Dietary Glutamate Will Not Affect Pain in Fibromyalgia
RINIE GEENEN, ERICA L. JANSSENS, JOHANNES W.G. JACOBS, and WIJA A. van STAVEREN
ABSTRACT.
Injection of glutamate into the masseter muscle has been suggested to evoke an increase in intensity of and sensitivity to pain. A case study showed that a diet low in monosodium glutamate (MSG) might accomplish pain relief in fibromyalgia (FM). To clarify the possible pain-modulating effect of dietary glutamate, theoretical considerations about modes of action and empirical findings of reduced intake, common daily intake, and ingestion of relatively large amounts of glutamate are discussed. Of the total amount of dietary glutamate, hardly any enters the circulation. When relatively high concentrations of glutamate are ingested without food, a short-lived increase in serum and intramuscular glutamate concentrations is observed. However, glutamate concentration in the central nervous system (CNS) is maintained fairly independently of fluctuations in serum concentrations. Even extreme serum glutamate concentrations are not expected to enhance pain via glutaminergic activation of N-methyl-d-aspartate receptors. The "MSG symptom complex" does not include widespread pain among the symptoms and is based on other processes than increase of glutamate in the CNS. Thus, based on present knowledge about glutamate consumption and its metabolism in humans, dietary reduction of glutamate will not accomplish pain relief in patients with FM. There is a possibility that pharmacological doses of glutamate may enhance pain in FM, but this needs further investigation. (J Rheumatol 2004;31:785-7)
Key Indexing Terms:
FIBROMYALGIA
PAIN
DIET
GLUTAMATE
MONOSODIUM GLUTAMATE
DIETARY AMINO ACIDS
From the Department of Health Psychology, Utrecht University; the Division of Human Nutrition and Epidemiology, Wageningen University; the Department of Rheumatology and Clinical Immunology and the Division Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
R. Geenen, PhD, Assistant Professor; E.L. Janssens, MSc; J.W.G. Jacobs, MD, PhD, Associate Professor; W.A. van Staveren, PhD, Professor.
Address reprint requests to Dr. R. Geenen, Department of Health Psychology, Utrecht University, PO Box 80140, 3508 TC Utrecht, The Netherlands. E-mail: R.Geenen@home.nl
Submitted May 21, 2003; revision accepted October 6, 2003.
