Abstract: The present invention includes an aqueous solution, comprising boric acid and non-colloidal silicic acid. This solution can also comprise a water absorbing additive. The solution contains bioavailable non-colloidal silicic acid, and the solution is stable for more than one year. The invention also describes a method for the preparation of a solution in which one or more silicon and boron compounds are hydrolysed in an acidic solution containing one or more dissolved water absorbing additives.