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喜欢科学,偏爱自然科学。也喜欢技术,儿时喜围观打锡壶的和锔盆锔锅的。当过工人,当过兵,第二故乡是湖南、广西和广东。

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关于抗氧化剂的一些真相  

2014-11-21 20:39:46|  分类: 生命与健康 |  标签: |举报 |字号 订阅

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(1)

如果你曾去过保健食品商店,那么你很可能看到过成排的抗氧化物(剂)制剂在出售。抗氧化物如今很受青睐。??出售他们所声称的富含抗氧化物的超级食品从预防癌症到延缓衰老样样都行。这类食物包括绿茶、枸杞、?籽,以及甚至于红酒和黑巧克力。你也许没有学习过生物化学或营养学,不过就如我们所被告知的,你可能对下面这些基本的声称并不陌生:氧化物是坏的,因此抗氧化物一定是好的,如果少量抗氧化物有好处,那么肯定是多多益善。这就是抗氧化物理念的概括。不过真正的情况看来不那么简单。

(00m04s) If you’ve ever gone into a health food shop then you’ve likely seen rows and rows of antioxidants supplements for sale. Antioxidants are big news. (Foods suppliers sell?) what they claim are antioxidant-rich super foods would do everything from preventing cancer to slowing aging. These foods include green tea, goji berries, ??? seeds, and even red wines and dark chocolate. Then you might not study biochemistry or dietetics, but you probably are familiar with the basic claim, if, as we are told, oxidants are bad, so antioxidants must be good, and if a little antioxidants is good, surely more must be better. That is the antioxidants claim in a nutshell. But the whole story doesn’t seem to be that simple.

(2)

氧化物(剂)也被称为自由基,是我们的细胞把食物转化成能量时产生的纯自然的化学物。不过氧化物也会由下列活动产生:阳光照射我们的皮肤和眼睛,吸烟,饮酒,空气污染以及运动。是的,运动。氧化物是非常活跃的化学物,它们是铁生锈或者切开的苹果变成棕色的原因。氧化物是一把双刃剑,对于生命它是必须的,可是它也会带来伤害。

抗氧化物是一些能减缓或者阻碍这种氧化过程的分子。抗氧化物可以分为两大类:或溶解于水,或溶解于脂肪。脂溶性抗氧化物包括维生素A和β-胡萝卜素,除了辅酶Q以外它们还可以从黄色、橙色和红色的水果和蔬菜中得到。这些脂溶性抗氧化物常常保护细胞膜。水溶性的抗氧化物包括维生素C和谷胱甘肽,它们主要与存在于你血液和细胞内部水分中的氧化物发生反应。

(01m15s) Oxidants are also called free radicals and are entirely natural chemicals produced when our cells turn food into energy. But oxidants are also produced by sunlight in our skin and eyes, cigarette smoke, alcohol, air pollution, and even exercise, yes, exercise. Oxidants are very reactive chemicals and they are the reason why iron will rust or a cut apple will turn brown. Oxidation is a twin edged sword. It is essential for life, but it can also cause damage.

Antioxidants are molecules that tend to slow or block this oxidation. Antioxidants fall into two main classes: they either dissolved in water, or in fat. Fat-soluble antioxidants include vitamin A and beta-carotene which you get from the yellow, orange and reddish fruit and vegetables as well as coenzyme Q. These fat-soluble antioxidants often protect cell membranes. The water-soluble antioxidants include vitamin C and glutathione; they react mainly with oxidants that exist in the water inside your cells and in your blood.

(3)

我们都知道运动能健壮肌肉,延长寿命。运动还能降低II型糖尿病和胰岛素抵抗的风险。不过人们在2009年发现如果你运动并且摄取抗氧化物制剂的话,你就突然失去了运动的所有益处,也就是你的肌肉不会增强,而且也不能预防糖尿病。换句话说,瓶子里装的抗氧化物对你有害。

对于肺癌我们发现了同样的结果。我们都知道吸烟能导致肺癌。如果给予肺癌患者富含天然抗氧化物的饮食,他们会比预期生存的久一点。这样看来人们很自然的期待,如果用一点抗氧化物有益的话,肯定大量的抗氧化物将会更好。于是研究者们试着给予额外添加的抗氧化物,也就是说,来自于瓶子装的制剂而不是自然食物。试验结果令人吃惊:患者的生存没有延长。实际上他们的死亡提前了。额外的抗氧化物缩短了他们的寿命预期。

(02m55s) Now we all know that physical exercise helps build muscle and improves life expectancy. Exercise can also improve your risks with regard to type II diabetes and insulin resistance. But in two thousand and nine it was discovered that if you do exercise and take antioxidant supplements suddenly you lose all the health promoting effects of exercise, so your muscles don’t get bigger and you don’t get protected from diabetes. In other words, antioxidants from a bottle were bad for you.

We found the same result with lung cancer. Now we all know that smoking cigarettes can cause lung cancer. If you give people with lung cancer a diet rich in natural antioxidants they will live a bit longer than expected. So it seems natural to expect that if a little bit of antioxidants is good and surely lots of antioxidants would be better. So the researchers try giving extra supplemental antioxidants, in other words, antioxidants from a bottle not food. The results were astonishing: people did not live longer. In fact they died sooner. The additional antioxidants shortened their life expectancy.

(4)

我们尚不完全明白其中的机理,不过让我告诉你我们已知的道理吧。

首先,当我们运动时,我们会产生氧化物。这是坏事吗?不是!我们自然产生的氧化物会激发我们的细胞制造我们自己的抗氧化物,而它们给予我们运动的益处。我们的自然抗氧化物不只让我们的肌肉更强壮,它们还有一些预料之外的功能,比如说帮助我们防护空气污染。

其次,那么自然食物中的抗氧化物呢?看起来它们在我们的体内的作用与我们运动产生的自然抗氧化物的作用是相同的。别忘了完整的食物[注]中还有很多别的好物质:如膳食纤维等许多我们可能还没有发现的好东西。这些生物活性物质几乎可以肯定与自然食物中的抗氧化物联合起着作用。

第三,看来,当你摄入瓶装的抗氧化物制剂时,它们实际上妨碍了我们的机体制造它自己的自然抗氧化物,尽管这些补充剂提供了抗氧化物,但并不能弥补你自己内生的抗氧化物的损失。2012年的一项研究观察了200,000位健康人和81,000位各种疾病的患者。研究发现抗氧化物补充剂没有带来益处。

[注]:完整的食物我理解就是诸如全麦粉、糙米等尽量少加工,尽量保持其完整成分的食物

——《卡尔博士的科学伟大时刻》/《抗氧化物:21世纪的蛇油?》,ABC 2014/11/12

(04m19s) And we don’t have the full story yet, but let me tell you what we do have.

First, when we humans exercise we manufacture oxidants. Is this bad? No! Our natural oxidants then trigger our cells to make our own natural antioxidants, which then give us the benefits of exercise. Not only do our natural antioxidants make our muscles stronger, they also do unexpected stuff, such as protect us from air pollution.

So second, what about the antioxidants in natural foods? Well, it seems that they work inside our bodies in the same way as do our natural antioxidants that we trigger with exercise. And don’t forget all of the other good stuff in the whole foods: the fiber and all the other plenty goodness that we haven’t even discovered. This bioactive stuff almost certainly works hand in hand with the antioxidants from natural foods.

Third, it seems when you take supplemental antioxidants form a bottle, they actually prevent your body from making its own natural antioxidants, even though the supplements provide antioxidants they don’t balance the loss of your own native antioxidants. A two thousand and twelve study looked at two hundred thousand healthy people and eighty-one thousand people with various diseases. The study found that no benefits from antioxidants supplements.

-- Dr. Karl’s Great Moments in Science / Antioxidants: the 21 century snake oil?  ABC 2014/11/12

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