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Silica is silicon dioxide, one form of which is commonly known as sand. It is, by definition, inorganic. However, some plants absorb silicon compounds, such as monosilicic acid, from the soil, which are then converted by the plants into a non-crystalline form of silica called a phytolith. Phytoliths could be considered "organic silica" since they are manufactured by plants, but, strictly speaking, to a chemist, they are still inorganic, since the chemical structure does not contain carbon. The term organic is ambiguous: to a chemist, it must contain carbon, to a biologist, it is "related to, or derived from living organisms."〔(【引用サイトリンク】title=Merriam-Webster Dictionary )〕 It is conceivable that silica could be hydrolyzed in mammalian gastrointestinal tracts to orthosilicic acid, which could be bioavailable, but the extent to which this occurs is unknown. According to the Framingham and Framingham Offspring studies, the main food sources for silicon in humans are beer, bananas, and string beans. However, giving foods to human volunteers and then measuring the absorption of silicone compounds gave some results that conflicted with the epidemiological figures, such as regarding bananas: Food-based, phytolithic silica is digested and absorbed from the gastrointestinal tract. Silicon in grains and grain products (rice, breakfast cereals, breads, and pasta) was readily absorbed, as indicated by the mean urinary excretion of 49 ± 34% of intake (range: 10–100%). However, except for green beans and raisins, the silicon in vegetables and fruit was less readily absorbed, as indicated by the mean urinary excretion of 21 ± 29% of intake (range: 0–40%). Surprisingly, silicon uptake was low (2.1 ± 1.2% of intake) from bananas, which are high in silicon (5.4 mg Si/100 g edible portion) and were one of the highest contributors to silicon intake in the Framingham cohorts. This suggests either that silicon is mainly present in an unavailable form in bananas or that this silicon is absorbed late from the gastrointestinal tract (after 6 h). In general, however, silicon was readily available from foods and in many cases, it showed absorption similar to that of silicon from fluids.〔(【引用サイトリンク】title=Dietary silicon intake and absorption )〕 There may be a human nutritional requirement for silicon, but not for silica per se. This subject has been the subject of scientific controversy for decades. There is no conceivable way that silica itself could be considered essential, since there is no known method by which it can be absorbed or used as such in the human body other than by being converted into soluble silicon compounds. French scientist J. Loeper, of the Laboratoire de Médecine Expérimentale in Paris, and UCLA's Dr. Edith Muriel Carlisle, published numerous studies over a period of decades touting the importance of silicon in human nutrition. Loeper hypothesized that a deficiency contributed to numerous diseases. As described by Forrest Nielsen of the USDA's Agricultural Research Service in 2003, Silicon was actually first reported as possibly being an essential nutrient more than 30 years ago. For the next 25 years, the battle of bringing attention to the nutritional importance was fought, not too successfully, by a scientist who promoted the hypothesis that inadequate dietary silicon could contribute to diseases associated with aging such as atherosclerosis, high blood pressure, osteoarthritis and osteoporosis. After this scientist's death, studies examining the nutritional importance of silicon came to a standstill until about 2 years ago. Then several research groups reported new findings indicating that silicon is important for joint cartilage and bone formation and maintenance, thus boosting the suggesting that silicon is a nutrient of concern for osteoporosis, and perhaps osteoarthritis.〔(【引用サイトリンク】title=Silicon: An Essential Nutrient of Good Bone Health )〕 "Alternate" health practitioners and advocates make numerous claims for "silica," touting its supposed efficacy in preventing and treating various diseases, such as the claims being made below. Note that, except for the Jugdaohsingh article, found in a 2007 issue of the Journal of nutrition, health and aging, the sources cited are secondary and non-scientific, and many of the claims are speculative: Organic silica aids in bone and cartilage growth, accelerates healing, prevents bone injuries and helps with arthritis. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Organic silica」の詳細全文を読む スポンサード リンク
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