You are due for your regular diet MOT (moment of truth). You take the smart card containing your DNA profile, which is your genetic signature, to the diet clinic and provide a pin-prick of blood. Your blood is analysed and compared to your DNA. After a short wait a dietary prescription tailored to your specific genetic needs and perfectly balancing your macro- and micro-nutrients needs is prepared. Your prescription for the next few months is nothing like the one prepared for your Italian friend or your boss, who is a second generation Indian. Even your brother, who leads a much more hectic lifestyle than you, has been recommended a completely different range of foods. At the moment this is a fantastic scenario, but it is one that scientists are already predicting could become technically possible in the future.

Not so long ago, the study of nutrition and genetics ran on separate parallel tracks. Now the tracks are merging as scientists investigate the interaction between our genes and nutrition. This new area of study, known scientifically as Nutrigenomics, or in a more consumer friendly term as “Individualised Nutrition”, is already providing promising information that could help us tailor dietary advice more effectively to enhance health and prevent some diseases.

But this is no simple task. Take heart disease for example. There is not just one gene responsible for running the cardiovascular system - at least 20,000 genes are involved. Although each gene will only have a small effect, certain “marker genes” can give an overall indication of a particular risk factor for developing heart disease. For example, a gene that is involved in the control of blood cholesterol has been identified. Apart from the most common variation of this gene, there are two other variations that either put people at a greater than average risk of high cholesterol levels, or protect them.

It has been found that where lifestyle-related risk factors for heart disease are low, for example in people who are physically active and consume a low-fat diet, it does not make much difference if you have the gene variant that predisposes you to high blood cholesterol levels. On the other hand, where lifestyle-related risk factors are high, perhaps an individual smokes, is physically inactive and eats lots of saturated fat, having that gene will result in higher blood cholesterol levels.

It has also been shown that when a group of people follow a therapeutic (curative) diet to reduce total blood cholesterol levels over a period of time, some people have a dramatic beneficial metabolic response whilst others do not respond at all. Clearly for the non-responders it is a waste of time coping with a change of diet, whereas for the hyper-responders it is well worth the effort. The key is to find a particular gene variation that the hyper-responders have in common. Once this information is available it would enable targeting of dietary advice to those people most likely to benefit.

Apart from heart disease, several other genetic variations have been found to be relevant to nutrition1. Genes that control folate metabolism have been linked to conditions such as neural tube defects, and a series of genes have been identified that are linked to the absorption and regulation of iron levels in the body. There is also evidence, from twin and sibling studies, that suggests that genetic factors are a major determinant of bone mineral density and structure.

There is no doubt that our genetic make-up predisposes us to react to our environment in different ways. Future research will make it possible for us to find out how to best manage our environment and diet to suit our physiology. As Jose Ordovas, Professor in Nutrition and Genomics at Tufts University, Boston, USA says 2: “It is not a matter of nature or nurture; it is a matter of nurturing our nature”

References

• Elliot R and Jin Ong T (2002) Nutritional genomics a clinical review. British Medical Journal. 324: 1438-1442
• Nutrition Society Summer Meeting (2003) Individual variability in the nutritional response. Kings College London. (http://www.nutritionsociety.org/news/newsPage.html).

FOOD TODAY 03/2004