Headache and mechanical sensitization of human pericranial muscles after repeated intake of monosodium glutamate (MSG)
1 Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Vennelyst Boulevard 9, Aarhus C 8000, Denmark
2 Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
3 Section of Oral Medicine, Clinical Oral Physiology, Oral Pathology & Anatomy, Department of Odontology, Faculty of Health Sciences, University of Copenhagen, Nørre Allé 20, Copenhagen, 2200 København N, Denmark
4 MindLab, Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Nørrebrogade 44, Aarhus C 8000, Denmark
The Journal of Headache and Pain 2013, 14:2 doi:10.1186/1129-2377-14-2Published: 24 January 2013
A single intake of monosodium glutamate (MSG) may cause headache and increased muscle sensitivity. We conducted a double-blinded, placebo-controlled, crossover study to examine the effect of repeated MSG intake on spontaneous pain, mechanical sensitivity of masticatory muscles, side effects, and blood pressure.
Fourteen healthy subjects participated in 5 daily sessions for one week of MSG intake (150 mg/kg) or placebo (24 mg/kg NaCl) (randomized, double-blinded). Spontaneous pain, pressure pain thresholds and tolerance levels for the masseter and temporalis muscles, side effects, and blood pressure were evaluated before and 15, 30, and 50 min after MSG intake. Whole saliva samples were taken before and 30 min after MSG intake to assess glutamate concentrations.
Headache occurred in 8/14 subjects during MSG and 2/14 during placebo (P = 0.041). Salivary glutamate concentrations on Day 5 were elevated significantly (P < 0.05). Pressure pain thresholds in masseter muscle were reduced by MSG on Day 2 and 5 (P < 0.05). Blood pressure was significantly elevated after MSG (P < 0.040).
In conclusion, MSG induced mechanical sensitization in masseter muscle and adverse effects such as headache and short-lasting blood pressure elevation for which tolerance did not develop over 5 days of MSG intake.