Why can’t a tomato just be a tomoto and we just grow and eat more blackberries?

October 26, 2008

Scientists have grown genetically-engineered purple tomatoes in an unusual endeavour to promote healthy food.

The tomatoes include two genes taken from the snapdragon flower (Antirrhinum majus) to enable them to express a compound called anthocyanin, the purple pigment found in high levels in fruit such as blackberries and cranberries.

Previous research has found that anthocyanins offer protection against certain cancers, cardiovascular disease and degenerative diseases, and may also hinder inflammation, obesity and diabetes.

The study is published online on Sunday by Nature Biotechnology, a journal of the London-based Nature Publishing Group.

Researcher Cathie Martin from the John Innes Centre, a biotechnology institute in Norwich, eastern England, said the point behind the purple toms was to boost the healthiness of diets.

More than 20 years ago, the National Cancer Institute of America initiated a “five-a-day” programme to encourage Americans to consume at least five portions of fruit and vegetables daily.

But the numbers of Americans achieving this goal has declined over the last 10 years. Less than one in four reach the “five-a-day” target.

The failure of awareness campaigns has shifted the balance in favour of food with higher levels of healthy compounds, especially in ingredients that people eat in large amounts, argued Martin.

“Most people do not eat five portions of fruits and vegetables a day, but they can get more benefit from those they do eat if common fruit and veg can be developed that are higher in bioactive compounds,” she said.

After creating the purple tomatoes in a lab, the team tested the products on mice that they had engineered to make them susceptible to cancer.

Mice fed with the high-anthocyanin tomatoes “showed a significant extension” of lifespan, they found.

“This is one of the first examples of metabolic engineering that offers the potential to promote health through diet by reducing the impact of chronic disease, and certainly the first example of a GMO [genetically-modified organism] that really offers a potential benefit for all consumers,” Martin said.

“The next step will be to take the preclinical data forward to human studies with volunteers to see if we can promote health through dietary preventive medicine strategies.”

Genetically-modified food has focused mainly on gene changes that offer advantages to farmers.

Examples include corn that exudes a natural toxin to kill insect pests, and rapeseed, also called canola, that resists a pesticide, thus enabling the farmer to spray his entire field in one go, killing weeds but not the crops.

There have also been other schemes to boost the healthiness of food, such as “golden rice” and genetically-modified bananas that included inserted genes to increase levels of vitamin A. But none is commercially available for human consumption.

Opponents say food deficiencies are linked to poverty and other social issues that cannot be resolved by gene technology.

They also contend that genetic modification may have impacts for human health and the environment.

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