[Vitamin K adequacy ina representative sample of Spanish adults. Dietary determinants]

Vitamin K is an essential element in the coagulation, which is also involved in gamma-carboxylation reactions of proteins as osteocalcin, which may exert a protective effect against age-dependent bone loss. But there is also evidence that both osteocalcin as vitamin K can have a benefit on the metabolism of glucose, insulin sensitivity and type 2 diabetes mellitus. Therefore, the aim of the present study is to analyse the adequacy of vitamin K intake and food sources in a representative sample of Spanish adults.

A sample of 1068 adults (521 men and 547 women) with ages ranging from 17 to 60 years, was selected in ten Spanish provinces to constitute a representative sample of the population nationwide. The dietary study was carried out by using a "Food record questionnaire" for 3 consecutive days, including a Sunday. Personal, anthropometric and health data were also collected.

The intake of vitamin K (170.2 ± 14.5 μg/day) was lower than the established adequate intake for vitamin in the 30.2% of the studied participants. Vitamin intake increases with age (r = 0.201, p < 0.05), in fact, those participants who meet the adequate intake are older (34.5 ± 12.8 years) than those who do not meet the adequate intake (with a mean age 29.1 ± 11.9 years) (p < 0.001). Vitamin K intake also increases with weight (r = 0.106, p < 0.05) and height (r = 0.282, p < 0.05), however the participants with overweight/obesity have a significantly lower intake (168.2 ± 13.5 g/day) than those individuals with normal weight (171.1 ± 14.9 μg/day) (p < 0.01). The major food source of vitamin K are vegetables (45.35% of the intake comes from this food group), followed by fats and oils (13.28%), pulses (11.69%), meat (10.62%), cereals (5.33%) and fruits (4.60%). Meeting adequate intake for vitamin K is favoured by the increase in the consumption of vegetables (OR 0.329; CI95%: 0.279, 0.387), dairy (OR 0.815; CI95%: 0.690, 0.963), pulses (OR 0.091; CI95%: 0.054, 0.154) and fruits (OR 0.774; CI95%: 0.677, 0.885) (p < 0.001). A positive correlation was found between vegetable consumption and the intake of vitamin K (r = 0.432, p < 0.001). Adults with an inadequate intake of vitamin K have a lower consumption of vegetables (2.04 ± 1.16 servings/day) than adults with adequate intake (3.78 ± 1.65 servings/day) (p < 0.001).

The intake of vitamin K was lower than adequate intake in a significant percentage of the Spanish population (30.2%), which highlights the need to increase the consumption of vegetables, the major source of the vitamin (which are consumed in insufficient amount, by the 49.6% of the studied population), and to improve the diet as a whole, monitoring the intake of vitamin K, in order to obtain a nutritional and health benefit.