Vitamin K

Vitamin K interactions:

Vitamin K and use of antibiotics: Vitamin K levels may be reduced by the use of any antibiotics, especially quinolones partly due to the reduction of gut flora which contributes to production of vitamin K. This may be especially be concerning when a patient is taking warfarin with antibiotics which may result in significant elevation of the PTINR and should be monitored by daily PTINR levels. (1)

Vitamin K affected by vitamin E intake:

Vitamin K level may be reduced by vitamin E intake. Researchers conducted a study to determine if vitamin E supplementation affects vitamin K status or blood clotting time in patients not treated with warfarin. Their study involved 38 men and women with rheumatoid arthritis and 32 healthy men participating in two independent 12-week randomized clinical trials of vitamin E supplementation. All trial participants were given 1000 IU/day of natural vitamin-E. The researchers used plasma concentration of proteins induced by vitamin K absence-factor II, or PIVKA-II for short, as a sensitive measure of vitamin K status. A normal value for PIVKA-II is 2.4 ng/mL or less and values higher than this indicate poorer vitamin-K status. At the end of the 12-week supplementation period PIVKA-II had increased from 1.7 to 11.9 ng/mL in the rheumatoid arthritis group and from 1.8 to 5.3 ng/mL in healthy men. Thus, it would appear that supplementation with a high dose of vitamin E does indeed reduce body stores of vitamin K. The researchers concluded that high-dose vitamin E supplementation does reduce vitamin K status, but are uncertain whether this interaction is immaterial, beneficial (reduced stroke risk) or harmful (loss of bone density). (2)