HFCS v. Diabetes: Correlation does not mean causation.

The latest study[1] on the evils of High Fructose Corn Syrup (HFCS) so annoys the Corn Refiners Association that it broke the study’s embargo.

Reporters were not supposed to write about the study until today, but the Corn Refiners issued a press release[2] yesterday: “Caution: New Study Alleging HFCS-Diabetes Link is Flawed and Misleading.”

The New York Times quickly posted its own pre-embargo account[3].

Why the fuss?  The study reports that countries with the highest levels of HFCS in their food supplies also have a 20% higher prevalence of diabetes in their populations.  This is a correlation between HFCS and diabetes.  It does not mean that HFCS causes diabetes—an important distinction.

But the authors’ press release (sent to me in an e-mail message) makes it sound like causation.  They say (also see Dr. Goran’s comments added to this post below):

HFCS appears to pose a serious public health problem on a global scale,” said principal study author Michael I. Goran…The study adds to a growing body of scientific literature that indicates HFCS consumption may result in negative health consequences distinct from and more deleterious than natural sugar.

This conclusion is based on their observations that the amounts of other sugars in the food supplies of countries with high and low HFCS are about the same.  But HFCS is a form of sugars that adds to total sugar availability.

The authors obtained information about diabetes and obesity prevalence and HFCS and other dietary factors in the food supply from existing sources of data, all of them questionable.   The data do not distinguish between type 1 and type 2 diabetes, for example, and the two different sources of data on diabetes prevalence give different results.

Inconsistencies abound.  For example, Mexico has more diabetes than does the U.S., but rather low HFCS availability (Mexicans prefer sucrose in their sodas).  Some countries with high diabetes rates report no HFCS availability at all.

As with all correlational studies, something else could be going on that causes HFCS, sugars of all types, and diabetes to increase.

That was the point I was trying to make when I spoke to Stephanie Strom of the New York Times[4]:

 “I think it’s a stretch to say the study shows high-fructose corn syrup has anything special to do with diabetes,” Dr. Nestle said. “Diabetes is a function of development. The more cars, more TVs, more cellphones, more sugar, more meat, more fat, more calories[5], more obesity[6], the more diabetes you have.”

She noted that the study “falls right in the middle of the Corn Refiners fight with the Sugar Association,” a reference to the legal war being waged between the two industry groups over the marketing of high-fructose corn syrup.

The Corn Refiners press release[7] quotes its president, Audrae Erickson:

This latest article by Dr. Goran is severely flawed, misleading and risks setting off unfounded alarm about a safe and proven food and beverage ingredient.  There is broad scientific consensus[8] that table sugar and high fructose corn syrup are nutritionally and metabolically equivalent…The bottom line is this is a poorly conducted analysis, based on a well-known statistical fallacy, by a known detractor of HFCS whose previous attack on the ingredient was deeply flawed and roundly criticized.

Whew.

Yes, HFCS is sugar(s)—glucose and fructose.  So is table sugar (sucrose).

But the bottom line goes for both: Everyone would be better off eating less sugar(s).

1 2

Share