Silica (silicon dioxide) is used in some powdered foods to ensure that they are free flowing. It is also used heavily in the manufacture of steel, thermal insulation, electronic circuit boards, semiconductors, and optical fibers. While its industrial uses are many, its health benefits appear to be nil.
Silica is a compound that is found in soil. There are people who have made the asinine assumption that it must be beneficial to health based on this. Another basis for the assumption about silica's benefits is the fact that trace amounts of it are found inside fruits and vegetables, which could produce some minor contributions to good health, but mostly to the health of those fruits and vegetables. Supplementing with silica has not been shown to provide any health benefits to humans, and all silica supplements contain far more silica than anyone could consume naturally.
Silica dust is a known carcinogen, lung irritant, and a central nervous system toxin. Although, it has been shown to be relatively neutralized when filtered through the human digestive system. This somewhat makes the point about how stupid silica supplementation really is. Since it is destroyed by the human digestive system, injections would be the only way to actually supplement with it. The website owners who profit from the fraud of silica supplements claim that it does all of the following:
The list of supposed silica benefits goes on practically forever, so this is not a full listing of claims. It would be much simpler to list what its sales people do not make any claims about. The latter would be a very short list. Those who have a health condition, could search the Internet for their ailment alongside the word "silica", and they would undoubtedly find accolades about it being the very "miracle" that they had been seeking. Some companies have appeared on the market being dedicated to selling only silica, at prices which exceed those of real supplements. They are essentially selling sand as a high-priced dietary supplement, but it does not actually supplement any nutrient.
When silica is obtained from the horsetail plant (the standard process), it can actually cause a thiamine (vitamin B-1) deficiency. Thiamine is a real nutrient with real benefits. On the other hand, a silica (dirt) supplement simply is not going to be of much use to anyone, except the salesmen. A wise person should instead eat a balanced diet of natural foods, avoid refined sugars, and avoid chemicals. Sure enough, he will get trace amounts of silica in his diet too. Likewise, he will get trace amounts of other unnecessary elements which we would also never recommend supplementing with, like arsenic.
"Studies in mice suggest that horsetail [source of silica supplements] may change the activity of the kidneys, causing abnormal control of the amount of water and potassium release. Low potassium, which in theory may occur with horsetail, can have negative effects on the heart."
The above quote cites the only known effect of silica supplementation. Eventual heart attacks are hardly a desirable effect of any supplement. We do not know the effect of supplementing with silica over an extended period of time. No one knows. All we know with certainty is that silica supplementation has never been proven to have any benefits for humans whatsoever, and we also know that it so thoroughly destroys the kidneys of laboratory animals that they become prone to having heart attacks.
Regular vitamins and supplements, which contain small amounts of silica are not harmful; but the presence of silica will not present any therapeutic effect, either.