226 Glossary
of muscles, helps in the formation of insulin and helps prevent macular
degeneration (one of the most common causes of vision loss in the elderly)
and helps prevent the onset of cataracts. It is important for blood stability
exerts a normalising effect on the prostate and development of all repro-
ductive organs. Zinc is critical in the male sex drive and is involved in
hormone metabolism, sperm formation and sperm motility. It helps prevent
and reduce the length and severity of the common cold.
Zone: An area distinguished by a range of annual average minimum temperatures
and used in describing plant hardiness. Regions that share similar climatic
and rainfall conditions producing similar growing seasons.