People with higher dietary intake of vitamin K are less likely to develop or die of cancer, particularly lung or prostate cancers.
Vitamin K exists in two natural forms: vitamin K1, or phylloquinone, found largely in green leafy vegetables, as well as some vegetable oils, such as canola and soybean oils; and vitamin K2, or menaquinone, for which meat and cheese are the primary dietary sources.
To evaluate the association between dietary intake of vitamin K1 and vitamin K2, researchers analysed data on 24,340 cancer-free German adults, aged between 35 and 64 years. The researchers estimated the participants' usual vitamin K intake based on a detailed dietary questionnaire. Over the next decade, 1,755 participants were diagnosed with colon, breast, prostate or lung cancers, of whom 458 died during the study period.
It was found that one quarter of the study participants with the highest intake of vitamin K2 were 28 percent less likely to have died of any of the cancers than the one-quarter of men and women with the lowest intake of vitamin K2, even when factors like age, weight, exercise habits, smoking and consumption of certain other nutrients, like fibre and calcium, were taken into account. Of the one-quarter of study participants who got the least vitamin K2, 156 - or 2.5 percent - died of one of the four cancers, while 1.5 percent of participants with the highest intake of vitamin K2.
When the researchers looked at the cancer types individually, there was no clear link between either form of vitamin K and breast cancer or colon cancer. However, higher consumption of vitamin K2 was linked to a lower risk of developing or dying from lung cancer - a disease for which smoking is the major risk factor - or of developing prostate cancer. Of the one-quarter of study participants with the lowest vitamin K2 intakes, 47 - or 0.8 percent - developed lung cancer, versus 0.4 percent of the one-quarter who got the most vitamin K2 in their diets. When it came to prostate cancer, there were 111 cases among the one-quarter of men with the lowest vitamin K2 intakes, and 65 cases in the group with the highest consumption.
The results suggest that vitamin K2 provides protection against the risk of developing various cancer types of cancer, lung and prostate cancer in particular. However, further studies of dietary vitamin K and prostate cancer are warranted.