Many patients tell me that monosodium glutamate (MSG) gives them headaches, but we never had a scientific study to explain or support this observation.  A study by Brian Cairns and his colleagues in the November issue of journal Pain reveals possible mechanism by which this happens.  The researchers found that rats given MSG had an elevated level of glutamate in their muscles and that MSG made the muscles more sensitive to pressure.  Glutamate is a neurotransmitter that promotes pain transmission in the nerveous system and therefore the authors concluded that MSG could increase pain sensitivity in humans as well.  The bottom line, if you are prone to headaches or have chronic pain, stay away from MSG.