Curious to see what we know about the health benefits of vitamin supplements, I went looking with my assistant David Ortiz. We found this fantastic 2007 JAMA meta-analysis of 385 publications regarding 232,000 subjects. Bottom line: on average supplements increase an ordinary adult’s chance of dying by 7%. While selenium reduces death rates by 0.2%, beta carotene increases them by 9%, vitamin C and E by 6%, and vitamin A by 20%. Maybe you should take selinium, but mostly just stay away from supplements. From now on, I’ll avoid multivitamins. Quotes:
I was under the impression that vitamins were basically health supplements of stuff you don't need on a daily basis but are good for you. This article just confirms the status quo.
Well not only is it hard to believe that authors of 385 studies chose to test dosage levels known to be deadly, it has been three years since this JAMA paper and no critic has yet bothered to redo the analysis with higher order moments, or restricted to low-dose studies.
Except that is exactly the problem with medical research, or so this guy says:
Look at the motivation of the JAMA study: to assess *antioxidant* supplements. All this shows is that antioxidants are not the answer (hint: free-radicals are not the cause of aging). Some of us already knew that. It also tells us that beta-carotene, vitamin A & E are toxic in large doses. And guess what, we already knew that as well.
So it's not really news. I shall continue taking supplements of essential nutrients.
Enough vitamin A is toxic no matter the source.I agree, and that's my point. The focus is on one source when in fact the real issue lies with each individual item being consumed.
A much larger problem in today's world is the availability of so much information, and yet we still over simplify matters to such a degree as this.
If supplements really are, on average, harmful, then it is important to learn why this is so. After all, a substantial fraction of the foods in your local supermarket have been "enriched" with added vitamins, and some minerals too. Just read the ingredients labels and you'll see them there. This practice is normally defended as yielding large reductions in the incidence of vitamin deficiency diseases (such as rickets, scurvy, etc). If consuming all those "supplements" in your food is actually good for you, then why should it be harmful in pill form? Alternatively, does this study argue for ending or limiting the widespread practice of adding vitamins to foods?
"Toxic" has several meanings. Robin is reading "toxic" as "deadly" when Phil clearly intends the "harmful" meaning. Robin's dismissal of Phil's detailed criticism is flippant and seems to fall under the "But somebody would have noticed" category. Agreed with Jim Babcock that this smacks of confirmation bias on Robin's part as well.
Enough vitamin A is toxic no matter the source. The problem with supplements is that you are getting far more of the vitamin than in most natural foods (also in a more concentrated dose, if that makes a difference). I remember reading about a health food faddist about 15 or 20 years ago who had managed to eat enough carrots in a short enough time to encounter vitamin A toxicity. And survival manuals and books about eskimos point out that polar bear liver is dangerous because even fairly small amounts can cause vitamin A toxicity.
I did megadoses of vitamins for a couple of years in the mid to late 1980s, I quit largely because there was pretty good data coming out that large doses had no additional benefit over normal dietary levels and some definitely caused problems.
If Vitamin A, for example, is not bad for a person in and of itself, then taking a Vitamin A supplement would not be bad for a person.
So in all of this condensed data, what makes the difference between getting Vitamin A naturally, and via a supplement?
Are supplements somehow themselves harmful? I haven't seen that stated outright. Is there an inordinate amount of unhealthy people taking them in a last ditch effort to regain their vitality? Is it simply a matter of dosage? Maybe a large percentage of people are taking supplements, and behaving unhealthily in other ways under the misconception that the supplements are offsetting the behavior.
But since vitamins are themselves not harmful, it seems rather dishonest to dismiss vitamin supplements as unhealthy simply because they are supplements.
Although I think Robin is generally right here (that if you can justify dismissing this study, then you can justify ignoring just about any study you don’t like)
I don't actually see this. I think Robin's reply can be turned back on itself: if you can brush off Phil's criticism by saying "you can always complain that they didn’t try some particular variation you like", then you can brush off just about any criticism you want.
I think that on the contrary, not all criticisms of an analysis are equal. Some are better than others. And choosing an appropriate analysis is not a question of personal taste ("some particular variation you like"). There really are good reasons for choosing one over another apart from arbitrary whim. If it were a matter of whim, it would not be science. Given that some are better than others, then it is possible to err, and possible for someone like Phil to catch the error, and that catch does not deserved to be brushed off as if it were a mere idiosyncratic fancy.
Robin suggests producing a competing analysis. Well, suppose one is produced. Then what? How are we to decide between the two analyses? How else but by an argument much like the one Phil already made? But if such an argument should carry weight then (and it must, for without it, we cannot choose between analyses), then logically it must carry weight now.
Although I think Robin is generally right here (that if you can justify dismissing this study, then you can justify ignoring just about any study you don't like), it seems like a waste of time to argue about it. Why not just find out?
How much would it cost for LW/OB readers to commission someone to redo the analysis with PhilGoetz's objection in mind? Employing one grad student for a month only costs about $2000 (and we could take donations through a WePay-like service which only charges credit cards if enough people pledge to donate).
Good point. i'd add that even if I, the random blogger, actually did this re-analysis, and did it correctly, what journal would actually publish me? You need the right credentials first.
Why would hundreds of medical researchers (on whose studies the meta-analysis was based) choose variations likely (according to the critics) to prove harm, when the incentives in medical research go in the opposite direction by creating pressures to prove efficacy, which here means decreased mortality? Such a question needs to be asked because the inability to answer it bears on the probability you assign to the claim that the underlying studies' doses were toxic.
The medical consensus is that these the doses "officially" set as toxic are far too low, and doses 2 or three times the maximum dose used in the study of Vitamin A are, for specific conditions, commonly prescribed by doctors without the patient experiencing toxic reactions.
Toxicity, moreover, has well-defined symptoms. Are we to assume that the subjects developed toxic reactions that the doctors conducting the underlying studies disregarded? This, repeated in hundreds of underlying studies?
The study's severe critics must say: high doses produce a kind asymptomatic life-shortening toxicity. But this is an assumption that its asserter must prove, when toxicity producing immediate symptoms is the only kind of toxicity that anyone has been able to identify.
I was under the impression that vitamins were basically health supplements of stuff you don't need on a daily basis but are good for you. This article just confirms the status quo.
Well not only is it hard to believe that authors of 385 studies chose to test dosage levels known to be deadly, it has been three years since this JAMA paper and no critic has yet bothered to redo the analysis with higher order moments, or restricted to low-dose studies.
Except that is exactly the problem with medical research, or so this guy says:
Look at the motivation of the JAMA study: to assess *antioxidant* supplements. All this shows is that antioxidants are not the answer (hint: free-radicals are not the cause of aging). Some of us already knew that. It also tells us that beta-carotene, vitamin A & E are toxic in large doses. And guess what, we already knew that as well.
So it's not really news. I shall continue taking supplements of essential nutrients.
Is there a selection bias here? Admittedly I haven't read the study.
You've remarked "After getting high-efficiency washers, consumers increased clothes washing by nearly 6 percent."
Enough vitamin A is toxic no matter the source.I agree, and that's my point. The focus is on one source when in fact the real issue lies with each individual item being consumed.
A much larger problem in today's world is the availability of so much information, and yet we still over simplify matters to such a degree as this.
It only looked at 5 supplements, at least two of which were previously well known to be bad for you.
So: *some* supplements are bad for you - and scientists have known that for a long time.
If supplements really are, on average, harmful, then it is important to learn why this is so. After all, a substantial fraction of the foods in your local supermarket have been "enriched" with added vitamins, and some minerals too. Just read the ingredients labels and you'll see them there. This practice is normally defended as yielding large reductions in the incidence of vitamin deficiency diseases (such as rickets, scurvy, etc). If consuming all those "supplements" in your food is actually good for you, then why should it be harmful in pill form? Alternatively, does this study argue for ending or limiting the widespread practice of adding vitamins to foods?
"Toxic" has several meanings. Robin is reading "toxic" as "deadly" when Phil clearly intends the "harmful" meaning. Robin's dismissal of Phil's detailed criticism is flippant and seems to fall under the "But somebody would have noticed" category. Agreed with Jim Babcock that this smacks of confirmation bias on Robin's part as well.
Enough vitamin A is toxic no matter the source. The problem with supplements is that you are getting far more of the vitamin than in most natural foods (also in a more concentrated dose, if that makes a difference). I remember reading about a health food faddist about 15 or 20 years ago who had managed to eat enough carrots in a short enough time to encounter vitamin A toxicity. And survival manuals and books about eskimos point out that polar bear liver is dangerous because even fairly small amounts can cause vitamin A toxicity.
I did megadoses of vitamins for a couple of years in the mid to late 1980s, I quit largely because there was pretty good data coming out that large doses had no additional benefit over normal dietary levels and some definitely caused problems.
Robin should provide Phil with the data so he can analyze it.
If Vitamin A, for example, is not bad for a person in and of itself, then taking a Vitamin A supplement would not be bad for a person.
So in all of this condensed data, what makes the difference between getting Vitamin A naturally, and via a supplement?
Are supplements somehow themselves harmful? I haven't seen that stated outright. Is there an inordinate amount of unhealthy people taking them in a last ditch effort to regain their vitality? Is it simply a matter of dosage? Maybe a large percentage of people are taking supplements, and behaving unhealthily in other ways under the misconception that the supplements are offsetting the behavior.
But since vitamins are themselves not harmful, it seems rather dishonest to dismiss vitamin supplements as unhealthy simply because they are supplements.
Although I think Robin is generally right here (that if you can justify dismissing this study, then you can justify ignoring just about any study you don’t like)
I don't actually see this. I think Robin's reply can be turned back on itself: if you can brush off Phil's criticism by saying "you can always complain that they didn’t try some particular variation you like", then you can brush off just about any criticism you want.
I think that on the contrary, not all criticisms of an analysis are equal. Some are better than others. And choosing an appropriate analysis is not a question of personal taste ("some particular variation you like"). There really are good reasons for choosing one over another apart from arbitrary whim. If it were a matter of whim, it would not be science. Given that some are better than others, then it is possible to err, and possible for someone like Phil to catch the error, and that catch does not deserved to be brushed off as if it were a mere idiosyncratic fancy.
Robin suggests producing a competing analysis. Well, suppose one is produced. Then what? How are we to decide between the two analyses? How else but by an argument much like the one Phil already made? But if such an argument should carry weight then (and it must, for without it, we cannot choose between analyses), then logically it must carry weight now.
Although I think Robin is generally right here (that if you can justify dismissing this study, then you can justify ignoring just about any study you don't like), it seems like a waste of time to argue about it. Why not just find out?
How much would it cost for LW/OB readers to commission someone to redo the analysis with PhilGoetz's objection in mind? Employing one grad student for a month only costs about $2000 (and we could take donations through a WePay-like service which only charges credit cards if enough people pledge to donate).
Good point. i'd add that even if I, the random blogger, actually did this re-analysis, and did it correctly, what journal would actually publish me? You need the right credentials first.
Why would hundreds of medical researchers (on whose studies the meta-analysis was based) choose variations likely (according to the critics) to prove harm, when the incentives in medical research go in the opposite direction by creating pressures to prove efficacy, which here means decreased mortality? Such a question needs to be asked because the inability to answer it bears on the probability you assign to the claim that the underlying studies' doses were toxic.
The medical consensus is that these the doses "officially" set as toxic are far too low, and doses 2 or three times the maximum dose used in the study of Vitamin A are, for specific conditions, commonly prescribed by doctors without the patient experiencing toxic reactions.
Toxicity, moreover, has well-defined symptoms. Are we to assume that the subjects developed toxic reactions that the doctors conducting the underlying studies disregarded? This, repeated in hundreds of underlying studies?
The study's severe critics must say: high doses produce a kind asymptomatic life-shortening toxicity. But this is an assumption that its asserter must prove, when toxicity producing immediate symptoms is the only kind of toxicity that anyone has been able to identify.
Rerun with log-transformed values. Virtually all data which takes non-negative value should be log-transformed before any statistical analysis.