From what I understand, silica is considered non-toxic. I also understand that many people do what you are doing is doing "loading doses" of silica in order to get it into their system quickly and then taper down to a maintenence dose. On some boards people have said that increasing silica intake was beneficial, and others have said that taking the recommended dose worked just as well. So it seems to depend on the individual.
Here is some information I found for you regarding doses.
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The average daily intake of silica from the diet is approximately 20 to 50 milligrams per day, but the optimum dose is higher. Researchers are finding that by supplementing the diet with a minimum of 40 milligrams of silica a day, the skin shows an improvement of elasticity, texture and thickness. Added benefits include helping weakened teeth and gums, strengthening bones, and decreasing hair loss. Overall, silica was found to help the body repair, rebuild, strengthen, and lessen or eliminate many body ailments associated with aging.
Silica is considered safe and virtually non-toxic. For easiest assimilation, the best form is to take it in liquid, for internal assistance, or lotion for direct application to the skin. Nutritionists can recommend as much as 1000 milligrams per day
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The above quote was taken from this link
http://www.appliedhealth.com/ahs_digest/digest050199.html
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