Thursday, November 02, 2006

Heard yet about resveratrol ?

Yes, it’s back to red wine today, the subject of a post here a few days ago. Why return so soon ? It’s due to my having spotted an article by Nic Fleming, science correspondent of the Telegraph, about a particular substance in grape skins that is reckoned to have an anti-ageing, life-prolonging effect - at least in obese mice, and a range of lower life forms ( fish, yeast etc).

The substance is called resveratrol. It’s one of those so-called polyphenols. On the right is a model of what the molecule looks like, colour coded to show up key features. Now that’s where this particular blogger has great trouble in preparing his day’s post. You see, it’s like this: he labours under this absurd and masochistic 'duty to explain' where chemistry is concerned .

Duty to bore the pants off, more like it .....

If I were using a pen or pencil, the wastepaper bin would now be full of discarded drafts – either too detailed, or too dumbed down. (I do not envy MSM science writers one little bit their job of making science accessible, but without over-egging the pudding. )

So here’s what I propose to do. I’ll simply add a few extra sentences for now, explaining briefly what all the excitement is about, and then publish. Those who are interested may find that I have later tacked on some extra information, as and when I can get my act together. Late additions will be in blue.

The obvious question is: how does resveratrol work in mice, and would it have the same effect in people ? That’s the interesting thing. Up until recently, it’s been supposed that polyphenols might delay ageing, and prolong lifespan, by their antioxidant properties – mopping up the free radicals that are formed when our bodies use oxygen to release energy from food. But there are dozens of different antioxidants in the diet – vitamins C, E etc- so who's to say which is best, under which conditions ? But this particular polyphenol, resveratrol, apparently works by an entirely different mechanism that has nothing to do with its antioxidant properties. It's to do with particular proteins ("sirtuins") that protect DNA.

I’ll spare you the details, and just leave it at saying this. It’s long been known that one can extend the lifespan of mice by keeping them on a low-calorie diet. And it’s believed that works by the second (non-oxidative) mechanism involving those sirtuins. Trouble is, no one knows if calorie-deprivation prolongs human life . That’s well nigh impossible to test, except possibly in cooperative lifers in prison ! And even if it did, would you want to half-starve yourself, even if it gained you some extra years ? For what ? The prospect of yet more starvation ?

But here’s the good news – perhaps – though it’s still early days. Resveratrol is supposed to work by the same mechanism as calorie restriction, ie on sirtuins . If that can be confirmed in humans, it means one could take the stuff as an alternative to starvation, either by increasing consumption of the few items which have the stuff ( notably red wine - yes please- or peanuts) or possibly (and more controversially) in the form of a dietary supplement or pill *.

As indicated, the best source of resveratrol is red wine (especially if made from Muscadine grapes ). But it’s not in white wine, or grape juice. Why is that ? Resveratrol is only in the skin of the grape (where it protects again fungal attack). It's not in the juice, and, what's more, cannot dissolve out into the juice, on account of it being virtually insoluble in water. But when the grape juice is fermented in the presence of the skins (to make red wine), the resveratrol is gradually dissolved out by alcohol. So you see why there’s no resveratrol in grape juice (skins discarded) or in white wine ( fermented in absence of skins) .

It's been suggested that red wine might explain why French suffer fewer heart attacks than we Brits, despite having as much, if not more saturated fats in their diet.

*Although speaking for myself, I have a strong aversion to the idea of popping pills, just because someone’s done some research and found this or that. Who knows what they haven’t yet discovered, eg some untoward effects elsewhere in the body ? Some years back, there used to be a dreadful woman who wrote for one of the Sunday papers about health and nutrition, who was constantly scouring the shelves of health food shops for the latest miracle supplement, and concluded each article with the words " So I naturally take two of those pills as well each day". Not surprisingly, she later had to take permanent sick leave, malady unspecified ....


Anonymous said...

There is more detail on it at wikipedia, including foods, supplement info, and the science behind it.


sciencebod said...

Thanks Anthony

I'd almost given up hope getting a comment on this subject ...

Maybe folk don't want to think of wine as medicine !

29 Jan 2007 !