Broccoli is known for its anticancer properties but it could also boost the immune system in older people and slow down the effects of ageing, according to new research.

A chemical found in cruciferous vegetables called sulforaphane was found to activate a number of antioxidant genes and enzymes in immune cells. These prevent free radicals from damaging cells.

Free radicals are byproducts of normal body processes, such as the conversion of food into energy. They are a supercharged form of oxygen, which can cause oxidative tissue damage leading to disease - for example, triggering the inflammation process that causes clogged arteries.

Oxidative damage to body tissues and organs is thought to be one of the major causes of ageing.

"The mysteries of ageing have always intrigued man," wrote chief author Dr Andre Nel, from UCLA in the Journal of Allergy and Clinical Immunology.

"While we have known for some time that free radicals are important in ageing, most of the past attention has focused on the mechanisms that produce free radicals rather than addressing the pathways used by the body to suppress their production.

"Our study contributes to the growing understanding of the importance of these antioxidant defence pathways that the body uses to fight free radicals," said Dr Nel.

"Insight into these processes points to ways in which we may be able to alleviate the effects of ageing."

The delicate balance between pro-oxidant and antioxidant forces in the body could determine the outcome of many disease processes that are associated with ageing, including cardiovascular disease, degenerative joint diseases and diabetes, as well as the decline in efficiency of the immune system's ability to protect against infectious agents.

"As we age, the ability of the immune system to fight disease and infections and protect against cancer wears down as a result of the impact of oxygen radicals on the immune system," Nel said.

"Our defence against oxidative stress damage may determine at what rate we age, how it will manifest and how to interfere in those processes," Nel said.

"In particular, our study shows that a chemical present in broccoli is capable of stimulating a wide range of antioxidant defence pathways and may be able to interfere with the age-related decline in immune function."

花椰菜具有闻名的抗癌功能，但是一项新的研究表明，它也能够刺激中老年人的免疫系统并且延缓衰老。

业已发现，在十字花科蔬菜中发现的一种被称为萝卜硫素的化学成分，能够活化免疫细胞内的许多抗氧化剂基因和酶。它们能阻止自由基破坏细胞。

自由基是正常生理过程例如食物转化为能量过程的副产物。它们是超动力形式的氧，可能引起组织的氧化损伤而导致疾病--例如触发导致动脉堵塞的炎症过程。

对身体组织和器官的氧化损伤被认为是衰老的最主要原因之一。

"衰老之谜始终让人感兴趣，" 加州大学洛杉矶分校《变态反应和临床免疫学杂志》的首席作家安德烈·讷尔博士写道。

"当我们已经有一段时间知道自由基是衰老的重要因素的时候，过去的大多数注意力都集中在自由基的产生机理上，而不是致力于由身体采取途径来抑制它们的产生。

"我们的研究有助于扩大理解这些由身体用来对抗自由基的抗氧化剂防御途径的重要性，"讷尔博士说。

"深入了解这些过程向我们指出了可能减缓衰老作用的途径。"

身体中促氧化剂和抗氧化剂之间的微妙平衡可能决定很多与衰老有关的疾病过程的结果，这包括心血管疾病、退行性关节疾病和糖尿病，以及是免疫系统防止感染的能效的下降。

"当我们变老时，免疫系统抵御疾病和传染病以及预防癌症的能力，由于氧自由基对免疫系统作用的结果而削弱，"讷尔说。

"我们对抗氧化应激伤害的防御能力可能决定我们以什么速度衰老、它将如何体现以及如何去干预那些过程，"讷尔说。

"特别是，我们的研究表明，花椰菜中存在的一种化学物质能够刺激各式各样的抗氧化剂防御途径，并且能够干预免疫功能因年龄关系的下降。"