Does vitamin D help protect against cancer?
8th March 2018 – High levels of vitamin D may be linked to a lower risk of developing some cancers, a study has found.
Japanese-based researchers say the vitamin may be particularly effective at protecting against liver cancer.
The sunshine vitamin
Vitamin D is known as the 'sunshine vitamin' because our bodies produce it when sunlight falls on our skin. However, it is also present in some foods such as oily fish, eggs, and fortified breakfast cereals. It can also be taken as supplements.
Vitamin D deficiency may cause disorders associated with weak bones. However, some evidence has emerged suggesting that vitamin D may be associated with other diseases, including bowel and lung cancers.
However, associations with other types of cancers, as well as cancers overall, are not well documented.
These studies have mainly been carried out in European and American populations. The latest research, published in The BMJ, looked at whether the same link might be seen in an Asian population.
The researchers analysed data from a Japanese health study involving 33,736 men and women aged between 40 and 69. Participants had provided details about their medical history, diet, and lifestyle. Their vitamin D levels were measured from blood samples.
The participants were split into 4 groups, from the lowest to the highest levels of vitamin D.
Over an average of 16 years, 3,301 new cases of cancer were diagnosed.
The researchers found that participants in the quartile with the highest vitamin D levels had a 22% lower risk of cancer compared with those in the bottom quartile.
When they examined the effects on specific cancers, they found that higher vitamin D levels were also associated with a lower (30-50%) relative risk of liver cancer. This association was more evident in men than in women.
No association was found for lung cancer or prostate cancer.
The authors also note that none of the cancers examined showed there was any increased risk associated with higher vitamin D levels.
The conclusions were reached after the researchers took into account other factors linked to cancer, such as age, weight, physical activity levels, smoking, alcohol intake, and diet.
Evidence 'is mixed'
Commenting on the findings in an email, Sophia Lowes from Cancer Research UK, says: "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.
"It's not clear whether being deficient in this vitamin just reflects poor general health rather than having a direct impact on cancer risk.
"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."
In 2016, the Scientific Advisory Committee on Nutrition recommended that everyone over the age of 1 should have 10 micrograms of vitamin D each day to protect musculoskeletal health.
The committee also looked at possible links between vitamin D and other diseases, including cancer, but found insufficient evidence to draw any firm conclusions.