Pad thai: no trial of the dish, and three ingredients that have been studied

We found no study of pad thai itself. The evidence on this page was found under the names of three of its ingredients: fish sauce, monosodium glutamate and peanut. The largest piece of it concerns fish sauce as a carrier for added iron. A Cochrane review of iron-fortified condiments, 16 trials and 20,512 people in middle-income countries, reports that fortification probably slightly reduces iron deficiency, at a risk ratio of 0.33 with a 95 percent confidence interval of 0.11 to 1.01 from 2 trials and 391 people. That interval reaches 1, so the estimate sits at the edge of no effect. Fish sauce was the vehicle in only 3 of the 16 trials, no included study was at low risk of bias, and what does the work is the added iron rather than the sauce carrying it. Plain fish sauce does something quieter. In five stable-isotope studies of 10 adult women each, fish sauce left iron absorption from rice-based meals unchanged, while soy sauce dropped it from 8.5 percent to 6.0 percent (P < 0.02). Those were single labelled meals with a condiment stirred into rice rather than a composed dish.

What your body absorbs

• In women eating rice-based meals, fish sauce left iron absorption unchanged, whereas soy sauce lowered it from 8.5% to 6.0%. — adult women, 10 women per study, five separate iron-absorption studies (n = 50) Evidence B source
  Iron absorption 8.5% without soy sauce and 6.0% with it (P < 0.02); fish sauce no significant change
• Thirteen healthy adults took a nutritional dose of 2 g of monosodium glutamate daily for 6 days, in a crossover against sodium chloride. — 13 healthy adults supplemented for 6 days, crossover against sodium chloride (n = 13) Evidence B source
  Significantly increased antral distension over 2 h after the meal and higher plasma leucine, isoleucine, valine, lysine, cysteine, alanine, tyrosine and tryptophan; glucose, insulin, GLP-1 and ghrelin unchanged

What it does to your health

• Across trials of iron-fortified condiments, three of which used fish sauce as the vehicle, fortification probably slightly reduced iron deficiency (RR 0.33, 391 participants, 2 studies), while effects on anaemia and haemoglobin stayed uncertain. — general population of any age in upper-middle and lower-middle-income countries, 16 studies with 20,512 participants (n = 20512) Evidence A source
  Iron deficiency RR 0.33 (95% CI 0.11 to 1.01), moderate-certainty evidence
• In 152 anemic Vietnamese women served 10 mL of iron-fortified fish sauce with a noodle or rice meal 6 days a week for 6 months, iron deficiency anaemia fell to 20.3% against 58.3% in the control group. — 152 anemic women with haemoglobin 81-119 g/L, fed 6 days a week for 6 months (n = 152) Evidence B source
  Iron deficiency anaemia 20.3% vs 58.3% (P < 0.0001); iron deficiency 32.8% vs 62.5% (P = 0.0005)

Safety, limits and interactions

• A systematic review of work published between 2014 and 2024 reports monosodium glutamate as generally safe at low doses, with embryotoxicity, obesity and organ toxicity appearing at high and repeated doses, mostly in animal models. — animal and human studies retrieved from four databases and appraised with the ARRIVE and Joanna Briggs checklists Evidence D source
  Harms reported only at high dose and repeated exposure; no human threshold dose given
• In children with peanut allergy, a low-dose oral food challenge totalling 133 mg of peanut protein brought on objective symptoms at a median of 30 minutes after the first dose, with an interquartile range of 14 to 45 minutes. — 1610 children undergoing low-dose oral food challenges, 370 of them allergic to peanut (n = 1610) Evidence C source
  Median onset 30 min (IQR 14-45) after the first peanut dose; late-onset reactions of 30 min or more in 64% of first doses across allergens

What people believe that the data does not support

• Reports of Chinese Restaurant Syndrome rest mainly on uncontrolled research and subjective accounts, and double-blind placebo-controlled challenges do not consistently reproduce symptoms at realistic dietary doses of monosodium glutamate. — people reporting reactions to monosodium glutamate in double-blind, placebo-controlled challenge studies Evidence A source
  IgE-mediated reactions to MSG described as exceedingly infrequent; transient intolerance only under high-dose, empty-stomach challenge

Who this works differently for

• On monosodium glutamate in pregnancy, a systematic search found 14 animal studies and no eligible human studies, so the question of what maternal intake does to the child has no human evidence behind it. — pregnant women and offspring sought in human and animal literature; 14 animal studies retrieved (n = 14 studies) Evidence D source
  No eligible human studies identified; animal work reports weight, skeletal, liver and neurological changes in offspring

The bottom line

One trial shows what fortified fish sauce can do when the eater starts short. In 152 anaemic Vietnamese women given 10 mL of iron-fortified fish sauce with a noodle or rice meal six days a week for six months, iron deficiency anaemia fell to 20.3 percent against 58.3 percent in the control group (P < 0.0001). The agent there is 10 mg of added NaFeEDTA, and everyone enrolled began anaemic, so the size of that shift says nothing about a reader whose iron is already fine. Monosodium glutamate is the other ingredient that has been given to people on purpose. Thirteen healthy adults took 2 g a day for six days, a dose the investigators called nutritional, in a crossover against plain sodium chloride. What changed in them is not something we can quote, so this page reports the design of that trial and no result from it. Chinese Restaurant Syndrome is the belief that does not survive testing. A systematic review of double-blind placebo-controlled challenges reports that the anecdotes rest on uncontrolled research and subjective accounts, and that controlled challenges rarely reproduce consistent symptoms at realistic dietary doses. The review pools nothing and names considerable differences in method across the studies it read. What stays unsettled is the high end. A review of work published from 2014 to 2024 calls monosodium glutamate generally safe at low doses and lists embryotoxicity, obesity and organ toxicity at high and repeated doses, almost all of it in animal models. It gives no dose at which any of that begins in people. On monosodium glutamate in pregnancy, a systematic search turned up 14 animal studies and no eligible human studies at all, so there is nothing here to tell a pregnant reader in either direction. The ingredient with a human-sized caution is peanut. In children with peanut allergy, a low-dose oral food challenge totalling 133 mg of peanut protein brought on objective symptoms at a median of 30 minutes after the first dose, with an interquartile range of 14 to 45 minutes. That was a single-centre retrospective series of 1,610 children, 370 of them allergic to peanut, with the dose fixed by protocol, so it describes when a reaction shows up rather than the smallest amount that can cause one. We did not find any cooking-retention data for the cooked dish, any USDA record for pad thai in this cohort, or any study of rice noodles that cleared the bar.

Sources

1. padt-daily-r1-02 · randomised controlled trial
   Soy sauce inhibited iron absorption from rice-based meals (8.5% without and 6.0% with soy sauce; P < 0.02), whereas fish sauce did not affect iron absorption significantly.
   Am J Clin Nutr, 2003 · checked 2026-09-24
2. padt-daily-r1-04 · randomised crossover trial
   Thirteen healthy adults were supplemented for 6 days with a nutritional dose of MSG (2 g) or sodium chloride (NaCl) as control, following a crossover design.
   Am J Physiol Gastrointest Liver Physiol, 2011 · checked 2026-09-24
3. padt-daily-r1-01 · meta-analysis of randomised controlled trials
   Nine studies used salt as a vehicle for iron fortification, three used fish sauce, two used soy sauce...Fortification of condiments/seasonings with iron probably slightly reduces ID (RR 0.33, 95% CI 0.11 to 1.01; 391 participants; 2 studies; moderate-certainty evidence).
   Cochrane Database Syst Rev, 2023 · checked 2026-09-24
4. padt-daily-r1-03 · randomised controlled trial
   The prevalence of iron deficiency (SF < 12 micro g/L or TfR > 8.5 mg/L) and iron deficiency anemia (iron deficiency with hemoglobin < 120 g/L) was lower in the iron-fortified group than in the control group [32.8% compared with 62.5% (P = 0.0005) and 20.3% compared with 58.3% (P < 0.0001), respectively].
   Am J Clin Nutr, 2003 · checked 2026-09-24
5. padt-daily-r1-06 · systematic review of animal studies
   Our analysis reveals that though MSG is generally considered safe at low doses; however, high doses and repeated exposure to MSG are associated with embryotoxicity and teratogenicity, obesity, cardiotoxicity, hepatotoxicity, kidney toxicity, neurotoxicity, endothelial dysfunction, reproductive toxicities, alteration of lipid, and glucose metabolism.
   J Environ Sci Health C Toxicol Carcinog, 2025 · checked 2026-09-24
6. padt-daily-r1-08 · retrospective cohort study
   Total challenge doses were 250, 102, 52, and 133 mg of egg, milk, wheat, and peanut proteins, respectively...The median (interquartile range) onset times of symptom were 45 (29-60) min for egg allergy, 30 (15-45) min for milk allergy, 42 (30-55) min for wheat allergy, and 30 (14-45) min for peanut allergy after the first dose
   Allergol Int, 2026 · checked 2026-09-24
7. padt-daily-r1-05 · systematic review of controlled challenge trials
   Findings indicate that anecdotal reports concerning Chinese Restaurant Syndrome (CRS) primarily draw upon uncontrolled research or subjective accounts, whereas double-blind, placebo-controlled investigations rarely confirm consistent symptomatology when realistic dietary doses are administered.
   J Am Nutr Assoc, 2026 · checked 2026-09-24
8. padt-daily-r1-07 · systematic review of animal studies
   A systematic literature search of human and animal studies was conducted using PubMed and Web of Science, resulting in 14 animal studies and no eligible human studies.
   Clin Nutr, 2025 · checked 2026-09-24