Vitamin K is considered to be involved in the pathological mechanisms of coronary artery calcification (CAC). Correlation between CAC and plasma vitamin K levels was studied. A total of 103 patients, with at least one coronary risk factor, were studied. CAC was measured using 64-slice multislice computed tomography (MSCT) and divided into three groups: none (CAC score = 0; n 25), mild to moderate (0 < CAC score < 400; n 52) and severe (CAC score > 400; n 26). Phylloquinone (PK) and menaquinone (MK)-4 and MK-7 were measured by HPLC-tandem MS. Mean age of patients was 64 (sd 13) years, of which 57 % were male. Median CAC score was 57·2. Median levels of PK, MK-4 and MK-7 were 1·33, 0 and 6·99 ng/ml, showing that MK-7 was the dominant vitamin K in this population. MK-7 showed a significant inverse correlation with uncarboxylated osteocalcin (ucOC, P = 0·014), protein induced by vitamin K absence of antagonist-2 (PIVKA-2, P = 0·013), intact parathyroid hormone (P = 0·007) and bone-specific alkaline phosphatase (P = 0·018). CAC showed an inverse correlation with total circulating uncarboxylated matrix Gla protein (t-ucMGP, P = 0·018) and Hb (P = 0·05), and a positive correlation with age (P < 0·001), creatinine, collagen type 1 cross-linked N-terminal telopeptide (NTX, P = 0·03), pulse wave velocity (P < 0·001) and osteoprotegerin (P < 0·001). However, CAC did not have a significant correlation with plasma levels of PK, MK-4 or MK-7. In conclusion, plasma MK-7, MK-4 or PK level did not show significant correlation with CAC despite the association between plasma vitamin K levels and vitamin K-dependent proteins such as ucOC or PIVKA-2.

Vitamin K acts as a cofactor during the γ-carboxylation of vitamin K-dependent proteins. Undercarboxylated osteocalcin (ucOC) is a suggested biomarker of vitamin K status. The +2255 polymorphism of the vitamin K epoxide reductase gene (VKORC1) was shown to be associated with the recycling rate of the active form of vitamin K. We investigated the association between dietary vitamin K intake and serum ucOC and hypothesized that this association might vary by VKORC1 genotype. ucOC and total intact osteocalcin (iOC) concentrations were quantified using specific ELISA tests in serum samples of 548 male and female participants (aged 18–81 years) of the Bavarian Food Consumption Survey II. ucOC was expressed relative to iOC (ucOC/iOC ratio). Dietary intake of vitamin K (phylloquinone and menaquinones) was estimated from three 24 h dietary recalls using previously published food composition data. The association between dietary vitamin K intake and ucOC/iOC ratio was analysed using linear and non-linear regression models. Median intakes of phylloquinone/menaquinones were 83·4/37·6 μg/d in men and 79·6/29·8 μg/d in women, respectively. As expected, vitamin K intake was significantly inversely associated with the ucOC/iOC ratio. The ucOC/iOC ratio differed significantly across variants of the +2255 polymorphism in the VKORC1 gene. Stratification by VKORC1+2255 genotype revealed that only in carriers of the GG genotype (39 % of all participants) did the ucOC/iOC ratio significantly decrease with increasing intake of vitamin K. Thus, the results show that the inverse association between dietary vitamin K intake and serum ucOC depends on a functionally relevant allelic variant of the VKORC1 gene.

Phylloquinone is converted into menaquinone-4 and accumulates in extrahepatic tissues. Neither the route nor the function of the conversion is known. One possible metabolic route might be the release of menadione from phylloquinone by catabolic activity. In the present study we explored the presence of menadione in urine and the effect of vitamin K intake on its excretion. Menadione in urine was analysed by HPLC assay with fluorescence detection. Urine from healthy male volunteers was collected before and after administration of a single dose of K vitamins. Basal menadione excretion in non-supplemented subjects (n 6) was 5·4 (sd 3·2) μg/d. Urinary menadione excretion increased greatly after oral intake of the K vitamins, phylloquinone and menaquinone-4 and -7. This effect was apparent within 1–2h and peaked at about 3h after intake. Amounts of menadione excreted in 24h after vitamin K intake ranged, on a molar basis, from 1 to 5% of the administered dose, indicating that about 5–25% of the ingested K vitamins had been catabolized to menadione. Menadione excretion was not enhanced by phylloquinone administered subcutaneously or by 2′,3′-dihydrophylloquinone administered orally. In archived samples from a depletion/repletion study (Booth et al. (2001)Am J Clin Nutr74, 783–790), urinary menadione excretion mirrored dietary phylloquinone intake. The present study shows that menadione is a catabolic product of K vitamins formed after oral intake. The rapid appearance in urine after oral but not subcutaneous administration suggests that catabolism occurs during intestinal absorption. The observations make it likely that part of the menaquinone-4 in tissues results from uptake and prenylation of circulating menadione

To explore whether differences in vitamin K nutrition might, at least in part, underlie differences in fracture incidence between Asian and European populations, the vitamin K status of older individuals in Shenyang, China (eighty-six men, ninety-two women) and in Cambridge, UK (sixty-seven men, sixty-seven women) was compared. Dietary information was collected by food questionnaire in Shenyang and food diary in Cambridge and used to estimate the intake and sources of phylloquinone. Fasting blood was analysed for phylloquinone, triacylglycerol, total osteocalcin (tOC) and undercarboxylated osteocalcin (expressed as percentage of tOC; %ucOC). The mean intakes of green leafy vegetables were 127 (SD 90) g/d in Shenyang and 39 (SD 48) g/d in Cambridge. The estimated phylloquinone intakes (geometric means) were 247 (95% CI 226, 270) μg/d in Shenyang and 103 (95% CI 94, 112) μg/d in Cambridge. Plasma phylloquinone concentrations (geometric means) were significantly higher in the Shenyang subjects (2·17 (95% CI 1·95, 2·42) nmol/l) than in the Cambridge subjects (0·69 (95% CI 0·63, 0·76) nmol/l; P<0·001). Plasma phylloquinone concentration was positively related to phylloquinone intake in both the Shenyang (coefficient 0·17 (SE 0·08); P=0·03) and Cambridge subjects (coefficient 0·29 (SE 0·10); P=0·005). tOC concentration and %ucOC (after adjusting for tOC) were significantly lower in the Shenyang than in the Cambridge subjects (tOC 25·2 (SE 4·2) % and %ucOC 68·5 (SE 10·0) % lower respectively; P<0·001). After adjusting for tOC and triacylglycerol, %ucOC was negatively related to plasma phylloquinone concentration in both the Shenyang (coefficient −0·41 (SE 0·11); P=0·0003) and Cambridge subjects (coefficient −0·17 (SE 0·07); P=0·02). The present study demonstrates that older individuals in northern China have a better vitamin K status compared with their British counterparts in Cambridge, UK.

The difference between vitamin K metabolism in the liver and that in the bone of vitamin K-deficient rats was examined. After 17 d administration of vitamin K-deficient food, vitamin K in the liver was almost depleted, and prothrombin time (PT) was prolonged. Serum total osteocalcin level was slightly decreased by vitamin K deficiency, whereas serum undercarboxylated osteocalcin level did not change. The level of menaquinone (MK)-4 as well as that of phylloquinone was decreased, but approximately 40 % of the initial level still existed in the femur after the 17 d period. A single-dose administration of vitamin K (250 nmol/kg body weight) markedly increased vitamin K level in the liver but not in the femur. These results suggest that the turnover of vitamin K in the bone is slower than that in the liver, and bone metabolism may be little affected by the short period of intake of vitamin K-deficient food. However, intake of a larger amount of vitamin K is required for its accumulation in the bone than in the liver. Furthermore, the counteracting effect of MK-7 on prolonged PT in vitamin K-deficient rats was found to be higher than phylloquinone or MK-4.

The effect of maternal phylloquinone supplementation on vitamin K in breast milk was studied to establish: (1) if phylloquinone is the source of menaquinone-4 in breast milk; (2) the dose–effect relationship between intake and obtainable levels. Four groups of lactating mothers with a full-term healthy infant participated and took oral phylloquinone supplements of 0·0 (n 8), 0·8 (n 8), 2·0 (n 8), and 4·0 (n 7) mg/d for 12 d, starting at day 4 post-partum. Milk samples were collected on days 4, 8, 16, and 19. Blood samples were collected on days 4 and 16. Vitamin K and vitamin E concentrations, the latter for reason of comparison, were assayed. Phylloquinone and menaquinone-4 were present in all milk samples: 5·84 (SD 2·31) AND 2·98 (sd 1·51) nmol/l (n 31) respectively, in colostrum (day 4 sample). A strong correlation between the vitamers was found (r 0·78, P<0·001). Breast-milk phylloquinone levels were raised in a dose-dependent manner: 4-, 12-, and 30-fold on day 16 for the 0·8, 2·0, and 4·0 mg group respectively. In addition, menaquinone-4 levels were higher: 2·5- (P<0·05) and 7-fold (P<0·001) in the 2·0 and 4·0 mg groups respectively. Plasma of supplemented subjects contained 3-, 5-, and 10-fold higher phylloquinone levels on day 16. Detectable menaquinone-4 was found in ten of thirty-one day 4 plasma samples. All day 16 plasma samples of the 4 mg supplemented group contained the vitamin. There was no correlation between the K-vitamers in plasma. Vitamin E and phylloquinone appear to differ in their distribution in breast milk, milk:plasma concentration ratios were ≤1 and 3–5 for vitamin E and phylloquinone respectively. The milk:plasma concentration ratio of menaquinone-4 was >10. In conclusion, dietary phylloquinone is a source of menaquinone-4 in breast milk. Phylloquinone supplementation to lactating mothers may be of benefit to the newborn infant, since both phylloquinone and menaquinone-4 are raised by supplementation.

This paper reports the compilation of a food composition database for phylloquinone (vitamin K1) derived from the direct analysis of foods, recipe calculation and the assignment of values based on food similarities. All the basic and other food items used in these calculations had been analysed by HPLC and about 170 of the items had been obtained and assayed in the UK. Recipe calculations took account of the cooking method and changes in water and fat content. Currently, approximately 1501 food items with Royal Society of Chemistry/Ministry of Agriculture, Fisheries and Food food codes have been allocated a vitamin K1 value, and a further 282 new recipe codes are included in the database. Representative values from each food group are reported together with an indication of the potential variation. Detailed examples of some recipe calculations are included, and also the impact of changing the type of fat in recipes. Vitamin K1 is associated with, and most abundant in, photosynthetic tissues of plants. Accordingly, the highest concentrations (3000–6000 μg/kg) are found in dark-green leafy vegetables and herbs, such as kale, parsley, spinach and green cabbage. Intermediate concentrations (1000–2000 μg/kg) are found in plants with paler leaves such as white cabbage and lettuce or in green, non-leafy vegetables such as broccoli and brussel sprouts. Fats and oils contain variable amounts of vitamin K1 with the highest concentrations (300–1300 μg/kg) in soyabean, rapeseed and olive oils and the margarines based on them. Other foods such as dairy products, meat dishes and cereal-based foods (bread, biscuits, cakes, desserts etc.), although not in themselves particularly rich in vitamin K1 (< 200 μg/kg), may contribute significantly to intakes when consumption of green vegetables is poor. Within the scope of this present study, it has not been possible to address issues such as inter-sample variability, losses during storage or the bioavailability from different foods and further work on these aspects is needed.

The aim of the present study was to assess how high doses of dietary vitamin K influence the intestinal profile of K-vitamins in vitamin K-deficient rats, and whether the induced changes are reflected in the hepatic vitamin K store. Vitamin K-deficient rats were fed for 10 d on diets containing different forms of vitamin K, and it was determined how these diets affected the vitamin K concentration at various sites of the instestine, serum, and the liver. It was found that the absorption of phylloquinone from standard food is not more than 10 %, while the absorption of pharmacological doses of oil-solubilized phylloquinone and menaquinone-4 was also far from complete (18 and 55 % respectively). High intakes of phylloquinone suppress the colonic production of all higher menaquinones. High menaquinone-4 intake induces very high menaquinone-8 concentrations, both in the colonic contents as well as in the liver. These data suggest that menaquinone-4 may be converted into menaquinone-8 (but not into other menaquinones) via a metabolic pathway which has not been reported previously.

The human vitamin K requirement is not known precisely, but the minimal requirement is often assumed to be between 0·5 and 1 x 10−6g/kg body weight. In the present study we addressed the question to what extent circulating vitamin K concentrations are influenced by the form in which the vitamer is consumed. The experimental group consisted of five healthy volunteers who received phylloquinone after an overnight fast. On the first day of three successive weeks the participants consumed 1 mg (2·2 µmol) phylloquinone, either in the form of a pharmaceutical preparation (Konakion®), or in the form of spinach + butter, or as spinach without added fat. Circulating phylloquinone levels after spinach with and without butter were substantially lower (7·5- and 24·3-fold respectively) than those after taking the pharmaceutical concentrate. Moreover, the absorption of phylloquinone from the vegetables was 1·5 times slower than from Konakion. In a second experiment in the same five volunteers it was shown that relatively high amounts of menaquinone-4 enter the circulation after the consumption of butter enriched with this vitamer. It is concluded that the bioavailability of membrane-bound phylloquinone is extremely poor and may depend on other food components, notably fat. The bioavailability of dietary vitamin K (phylloquinone+menaquinones) is lower than generally assumed, and depends on the form in which the vitamin is ingested. These new insights may lead to a revision of the recommended daily intake for vitamin K.

We measured the vitamin K status in postmortem human tissues (brain, heart, kidney, liver, lung, pancreas) to see if there is a tissue-specific distribution pattern. Phylloquinone (K1,) was recovered in all tissues with relatively high levels in liver, heart and pancreas (medians, 10·6 (4·8), 9·3 (4·2), 28·4 (12·8) pmol(ng)/g wet weight tissue); low levels (< 2 pmol/g) were found in brain, kidney and lung. Menaquinone-4 (MK-4) was recovered from most of the tissues; its levels exceeded the K1 levels in brain and kidney (median, 2·8 ng/g) and equalled K1 in pancreas. Liver, heart and lung were low in MK–4. The higher menaquinones, MK-6–11, were recovered in the liver samples (n 6), traces of MK-6–9 were found in some of the heart and pancreas samples. The results show that in man there are tissue-specific, vitamin-K distribution patterns comparable to those in the rat. Furthermore, the accumulation of vitamin K in heart, brain and pancreas suggests a hitherto unrecognized physiological function of this vitamin.

The present study was undertaken to determine whether there is selective tissue distribution of vitamin K in the rat and whether this distribution mirrors the distribution of tissue vitamin K metabolism. The effects of feeding a vitamin K-free diet followed by resupplementation with phylloquinone (K1) were studied. K1 was recovered in all tissues. In K1 -supplemented rats, most tissues accumulated K1 relative to plasma K1 with the highest levels in liver, heart, bone, and cartilaginous tissue (sternum). Low K1 levels were found in the brain. In the K1-free rats, relatively high K1 levels were still found in heart, pancreas, bone and sternum. Surprisingly, menaquinone-4 (MK-4) was detected in all tissues, with low levels in plasma and liver, and much higher levels in pancreas, salivary gland and sternum. MK-4 levels exceeded K1 levels in brain, pancreas, salivary gland and sternum. Supplementation with K1, orally and by intravenous infusion, caused MK-4 levels to rise. Some accumulation of K1 and MK-4 in the mitochondrial fraction was found for kidney, pancreas and salivary gland. In the liver the higher menaquinones (MK-6–9) accumulated in the mitochondria. The results indicate that: (1) there is selective tissue distribution of K1 and MK-4, (2) dietary K1 is a source of MK-4. The results also suggest there may be an as yet unrecognized physiological function for vitamin K (MK-4).