Mercury in high-fructose corn syrup: What it means for you

We recently reported on two new studies that investigated potential mercury contamination in high-fructose corn syrup, a sweetener commonly used in ready-to-eat foods. We've been working with our senior scientists to figure out what these findings mean for consumers.

One peer-reviewed study, published in the journal Environmental Health, tested 20 samples of high-fructose corn syrup and found that nine of the samples contained detectable levels of mercury. Further research spurred by that investigation was performed by an advocacy group, the Institute for Agriculture and Trade Policy (IATP). It tested a variety of retail foods and beverages that listed high-fructose corn syrup as the first or second ingredient, and detected mercury in 17 of 55 samples.

Because there is no definitively safe level of mercury exposure, some of these findings raise a degree of concern. But both studies have significant limitations and neither demonstrates that eating foods with high-fructose corn syrup exposes consumers to more mercury than other foods. There are, however, more compelling health reasons for Americans to reduce high-fructose corn syrup consumption, along with other sugars. Consuming too much of any caloric sweetener can contribute to obesity, type 2 diabetes, and other health problems.

The authors of the Environmental Health study speculate that the mercury may have found its way into the sweetener by way of mercury-grade caustic soda or hydrochloric acid during the manufacturing process. But the researchers were unable to confirm a link between the use of mercury-tainted raw materials and the presence of mercury in the high-fructose corn syrup samples. Further, the very small number of samples—20—were collected from manufacturing plants back in 2005, which means that they may not reflect current manufacturing processes.

The Corn Refiners Association, a trade group that represents the high-fructose corn syrup industry, disputes the timeliness of the study. Lisa Winternitz, a spokeswoman for the association, said, "The study appears to be based on outdated information since the corn industry has used mercury-free versions of the two re-agents mentioned in the study, hydrochloric acid and caustic soda, for several years." 

The IATP tests of mercury in retail food products containing high-fructose corn syrup, which were collected in 2008, also fall short in regard to a cemented conclusion. The total mercury found in the retail products was often just over detectable levels. The highest sample of mercury discovered was 350 parts-per-trillion, far less than the .1 and higher parts-per-million of methyl mercury in fish that Consumers Union and other organizations are concerned about.

Unfortunately, the IATP researchers didn't compare the mercury levels of the products they tested with products that don't contain high-fructose corn syrup. That's an issue because mercury is a common pollutant in the environment, which is how it finds its way into fish, for example. So it's possible that other potential sources of mercury contaminated the tested products, such as through fertilizer, soil and air contaminants, and other raw materials.

Finally, neither study identifies the type of mercury found. While all mercury can be harmful to human health, it's unclear if the retail products contained methyl mercury, which is found in seafood and poses the greatest health risks in foods. The other option is elemental mercury, which is somewhat less toxic if ingested.

CRs Take. While these studies are not conclusive, they do raise important questions about potential mercury contamination in foods. More information is needed about food ingredients that may be processed with agents made in mercury cell chlor-alkali plants and the potential for such processes to contaminate foods directly, or indirectly, through environmental releases. But given that mercury-free alternatives exist, government and industry both should work to eliminate any exposures that may be generated by mercury-cell processes.

Consumers Union recommends that the Food and Drug Administration investigate the use of mercury cell chlor-alkali plants in producing food-grade processing aids, and expand its current mercury surveillance program to test more foods and food ingredients, including high-fructose corn syrup, for mercury.

--Kevin McCarthy, associate editor