A new US study has linked intakes higher than 800 IU of vitamin D per day with an up to 63% decreased risk of developing lung cancer in never-smoking, postmenopausal women.
The study analyzed the dietary and supplement intakes of vitamin D of 128,779 postmenopausal women, including 1,771 women who developed lung cancer within 17 years (1). While no significant association betwe-en vitamin D intakes and lung cancer risk was observed overall, a clear association with a lower risk of de-veloping lung cancer was seen among participants who never smoked in their lives and had a total vitamin D intake higher than 400 IU/day. Participants who took more than 800 IU per day had a 63% decreased risk of lung cancer compared to those who took less than 100 IU/day. Among the participants who had received a daily supplementation of 1 gram of calcium plus 400 IU of vitamin D3 or a placebo, a lung cancer risk reduc-tion was only observed in those who had a daily vitamin A intake lower than 1000 micrograms of retinol equivalents.
The researchers commented that vitamin D has been suggested to have cancer-preventing effects by regulating cell division and growth (proliferation) as well as the development of new blood vessels (angio-genesis) (2, 3). The observation that increased vitamin D intakes only showed efficacy among study partici-pants who never smoked may indicate that vitamin D may be more effective at preventing or reversing tumor development which is not tobacco-related. According to the scientists, the association between comb-ined vitamin D and calcium supplementation and lung cancer risk reduction observed in a subgroup of smo-king and non-smoking participants with lower vitamin A intake must be interpreted with caution because of the small number of lung cancer cases in this group. Increased intakes of beta-carotene in supplements did not influence lung cancer risk.