Sand is safe to eat…..well silicon is, anyway, says the European Food Safety Authority (EFSA), which has advised it is "unlikely to pose a risk of adverse health effects".

Although not an essential dietary component, silicon naturally occurs in foods as silicon dioxide (silica) and silicates, and is added as anti-caking and anti-foaming agents as silica, silicates and dimethylpolysiloxane; silicate-containing antacids are also widely used.

EFSA says the only reported silicon-related problems in humans have been occasional kidney stones. In rats and mice, high doses impeded growth. The typical dietary intake (20-50 mg silicon/day) is likely to be safe, concluded the authority.