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Dose matters: acceptable daily intake of food additives

Caramel color in food additives

Caramel colors are used in a large number of processed food (candies, dairy products, breakfast cereals, dried pasta, canned and preserved vegetable and fruits, etc) and drinks, including beverages. Recent studies have found carcinogenic effects associated with exposure levels much lower than those levels previously considered acceptable. As a consequence of these recent findings, changes in the legislation in California, include the requirement of warning labeling indicating potential carcinogenic effects of these products, uneasy for manufacturers. Media attention has triggered a series of request for clarification by Member States.

Acceptable Daily Intakes by different agencies

Caramel colors are classified according to the reactants used in their manufacture process, as below specified. Derived constituents include 4-methylimidazole (4-MI) and 2-Acetyl-4-tetrahydroxybutylimidazole (THI), both under carcinogenic testing studies, mostly searching for alveolar/bronchiolar neoplasms, i.e. lung cancer, in lab animals.

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has published in 2011, Acceptable Daily Intake (ADI) levels that had been identified in 1985 and 2000 for the followings:

CLASS I plain caramel or caustic caramel: not specified for plain caramel
CLASS II caustic sulphite caramel: 0-160 mg/kg body weight
CLASS III ammonia caramel: 0-200 mg/kg bw
CLASS IV sulphite ammonia caramel: 0-200 mg/kg bw

The European Food Safety Authority has re-evaluated caramel colors toxicity and carcinogenicity in 2004, and established a group ADI of 300 mg/kg body weight. This figure was based on the review of dose-response studies using lab rats, for which health effects, i.e, lung cancer, were not observable at levels of 30 g/kg body weight, using an uncertainty factor of 102 as precautionary measure. The EFSA also evaluated exposures among European population and found average ADI figures not very different, and eventually above the identified ADI.

Recent results (2011) published by the US National Toxicology Programme study used different methods and reached different results. The US NTP relied on dose- responses testing using lab mice, given the uncertain observations seen in lab rats. However, based on available partial results of the US NTP, the EFSA claimed that dose-responses results observed in mice were threshold, and the alveolar/bronchiolar neoplasm occurs in mice spontaneously at high incidence. For the precautionary principle, the US NTP study used the non significant risk level of less than 1 in 105 to reach the total ADI of 16 µg/day. This result was made available for public comments and reviewed by peer scientists, before amendments were made to the Safe Drinking Water and Toxic Enforcement Act, also known as Proposition 65. As a result, manufacturers for consumption in California are asked to provide warning signs indicating that the product contains potential carcinogenic substances. At this point manufacturers' reactions and media attention were raised.

In summary, the FAO/WHO JECFA ADI figure of 200 mg/kg bw, which can be translated into a total intake of 14x106 µg/day for a 70 kg body weight person, differs significantly from the NTP figure of 16 µg/day for the a person of a similar body weight. To compare, the Centre for Science for the Public Interest published observed levels of around 14 x 104 µg of 4-MI in a 12 ounce can of beverage.

In other words, one person can reach the FAO/WHO ADI with 100 cans of certain sodas; or one person cannot drink a single can of soda to stay below the NTP acceptable daily intake, not counting exposures through many other processed foods that contain similar additives. These discrepancies are not trivial, and deserve further scientific investigation and public debates, including multi-stakeholder participation. Methodological comparison is required to further clarify these ADI figures, including better acknowledgement on precautionary figures to be used (102 used by FAO/WHO JECFA and EFSA, and 106 used by US NTP). Moreover, based on general precautionary principle, policy makers should encourage manufacturers to seek for safer alternative products. This is a significant task considering the extensive use of these caramel color products in the processed food industry.

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