Is monosodium glutamate (MSG) bad for one's health?

Is Ajinomoto (MSG) Bad for Health?

Monosodium glutamate (MSG/Ajinomoto) is generally safe at typical dietary doses, but high doses or repeated exposure may cause transient symptoms like headache and should be consumed in moderation, particularly avoiding large amounts on an empty stomach.

Safety Profile at Normal Dietary Intake

The evidence shows MSG is classified as "generally recognized as safe" (GRAS) by regulatory agencies when consumed at typical dietary levels 1. The largest double-blind, placebo-controlled study to date (130 subjects) found that MSG given with food produced no consistent or reproducible adverse reactions 1. This is critical: the context of consumption matters significantly.

Documented Acute Effects

When consumed in large doses without food, MSG can trigger symptoms in susceptible individuals:

• Headache: Occurred in 8/14 subjects with repeated MSG intake (150 mg/kg daily) versus 2/14 with placebo over 5 days 2
• Muscle sensitivity: Pressure pain thresholds in masseter muscles were reduced after MSG on days 2 and 5 2
• Blood pressure elevation: Significant but short-lasting increases were observed 2
• No tolerance development: These effects persisted without adaptation over 5 consecutive days of exposure 2

The key finding is that these symptoms occurred with excessive dosing (150 mg/kg) that far exceeds normal dietary intake 3.

Chronic High-Dose Concerns

Preclinical studies suggest potential risks with chronic high-dose exposure, but these have limited relevance to human dietary intake:

• Animal studies link MSG to obesity, diabetes, hepatotoxicity, and neurotoxicity 4, 5
• However, these studies used doses and administration routes (often injections) that don't reflect human dietary consumption patterns 3
• The mechanisms proposed include hypothalamic lesions, oxidative stress, and metabolic disruption 4

Critical caveat: These animal studies have significant methodological flaws and use dosing regimens that are not representative of human dietary exposure 3.

Clinical Recommendations

For typical consumers:

• MSG is safe when consumed as part of regular meals at amounts typically used in food preparation 1, 3
• Avoid consuming large amounts on an empty stomach, as this increases symptom likelihood 1

For individuals reporting MSG sensitivity:

• Symptoms are inconsistent and not reliably reproducible even in self-identified sensitive individuals 1
• The so-called "Chinese Restaurant Syndrome" has little supporting evidence in controlled trials 3
• If symptoms occur, they are typically transient and resolve without intervention 2

Populations requiring caution:

• Those with hypertension should be aware of the sodium content (MSG contains approximately 12% sodium by weight) and the potential for acute blood pressure elevation 2
• Pregnant women should follow general dietary moderation principles, though specific human pregnancy data are lacking 5

Bottom Line

The dose makes the poison. MSG consumed as a flavor enhancer in normal food preparation poses minimal risk 1, 3. The global consumption exceeding 3 million metric tons annually reflects its widespread acceptance 4, but this doesn't negate the need for moderation. Avoid megadoses on an empty stomach and be mindful of total sodium intake from all sources 2.