From waistline to bottom line

The study of nutrient-gene interactions has been christened 'nutrigenomics'. Its application is to understand the molecular mechanisms of how nutrients influence biological processes. Although the influence of diet has been recognised as an important constituent in the development of human health and disease, recent evidence has highlighted the cause and effect relationships in vivo.

Recently, two areas of research - inflammation and obesity - have reignited the issue of individualised nutrition and genetic manipulation. In January 2007, the Journal of Molecular Medicine highlighted the relationship between genes, dietary fat and humans' risk of obesity. In this landmark study, researchers from Tufts University in Boston, US, examined how calories from fat, carbohydrate and protein might interact with genes to influence the risk of obesity among adults.

The results show variation in a particular gene (apolipoprotein A5 gene APO5), that produces a protein involved in the metabolism of fats in the body. For 13% of the 2,280 participants carrying the gene, fat intake was not correlated to increased body mass and this remained the case despite age, sex, physical activity status, or the number of total calories consumed.

Although this suggests that those who carry the APO5 gene may be partly immune to the influence of dietary fats (particularly monounsaturated fatty acids) as a cause of obesity, carrying it does not preclude obesity caused by excessive caloric intake, or protect against the harmful influence fats can have on health.

A study released in April identified a gene (FTO) that indicates why some people put on weight but others do not. However, carriers of this gene are not destined to be obese, they are simply at a 70% risk of it, compared to non-carriers.

Studies show that those who carry both genes are likely to have 15% more body fat and 3kg more weight - and if you have only one of the FTO gene pair, 50% of these values. But the presence of the gene is no more than another risk factor.

The media has reported the action of this gene as offering the potential for a holy-grail cure for obesity but this is simply not the case. The message must be of risk identification that can still be controlled by reduced food intake and/or exercise. FTO genes may form part of nutrigenomic profiling in much the same way as we use blood pressure to indicate risk of cardiovascular disease.

So what about applications of nutrigenomics and the personalisation of supplement/food recommendations? One company may be getting us a little closer.

New Jersey-based WellGen announced in mid-April the ability of its proprietary black tea ingredient to influence the expression of genes that modulate inflammation. The company used a nutrigenomic platform to identify how bioactives influence inflammatory response and developed intellectual property-secured natural products based around these predictions.

However, the commercialisation of this should be interesting, given that any study that claims to measure the influence of a bioactive in vivo would need to control for activity and diet, as we know both influence gene expression. It is also likely proprietary ingredients using such processes would be classified as medicines. And as multiple factors influence biological responses, how effective can the commercialisation of nutrigenomically developed products be? We still have a long way to go in this area. Tailoring ingredients and food to the individual will require the mapping of each individual's genetic make-up.

Issues relating to the dose response of these so called nutrigenomic ingredients have still not been fully addressed given that some bioactives directly influence gene expression and the subsequent metabolism of many nutrients.

From the waistline of the obesity gene to the fiscal bottom line, the genetics race is underway in its bid to take a significant slice of the functional food market. Nutrigenomics can help us select proprietary ingredients or assist in the identification of human biomarkers but, as with unravelling the intricacies of the double helix, the work is far from complete.

To date, no cost effective, rapid genetic profiling system can predict how any ingredient can interact across a free living population. This poses a major commercial barrier to nutrigenomics as an effective approach to individualised nutrition. Nutrigenomics is coming, but genetically tailored supplementation and foods are still some way off.

Dr Mark Tallon is a consultant and co-founder of dietary supplements firm CR-Technologies. Email him at: oxygenix2004@aol.com