High levels of vitamin D may be linked to a lower risk of developing cancer, including liver cancer, a study published today in the British Medical Journal has said.
The researchers said their findings support the theory that vitamin D might help protect against some cancers.
Vitamin D is made by the skin in response to sunlight. It helps to maintain calcium levels in the body to keep bones, teeth and muscles healthy.
While the benefits of vitamin D on bone diseases are well known, there is growing evidence vitamin D may benefit other chronic diseases, including some cancers.
But so far, most studies have been carried out in European or American populations, and evidence from Asian populations is limited.
As vitamin D concentrations and metabolism can vary by ethnicity, research was carried out to see whether similar effects would be seen in non-Caucasian populations.
They analysed data from the Japan Public Health Centre -based Prospective (JPHC) Study, involving 33,736 male and female participants aged between 40 to 69 years of age.
At the start of the study, participants provided detailed information on their medical history, diet and lifestyle, and blood samples were taken to measure vitamin D levels.
Vitamin D levels varied depending on the time of year the sample was taken, tending to be higher during the summer and autumn months than in the winter or spring.
After accounting for this seasonal variation, samples were split into four groups, ranging from the lowest to highest levels of vitamin D.
Participants were then monitored for an average of 16 years, during which time 3,301 new cases of cancer were recorded.
After adjusting for several known cancer risk factors, such as age, weight (BMI), physical activity levels, smoking, alcohol intake and dietary factors, the researchers found that a higher level of vitamin D was associated with a lower (around 20 per cent) relative risk of overall cancer in both men and women.
Higher vitamin D levels were also associated with a lower (30 to 50 per cent) relative risk of liver cancer, and the association was more evident in men than in women.
No association was found for lung or prostate cancer, and the authors note that none of the cancers examined showed an increased risk associated with higher vitamin D levels.
The authors said their findings support the theory that vitamin D may protect against the risk of cancer, but that there may be a ceiling effect, which may suggest that there are no additional benefits beyond a certain level of vitamin D.
“Further studies are needed to clarify the optimal concentrations of vitamin D for cancer prevention,” the study’s authors concluded.
Source: Irish Times