Filed under: Inside The BPP
1:05 PM ET | 05-29-2008 | permalink
Sorry to be off-topic, but there is no thread for this.
I was listening to Sue Horton talk about how micro-nutrients could improve the health and economic well being of impoverished children when my BS Meter pegged. She said giving zinc and other micro-nutrients to Guatemalan children improved their earning power by up to 50%. How would such a study be done? Would it be random and double blind? I did some further research and found the paper she was citing (badly) "Effect of a nutrition intervention during early childhood on economic productivity in Guatemalan adults".
From the study itself:
Findings Exposure to atole before, but not after, age 3 years was associated with higher hourly wages, but only for men. For exposure to atole from 0 to 2 years, the increase was US$0??67 per hour (95% CI 0??16--1??17), which meant a 46% increase in average wages. There was a non-significant tendency for hours worked to be reduced and for annual incomes to be greater for those exposed to atole from 0 to 2 years.
1) The study wasn't double-blind, it wasn't even single blind
2) It wasn't just about zinc. They used two types of grain, one of which had a greater diversity of nutrients including zinc. If there was an effect, this study could not show what about that grain caused it. It is plausible that the good grain was tastier so the children ate more of it.
3) It wasn't very random. Children in two villages were given one type of grain and children in two other villages were given another. There was no control for the economies of these villages in general.
4) The difference was only in hourly wages. The differences in annual income were not statistically different.
5) What differences there were only applied to men. Women showed no benefit from the different diet.
Sensationalistic reporting like this just really twists my panties. Poor families need many things: better and more food, vaccinations, education, opportunities, and even better information about breast feeding. People who think for just a few pennies we can make everything all better are doing the problem a disservice by trivializing it.
You guys should get your own BS Meter. $29.95 at Target.
Sent by Dave Wiley | 3:31 PM ET | 05-29-2008
Gosh, if there were only some (highly? well, relatively highly)-paid professionals whose job was to analyze claims and share that analysis with the general public! We might call them, oh, let's try something sort of French... how about "journalists"?
Nah, pseudoscience and bad science and misinterpreted science make such good copy!
In the meantime, thanks Dave Wiley...
Sent by Marc Naimark | 11:46 AM ET | 05-30-2008
Fellas, in the spirit of transparency I'll tell you all I know about the subject. Last week we interviewed the organizer of the Copenhagen Convention. As I was reading up on the papers presented a few popped out at me. A reporter for "Reason" magazine, which I always enjoy reading wrote up Sue Horton's presentations. Here was the graph that I found very interesting
"To highlight the importance of micronutrients, Horton cited a 2008 longitudinal study in Guatemala which followed up with men who had received supplements when they were three years old and younger between 1969 and 1977. Amazingly, the men who had received supplements below age three had wage rates which were 34 to 47 percent higher than those of controls, and annual incomes which were 14 to 28 percent higher."
here is a link to that Reason post:
The study in question was a longitudinal study started in the late 60;s. sometimes under those circumstances it is hard to be double blind, meaning neither the researchers nor the subjects know who is being "treated" who isn't Sometimes ethics dictates that you must inform poor villagers something like, "we're trying to help you because we think zinc may be healthy". Also it suggested that while womens wages didn;t raise (may have something to do with how they value the work of women) it did say that their intelligence improved and that Anyway it was a very famous survey sponsored by INCAP which is the
Instituto de Nutrici??n de Centro Am??rica y Panam??. Here is a link to that study:
Here is a link to another studies about the benefits of Zinc
Zinc Supplementation Improves the Growth of Stunted Rural Guatemalan Infants
none of these studies suggest Zinc supplements are a cure all, but I thought it was a good area to explore, especially on a discussion of the Cost/benefits of solving dire world problems.
Sent by Mike Pesca, NPR | 2:07 AM ET | 06-01-2008
As the person who produced the segment, I would add...
If we erred, it would only have been in making the numbers in the study in question sound overly definitive. However, it's not the first study in which zinc supplements were shown to have substantial benefits for people in the developing world. In fact it wasn't even the first time it was shown in Guatemala. And there have also been studies that have shown a link between a person's health and nutrition and the amount of money that they're likely to make in their lifetimes.
So the basic idea that people in developing countries will earn more money on average if they grow up with the correct intake of certain micronutrients has a strong grounding in previous studies. It's much easier to question just *how much* more they'll earn. So perhaps we should have qualified the finding somewhat. The study found that the men who had received supplements below age three had wage rates which were 34 to 47 percent higher than those who didn't. Perhaps another study, with the differences that you suggest, would yield different numbers. But to dismiss the entire study as "BS," to use your less-than-technical term, when it's in keeping with previous findings and has the approval of our expert guest, is unreasonable.
Sue Horton, by the way, has worked in a dozen developing countries and is the provost of her university. She's not new to this field of study. So I think we were correct to give credence to the core conclusion of the study in question--That people in developing countries who get the right amount of key micronutrients will, on average, earn more money.
Sent by Dan Pashman, NPR | 10:07 AM ET | 06-02-2008
Thanks to Dan and Mike for your thoughtful replies. I think Mike and I went down very similar google trails. I just read Rivera et al reference and was pleased with its rigor. The conclusion, however, was very specific. Stunted infants (possibly from zinc deficiency) showed better growth through zinc supplementation. Infants who were average showed no benefit.
With respect to the original study (http://siteresources.worldbank.org/HEALTHNUTRITIONANDPOPULATION/Resources/281627-1114107818507/040308HoddinottetalNutritionWageLancet2008.pdf) , I won't repeat my earlier arguments save one. I quoted the conclusions section for this paper where it said "There was a non-significant tendency for hours worked to be reduced and for annual incomes to be greater..." This means there was a difference ("Annual incomes which were 14 to 28 percent higher"), but it didn't fall outside of the statistical error. This casts the whole idea of a general economic benefit into doubt.
I used an unfortunate phrase containing the words BS. It would have been clearer and nicer but less pithy to say: caused me to become more skeptical than usual. We westerners are constantly being bombarded by magic bullets. All we need is green tea or shark cartilage or megadoses of vitamin C and our cancer risk will go down or our joints won't hurt or we won't get colds or our attractive coworkers will constantly hound us for sexual favors. Usually the science behind these claims is non-existent or in the better cases the science is insufficient to support the claims being made. When I heard Sue Horton say that zinc could improve the economic well-being of these third world children it sounded like it was coming from the same place. I was actually surprised by the quality of the study she alluded to, but was not surprised to find out that it's conclusions were overstated. The rule of thumb in science is the more significant the claim the better the evidence has to be to support it. Zinc supplements leading to future economic success is a hugely significant claim. The science behind it was not that great. More to the point I believe it distracts from other more prosaic forms of aid we could provide these families for similar cost.
At the very least it would have been nice to hear some of Sue Horton's more grandiose claims questioned during the interview.
Sent by Dave Wiley | 4:12 PM ET | 06-02-2008
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