A purple tomato genetically engineered to contain nutrients more commonly seen in dark berries helped prevent cancer in mice, British researchers said on Sunday.

The finding, published in the journal Nature Biotechnology, bolsters the idea that plants can be genetically modified to make people healthier.

Cancer-prone mice fed the modified fruit lived significantly longer than animals fed a standard diet with and without regular tomatoes, Cathie Martin and colleagues at the government-funded John Innes Center in Britain reported.

"The effect was much bigger than we had expected," said Martin, a plant biologist.

The study focused on anthocyanins, a type of antioxidant found in berries such as blackberries and blackcurrants that have been shown to lower risk of cancer, heart disease and some neurological diseases.

While an easy health boost, many people do not eat enough of these fruits, the researchers said.

Using genes that help color the snapdragon flower, the researchers discovered they could get the tomatoes to make anthocyanins -- turning the tomato purple in the process.

Mice genetically engineered to develop cancer lived an average of 182 days when they were fed the purple tomatoes, compared to 142 days for animals on the standard diet.

"It is enormously encouraging to believe that by changing diet, or specific components in the diet, you can improve health in animals and possibly humans," Martin said in a telephone interview.

The researchers cautioned that trials in humans are a long way off and the next step is to investigate how the antioxidants actually affect the tumors to promote better health.

But the findings do bolster research suggesting that people can significantly improve their health by making simple changes to the daily diet, other researchers said.

"It's exciting to see new techniques that could potentially make healthy foods even better for us," said Dr. Lara Bennett, science information officer at Cancer Research UK.

"But it's too early to say whether anthocyanins obtained through diet could help to reduce the risk of cancer."

英国研究人员于上周日称，一种转基因紫番茄富含黑浆果中常见的营养成分，可以防止老鼠体内的癌细胞蔓延。

这项研究结果在《自然生物工艺学》期刊上发表，支持了转基因植物能够促进人类健康这种理论。

英国政府资助的约翰•英纳斯研究中心的植物学家凯西•马丁及其同事们称，有患癌倾向的老鼠食用这种转基因西红柿后，寿命明显长于吃普通食物的同类老鼠。

马丁说：“这种西红柿的功效远远超出了我们的预期。”

该研究的主要对象是黑莓和黑醋栗等浆果中富含的一种抗氧化物质——花青素。研究表明，花青素能够降低患癌症、心脏病和其他一些神经系统疾病的风险。

研究人员称，这种促进健康的方法简单易行，但人们却很少吃这些水果。

研究人员从金鱼草的花朵中提取了可产生花青素的基因，然后将其转移至普通西红柿中，就培育出了紫色的番茄。

研究人员利用转基因技术，让两组老鼠患上癌症，结果证明，食用紫番茄的老鼠平均存活182天，食用标准食物的老鼠平均寿命为142天。

马丁在电话采访中说：“这让我们深受鼓舞，我们相信通过改变饮食或饮食中的特定成分能够促进动物乃至人类的健康。”

一些研究者警告说，以人类为实验对象为时尚早，下一步的工作是要研究花青素是如何抑制肿瘤、促进健康的。

另有一些研究者认为，这一发现进一步证实了此前的研究成果，即人们可以通过改变日常饮食来改善健康。

英国癌症研究所的科学信息员莱拉•贝内特说：“很高兴看到新科技能为我们带来更健康的食品。”

“但目前判定通过饮食摄取的花青素能否降低患癌几率还为时尚早。”