Friday, June 24, 2011

Vitamin K

A number of studies examining vitamin K are emerging due to its
effect with bone health and prevention of vascular calcification. This
nutrient is frequently avoided in patients on warfarin therapy; however,
adequacy and consistency of vitamin K intake are important for stable
PT-INRs.PT-INR is a lab test done to determine how long it takes for
the blood to clot (prothrombin time). Variability in clotting time can put
patients at risk for excessive bleeding if on warfarin.In CKD patients,
cardiovascular disease is a risk and a significant cause of mortality.

Calcium and vitamin D have long been identified as big players in the
prevention of osteoporosis. Osteopenic changes can occur rapidly in patients
after gastric bypass. However, vitamin K is a cofactor necessary for
activation of osteocalcin, a hormone that allows calcium to get into bone.
Insufficient vitamin K and subsequently inadequate levels of osteocalcin,
could impact calcium deposits in blood vessels and even the kidney. Both
vitamin D and vitamin K deficiencies have been associated with vascular
calcification in CKD patients.

Matrix Gla protein (MGP) is vitamin K dependent. It acts as a calcification
inhibitor in the vascular system. Adequate levels of MGP may play a
significant role in prevention of vascular calcification.

In a study reported in 2004, more than half of the patients four years post
BPD were shown to be deficient in vitamin K. As noted in the ASMBS article,
prothrombin time has been used as an indicator for deficiency and patients
post RYGB had levels suggestive of deficiency compared to LAGB patients and
controls.This may not only be an issue for patients who have
malabsorptive bariatric procedures. There was a case report of fetal
cerebral hemorrhage resulting from maternal vitamin K deficiency following
gastric adjustable banding.

It is reasonable to evaluate food intake in patients with hemodialysis
following weight loss surgery, as some foods that may be discouraged due to
elevated serum potassium or phosphorus levels may also be those that are a
good sources of vitamin K.

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