Antifreeze proteins: characteristics, occurrence and human exposure

Antifreeze proteins (AFPs), also known as ice structuring proteins, bind to and influence the growth of ice crystals. Proteins with these characteristics have been identified in fish living in areas susceptible to ice formation and in numerous plants and insects. This review considers the occurrence of AFPs and relates it to the likely intake by human populations, with a view to forming a judgment about their safety in foods. Intake of AFPs in the diet is likely to be substantial in most northerly and temperate regions. Much of this intake is likely to be from edible plants, given their importance in the diet, but in some regions intake from fish will be significant. Inadequate data exist to estimate intakes from plants but estimates of intake of AFP from fish are presented for two countries with very different fish consumption, the USA and Iceland. Typical short-term exposure, for instance a portion of cod may contain up to 196 mg AFGP, while the AFP content of the same weight of ocean pout would be up to 420 mg. Average available fish AFP in the diet is calculated to be around 1-10 mg/day in the USA and 50-500 mg/day in Iceland, but these estimates are subject to considerable uncertainty. As far as can be ascertained, AFPs are consumed with no evidence of adverse health effects, either short- or long-term. Given the structural diversity of AFPs, one firm general conclusion that can be drawn from the history of consumption of AFPs is that their functional characteristics do not impart any toxicologically significant effect, in a way that, for instance, a property such as cholinesterase inhibition would. Furthermore, specifically in the case of fish AFPs where some consumption data are available, it is reasonable to infer a lack of allergenicity from the absence of reports of this effect. (C) 2002 Elsevier Science Ltd. All rights reserved.