.
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