Silicon: Safety Assessment

The United Kingdom’s Expert Group on Vitamins and Minerals (EVM) last assessed vitamins and minerals for safety in 2003 and, where sufficient data were available, set a so-called Safe Upper Level (SUL) or Guidance Level for each micronutrient. This SUL or Guidance Level reflects the safe maximum amount of a micronutrient that will not cause any side effects when taken daily from all sources for a lifetime.

The maximum safe daily intake for silicon is 760 mg. The above safe maximum amount is for elemental silicon and is equivalent to approximately 1,500 mg of silicon dioxide (silica).

Adverse effects due to high silicon intake via conventional foods are not known. In animal studies, no adverse effects occurred at intakes of 3 g of silicon dioxide per kg of body weight per day.

The NOAEL (No Observed Adverse Effect Level) – the highest dose of a substance that has no detectable and measurable adverse effects even with continued intake – was set by EVM at 2.5 g (2,500 mg) of silicon dioxide per kg body weight per day based on animal studies. This amount is approximately 100 times the safe daily maximum for silicon for a person weighing 70 kg.

Adverse effects of excessive silicon intake

Patients taking magnesium trisilicate as an antacid (drug used to neutralize stomach acid) have been found to have nephrolithiasis (kidney stones) as a long-term side effect, which is attributed to the silicon contained in the drug.

Long-term inhalation of dusts containing silicon in large quantities caused silicosis (dust lung disease) as well as nephropathy (kidney disease) in workers in the ceramics industry. Such adverse effects cannot occur via oral silicon intake from food.

In animal studies, 7.5 g (7,500 mg) of silicon dioxide per kg body weight per day, ingested over 21 months, led to growth disorders.

Significant human studies on the safety of sustained high silicon intake are unfortunately lacking, but results from animal studies indicate that relatively large amounts of silicon are also tolerated in humans without undesirable side effects.