Calcium silicate and silicon dioxide/silicic acid gel added for nutritional purposes to food supplements

Following a request from the European Commission to the European Food Safety Authority, the Scientific Panel on Food Additives and Nutrient Sources added to Food has been asked to deliver a scientific opinion on calcium silicate, silicon dioxide and silicic acid gel added for nutritional purposes to food supplements. The present opinion deals only with the safety of calcium silicate, silicon dioxide, silicic acid gel as sources of silicon, and with the bioavailability of silicon from these sources. The Panel notes that one petitioner also applied for the use of calcium silicate as a source of calcium. The safety of silicon and calcium itself, in terms of amounts that may be consumed, and the consideration of silicon as a nutrient, are outside the remit of this Panel. Silicon occurs naturally in foods as silicon dioxide (SiO2, silica) and silicates. High levels of silicon are found in foods derived from plants, and particularly cereals, whereas silicon levels are lower in foods from animal sources. Orthosilicic acid [Si(OH)(4)] is the major silicon species present in drinking water and other liquids, including beer, and is the most readily available source of silicon to man. After oral consumption, the main chemical species by which silicon is absorbed is orthosilicic acid. Silicates (i.e. E551, silicon dioxide, amorphous; E552, calcium silicate, hydrous/anhydrous; E553a(i), magnesium silicate; E553a( ii), magnesium trisilicate; E553b talc; E554 sodium aluminosilicate) are approved food additives within the EU. The petitioner indicated that silicon dioxide will be added to food supplements to supply up to 700 mg silicon/day. Silicic acid gel under the form of a colloidal dispersion will be added to supply 196 mg silicon/day. The Panel however notes that the essentiality of silicon for man has not been established and that a functional role for silicon has not been identified. A recommended intake for silicon has not been set. No specific data on the bioavailability of either silicon or calcium from calcium silicate have been provided. The Panel notes the low solubility of calcium silicate in hydrochloric acid and its practical insolubility in water, but in the absence of specific data, cannot reach a conclusion on the bioavailability of either calcium or silicon from the source. No data have been submitted on the bioavailability of silicon from either silicon dioxide or silicic acid gel. However, several studies have shown that silicon present under similar form was readily available from foods and in many cases showed absorption similar to that of silicon from liquids. Furthermore, given the conversion of silicon dioxide/silicic acid to orthosilicic acid upon hydration, and the bioavailability of silicon from orthosilicic acid, the Panel considers that silicon from silicon dioxide/silicic acid gel is bioavailable. The Expert group on Vitamins and Minerals (EVM) set a Safe Upper Level for daily consumption of silicon at 700 mg silicon/day for adults over a lifetime (equivalent to 12 mg silicon/kg body weight/day for a 60 kg adult). The Tolerable Upper Intake Level (UL) for calcium is 2500 mg/day for adults (equivalent to 41.3 mg calcium/kg body weight/day). The EFSA Panel on Dietetic products, Nutrition and Allergies (NDA) was unable to set a UL for silicon, but estimated that the typical dietary intake of 20-50 mg silicon/day (equivalent to 0.3-0.8 mg/kg body weight/day in a 60 kg person) is unlikely to cause adverse effects. For calcium, the mean and 9 7.5th percentile anticipated total exposure from food and food supplements would vary from 823 to 1084 mg/person/day and 1560 to 2110 mg/person/day, respectively. The Panel concludes that, in view of the Safe Upper Level for silicon of 700 mg silicon/day established by the EVM for supplemental use and of 2500 mg calcium/day for adults established by the SCF, the exposure to calcium and to silicon resulting from the proposed uses of calcium silicate as a source of respectively silicon and calcium in food supplements, the use of calcium silicate in food supplements at the proposed use levels is of no safety concern, provided that it complies with the specifications for its use as a food additive. The Panel also concludes that the use of silicon dioxide up to 1500 mg SiO2/day (equal to 700 mg/day) and of silicic acid gel to supply up to 200 mg silicon/day, added to food supplements, is kof no safety concern.