How much silica do I absorb into my body each day?

Since silicon is the second most common element in our environment, it is continuously absorbed via the air or in food. Many natural foods, especially with a plant origin, contain high levels of silica. Therefore, it is virtually impossible to say just how much silica humans absorb each day. For synthetic amorphous silica (SAS) used in food additives the maximum level is up to 1500 mg per day. 

It is estimated that a person with a body weight of 70 kilograms absorbs about 20-320 mg SAS per day. The body excretes most natural and synthetic amorphous silica (SAS) before it reaches the bloodstream.

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Food, especially food of plant origin, can contain high levels of natural silica (corresponding to a daily silica intake of up to 400 mg and more, but only a small part of this is reabsorbed). Beer also contains a large amount of natural silica, which can exceed 100 mg per liter. (Casey et al. J. Sci. Food Agric. (2010) 90, 784–788.) Since silica in beer is in a colloidal dissolved form, resorption may be higher than with solid food. Food supplements sold in the European Union may contain a daily dose of 1500 mg SAS. (The EFSA Journal (2009) 1132, 1-24.) 
In contrast, the average daily intake of synthetic amorphous silica (in the form of E 551) is estimated to be 0.28-4.53 mg/kg body weight, which corresponds to about 21 – 324 mg per day for someone weighing 70 kg. (Fruijtier-Polloth, C. Arch. Toxicol. (2016) 1-32.) 

It must also be considered that only a very small part of SAS is actually reabsorbed, in other words, gets into the bloodstream. Most silica is excreted unchanged with the stool before it reaches the bloodstream.