Fats and proteins aren’t the only foods drawing attention, however. On his blog, Dr. Yoni Freedhoff, the medical director of the Bariatric Medical Institute, a weight management center in Canada, recently slammed The Daily Mail for running an enormous front page headline declaring, “Diabetes Warning on White Rice: Millions who regularly eat it are at risk.” The article was a about a paper published in March in the British Medical Journal by some of the same Harvard researchers behind the red-meat-mortality paper. They reviewed data from four observational studies involving over 350,000 people and found an association between rice consumption and diabetes, but stressed that the findings had “few immediate implications for doctors, patients, or public health services.”
Arguing that The Daily Mail had “overstated” the risk of eating rice, an analysis at the UK’s excellent NHS Choices website, run by the publicly-funded National Health Service, explained that:
The main limitation with cohort studies such as the ones pooled in this review is that they may not have adjusted for all relevant factors that could be associated with intake of rice and with risk of diabetes. These include other dietary factors such as alcohol intake, physical activity and being overweight or obese. Also, studies assessing food intake can be particularly prone to some inaccuracy. Participants usually have to estimate their typical dietary intake, which can be hard to recall and variable over time.
Despite these significant limitations, however, journalists continue to seize upon the latest observational research studies and tout their findings with little to no qualification. As Gary Schwitzer put it in a post for HealthNewsReview in early March:
Last week we saw stories about citrus fruits protecting women from stroke. This week it was stories about “sleeping pills could kill 500,000.” This week we also had stories about “omega-3 fatty acids protecting the aging brain” and about “Vitamin A may slash melanoma risk.” Sometimes it’s stories about lower risk (or protection), sometimes it’s stories about higher risk.
Week after week, year after year, for 6 years now, we have written about news stories that fail to explain the limitations of observational studies to readers. They use causal language - suggesting cause-and-effect findings - for studies that cannot prove cause-and-effect.
Unfortunately, those stories are like candy to undiscerning readers, but reporters who want to do better can turn to HealthNewsReview’s useful primer on observational studies titled, “Does the Language Fit the Evidence? Association Versus Causation.” It’s a simple, clear-cut guide to how various studies are designed and to how journalists can evaluate them with a more skeptical eye.
It is all well and good to point out the obvious: there are many (perhaps the vast majority) of articles on diet and nutrition that either largely wrong or fact free. Nothing will change until the cost of disseminating such is increased, either by exposing academic ineptitude more forcefully or driving poor journalists from their profession. At present neither the academic or journalistic institutions seem willing to deep dive to determine who is failing the system.
The most common defense of the plethora of terrible diet/ nutrition studies is the difficulty in performing a scientifically valid study. If physics took the same approach, we would still be stuck with alchemistry. Scientifically understanding the role of diet on human health has to be much easier than observing neutrinos and anti-particles.
#1 Posted by Robert Bramel, CJR on Wed 11 Apr 2012 at 12:08 PM
"Scientifically understanding the role of diet on human health has to be much easier than observing neutrinos and anti-particles."
Not necessarily. The human body isn't exactly a standardized or clean lab to work in, unlike the environments physicists can manufacture for themselves.
#2 Posted by Thimbles, CJR on Wed 11 Apr 2012 at 03:37 PM
Thimbles is right: I think it's actually a LOT harder to understand the role of diet on human health than it is to observe neutrinos and anti-particles. There are many variables at play and ethical limitations that limit what we can and cannot control for. For example, the claim has been made that it's impossible for someone to become obese without consuming carbohydrates, but we can't test that in a meaningful way because overfeeding experiments are no longer considered ethical and would have a hard time getting approved by human subjects committees. Individuals perform these types of experiments on themselves (see the Twinkie diet, for example), but N=1 experiments don't tell us much because we know that response to diet and exercise varies across individuals.
Personally I don't think observational epidemiology is "bad science," I think it just gets misinterpreted, and much of that misinterpretation is the media's fault. Researchers can insert all the caveats they want about correlation vs. causation, but journalists (or their editors) will continue to ignore them in the quest for an eye-catching story. Observational epidemiology can reveal apparent associations that help focus additional research.
#3 Posted by brad, CJR on Wed 18 Apr 2012 at 11:10 AM