Safety of organic silicon (monomethylsilanetriol, MMST) as a novel food ingredient for use as a source of silicon in food supplements and bioavailability of orthosilicic acid from the source

Following a request from the European Commission, the EFSA Panel on Food Additives and Nutrient Sources added to food (ANS) was asked to deliver an opinion on the safety of organic silicon (monomethylsilanetriol, MMST) as a novel food ingredient for use as a source of silicon in food supplements, and on the bioavailability of silicon from this source. MMST is proposed to be used as an aqueous solution at a concentration of 4.1 mM, corresponding to 115 mg Si/L. The anticipated intake of silicon from the proposed uses and use levels of 60–90 mL/day of MMST solution corresponds to approximately 7–10 mg Si/day. Data from in vitro and in vivo tests showed no genotoxic effect of MMST. From a 90-day toxicity study in rats a no observed adverse effect level (NOAEL) was set at the concentration of 20.5 mM of MMST, corresponding to 232 mg/kg body weight (bw) per day of MMST, the highest dose tested and technically achievable. The Panel considered these data as fulfilling the requirements for the evaluation of the safety of the novel food ingredient and did not request additional testing neither for chronic toxicity and carcinogenicity nor for reprotoxicity and developmental toxicity. The Panel therefore concluded that the proposed use and use levels of MMST as a source of silicon to be used in food supplements is not of safety concern. The conversion of MMST to orthosilicic acid (OSA), the form under which silicon is typically present in food, could not be directly measured, and therefore, the Panel based its opinion on the indirect evidence provided and concluded that OSA is released from MMST and silicon bioavailable from the source. The Panel did not conclude on the safety of MMST in terms of the amount of silicon that may be consumed, as this is outside the remit of the ANS Panel.