This article is more than 2 years old

This article is more than 2 years old

Vitamin D may offer protection against cancers, new research suggests, although experts are split over whether individuals should start taking supplements.

The vitamin plays an important role in the body, including in bone health and muscle strength and in preventing conditions such as rickets.

It is produced when sunlight hits our skin, can also be found in certain foods such as eggs and fatty fish, and can be taken as a supplement.

Now researchers in Japan say higher levels of the vitamin are linked to a lower risk of cancer, in particular liver cancer.

“We believe vitamin D has a maybe weak, but beneficial effect across many cancers,” said Taiki Yamaji, coauthor of the study from the Center for Public Health Sciences at the National Cancer Center in Tokyo.

It is not the first study to suggest that people with low levels of vitamin D might be at increased risk of a number of cancers, but the evidence is far from clear, with some studies showing no such effect and others suggesting protective effects against particular cancers but not others.

The latest study, published in the BMJ, sought to unpick the issue. The team looked at levels of the biologically active form of vitamin D in blood samples taken from more than 30,000 middle-aged individuals at health centres across Japan during the early 1990s. The participants were followed up over a median of 16 years.

The researchers based their analysis on data from 3,301 participants who developed cancer after signing up to the study and 4,044 randomly selected participants, 450 of whom developed cancer.



After taking into account factors including age, sex, smoking status and family history of cancer, as well as seasonal differences in circulating vitamin D, the team found that higher levels of circulating vitamin D are linked to a lower risk of cancer overall.



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Compared with the quartile of participants with the lowest levels of circulating vitamin D, the quartile with the highest levels had a 22% lower risk of cancer. The team say there was no difference in the effect of vitamin D based on sex.

Looking at specific cancers, the team found about a 50% lower risk of liver cancer, once diet was also considered, for the group with the highest vitamin D levels compared with the lowest.



A weaker effect was found for premenopausal breast cancer but there was no clear link for other cancers, including lung cancer, colorectal cancer, prostate cancer or breast cancer as a whole.

The team found that the link to a lower total cancer risk was seen even when liver cancer was taken out of the mix. That, said Yamaji, could be because smaller effects of vitamin D on other cancers might add up when they are considered together.

However, the authors note that the study has limitations, including that levels of vitamin D were only taken at one point in time, that participants might have been more health-conscious than the general public and that the number of cases of rare cancers was small.

Sophia Lowes from Cancer Research UK said: “Although this study suggests that higher vitamin D levels in the blood could mean lower cancer risk in Asian populations, overall the evidence for a possible link has been mixed.”

Lowes added that it was not clear whether being deficient in vitamin D has a direct impact on cancer risk or just reflects poor health in general. “Enjoying the sun safely, while taking care not to burn and increase skin cancer risk, should help most people get enough vitamin D in summer,” she said.



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Julia Newton-Bishop, professor of dermatology and vitamin D expert from the University of Leeds, said the study chimed with others that had found a protective effect from vitamin D against cancer deaths.

Newton-Bishop said the latest study was consistent with findings from the scientific advisory committee on nutrition, which recommended that Britons should be taking 10 micrograms of vitamin D per day, given the variability in sunshine around the country and with seasons.

Newton-Bishop added: “I suspect from this paper and from other papers that vitamin D does have an effect, but it is relatively modest and it is more about avoiding a low level than taking high levels.”