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Sunshine vitamin could halve the risk of liver cancer

Vitamin D is manufactured by the body when the skin is exposed to sunlight. Image : Shutterstock
Vitamin D is manufactured by the body when the skin is exposed to sunlight. Image : Shutterstock

Researchers have found that people with higher levels of vitamin D have a reduced risk of developing the most common form of liver cancer, a disease with a particularly poor survival rate as it is often diagnosed at a late stage.

To combat this poor prognosis, European scientists are conducting a number of studies into the causes of liver cancer, which is on the rise in some European countries including the UK and France.

The research linking blood levels of vitamin D – the so-called sunshine vitamin – to the disease was carried out using data from the EPIC database, part-funded by the EU, which holds twenty years’ worth of information on the health and diet of more than 520 000 people from 10 European countries.

The study included 138 people from EPIC who had developed hepatocellular carcinoma, the most common form of liver cancer. The levels of vitamin D in their blood, taken prior to their cancer diagnosis, was compared with the vitamin D levels in control subjects who had not gone on to develop the disease.

They found that higher blood vitamin D levels were linked to a 49 % reduction in the risk of liver cancer, which held true regardless of factors such as obesity, smoking, pre-existing liver damage and liver ailments such as infectious hepatitis.

‘EPIC has produced an exceptionally large number of scientific publications and results that have highlighted how nutrition, obesity, for example, and related factors influence the incidence of cancer.’

Professor Elio Riboli, EPIC Coordinator at Imperial College London.

‘Vitamin D has been a focus of attention in cancer prevention during the last several decades due to its anti-carcinogenic effects,’ said Dr Veronika Fedirko, Assistant Professor of Epidemiology at Emory University in the United States, who led the project. ‘Our findings suggest a role for vitamin D in the aetiology (cause) of hepatocellular cancer, but it remains to be determined whether the association is causal as there may be other factors involved.’ 

Dr Mazda Jenab, the senior author and a scientist at the International Agency for Research on Cancer, added that there is steadily growing scientific evidence that low levels of vitamin D in the blood are a sign of increased risk for various cancers, in particular colorectal cancer, but that ‘public health advocacy for vitamin D supplementation for cancer prevention must be based on more evidence’.

Although there is some basic scientific evidence supporting the association between vitamin D and liver health, the study was the first detailed investigation into whether there is a direct link between levels of the vitamin and liver cancer in Europe.

Vitamin D is an unusual vitamin in that it is manufactured by the body when skin is exposed to sunlight. It is difficult to get adequate levels from food alone and people may need to take supplements to top up their levels, particularly in the winter months when sunshine is limited.

This finding is one of the latest to emerge from data collected through the EPIC project, which was set up in 1993 to investigate the link between nutrition and health.

‘For investigating cancers, and especially rare cancers such as hepatocellular carcinoma, it is very important to have access to a large cohort such as EPIC,’ said Dr Fedirko. ‘EPIC provides a unique opportunity to look at various exposures before the onset of disease, and multiple health outcomes that are very important for European and global populations.’

The health, nutrition and lifestyle data of half a million people has been tracked over two decades, meaning researchers now have access to a rich source of information for their work. This information includes details on the dietary and nutritional profile of more than 70 000 people who have gone on to develop cancer.

Importantly, the project collected data and blood samples from participants when they were healthy, meaning that it is one of the world’s best resources for exploring the causes of disease and identifying biomarkers for early detection. ‘In helping to fund and build this key resource, the EU has put itself at the forefront of research into cancer prevention,’ said Dr Isabelle Romieu from the International Agency for Research on Cancer, one of the project’s principal investigators.

In a previous study also using data from EPIC, the same researchers demonstrated that people with high levels of vitamin D in their blood were 40 % less likely to develop bowel cancer than people with low levels.

‘EPIC has produced an exceptionally large number of scientific publications and results that have highlighted how nutrition, obesity, for example, and related factors influence the incidence of cancer,’ said Professor Elio Riboli, EPIC coordinator at Imperial College London.

Other results to have come out of the data so far include a link between several cancers and excessive alcohol consumption and obesity, as well as an association between diet and cancer, with diets high in fish, fibre or low in red and processed meat reducing bowel cancer risk.

‘EPIC is now a very mature resource for research which is available to the scientific community,’ said Prof. Riboli.

Obesity links

The likelihood of developing liver cancer also increases four-fold if you are obese, a connection which is being investigated by the EU-funded OBECAN project.

There are several reasons for this link. One is that obese people store excess fat in their livers, which puts them at risk of fatty liver disease and cirrhosis, the biggest risk factor for liver cancer. Another is that obesity can lead to insulin resistance, which can make tumours grow faster, and the final link is that obese people also tend to have higher levels of inflammation in their bodies.

Dr Guadalupe Sabio Buzo, leader of OBECAN, said the project is trying to establish the most important factors associating obesity with liver cancer. ‘Is it the insulin, the fatty liver, or the inflammation?’ she said. ‘What is important to target or control in obese people to ensure that they get less liver cancer?’

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