a native hydrous magnesium silicate, sometimes with a small amount of aluminum silicate; used as a dusting powder. The inhalation of talc is associated with a wide variety of respiratory disorders.
Factors contributing to poor sleep include vitamin and mineral deficiencies. Magnesium deficiency can cause insomnia; lack of potassium can lead to difficulty staying asleep; and vitamin D deficiency has been linked to excessive daytime sleepiness.
Recent evidence for the nonskeletal effects of vitamin D, coupled with recognition that vitamin D deficiency is common, has revived interest in this hormone. Vitamin D is produced by skin exposed to ultraviolet B radiation or obtained from dietary sources, including supplements.