Could Free Glutamic Acid in Processed Food be the Surprise Ingredient in Mood Disorders?

Letter to the editor: Given the complex nature underlying mood disorders, and evidence that glutamic acid neurotransmitters play a role in the pathophysiology of mood disorders, and given the fact that mood swings are one of the reactions/symptoms that follow ingestion of ingredients that contain manufactured free glutamic acid (MfG), it is proposed here that consideration of the possibility that ingestion of MfG in processed and ultra-processed foods causes or exacerbates mood disorders would be in order.

The symptoms of glutamate toxicity following ingestion of glutamate are many and varied. The Truth in Labeling Campaign maintains a list of adverse reactions experienced by MSG-sensitive people which includes depression, mood swings, rage reactions, migraine headache, dizziness, light-headedness, mental confusion, anxiety, panic attacks, and hyperactivity among the neurological reactions; with cardiac, circulatory, gastrointestinal, muscular, visual, respiratory, urological/genital, and skin reactions as well. Mood swings, however, are essentially experienced by all.

For a short time, the FDA Adverse Reactions Monitoring System collected unsolicited reports of adverse reactions to monosodium glutamate (MSG) (Table 1).

Table 1.

Symptoms Attributed to MSG in Complaints Submitted to FDA. ^*

Reported Symptoms	No. of Reports	% Of Reports	% Of Complaints
Headache	315	43.9%	17.9%
Vomiting and Nausea	136	19.0%	7.7%
Diarrhea	104	14.5%	5.9%
Abdominal pain and cramps	95	13.2%	5.4%
Change in mood quality or level	93	13.0%	5.3%
Change in heart rate	90	12.6%	5.1%
Dizziness or problems with balance	63	8.8%	3.6%
Difficulty Breathing	59	8.2%	3.4%
Fatigue, Weakness	54	7.5%	3.1%
Localized Pain or Tenderness	46	6.4%	2.6%
Sleep Problems	44	6.1%	2.5%
Change in Sensation (Numbness, Tingling)	42	5.9%	2.4%
Change in Body Temperature	41	5.7%	2.3%
Change in Vision	40	5.6%	2.3%
Change in Activity Level	35	4.9%	2.0%
Chest Pain	34	4.7%	1.9%
Local Swelling	32	4.5%	1.8%
Difficulty Swallowing	25	3.5%	1.4%
Joint and Bone Pain	23	3.2%	1.3%
Changes in Skin and Nail Coloration	21	2.9%	1.2%
Blood Pressure Changes	21	2.9%	1.2%
Other Neurological	21	2.9%	1.2%
Other Symptoms (reported by less than 20 complaints)	331	-----	18.80%

*

Some consumers described more than one symptom attributed to MSG.

From 1980 through the end of 1996, the FDA Center for Food Safety and Applied Nutrition received 717 unsolicited reports describing adverse reactions attributed to monosodium glutamate (MSG).

This summary was provided by Technical Information Specialist (HFS-728) on June 26, 1997.

There are more than 40 food ingredients used in processed and ultra-processed foods that contain MfG. All cause reactions when amounts ingested exceed an individual's tolerance for MfG. ¹

Prior to 1957, free glutamate available to consumers came largely from MSG (brand name Accent) marketed as a flavor enhancer, and there had been no published reports of either glutamate-induced adverse reactions or brain damage. The free-glutamate component of MSG was being made by extraction of glutamate from a protein source, a slow and costly procedure, and there was not enough manufactured free glutamate in processed food to cause adverse reactions or cause glutamate to become excitotoxic.

That changed in 1957 with the advent of glutamate production by bacterial fermentation. Glutamate could then be mass-produced in virtually unlimited quantities, and Ajinomoto began to market its new product aggressively. Shortly thereafter, food manufacturers found that profits could be increased by utilizing flavor-enhancers (additives that contained free glutamate). Over the next two decades, the marketplace became flooded with manufactured/processed free-glutamate added to processed foods in ingredients such as hydrolyzed proteins, yeast extracts, maltodextrin, soy protein isolate, and monosodium glutamate (MSG).

Today, free glutamate is found in abundance in a variety of ingredients used in processed and ultra-processed foods, snacks, infant formulas, enteral care products, dietary supplements, protein-fortified foods, drinks made from protein powders, and in many of the so-called “plant-based” products.

Soon after use of genetically modified bacteria in the production of MSG began, availability of MSG and other MfG-containing products increased to the point where there was more than sufficient MfG to become excitotoxic if a number of processed and ultra-processed foods were consumed during the course of a day.

Holton and others have demonstrated the effectiveness of a low free-glutamate diet in reducing the symptoms Of Gulf War illness -- symptoms that include mood disorders. ²

The possibility that free glutamate consumed in processed foods causes or exacerbates mood disorders might hold the key to a better understanding and treatment of these mental health problems.