Nutrition Questions and Dietary Fads

[MrWookie]

Katy,

DB is right when he's talking about the water soluble vitamins. The flip side of those is that you can't really get too much of them. If you guzzle OJ like a fiend to try and OD on vitamin C or something, your body just passes all the excess out in your urine.

You actually do have to be careful with some of the fat-soluble vitamins, like vitamin A. Since it doesn't dissolve in water, it just hangs out in your body until it's needed. If you eat way, way too much, it can become toxic.

For free radicals and antioxidants, I'm skeptical. Reactive Oxygen Species (ROS) produced by your cells' mitochondria as a normal by product of your metabolism are extremely reactive. Some, like hydroxide radical, will react with virtually the first thing it touches. Fortunately, your body has mechanisms to reduce the output of OH radical and instead put out the less harmful nitric oxide. Still, though, it seems like for antioxidants to have any effect, they'd have to be at a comparable concentration to other things in your cells that these free radicals might react with. Your cells are roughly 200 mg/mL protein, but people take these antioxidants at levels where their concentrations will be, oh, 4-5 orders of magnitude below this. Since proponents say that these antioxidants suck up the ROS directly, they have to be around to bump into an ROS molecule before it reacts w/ something else. If people argue that some of these compounds are stimulating your body's natural defenses against ROS, that I could believe, but I'm skeptical about how effective they are at chewing up ROS on their own.

[katyseagull]

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Fortunately, your body has mechanisms to reduce the output of OH radical and instead put out the less harmful nitric oxide. Still, though, it seems like for antioxidants to have any effect, they'd have to be at a comparable concentration to other things in your cells that these free radicals might react with.

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Thanks for your thoughts, Wookie. My concern is that the scientists have a very crude understanding of how the body works and how it utilizes various forms of nutrients. The article I linked tries to point out that just because something works in a test tube does not mean it will automatically work in the body. That's what they've discovered with antioxidant supplements. In fact, some studies indicate that it is not helpful and is possible harmful.

In 1992, researchers were studying lung cancer and found that the antioxidant beta carotene showed promise against cancer. They recruited 18,000 for a controlled study.


" the researchers pulled the plug two-thirds of the way through after discovering, to their surprise and horror, that those taking supplements were faring worse than the controls."

Also in the 1990s, researchers found that a diet high in vitamin E significantly reduced the incidence of heart disease. However, experiments using vitamin E supplements have been very disappointing. Several of the studies showed no effect and one showed that it caused harm.


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In fact, despite good evidence that vitamin E is a powerful antioxidant in the test tube, there is now serious doubt that it acts the same way in the body. "Vitamin E is not an antioxidant. In fact it must be protected against oxidation," says Angelo Azzi, a biochemist at Tufts University in Boston, Massachusetts. He points out that vitamin E exists in eight different forms in nature, all of which function as antioxidants in the test tube. Yet the body only uses one form, alpha tocopherol, which is pulled out of the bloodstream by a highly specialised protein in the liver. All the other forms are excreted. Azzi argues that evolution is unlikely to have gone to such great lengths simply to obtain an antioxidant from the diet. "There are millions of antioxidants," he says.

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The conclusion is becoming clear: whatever is behind the health benefits of a diet rich in fruits and vegetables, you cannot reproduce it by taking purified extracts or vitamin supplements. "Just because a food with a certain compound in it is beneficial, it does not mean a nutraceutical [with the same compound in] is,"

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I'm still very curious how they came up with the daily requirements for vitamins. Anyone know? I read one article that said it was based on very old data having to do with scurvy. I've no idea if that's true or not.

[Blarg]

From what I've read, politics plays a part.

[Jay.]

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I'm still very curious how they came up with the daily requirements for vitamins. Anyone know? I read one article that said it was based on very old data having to do with scurvy. I've no idea if that's true or not.

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That's right. A lot of the recommended intakes are based on amounts to prevent disease x. The recommended intakes really are stupid though. Large difference from governments to governments and then huge difference from governments to health books. Even with all that, there's huge difference from person to person. Just eat a good diet.

[Shadowrun]

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Thanks for your thoughts, Wookie. My concern is that the scientists have a very crude understanding of how the body works and how it utilizes various forms of nutrients.

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Be glad you dont live in a time period where giving birth was a serious health risk, or the getting leeched for any health reason, or even thinking that baths are harmful.

P.S. Basically, im curious if you think we have a very "crude" understanding now, what do you think we had before?

[Blarg]

Water intake has been correlated to mood, too. By way of anecdote, I tried myself to see if increasing my water intake seemed to make much difference, and it did. I feel noticeably more energetic when I'm drinking more water than usual. Even when I'm not sprinting to the bathroom.

As to why, I don't know, but water is sometimes called the universal solvent. Your body needs it for most everything it does. It certainly needs it for passing waste out of your body. As well as helping me do all kinds of other things, I'm figuring it helps me get waste out faster when I drink a lot of it. That might have spillover effects into my mood.

[Zameus]

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Water intake has been correlated to mood, too. By way of anecdote, I tried myself to see if increasing my water intake seemed to make much difference, and it did. I feel noticeably more energetic when I'm drinking more water than usual. Even when I'm not sprinting to the bathroom.

As to why, I don't know, but water is sometimes called the universal solvent. Your body needs it for most everything it does. It certainly needs it for passing waste out of your body. As well as helping me do all kinds of other things, I'm figuring it helps me get waste out faster when I drink a lot of it. That might have spillover effects into my mood.

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Blarg, water is useless without a loofah. You should know this by now [img]/images/graemlins/wink.gif[/img]

[Blarg]

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Water intake has been correlated to mood, too. By way of anecdote, I tried myself to see if increasing my water intake seemed to make much difference, and it did. I feel noticeably more energetic when I'm drinking more water than usual. Even when I'm not sprinting to the bathroom.

As to why, I don't know, but water is sometimes called the universal solvent. Your body needs it for most everything it does. It certainly needs it for passing waste out of your body. As well as helping me do all kinds of other things, I'm figuring it helps me get waste out faster when I drink a lot of it. That might have spillover effects into my mood.

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Blarg, water is useless without a loofah. You should know this by now [img]/images/graemlins/wink.gif[/img]

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Yeah, I'm probably just being poisoned by my own testicles, so it's clouding my thinking.

[75s]

Actually, all of these health tips inlcude a 20 min high heartrate workout (resting*2.7). Most people don't get this daily. Also, those are 8oz glasses (kinda small) but yes, people get dehydrated.

[diebitter]

I think vitamins/mineral supplement are important if you do a lot of exercise or manual work, if you have a lifestyle that depletes them excessively (smoking and drinking), or if you're old or pregnant. Doesn't hurt the developing stages of life either (childhood, teendom). Otherwise a reasonable diet is more than enough for anyone.


More important are the water-based vitamins such as B and C. Humans don't have the capacity to store these, so they are needed in a diet. If you have low energy and you have a processed diet or don't each much veggies/fruit, decent vitamin B complex supplements will work wonders for you in a few days of taking (you need to keep taking them though). If you're prone to colds and infections, vit C will likewise work wonders.


These vitamins and their role are well understood by scientists who study metabolism, and they have clear and reasonably understood roles there.

Fish oils I think have proven benefits.

Antioxidants and combating free radicals - yes I do believe this is real - I'm pretty sure this has firm scientific basis.


Where I remain somewhat cynical (though weakly - if a scientist proves benefits by direct analysis of metabolism, or a very strong correlational link) about stuff like ginseng and st johns wort. There might be something there. I remain deoubtful till proper scientific examination shows something.



One of the things that is amusing/irritating about the whole nutrition thing though, is that it seems that one week, one scientist says X is bad for you, and the next, it's good for you. I used to be a scientist, so I'm well aware that science is based on hypotheses that are testable and available for refutation rather than a provider of absolute truths, but even so...it's sometimes a little exasperating.