Siân Astley and Helen Wallace disagree

Dear Siân,

Nutrigenomics is being promoted as a solution to chronic diet-related diseases such as heart disease, cancers and diabetes. Commercial interest in this new science has two aims: developing new food products and personalising diets. Functional foods, such as cholesterol-lowering spreads and probiotic yoghurts, will be marketed as tailored to an individual's genes, and maybe other biological measurements, to 'optimise' a person's health.

However, personalised nutrition will not help to tackle the current epidemic of diseases linked with overeating. Genetic tests and functional foods are targeted at the wealthy and do nothing to help poorer people who are at higher risk of heart disease and diabetes.

The usefulness of targeting dietary advice based on genetic make-up is also limited because genes are poor predictors of an individual's risk. Your diet tailored to your genes is marketing, not science – driven by food and biotech companies that seek to personalise and privatise dietary advice.

Personalised nutrition could harm health by targeting the wrong dietary advice at the wrong people, confusing healthy eating messages, undermining public health approaches, promoting new expensive products instead of fruit and vegetables, and diverting research and public health resources.

Personalised nutrition is a false solution to the global epidemic of obesity.

Yours, Helen

Dear Helen,

Nutrigenomics is a science, not a way of life, and personalised nutrition is not an alternative to public health policy but it does have much to contribute to the discussion.

Eating certain foods can protect us from a variety of age/ diet-related diseases, for example cancer and cardiovascular disease. But the risks are not the same for everyone; some people will develop these diseases earlier with more severe symptoms. The issue is not just these tragically early deaths. It is also lives blighted by disability that impact not only individuals and their families but national economies as well, through increased healthcare costs for an ageing population.

Differences in response to diet have been evident for years, for example cholesterol and saturated fat intake. In the past, nutrition research has been limited to a few 'likely' dietary compounds, a handful of relevant biochemical pathways and latterly a small number of candidate genes. Nutrigenomics allows a more holistic approach; understanding how the whole body responds to real foods at different life-stages.

Promotion of healthy eating and lifestyle are paramount and key messages are well established, but the ‘one-size-fits-all’ strategy is clearly not working. Consumers want something that meets their needs; personalising nutrition, as with other public health initiatives, may be more successful in achieving long-term change.

Yours, Siân

Dear Siân,

Personalising dietary advice means privatisating it, with different biotech and food companies selling different and potentially conflicting advice and associated supplements and new food products. Some unregulated genetic tests with misleading dietary advice are already being sold. This confuses healthy-eating messages, with potentially harmful consequences for public health.

With some exceptions, genetic differences appear to make only small and subtle differences to a person’s risk of diet-related disease and hence very little difference to the foods they should eat. There is little evidence that individual variability in cholesterol levels is genetically determined, except in relatively rare cases, and the most studied gene – called APOE – has been found to be of little use in identifying people who respond best to low-fat diets. The biological response to dietary fats is highly complex and will be hard to predict for any individual, whether genetic tests or other biological measurements are used.

Too much saturated fat, sugar and salt is bad for everyone and there is an enormous and growing gulf between dietary guidelines and what people actually consume. Tinkering with individual diets and new ingredients will not solve this problem – what is needed is political commitment to change unhealthy food production systems and marketing practices.

Yours, Helen

Dear Helen,

We have a long way to go in understanding how what we eat is absorbed, distributed, stored and used by our bodies; nutrigenomics gives us much broader and deeper insight, which in turn will enable experts to provide clearer, better nutritional and lifestyle advice for all.

Nutrigenomics will enable us to identify how much and how frequently existing foods should be consumed by, for example, 70 year olds, expectant mothers, toddlers and teenagers. It is here that the effects of individual genes may be relevant – tweaking an individual’s requirements. Personalised, not individualised, information will meet the needs of consumers who struggle to apply existing dietary and lifestyle advice, creating the gulf between what they know and what they do.

Like it or not, food and biotech industries and retailers are part of this process, and excluding them will not protect consumers’ health or pockets. Legislation against health fraud is paramount; failure to address ethical, legal and societal aspects of nutrigenomics will damage the public’s trust in personalised nutrition, not the promises peddled by charlatans.

Yours, Siân

Dear Sian,

You ignore the significant role that health inequalities and social and economic factors play in chronic diet-related disease, as well as how hard it will be to regulate these new health claims.

Today’s epidemic of obesity is influenced by agricultural practices and the global marketing of unhealthy foods. In Argentina, for example, the diet of the poor has shifted since the 1960s, from a varied balanced one, to one which depends on only 22 basic products, selected to satisfy the appetite but high in fats and sugars. The food industry fosters this behaviour by targeting the poor with mass, low-quality products that are cheaper but less healthy.

These marketing practices also affect low-income families in Britain, who suffer from ‘food poverty’. Poorer families tend to eat less healthily, consuming less fruit and vegetables and wholemeal bread and more white bread and processed meat products.

Personalised nutrition is a solution advocated by food manufacturers and biotech companies who want to sell both personalised nutritional advice and associated ‘healthier’ food products at a premium. Ignoring them is not an option, but nor is uncritical acceptance of their view that growth in expensive hi-tech ‘personalised’ foods will help to tackle the frightening global increase in diet-related diseases.

Yours, Helen

Dear Helen,

On the contrary, nutrigenomics takes into consideration not only the role of our genes, proteins and metabolism in our health but also life-stage and lifestyle. It will allow us to understand how the whole body responds to real foods, and the information that comes from nutrigenomics will enable consumers to make choices that suit them.

For some this will mean accessing new food products and genetic testing. For many it will mean applying sensible science-based dietary advice to their situation. The worried-wealthy-well will adopt these technologies sooner, despite the fact that arguably they least need the intervention because they are already diet and health conscious. But, the nature of our market economy means these new products will become available to all sectors of society with time.

Public health messages are, for a variety of reasons, failing change people's behaviour and to counteract flashy advertising promoting cheap nutritionally-empty foods. But demonising the food industry will not overcome rising obesity rates or poor dietary and lifestyle choices. Enabling and encouraging people to make healthy choices for themselves, and supporting the science underpinning their decisions, just might.

In the end, humans are complex and so too are their diets, making nutrition science and questions about health fiendishly difficult. Nutrigenomics is the ideal, and perhaps, the only tool able to answer the ultimate question - what should I be eating?

Yours, Siân

Dr Siân Astley is the NuGO (Nutrigenomics Organisation) Communications Manager at the Institute of Food Research, Norwich

Dr Helen Wallace is Deputy Director of Genewatch UK