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Durk Pearson and Sandy Shaw

around, it can scavenge the free-radical, but the radical doesn’t disappear. It becomes a lower energy, less reactive, more stable radical called a tocopherol radical.

Sandy: But you still have to get rid of it.

Durk: Yeah, it’s less dangerous than what you had before, but it’s not harmless. The way you get rid of that is it bumps up against an ascorbate ion– vitamin C– and that free electron hops on over. So now you have an ascorbyl radical, but you’ve regenerated the alpha tocopherol and it’s ready to do its job again.You get rid of the ascorbyl radical with glutathione peroxidase, a selenium-containing enzyme. There’s a long series of these reactions. At each step the radical has less energy. It becomes less reactive, less dangerous, and more stable, until you can finally pair it up with another unmatched electron. Then theycancel each other out, and you get rid of it. But this is why it’s necessary to have a system of free-radical scavengers, and to not just stuff yourself with only vitamin C or E.

Sandy: That’s one of the problems with some of the current vitamin studies. They run these clinical trials where they’re looking at what happens to people when you give them huge supplements of something like beta carotene, but they’re not giving them a system of nutrients such as you’d normally find in a plant carrying beta carotene.

Durk: For example, at high levels, beta carotene alone can act as a pro-oxidant, and it can speed up free-radical reactions. However, in conjunction with other anti-oxidants, like vitamin E for example, it can act as an anti-oxidant. So if you just give a person a large dose of beta carotene, and expose them to a lot of free-radicals– like in the case of a heavy smoker– you’re really asking for trouble.

David: I take it that you’re referring to the Finnish studies that showed a greater incidence of lung cancer among smokers who took just beta carotene supplements?

Sandy: Well, that was one of the problems, and of course, the average person in the study had over a thirty-five year history of heavy smoking. So we’re talking about people who already had done very extensive damage, and most of them may have already had pre-malignent conditions by the time they started on the beta carotene supplements.

Durk: And when you give them the beta carotene– without high levels of other anti-oxidants along with it– in conjunction with the free-radicals in the cigarette smoke (of which there’s a hell of a lot), you could actually end up causing more free-radical damage, rather than preventing it. Beta carotene alone,in the absence of other anti-oxidants in adequate quantities, can actually increase the level of free-radicals, rather than decrease it.

Sandy: This is especially true under conditions where there’s high oxygen pressure–such as is the case in the lungs. There’s a lot of oxygen in the lungs, compared to places where there’s low oxygen partial pressures, like in atherosclerotic plaques.

Durk: Beta carotene reduces the risk of atherosclerosis, but it might increase the risk of lung cancer, unless it’s taken in adequate quantities with other anti-oxidants, and this is one area where the experiments were not very well planned. I don’t think the people planning them understood what free-radicals werein a sense, because you can’t get rid of them by just giving one magic bullet. For example, in the Finnish study the authors themselves proposed that they did not have enough vitamin E along with the beta carotene, and they found that out in retrospect.

Sandy: They only had fifty miligrams of vitamin E, which is quite small.

Durk: And no study has ever shown any benefits from that, other than preventing vitamin E deficiency. Also people in Finland suffer from pathologically low levels of selenium. Remember what I said before about how, in order to get rid of that ascorbyl radical that you get from the tocopherol radical,

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