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."

英國研究人員于上周日稱，一種轉基因紫番茄富含黑漿果中常見的營養成分，可以防止老鼠體內的癌細胞蔓延。

這項研究結果在《自然生物工藝學》期刊上發表，支持了轉基因植物能夠促進人類健康這種理論。

英國政府資助的約翰•英納斯研究中心的植物學家凱西•馬丁及其同事們稱，有患癌傾向的老鼠食用這種轉基因西紅柿后，壽命明顯長于吃普通食物的同類老鼠。

馬丁說：“這種西紅柿的功效遠遠超出了我們的預期。”

該研究的主要對象是黑莓和黑醋栗等漿果中富含的一種抗氧化物質——花青素。研究表明，花青素能夠降低患癌癥、心臟病和其他一些神經系統疾病的風險。

研究人員稱，這種促進健康的方法簡單易行，但人們卻很少吃這些水果。

研究人員從金魚草的花朵中提取了可產生花青素的基因，然后將其轉移至普通西紅柿中，就培育出了紫色的番茄。

研究人員利用轉基因技術，讓兩組老鼠患上癌癥，結果證明，食用紫番茄的老鼠平均存活182天，食用標準食物的老鼠平均壽命為142天。

馬丁在電話采訪中說：“這讓我們深受鼓舞，我們相信通過改變飲食或飲食中的特定成分能夠促進動物乃至人類的健康。”

一些研究者警告說，以人類為實驗對象為時尚早，下一步的工作是要研究花青素是如何抑制腫瘤、促進健康的。

另有一些研究者認為，這一發現進一步證實了此前的研究成果，即人們可以通過改變日常飲食來改善健康。

英國癌癥研究所的科學信息員萊拉•貝內特說：“很高興看到新科技能為我們帶來更健康的食品。”

“但目前判定通過飲食攝取的花青素能否降低患癌幾率還為時尚早。”