Monosodium glutamate (MSG) is a sodium salt of the naturally occurring amino acid, glutamic acid, used as a flavor enhancer. It is responsible for the savory taste known as umami, the fifth basic taste. Since its discovery in 1908, MSG has been linked anecdotally to adverse reactions, including headaches and migraines. Despite its “Generally Recognized as Safe” (GRAS) status by the U.S. Food and Drug Administration (FDA), whether MSG can trigger these painful episodes remains a common consumer concern.
Scientific Evidence Linking MSG to Headaches
The scientific community has attempted to resolve the MSG-headache controversy primarily through rigorous double-blind, placebo-controlled studies, the highest standard of evidence. These trials have generally failed to establish a direct, consistent, and dose-dependent causal link between MSG consumption and the onset of migraines. A systematic review concluded that no statistically significant difference in headache incidence was observed when MSG was consumed with food.
Many early studies reporting a connection used extremely high doses of MSG, often five to ten times greater than the average daily intake, administered in a liquid solution without food. This methodology is criticized because food profoundly changes how the body metabolizes glutamate, and high doses in liquid compromise the study’s “blinding.” The transient symptoms sometimes reported after consuming MSG, such as flushing, tingling, and mild headache, are referred to as the “MSG symptom complex,” but these effects are not consistently triggered in controlled settings.
The International Headache Society removed MSG from its list of definite headache causes, reflecting the lack of robust evidence across large-scale studies. While some small studies have reported increased sensitivity after participants consumed a high dose (e.g., 150 mg/kg of body weight), the consensus is that MSG is not a universal migraine trigger for most people consuming it at typical levels.
The Biological Theory of Glutamate Sensitivity
The theoretical connection between MSG and headaches centers on glutamate’s role as the primary excitatory neurotransmitter in the central nervous system. While essential for normal brain function, excessive levels can lead to excitotoxicity—the over-excitation of nerve cells that disrupts neurotransmission and triggers pain pathways.
In individuals prone to migraines, the glutamatergic system is already implicated in the disorder’s pathophysiology. Glutamate is involved in trigeminovascular activation, central sensitization, and cortical spreading depression (CSD), the neurophysiological event underlying migraine aura. The theory suggests that an influx of dietary glutamate might perturb this sensitive system in susceptible individuals, potentially lowering the threshold for a migraine attack.
However, the glutamate in MSG is chemically identical to the glutamate produced naturally by the body and found in high-protein foods like aged cheese and tomatoes. The vast majority of ingested glutamate is metabolized in the gut and does not cross the blood-brain barrier. Therefore, while glutamate signaling is linked to migraine mechanisms, the direct consumption of MSG as a trigger is not definitively proven for most people.
Identifying and Avoiding MSG in Foods
For readers who suspect MSG is a personal trigger, a systematic approach to dietary modification can help confirm sensitivity. The FDA requires that pure MSG added to a product must be listed specifically as “monosodium glutamate” on the ingredient panel. This is the most straightforward way to identify the direct additive in packaged foods.
Avoiding MSG is complex because many common ingredients naturally contain high levels of free glutamate, which can produce the same reaction in sensitive individuals. These ingredients are not required to be labeled as “MSG” and include:
- Hydrolyzed vegetable protein.
- Autolyzed yeast.
- Yeast extract.
- Soy extracts.
- Protein isolate.
The term “natural flavor/s” can also be used for ingredients containing glutamic acid.
If attempting to eliminate MSG, an elimination diet should focus on removing both the direct additive and these common sources of free glutamate. Tracking symptoms in a headache diary while avoiding these ingredients for a trial period, typically two weeks, provides actionable data. Simply avoiding foods with a “No Added MSG” claim may be insufficient, as that claim is permissible even if the product contains ingredients naturally rich in free glutamate.