Women with a low vitamin K intake may be at increased risk of bone fractures, suggests research in this month's American Journal of Clinical Nutrition.
Low dietary vitamin K intake has been associated with an increased risk of hip fracture in men and women but the team from the US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston noted that there is little data on the association between dietary vitamin K intake and bone mineral density (BMD).
The researchers studied self-reported dietary vitamin K intake and measured BMD of the hip and spine in just over 1100 men and almost 1500 women aged 29 to 86 years old.
One of the most common forms of vitamin K is phylloquinone, which is found in some oils, especially soybean oil, and in dark-green vegetables such as spinach and broccoli.
Dietary and supplemental intakes of vitamin K were assessed with the use of a food-frequency questionnaire. They also accounted for factors including age, body mass index, smoking status, alcohol use, physical activity score, and menopause status and current oestrogen use among the women.
The team reports that women with the lowest vitamin K intake (around 70.2 µg daily) had significantly lower mean BMD than those with the highest intake of vitamin K (around 309 µg daily). These associations remained after controlling for variables and after stratification by age or supplement use. However no significant association was found between dietary vitamin K intake and BMD in men, they said.
The authors concluded: "Low dietary vitamin K intake was associated with low BMD in women, consistent with previous reports that low dietary vitamin K intake is associated with an increased risk of hip fracture. In contrast, there was no association between dietary vitamin K intake and BMD in men."