Wednesday, 7 May 2014

How healthy eating could starve out cancer

Image Source: Serial/Trash
Skin is not the only thing to wrinkle with age. Our genes also show signs of ageing – a process that can lead to cancer. A new study indicates that healthy eating can prevent cancer development and explains how this works.
When genes get old
Thanks to modern medical advancements, our average life expectancy has increased dramatically in recent decades. However, there is a paradox in our longevity: we now live long enough to develop cancer. Cancer is a genetic disease and, as we age, our genes – like our body – become more vulnerable. Some genes accumulate genetic mutations: if you think of genes as cookbooks for proteins, then these mutations are like typing errors in the recipe. Others acquire epigenetic modifications, which affect the way a gene works rather than its content – which, to use our analogy again, is like not being able to open and close the cookbook anymore. Both genetic and epigenetic changes can lead to cancer; however, the latter are especially interesting because they are affected by environmental factors that we can actually control, such as our diet.
How can we keep our genes young and prevent cancer? This is what Dr Nigel Belshaw, at the Institute of Food Research in Norwich UK, wanted to discover. His team looked for environmental factors that affect epigenetic markers associated with early colon cancer – a common and lethal cancer, responsible for over 610,000 deaths worldwide each year. Preventing colon cancer with small lifestyle changes would be a cheap, highly effective, and low-risk approach that turns the tide against this disease.
 Image Source: Shutterstock Copyright: Sebastian Kaulitzki
Lifestyle and cancer risk: the mystery unfolds
The researchers analysed a specific type of epigenetic modification called DNA methylation. Like other epigenetic markers, DNA methylation is a genetic switch: it can turn genes on and off, it can make the cookbook readable or make it impossible to open.
Our genes are hidden in tightly-wound DNA which is about two metres long in every single cell of our body. In this state, genes cannot be read and used by the cell to make proteins. Epigenetic switches can turn genes on by unwinding them, or turn them off by folding them back up, as in the case of DNA methylation. While this process is essential to our health, faulty folds in the DNA, much like wrinkles, can disturb gene function and lead to cancer.
What lifestyle factors might influence the formation of these epigenetic wrinkles in colon cancer? To answer this question, Belshaw’s group examined the cells lining the gut wall in healthy, cancer-free volunteers who consumed their usual diet without any supplements. The researchers looked at eleven risk genes, that, when their methylation is turned on, increase the risk of developing colon cancer.  They then quantified the relationship between methylated genes and cancer risk factors such as age, diet and obesity. Age was associated with the highest gene methylation, which fits with the observation that colon cancer risk increases exponentially after 50 years of age. However, other factors had small but significant effects. High body fat increased cancer-related methylation whereas high levels of the mineral selenium and vitamin D reduced it. This is consistent with what we know about the link between obesity and a high risk of colon cancer, as well as with the protective effects of vitamin D and selenium observed in previous studies.
Surprisingly, high blood folic acid, a vitamin found in leafy vegetables like spinach, increased gene methylation associated with colon cancer. We have been told that these foods are good for us, so how could they promote cancer? It is actually still unclear whether folic acid is a friend or a foe as previous studies indicate it may even have a protective function. This is an important issue as some countries add nutrients such as folic acid to food and this may expose people to increased risk of developing cancer. In a follow-up study, Dr Belshaw’s team will try to shed light on the potential dark side of excess folic acid intake.
Healthy ageing starts in the kitchen
Overall, these findings support the idea that healthy ageing is affected by what we eat. As we age, the epigenetic status of some genes can change leading to disease like cancer. Our diet seems to affect this process and bring important ingredients into our genes’ recipe. As Dr Belshaw says, “This raises the exciting possibility that lifestyle interventions may reverse age-related DNA methylation and consequently reduce the risk of disease”. An apple a day might be more effective in slowing down the ageing process than an anti-wrinkle cream.

This summary by Lucia Aronica was shortlisted for Access to Understanding 2014 and received the People's Choice award. It describes research published in the following article, selected for inclusion in the competition by the Biotechnology and Biological Sciences Research Council:

PMCID: PMC3572581
H.S. Tapp, D.M. Commane, D.M. Bradburn, R. Arasaradnam, J.C. Mathers, I.T. Johnson & N.J. Belshaw.
Aging Cell (2013) 12, 148-155.

Access to Understanding entrants are asked to write a plain English summary of a research article. For Access to Understanding 2014 there were 10 articles to choose from, selected by the Europe PMC fundersThe articles are all available from Europe PMC, are free to read and download, and were supported by one or more of the Europe PMC funders.

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