Opinion of the Scientific Panel on Additives and Products or Substances used in Animal Feed on the request from the Commission on the use of iodine in feedingstuffs

Iodine is an essential trace element for humans and animals. It is incorporated into the thyroid hormones that have multiple functions as regulators of cell activity. Iodine deficiency affects reproductive capacity, development of brain and progeny as well as growth. Nowadays clinically evident iodine deficiency in animals is rather scarce due to feed supplementation. The European Commission asked the European Food Safety Authority to evaluate the physiological requirements for iodine of the different animal species referred to in Directive 70/524/EEC and to advise the Commission on the possible detrimental effect on human and animal health or the environment of iodine, used at the current levels authorised under Directive 70/524/EC (4, 20 and 10 mg kg-1 feed for horses, fish and all other species, respectively). The iodine requirements for animals vary between 0.1 and 1.1 mg kg-1 feed, being higher for cats (up to 2 mg kg-1 feed). Within species the requirements are influenced by physiological demands for growth, reproduction or lactation and also by dietary factors (e.g. goitrogens). In most cases iodine supplementation of daily ration is necessary due to the low iodine content of plant feedingstuffs. Based on the limited available data the following maximum dietary iodine levels are considered as tolerated: 3 mg kg-1 feed for horses, 5 mg kg-1 feed for laying hens, higher than 60 mg kg-1 feed for farmed fish and 4 mg kg-1 feed for dogs. The iodine tolerance of pigs and fish is far above the EU regulations. The tolerances (proposed upper limits) are 3 to 10-fold higher than the requirement, allowing sufficient compensation for potential goitrogenic substances in feed. At present the upper safe level for dairy cow, calf, chicken for fattening, turkey, sheep, goat, rabbits and cats can not be determined. Higher dietary iodine supply results in increasing iodine excretion mainly by urine, but also via milk and eggs, and to a considerably smaller extent in body deposition (except sea food). Among food from terrestrial animals milk and eggs show the highest iodine concentrations. Milk iodine originates from feeding and several other sources (notably disinfectants). All available data on iodine concentrations in foods of animal origin as well as estimates of dietary intake in Europe do not support an association between current levels of iodine feed supplementation and risks of excessive iodine intake in humans. Information considered by FEEDAP Panel also indicates that feed manufacturing practice does not make full use of the maximum levels approved. However, the worst case scenario model calculations with milk and eggs based on the current approved maximum iodine level in feed, show that the Upper Limit for adults and adolescents could be exceeded. Reducing iodine to a maximum of 4 mg kg-1 complete feed for dairy cows and laying hens would result in a satisfactory margin of safety for the consumption of milk and eggs. In farmed fish supplementation of the diet with the maximum recommended levels (20 mg iodine kg-1) will still result in lower tissue concentrations than those found in wild marine fish. FEEDAP Panel stresses the fact that iodine supplemented feeds are not the single, nor possibly the major source, of iodine in human diet. Iodine-enriched salt, supplemented food items (including iodine rich algae), iodine tablets, and some iodine enriched beverages may all contribute to the overall iodine intake. Iodine in feed enters the environment via direct excretion of faeces and urine on pasture or spreading of sludge and slurry. This concentration is well below the background concentration and it is therefore not expected to pose an environmental risk. Finally, FEEDAP Panel expresses the need for more and updated data on iodine requirement and tolerance in animals as well as on the actual impact of iodine supplements in feeds on total iodine dietary intake of humans.