Tuesday, October 16, 2012

Medical junk science: Canned veggies may make kids fat

The war on BPA continues -- from the usual shoddy base

Can feeding your child canned soup and vegetables make her fat? According to study published in the Journal of the American Medical Association (JAMA), it just might — but only if your child is white. That’s the latest junk science “finding” from yet another study designed to condemn the chemical bisphenol A (BPA). Despite obvious flaws with the study and the implausibility of its findings, newspapers around the nation, news websites, blogs and others continue to declare that there is “more evidence” that BPA poses a health problem.

You would think that reputable medical journals like JAMA would focus on science that truly adds insight and value about medical research and public health. After all, the group that publishes it — the American Medical Association – states on its website that its mission is “[t]o promote the art and science of medicine and the betterment of public health.” But this study really doesn’t do that. It’s more akin  to political science than it is to medical research and may harm public health if it leads to bans on food packaging that uses BPA resins. BPA bans are used to prevent the development of deadly pathogens in our food, and there are no good substitutes.

Surely, all publications have a bias toward studies that come up with positive associations even if dozens of others fail to find associations. Positive findings are more interesting news, even though this bias can generate false impressions as to the state of research. But that alone does not explain why JAMA published this study, which, much like a recent study on BPA and heart disease, is so flawed that no one — let alone a serious medical journal — should take it seriously.

The JAMA obesity study used data from the National Health and Nutrition Examination Survey (NHANES), a Centers for Disease Control and Prevention (CDC) program to assess national health trends. Each year, CDC collects data from a different group of volunteers (rather than follow the same group), conducting physical exams and interviews. From this database, the JAMA study pulled data related to BPA levels found in urine and body fat measurements for 2,838 subjects aged 6- through 19 years old. It found that for some participants high BPA levels were associated with higher body fat, which it concluded suggests that BPA contributes to obesity.

Like the heart disease study, the JAMA obesity study is seriously flawed for two main reasons. First, it relies on “spot sampling” of BPA — measuring exposure via one urine sample per subject. The fact is BPA levels in urine change practically hourly, which means that one-time measurements tell us nothing! Second, it largely ignores the fact that the human body quickly metabolizes BPA before it can have any health impacts. For more background on these two issues, see my blog post on BPA and coronary heart disease.

Those two facts alone are reason enough for JAMA to reject publication of this study, but there are many other reasons why JAMA should have refused publication. First, the association they found — if it means anything at all — may simply suggest that children who eat processed foods (much of which is packaged in containers that use BPA resins) tend to be overweight. In fact, processed foods contain greater calories than do fresh produce. The study notes:
    Obese children may drink more canned or bottled beverages, or eat more canned food, and thus have higher urinary BPA levels. Similarly, although we adjusted for excessive caloric intake and television watching—lifestyle-associated risks for childhood obesity—it may be those sedentary children consume foods high in BPA.

Moreover, the association they found was not even particularly compelling or consistent. Specifically, it found that BPA is associated with higher body fat among non-Hispanic white children, but not for Hispanic or black children. Unless there is some compelling and plausible body of research to suggest why this is the case, such disparate results suggest that the association was little more than a statistical accident.

The study authors themselves admit up front in the “abstract” that they have not really discovered anything new. They note:
    BPA exposure is plausibly linked to childhood obesity, but evidence is lacking to date.

In the “discussion” section, they note the study’s key flaw:
    If BPA is rapidly and completely excreted, as suggested by the few adult pharmacokinetic studies to date, then a single measurement of urinary BPA concentration would be a poor proxy for long-term exposure.

However, they then enter into an unscientific rationalization to justify drawing conclusions from what is admittedly a “poor proxy”:
    Recent data from adults in NHANES 2003-2004, however, suggest that urinary BPA concentration does not decrease rapidly with fasting time, suggesting that it is stored in fat or other physiologic compartments.

In other words, the JAMA authors rest the validity of their methodology — and ultimately their conclusions — on an existing outside data source that simply “suggests” the human body stores BPA, which is hardly a scientific finding. In fact, the citation they provide for “recent” data goes to a single study from 2004 that also uses NHANES data and that is not very compelling for drawing the conclusions that JAMA authors use it to do.


NYC: Industry sues to block ban on sugary drinks

Soda makers, restaurateurs and other businesses sued Friday to try to block the city's unprecedented move to restrict sales of super-sized, sugary drinks, an effort the city called a coup for public health but the industry views as unfair and undemocratic.

"For the first time, they're telling New Yorkers how much of certain safe and lawful beverages they can drink," said Caroline Starke, a spokeswoman for the business groups, whose complaint also faults the city for making the decision through an unelected board. The groups include the American Beverage Association, the National Restaurant Association, a soft drink workers union and groups representing interests ranging from movie theater owners to Korean-American grocers.

A spokesman for Mayor Michael Bloomberg, the regulation's chief champion, called the lawsuit a groundless effort to stop a groundbreaking policy.

"This predictable, yet baseless, lawsuit fortunately will help put an even greater spotlight on the obesity epidemic," said the spokesman, Marc LaVorgna, who noted that the city also won fights over outlawing smoking in bars and offices and forcing fast-food restaurants to list calorie counts on their menus.

The beverage industry hinted it was considering a suit as soon as the city Board of Health approved the regulation last month. The rule would stop restaurants, cafeterias and concession stands from selling soda and other high-calorie drinks in containers larger than 16 ounces. It's set to take effect in March.

Bloomberg has called it a reasonable way to fight an obesity problem that takes a toll on many New Yorkers' health and city hospitals' budgets.

The measure keeps people from drinking extra calories without thinking, he says. For someone who drinks a soda every day, for example, downing a 16-ounce Coke instead of a 20-ounce one trims 14,600 calories a year, or the equivalent of 70 Hershey bars.

"Nobody is banning anything," the mayor said when the plan passed, noting that someone who wanted a second soda could get one.

The soda makers and sellers say the city is being a nanny-like nag to consumers and imposing an unfair, uneven burden on businesses. Manufacturers will have to get new bottles, and eateries will lose sales to competitors that aren't covered by the rule, they say. A customer who couldn't buy a 20-ounce soda at a pizzeria would be able to get a Big Gulp at a 7-Eleven, for instance, as convenience stores are under different regulations.

"(The rule) unfairly harms small businesses at a time when we can ill afford it," the suit says.

It also says the Bloomberg-appointed health board shouldn't dictate the size of soft drinks. Ten City Council members signed onto a July measure calling on the health board not to approve the rule; a New York Times poll in August showed that six in 10 New Yorkers opposed it.

The city says the board, made up of physicians and other health experts, is exactly the panel to make such decisions. It has held sway over matters ranging from milk inspection in the 1870s to banning lead paint in 1960, the city notes.


No comments: