Nevertheless, when OSA is present at concentrations higher than 2 mM, as in most products, it undergoes dehydration and polymerization, which leads to a reduced solubility and hence to a low bioavailability 5. ![]() Other works have described similar results for OSA, showing urinary excretion of approximately 50% of the ingested Si dose 15. 14 revealed that 43% of the Si administered as OSA was absorbed, whereas the bioavailability of orally polymeric Si was less than 5%. In this sense, a study by Sripanyakorn et al. In contrast, oligomeric and polymeric forms are poorly absorbable in the gastrointestinal tract. OSA, a monomeric form, is one of the most bioavailable sources of Si due to its high solubility 12, 13. However, similar to foods, the bioavailability of Si in oral dietary supplements greatly varies depending on the chemical form. However, no recommended dietary allowance for Si has been established. According to the European Food Safety Authority (EFSA), the estimated average dietary intake of Si is 20–50 mg/day 8, 9, 10, corresponding to 0.3–0.8 mg silicon/kg body weight/day for a 60-kg person, and these intakes are unlikely to cause adverse effects 5, 6, 11. The bioavailability of Si in foods and beverages depends on the Si total content and the form presented 6, 7. This mineral is naturally present in foods as Si dioxide (SiO 2) and silicates, while most Si in water is present as free orthosilicic acid (OSA H 4SiO 4) 5. Si is the second most common element in the Earth’s crust behind oxygen 4. Thus, oral supplemental Si is widely used in humans for improving osteoporosis 2, hair loss and nail and hair quality 3. Both in vitro and in vivo studies point out that Si exerts beneficial properties on the structural integrity of nails, hair and skin and on the synthesis of collagen and bone mineralization 1. The health benefits of silicon (Si) have been widely reported over the last decades 1. The 3 different oral Si formulations tested, in powder and liquid presentations, provide highly bioavailable Si and present an equivalent relative absorption in healthy humans. No significant differences in total urinary Si excretion were found after the intake of these 3 dietary supplements 34.6%, 32.4% and 27.2% of the ingested Si from G7 Aloe, G5 Siliplant and Orgono Powder, respectively, was excreted in urine over the 6-h follow-up period. Urine was collected at baseline and over the 6-h post-dose period in 2 separate 3-h collections for the analysis of Si concentration, which was conducted by inductively coupled plasma optical emission spectrometry as the gold standard method. ![]() All dietary supplements were administered at the same Si oral dose (21.6 mg) in a randomized, double-blind, crossover post-prandial study conducted in 5 healthy men. The purpose of the present study was to compare the relative absorption of a new powder presentation of silicon (Si) as orthosilicic acid with maltodextrin (Orgono Powder) compared to usual Si liquid presentations as orthosilicic acid with Equisetum arvense and Rosmarinus officinalis (G5 Siliplant) and orthosilicic acid with aloe vera (G7 Aloe).
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