By Steven Milloy
January 22, 2009, FoxNews.com
If you thought the food nannies’ appetite for dictating what beverages you may enjoy would be satisfied by their crusade against regular, sugar-sweetened soda, think again. Their new battle cry is shaping up to be, “None of the calories but all of the sin.”
Government-funded researchers led by the University of Texas’ Jennifer Nettleton analyzed diet and health data collected from 6,814 adults and reported in the journal Diabetes Care (Jan. 16) that daily consumption of diet soda was associated with “significantly greater” risks of type 2 diabetes and “metabolic syndrome.”
Although the researchers perfunctorily acknowledged that their study doesn’t prove a causal connection between diet soda and health problems, they nevertheless spent a great deal of space suggesting why their results might be plausible.
They hypothesized that artificial sweeteners may: “increase hedonistic desires for sweetness and more energy dense foods”; reduce dietary guilt and facilitate the overconsumption of other foods; and affect biological processes related to insulin resistance, glucose regulation and weight gain.
Though they acknowledged that “empirical data have not universally supported” the first two hypotheses and that studies are “lacking” concerning the last hypothesis, none of this seemed to dissuade them from proclaiming that their results were consistent with “accumulating evidence of the existence of these associations.”
But rather than hypothesizing — or fantasizing — about why their results might be plausible and consistent, they should have taken a harder, more objective look at their data and statistics.
First, their reported statistical correlations between daily diet soda consumption and diabetes and metabolic syndrome — 67 percent and 36 percent increases in “relative risk,” respectively — are too small to be considered as reliable indicators of any sort of real-life associations. As the National Cancer Institute once went to pains to point out in a press release, “In epidemiologic research, [increases in risk of less than 100 percent] are considered small and usually difficult to interpret. Such increases may be due to chance, statistical bias or effects of confounding factors that are sometimes not evident.”
That suite of deficiencies is precisely the problem with the study and, for that matter, the several prior studies the researchers generously referred to as “accumulating evidence.”
Diabetes and metabolic syndrome are common conditions that are multifactorial in origin and, therefore, difficult to study through epidemiologic analysis. The researchers admitted that not all risk factors were considered. Overlooked, for example, was the confounding factor of genetics, a key risk factor for both type 2 diabetes and metabolic syndrome. Data on the study subjects’ genetics, such as family medical history, wasn’t collected and factored into the statistical analysis. Could this omission be important?
It is clear from the study analysis that the more confounding factors the researchers considered, the weaker their statistical correlations became. Had a more complete and thorough data collection and analysis been undertaken, it’s quite possible that even their weak correlations would have entirely evaporated.
Another glaring problem is that the researchers don’t really know how much diet soda any study subject consumed during the 8-year-long study. Instead, they relied only on study subject guesstimates of consumption made at the beginning of the study period.
While the study doesn’t appear to add anything meaningful to what we know about diet and health, it will no doubt add grist to the growing campaign against diet soda that was launched by a 2005 report, also from University of Texas researchers.
That study reported that diet soda drinkers were at greater risk of obesity than sugar-sweetened soda drinkers and concluded that artificial sweeteners “might be fueling — rather than fighting — our escalating obesity epidemic.” It was an awfully big conclusion to be drawn from a study where, among other deficiencies, the study subjects’ consumption of diet beverages was once again guesstimated, rather than verified or validated by the researchers.
But if a study has been published, it must be true, right?
In its January 2009 issue, the self-proclaimed “healthy lifestyle” magazine, Prevention, labeled diet soda a “health food impostor” and stated that, “Drinking just one can or bottle a day increases your risk of metabolic syndrome, which packs on heart-unhealthy belly fat. Sip flavored seltzer water instead. Steer clear of those sparkling waters that contain artificial sweeteners: they’re just diet soda in disguise.”
The Idaho-Statesman (Jan. 13) ran a column from the “YOU Docs”– Mike Roizen, M.D. and Mehmet Oz, M.D. — that warned readers, “See those people in the soda aisle? They all have something in common: a higher risk of heart disease. And you may be one of them, even if you drink only one 12-ounce soft drink daily — be it regular or diet.”
New York Governor David Paterson recently proposed to tax non-diet sodas based on dubious claims about their role in weight gain. It’s not too hard to figure out where the junk science railroad may be headed next.
Steven Milloy publishes JunkScience.com and manages the Free Enterprise Action Fund. He is a junk science expert, and an adjunct scholar at the Competitive Enterprise Institute.