Student Questions: Sugary Behavior, Secondhand Smoke, and Wal-Mart
Answering more questions sent in by students.
Today we're giving some more quick answers to questions sent in by students. Any student anywhere is welcome to ask anything about a current popular misconception, a science question that affects our daily lives, or just anything you've heard that doesn't seem to quite make sense. Today's questions are about how sugar affects children's behavior, the real risks of secondhand smoke, the popular hatred of Wal-Mart, omega-3 fatty acid supplementation, and whether radiometric dating is actually useful for determining the age of an object. Let's start with Andrew:
Food Additives and Behavior
Certain additives like caffeine and alcohol certainly affect children's behavior in the same way they do adults, in fact to a greater degree because the children have such smaller body mass. But I think you're talking about more common ingredients like sugar or corn syrup. Nearly everyone has always accepted the belief that sugar makes kids hyperactive; in fact it's so deeply ingrained that even some researchers have had trouble accepting their own results. In one study, 35 children reported by their mothers to be "behaviorally sugar sensitive" were separated into two groups. Half were told they were given a sugary drink, half were told it was a sugar-free drink. Then the mothers played with the children and were individually interviewed. Overwhelmingly, mothers who were told their child was given sugar rated their behavior as hyperactive. In fact, all children received the same sugar-free drink. In this case, the perceived affect was confirmation bias by the mothers — where they picked up only on cues that supported their pre-existing conviction.
Another similar study found that 50 children whose mothers "knew" that their children's behavior was worsened by sugar were given a blinded test where the children were given either sugary or a sugar-free drink, and then observed — but this time the mothers didn't know which was which. No differences between the groups could be ascertained over three separate trials. And the lack of an effect extends to classroom performance, too. 16 hyperactive boys were given controlled diets of either sugar drinks or sugar-free drinks at measured intervals throughout two school days and were regularly given behavioral and cognitive tests. Again, there was no difference in performance between the groups.
Biochemically, the claim doesn't make sense for normal healthy children. The amount of sugar in the blood is carefully regulated by insulin. Whether you eat a lot of sugar or none at all should make no difference to your blood sugar level.
So Andrew, the evidence is pretty clear that sugary foods will not affect children's behavior, despite the widespread belief. The observed effect that all mothers can swear to is that they often see their children eating cake and juice at parties or other such gatherings, where the social environment does indeed contribute to mass insanity; and mothers quite naturally mistake correlation for causation.
This is a really interesting question. On the one hand you do have a rock-solid consensus of every major health organization in the world, including the National Institutes of Health, the Center for Disease Control, the World Health Organization, the Surgeon General's office, and the National Cancer Institute; that consensus being that there is no safe level of exposure to secondhand smoke. On the other hand you have an at least equal amount of research disputing this finding; research usually funded by the tobacco industry but also by consumer groups or think tanks like the Cato Institute. In addition, there is growing sentiment in the skeptical community along the lines of "No safe level? Come on..."
Usually when we have the scientists on one side and the interest groups on the other side of a science question, it's pretty easy to guess which side probably has the science right. And the scientists probably do in this case too. The ideal level of secondhand smoke is zero, just as the ideal amount of trans-fats you should eat is zero, and the ideal amount of alcohol to consume is zero. Nearly everyone consumes a non-zero amount of all three, and most people who don't overdo any of them will never encounter any ill effects. There's a big difference between living in a house with a chain smoker and the level of exposure from occasionally walking down the street and passing through someone's cigarette smoke.
The best conclusion is that the scientists are right that zero is probably ideal, but that a realistic low level of occasional exposure is probably harmless.
Is Wal-Mart Evil?
Wal-Mart truly is a lot bigger than any of the other apparently similar companies you can think of, so any complaint you'd have about any superstore is likely to apply to Wal-Mart to at least the same degree. Wal-Mart is the de facto poster child for anticorporate sentiment. When a Wal-Mart comes to town, small retailers who are unable or unwilling to adapt their businesses can often be put out of business. Although the requirement for businesses to adapt to changing market conditions has always existed independently of Wal-Mart, it can sometimes be a highly visible and dramatic change when a Wal-Mart comes to a small town, and so it always attracts attention. It's much like what happened when railroads first appeared, favoring some and abandoning others; and again when interstate highways did the same thing; and then again when Internet retailers began to appear and forced a paradigm shift across the board.
But that's only the initial objection to Wal-Mart as a company. When a lot of people hate you, a lot of microscopes get pointed at you; and many other criticisms are unearthed that (as you rightly point out, Jeff) do apply equally to many other companies. Some of these include Wal-Mart's resistance to unionization, its foreign product sourcing, low wages and lame benefits packages, and its exploitation of tax breaks commonly called corporate welfare. There's nothing about these criticisms that's unique to Wal-Mart; but since the public perception exists, it's a really easy target for opportunistic critics like documentary filmmaker Robert Greenwald, who capitalized on the sentiment with his 2003 film Wal-Mart: The High Cost of Low Price.
As the responsible skeptic can probably surmise, scholarly study of Wal-Mart done outside of pop culture is much more balanced. Most of the common criticisms of Wal-Mart are perfectly true, but they're hardly the complete picture. If you're interested in Wal-Mart's real effects on a community beyond what the protest signs reveal, you've got to dig in and read the research. Wikipedia provides a good list of links to a number of thorough studies.
Omega-3 Fatty Acids
In my video Here Be Dragons I show a bunch of pictures of examples of pop pseudoscience, and one of them is a bottle of fish oil tablets, sold as an omega-3 fatty acid supplement. I take heat for that all the time: People are always emailing me and saying "Hey, omega-3 fatty acids are actually good for you!" And that's true, they are. Your body needs them, and it can't synthesize them; you have to get them from the food you eat.
In fact, fish oil and other omega-3 supplements are prescribed by doctors as a treatment for a variety of illnesses. In many cases, there's not yet a conclusive consensus on how well supplementation treats these conditions, but lots of research is ongoing.
However, one fact has been determined with fairly good certainty. If you are healthy, if you do not have a specific condition that fish oil is intended to treat, if you eat anything like a half-decent diet, omega-3 fatty acid supplementation has not been found to have any plausible benefit. This is pretty much true of nearly all supplement products. A normal diet in any industrialized nation provides more than enough of nearly every nutrient your body has a use for. Anyone selling a product on television or in your supermarket's supplement aisle that claims it's a super-duper life prolonger that will make you healthier than healthy is taking you for a ride.
Does it have any value in the face of certain diseases or deficiencies? Quite probably. Does it have any value for a healthy person? No, Sarah, no hype is justified.
The Validity of Carbon Dating
This is a common objection that Young Earth Creationists raise to the scientifically determined age of the Earth. Radioactive decay rates are a known constant. By measuring the amount of an element in a compound and that of the element into which it naturally decays, a ratio can be established that tells us how long ago that compound was formed. There are more than a dozen commonly used types of radiometric dating, each optimal for a different type of compound, and each with its own error range and its own useful date range. Carbon-14 dating, that you mention, is used for establishing how long ago living matter died. Any scrap of wood or other organic matter stopped metabolizing carbon-14 when it died, and that carbon-14 in its cells has been decaying into carbon-12 ever since. How much is left tells us for a certainty how long ago it died. Carbon-14 dating is good for anything up to about 60,000 years ago.
Naturally, it's essential to know how much carbon-14 was in the environment throughout that period of time. Calibration scales have been established that tell us this. The amount of natural environmental carbon-14 is confirmed from a variety of sources. These include dendochronology, or tree rings; ice cores; ocean sediment cores; coral samples; and speleotherms, or cave formation samples. These combine to give us an extremely detailed, consistent, and precise knowledge of atmospheric carbon-14 levels throughout recent geological history. They account for volcanic events and even the era of atmospheric nuclear tests. These calibration sources are a great place to start your conversation with your friends. You can't deny radiocarbon dating without denying tree rings.
Other radiometric techniques can be used to date rocks and other objects on much longer time scales. While carbon-14 has a relatively short half-life of 5,730 years, the decay of potassium-40 to argon-40 has a half-life of 1.3 billion years, so potassium-argon dating is useful for dating the oldest rocks; but it's only accurate for rocks at least 100,000 years old. In addition to the useful date range, each method has a known error rate. For example, rubidium-strontium dating, with a half-life of 50 billion years, can date rocks as old as moon rocks up to about 3 billion years with an error of 30 to 50 million years, or about 1.5%.
Students, keep those questions coming! Just come to Skeptoid.com and click on "Answering Student Questions" for a simple form and instructions. If these guys did it, you can too. I'll look forward to hearing from you.
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