Silica found in "do-not-eat" packets is a desiccant (I'm not sure about this); and so is activated charcoal. Would consuming it have the same effect if one were to have a stomach ache?
The silica gel granules are granular silicon dioxide (SiO2), the same matrial from what is the normal sand.
The pure SiO2 has the same effect to health as when you eat sand.
But because the granules are larger, may cause appendix problems (im not an doc). Anyway, this is not chemical related problem.
It can cause dehydratation or other problems, what is caused by it absorbtion capabality.
The bigger problem is, than the standard silica gel granules aren't pure SiO2. The common additivas are what causes color change when it is moistured, like cobalt chloride or others and thise compounds can be toxic!
So, don't eat it!
Silica and charcoal are both adsorbents.
However, silica is polar thanks to its plentiful OH groups, it preferentially adsorbs water, and that's why it is encountered in desiccant packages. In the chemical laboratory one filters stuff through silica pads to separate polar materials out of solutions in non-polar solvents.
Activated charcoal is non-polar; it consists of aromatic rings, and it preferentially adsorbs non-polar molecules. It is used in deodorizing packages. In the lab, decolorizing charcoal is used in polar solvents to get rid of coloured impurities.
No, they are not equivalent.