Relevant data on silicon research in humans have been inventoried. Although there are reliable data on the clinical effects of Si in humans this mineral is almost completely neglected in Medicine. These clinical effects are compared with the results of an open label study with a liquid food supplement with bioavailable and stabilized oligomeric silicic acid and a low dose of boric acid (OSAB) in Amsterdam during 2004-2007. OSAB showed to be a safe and beneficial food supplement with significant effects on connective tissue, bone, cartilage, skin, hair, nails, etc. The data confirm earlier clinical data in which show that Si is at least beneficial for humans and animals. Due to a lack of sufficient data on the metabolism of Si in humans essentiality has not (yet) been established. Silicon must be considered ‘quasi-essential’ as defined by Epstein (1999) for plants.
Silicon is contained in plants and also present in animals including humans. The quantity in humans is 7 grams being more than all other trace elements together. Nevertheless Si is not (or hardly) considered as beneficial: there is a lot of scepticism in regular Medicine because silicon has been considered to be inert in humans. In 1973 the Joint FAO/WHO Expert Committee on Food Additives says: ‘data on orally administered silica and silicates appear to substantiate the biological inertness of these compounds’. This negative attitude is surprising because for several hundreds of years extracts of Siaccumulating plants like Equisetum arvense (horsetail) have been used therapeutically for aging disorders, Alzheimer’s disease, atherosclerosis, brittle hair, fractures, fragile nails, back pain, osteoporosis, skin disorders, tendinitis, improved wound healing and wrinkles. On the other hand there is a lack on sufficient data on the metabolism of silicon in animals and humans. The absorption and bioavailability of silicon of the different silicon sources (silicates, metasilicates, etc.) is hardly known. There are neither standardised methods nor assays for assessing the silicon status in humans and animals. In part 1 the clinical effects of Si in men are described followed by the data on metabolism of Si in part 2. In part 3 the preliminary results of the Amsterdam Silicon Study in humans are published, which will be compared with literature data.