High levels of the sunshine vitamin are likely to protect against breast cancer.
Women with high levels of Vitamin D have shown an 80pc reduction in the risk of the cancer.
A group of women aged 55 or older and without any cancer were studied over four years.
Their blood Vitamin D levels were monitored during this time.
Women with high levels of the vitamin cut their risk of breast cancer to one fifth of the risk for those who did not.
The study was limited to postmenopausal breast cancer. It showed “the strongest association yet between serum vitamin D and reduction of breast cancer,” said Professor Cedric Garland of the US San Diego Department of Family Medicine and Public Health.
Prof Garland has advocated the health benefits of vitamin D for many years.
In 1980, he and his late brother Frank C. Garland, also an epidemiologist, found that vitamin D had a favourable effect on breast, lung and bladder cancers, multiple myeloma and adult leukemia.
The study is published in the online issue of PLOS ONE.