BIOAVAILABILITY AND HEALTH BENEFITS OF PHYTONUTRIENTS
Location: Food Components and Health Laboratory
Title: Vitamin K absorption and kinetics in human subjects after consumption of 13C-labeled phylloquinone from kale
Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 13, 2009
Publication Date: April 27, 2010
Citation: Novotny Dura, J., Kurilich, A.C., Britz, S.J., Baer, D.J., Clevidence, B.A. 2010. Vitamin K absorption and kinetics in human subjects after consumption of 13C-labeled phylloquinone from kale. British Journal of Nutrition. 104(6):858-62.
Interpretive Summary: Vitamin K functions in a number of biological reactions involved in blood clotting and bone metabolism. Green, leafy vegetables are particularly rich dietary sources of vitamin K. However, fiber and other plant matrix characteristics of vegetables can inhibit the absorption of nutrients from plants. To investigate the body’s ability to absorb vitamin K from a green, leafy vegetable, we tagged the vitamin K in kale and fed a large serving of the tagged kale to adult volunteers. After eating the kale, the volunteers provided multiple blood samples over the next month, and the blood samples were analyzed for appearance of the tagged vitamin K. Using specialized mathematical techniques, we calculated that about 5 percent of the vitamin K was absorbed from the kale. We were also able to use the data to determine the size of each subject’s body vitamin K stores and how fast the vitamin K was eliminated from the blood and tissues. These results will be useful to health professionals in developing improved intake recommendations for vitamin K.
The absorption and plasma elimination of vitamin K was investigated by uniformly labeling phylloquinone in kale with carbon-13 and feeding the kale to study subjects. Seven healthy volunteers ingested a single 400 g serving of kale with 30 g vegetable oil. The kale provided 156 nmol of phylloquinone. Serial plasma samples were collected and analyzed for the appearance of 13C-phylloquinone by HPLC-MS. Six of the subjects showed significant amounts of labeled phylloquinone in plasma, though one subject’s plasma was not consistently enriched above the detection limit, and this subject’s baseline plasma phylloquinone level was the lowest of the group. After ingestion of the labeled kale, plasma 13C-phylloquinone concentration increased rapidly to a peak between 6 and 10 h, then rapidly decreased. Average peak plasma concentration for the 6 subjects with detectable 13C-phylloquinone was 2.1 nmolar. Plasma concentration-time data was analyzed by compartmental modeling. Modeling results demonstrated a mean bioavailability of phylloquinone from kale to be 4.7%. Plasma and tissue half-times for phylloquinone were found to be 8.8 and 215 hours, respectively.