Human Nutrition 3(3+0)

Lesson 23 : Vitamin K

Toxicity

• High doses of vitamin K can reduce the effectiveness of anticoagulant drugs such as warfarin, which is used to prevent blood clotting. People taking these drugs should maintain a consistent daily intake of vitamin K.
• Megadose supplements of vitamin A and E may pose a risk to vitamin-K status.
• Vitamin A interferes with absorption of vitamin K, and large doses of vitamin E decrease vitamin K–dependent clotting factors, thus promoting bleeding.
• Toxicity from food is rare, because the body excretes vitamin K much more rapidly than other fat-soluble vitamins.