After oxygen, silicon is the most abundant element on earth. Its presence in our bodies might be thought of as that of an environmental contaminant. From the health point of view, most interest has centered on toxicity to the lungs from inhalation of silica dust. However, it has been shown in animals that silicon is essential for normal growth. Its action appears to be connected with bone mineralization and formation of connective tissue. The best known form of silicon is silica or sand, but this is not the form that has been used to prevent growth abnormalities in animals. In a different chemical form, known as a 'salt' form, it appears to be more available to metabolic processes. Good sources are wholegrain cereals and citrus fruits.