Another Reason to Avoid HFCS? Trying to Get a Handle on How Much Risk There Is

[Continued from previous posts, here and here.]

Making sense of what the risks are based on the available information about mercury contamination in high-fructose corn syrup (HFCS) is challenging because there is so little of it. And, I’m trying to get to some kind of blogging closure because there are other topics to move on to. However, before the news cycle leaves it completely behind, I wanted to explore further what kinds of risks there might be from consuming mercury in HFCS, because there doesn’t to seem to be a lot of risk information being provided.

The paper published by Dufault et al., 2009 used the maximum concentration of mercury detected in their samples of HFCS, 0.57 ug/g (parts per million), along with the assumption that an individual consumed 50 g/day HFCS from all sources of food, to calculate an intake rate for mercury of 28.5 ug/day. That 50 g/day ingestion rate was obtained from a study of the amount and sources of dietary fructose among US adults and children conducted as part of the third National Health and Examination Survey (NHANES).

The results from the dietary fructose study were that the mean consumption of fructose was estimated to be 54.7g/day across all age groups and accounted for 10.2% of total caloric intake. The mercury analytical data used to estimate the 28.5 ug/day intake rate was from samples of HFCS straight from the factory. This makes this mercury intake rate a theoretical upper bound, assuming that someone consuming their 54.7 g/day HFCS is getting it all the time from sources that are contaminated with the maximum concentrations reported in the study (0.57 ug/g, or parts per million). Also, in imagining what this exposure scenario looks like, I get the mental image of someone eating HFCS “straight”, and not in food products. In addition, 28.5 ug/day intake rate is appreciably higher than other estimates of total mercury intake rate (the EU estimates dietary inorganic mercury intake to be around 4 ug/day). HFCS being a dominant source of dietary mercury would be a startling finding.

In contrast, the study published directly by IATP (data presented here) used a “market basket” approach, and analyzed mercury concentrations in ready-to-eat foods. Those concentrations are much lower than found in “raw” HFCS from the factory. This is not unexpected, because HFCS will be blended in other ingredients, presumably uncontaminated or less contaminated with mercury, to make the ready-to-eat foods. The highest concentration in food reported by IATP was 350 ppt or parts per trillion (pg/g, or picogram per gram), while the highest concentration reported in HFCS syrup was 570,000 pg/g (0.57 ug/g x 1,000,000 pg/ug). Combining IATP’s residue data with the consumption rates for food groups from the FDA’s Total Diet Survey corresponding to the foods analyzed in IATP’s study gives much lower mercury intake rates associated with HFCS consumption.

The highest mercury intake rate calculated for the ready-to-eat foods is 0.032 ug/day, which is for males aged 14 to 16 (the calculations are here). This isn’t an aggregate exposure analysis because it focuses only on the foods analyzed by IATP and almost certainly neglects some sources of dietary mercury. It would seem implausible this estimated intake rate is neglecting 99.9% of the dietary mercury sources related to HFCS consumption, though someone with more refined tools (and more time, meaning someone getting paid to do it) needs to map the IATP residue data to some other databases, perhaps USDA’s table of foods with added sugars, to get an idea of the total dietary intake of mercury from HFCS consumption.

When the mercury intake rates are converted to a body weight basis then compared with EPA Reference Doses for either inorganic mercury or methylmercury, the results suggest that HFCS consumption is probably a small contribution to someone’s overall risk from exposure to mercury. Again, the caution with this analysis is that it doesn’t account for all dietary sources of inorganic mercury, but the results leave me with the sense that mercury exposure isn’t the best reason to avoid consuming HFCS.