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Hearty
tomatoes?
In the latest Nature Biotechnology, Martine Verhoeyen of Unilever Research in the UK and colleagues, describe how they boosted the production of rutin, a compound found in the skin of tomatoes. Rutin is a flavonol, part of a larger group of compounds called flavenoids, and is believed to be a powerful antioxidant. The researchers noticed that flavonol production depended on the enzyme chalcone isomerase (CHI). By inserting a Petunia gene that encodes for CHI, they engineered tomatoes with skin that had up to a 78-fold increase in flavonol levels - around the same amount as onions. The researchers found that four subsequent generations of the tomatoes inherited the higher level of flavonol and that 65 per cent of the compound was retained when the tomatoes were processed into paste.This suggests the possibility of producing tomato-based products with increased health benefits. However Dr Shawn Somerset, Senior Lecturer in Human Nutrition at Griffith University described the development as "more than a gimmick than a major step forward in disease prevention". He said that the literature was not clear on whether it was flavonols or other components were responsible for the health benefits of fruit and vegetables. "We know fruit and vegetables protect against heart disease, we're not sure which particular components are responsible." "I think they're starting to pick winners too early," he said. Roger King from CSIRO Health Sciences and Nutrition agreed that the evidence on the cardiovascular benefits of flavonols was unclear. He said although evidence from animal and invitro studies was supportive, the evidence from epidemiological studies was conflicting. Mr King said the most useful functional food to be developed so far had been margarines with added plant sterols, research for which CSIRO has received commercial funding for in the past. "There's absolutely no doubt that these decrease plasma cholesterol and that this in turn decreases the risk of cardiovascular disease," he said. "Cholesterol is a useful biomarker that shows the health benefits of such margarines," he added. "Unfortunately we don't have an equivalent biomarker in humans that demonstrate the health benefits of flavenoids." Dr Somerset singled out low fat foods as being a useful contribution to improving public health but insisted there was no one answer. "First we thought vitamin C was the answer, then it was fibre and now it's bioflavenoids," he said. "Why don't we just eat an apple instead?". Dr Somerset said he was also concerned about the potential displacement of some other nutrient by the extra flavonols produced in the tomato. Anna Salleh - ABC Science
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