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Headache and mechanical sensitization of human pericranial muscles after repeated intake of monosodium glutamate
Akiko Shimada1, Brian E Cairns, Nynne Vad
1Section of Clinical Oral Physiology, Department of Dentistry, Faculty of Health Sciences, Aarhus University, Vennelyst Boulevard 9, Aarhus C 8000, Denmark. akiko.shimada@odontologi.au.dk
Background:
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.
Methods:
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.
Results:
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).
Conclusion:
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.
Insights
Repeated monosodium glutamate (MSG) intake can cause headaches and increase muscle sensitivity, with no tolerance developing over five days. This study investigated MSG
Area of Science:
- Neuroscience
- Pharmacology
- Physiology
Background:
- Monosodium glutamate (MSG) intake is linked to headaches and heightened muscle sensitivity.
- Previous research suggests potential adverse effects from MSG consumption.
- Understanding the impact of repeated MSG exposure is crucial for public health.
Purpose of the Study:
- To investigate the effects of repeated monosodium glutamate (MSG) intake on spontaneous pain.
- To assess mechanical sensitivity in masticatory muscles following MSG consumption.
- To evaluate side effects and blood pressure changes associated with repeated MSG intake.
Main Methods:
- A randomized, double-blinded, placebo-controlled, crossover study was conducted.
- Fourteen healthy subjects received daily MSG (150 mg/kg) or placebo for one week.
- Pain thresholds, muscle sensitivity, side effects, blood pressure, and salivary glutamate were measured.
Main Results:
- Headaches were more frequent with MSG intake (8/14) compared to placebo (2/14).
- MSG significantly reduced pressure pain thresholds in the masseter muscle on days 2 and 5.
- Elevated salivary glutamate and increased blood pressure were observed after MSG consumption.
Conclusions:
- MSG intake can induce mechanical sensitization in the masseter muscle.
- Adverse effects like headaches and transient blood pressure elevation occurred with MSG.
- No tolerance to these effects developed over the five-day study period.
