Fish sauce: a tablespoon of sodium, studied mostly as a way to deliver iron

A Cochrane meta-analysis of 4 studies in 2328 people found iron fortified condiments, fish sauce among them, linked to an anemia risk ratio of 0.34 (95% CI 0.18 to 0.65). The reviewers rate that evidence very low certainty, because every study carried a high risk of bias. Almost all the research on fish sauce works this way. Scientists in Vietnam, Cambodia and Thailand add iron, thiamine or iodine to it because people there use it daily. The sauce on a supermarket shelf is a different product. What it does carry is salt. One tablespoon (16 g) holds about 1256 mg of sodium in US survey data, with brands varying. The WHO asks adults to stay under 2 g of sodium a day, so one tablespoon uses more than half of it.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• One tablespoon of fish sauce (16 g) carries about 1,256 mg of sodium. — US survey food composition, per 16 g tablespoon Evidence E source
  Sodium 7851 mg per 3.5 oz (100 g), 1256 mg per tablespoon

What your body absorbs

• In stable isotope studies in adult women, adding 10 g of fish sauce to a rice meal did not significantly change iron absorption, while soy sauce lowered it from 8.5 to 6.0 percent. — Adult women, 10 per study, single labeled rice-based meals (n = 50) Evidence B source
  Fish sauce: no significant effect. Soy sauce: 8.5% vs 6.0% absorption (P < 0.02)
• Women absorbed about 3 percent of the iron added to fish sauce, with no difference between NaFeEDTA and ferrous sulfate. — Adult women, 10 per study, 10 g fortified fish sauce with 5 mg iron in a meal (n = 50) Evidence B source
  3.3% (NaFeEDTA) vs 3.1% (FeSO4), not significant
• In crossover isotope studies in 30 women, iron from ferrous sulfate fortified fish sauce was absorbed 50 to 100 percent better than from ferrous lactate or ferric ammonium citrate. — Adult women, 10 per study, rice and vegetable soup seasoned with fortified Thai fish sauce (n = 30) Evidence B source
  13.0% (FeSO4) vs 8.7% (ferrous lactate), P = 0.003; 11.7% vs 6.0% (ferric ammonium citrate), P < 0.001
• Adding chili to a rice meal with iron fortified fish sauce cut iron absorption by 38 percent in young women, while turmeric had no effect. — Healthy young women in Thailand, 10 per study, single test meals (n = 30) Evidence B source
  6.0% with chili vs 9.7% without (P = 0.0017)

What it does to your health

• A Cochrane meta-analysis found iron fortified condiments, including fish sauce, were linked to a risk ratio for anemia of 0.34 in 2328 people, but the certainty of this evidence is very low. — 4 studies, 2328 participants in middle-income countries (salt, fish sauce, soy sauce, curry powder vehicles) (n = 2328) Evidence A source
  Anemia RR 0.34 (95% CI 0.18 to 0.65), very low certainty
• A Cochrane review of foods other than salt, including fish sauce, found iodine fortification raised urinary iodine by about 38 ug/L. — 6 RCTs, 2032 participants, vehicles incl. biscuits, milk, fish sauce, water (n = 2032) Evidence A source
  SMD 0.59 (95% CI 0.37 to 0.81), about 38.32 ug/L, moderate quality

Safety, limits and interactions

• WHO recommends adults keep sodium below 2 g a day, a limit one tablespoon of fish sauce fills by more than half. — Adults, with lower limits for children Evidence E source
  Limit <2 g/day sodium (5 g/day salt)

Who this works differently for

• In a 6-month randomized trial in 152 anemic Vietnamese women, 2 tsp (10 mL) a day of iron fortified fish sauce lowered iron deficiency anemia from 58.3 to 20.3 percent versus control. — Anemic women in Vietnam, meal with 2 tsp (10 mL) fish sauce 6 days a week for 6 months (n = 152) Evidence B source
  Iron deficiency anemia 20.3% vs 58.3% (P < 0.0001), hemoglobin 116.3 vs 107.6 g/L
• In an 18-month village randomized trial in 576 Vietnamese women, NaFeEDTA fortified fish sauce cut iron deficiency from 22.3 to 4.0 percent and anemia from 24.7 to 8.5 percent. — Women of childbearing age in rural Vietnam, household fish sauce for 18 months (n = 576) Evidence B source
  Iron deficiency 22.3% to 4.0%, anemia 24.7% to 8.5% in fortified group, no change in control
• In a 21-week trial in 140 Cambodian students aged 6 to 21 with iron deficiency anemia, 2 tsp (10 mL) of fish sauce with 10 mg iron in school meals raised hemoglobin and ferritin compared with placebo sauce. — Students aged 6-21 with iron deficiency anemia in Kampot, Cambodia, 114 school meals over 21 weeks (n = 140) Evidence B source
  Hemoglobin and serum ferritin rose significantly vs placebo, no difference between NaFe-EDTA and FeSO4+citrate
• In a 6-month randomized trial in 90 pregnant Cambodian women, thiamine fortified fish sauce raised breast milk thiamine to 20.7 versus 14.4 ug/dL in controls. — Pregnant then lactating women in Prey Veng, Cambodia, ad libitum fish sauce for 6 months (n = 90) Evidence B source
  Breast milk thiamine 20.7 (low dose) and 17.7 (high dose) vs 14.4 ug/dL control
• In a 6-month randomized trial in 276 Cambodian women and their young children, thiamin fortified fish sauce raised women's erythrocyte thiamin to about 259 versus 184 nmol/L. — Nonpregnant women 18-45 and children 12-59 months in rural Cambodia, 6 months (n = 276) Evidence B source
  Women eTDP 259 (95% CI 245-274) vs 184 (169-198) nmol/L, P < .001

The bottom line

Plain fish sauce did not significantly change iron absorption when 10 g went into a rice meal, in isotope studies with 10 women each. Soy sauce, tested the same way, cut absorption from 8.5 to 6.0 percent. Iron added to the sauce was absorbed at about 3 percent, 3.3 for NaFeEDTA and 3.1 for ferrous sulfate, with no significant gap. In Thai women a rice and vegetable soup with ferrous sulfate sauce gave 13.0 percent absorption against 8.7 percent with ferrous lactate. Adding 4.2 g of dried chili to a meal with fortified sauce cut absorption by 38 percent, from 9.7 to 6.0 percent, while turmeric changed nothing measurable. The trials of fortified sauce are where the effects appear. In 152 anemic Vietnamese women eating a meal with 2 tsp (10 mL) of sauce carrying 10 mg of iron six days a week, iron deficiency anemia after 6 months stood at 20.3 percent against 58.3 percent in controls. In an 18 month trial randomized by village, 576 Vietnamese women saw iron deficiency fall from 22.3 to 4.0 percent and anemia from 24.7 to 8.5 percent, with no change in the control villages. In 140 Cambodian students aged 6 to 21 with iron deficiency anemia, fortified sauce in school meals for 21 weeks raised hemoglobin and ferritin against placebo sauce, and the abstract gives no sizes. Thiamine fortified sauce raised breast milk thiamine in 90 Cambodian women followed from pregnancy, to 20.7 and 17.7 against 14.4 micrograms per deciliter. In 276 Cambodian women it lifted red cell thiamine to about 259 against 184 nmol/L, a blood marker with no clinical outcome measured. A second Cochrane review, where fish sauce was one of several foods carrying iodine, found urinary iodine up by about 38 micrograms per liter in 6 trials of 2032 people, at moderate quality. The caution we can support is sodium, from the WHO limit above. We found no usable source on histamine in fish sauce and no study of fish allergy to this product. That leaves both questions open, and neither absence means the sauce is safe on those counts.

Sources

1. fsc-daily-r5-01 · Food composition dataset
   Fish sauce, fdc_id 2706457: Sodium, Na 7851 MG per 100 g; 1 tablespoon 16 g = 1256.2 MG
   USDA FoodData Central survey (FNDDS) 2024-10-31, fdc_id 2706457 · checked 2026-09-30
2. fsc-daily-r5-03 · Randomized 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 2026-09-30
3. fsc-daily-r5-04 · Randomized trial
   Iron absorption from NaFeEDTA- and FeSO(4)-fortified fish sauce (3.3% and 3.1%, respectively) and soy sauce (6.1% and 5.6%, respectively) was not significantly different.
   Am J Clin Nutr, 2003 · checked 2026-09-30
4. fsc-daily-r5-05 · Randomized crossover trial
   Fractional iron absorption (geometric mean; -1s.d., +1s.d.) was 8.7(3.6; 21.4)% for ferrous lactate compared to 13.0(5.4; 31.4)% from ferrous sulfate, P = 0.003 (study 1) and 6.0(2.5; 14.3)% from ferric ammonium citrate relative to 11.7(4.4; 30.7)% from ferrous sulfate, P < 0.001, in study 2.
   Eur J Clin Nutr, 2005 · checked 2026-09-30
5. fsc-daily-r5-06 · Randomized crossover trial
   Addition of freeze-dried chili (4.2 g dry powder, 25 mg polyphenols as gallic acid equivalents) reduced Fe absorption from the meal by 38% (6.0% with chili vs. 9.7% without chili, P = 0.0017).
   J Nutr, 2006 · checked 2026-09-30
6. fsc-daily-r5-10 · Cochrane systematic review
   We are uncertain about whether consuming condiments/seasonings fortified with iron in comparison to the same unfortified condiment reduces anaemia at the end of intervention (risk ratio (RR) 0.34, 95% confidence interval (CI) 0.18 to 0.65; 2328 participants; 4 studies; very low-certainty of evidence).
   Cochrane Database Syst Rev, 2023 · checked 2026-09-30
7. fsc-daily-r5-13 · Cochrane systematic review
   Pooled results from RCTs showed that urinary iodine concentration significantly increased following iodine fortification (SMD 0.59, 95% CI 0.37 to 0.81; 6 RCTs, 2032 participants; moderate-quality evidence). This is equivalent to an increase of 38.32 µg/L (95% CI 24.03 to 52.61 µg/L).
   Cochrane Database Syst Rev, 2019 · checked 2026-09-30
8. fsc-daily-r5-02 · WHO guideline
   WHO recommends a reduction to <2 g/day sodium (5 g/day salt) in adults (strong recommendation).
   WHO Guideline: sodium intake for adults and children, 2012 · checked 2026-09-30
9. fsc-daily-r5-07 · Randomized 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 2026-09-30
10. fsc-daily-r5-08 · Cluster randomized trial
    The prevalence of iron deficiency (SF < 12 microg/L) decreased from 22.3 to 4.0% and the prevalence of anemia (hemoglobin < 120 g/L) from 24.7 to 8.5% in Group F with no significant changes in Group C.
    J Nutr, 2005 · checked 2026-09-30
11. fsc-daily-r5-09 · Randomized controlled trial
    Both iron-fortified fish sauces increased hb and SF concentrations significantly as compared to placebo.
    Asia Pac J Clin Nutr, 2008 · checked 2026-09-30
12. fsc-daily-r5-11 · Randomized controlled trial
    Breast milk total thiamine concentrations were 14.4 μg/dL for the control group (95% CI, 12.3 μg/dL to 16.5 μg/dL) (to convert to nanomoles per liter, multiply by 29.6); 20.7 μg/dL for the low-concentration group (95% CI, 18.6 μg/dL to 22.7 μg/dL ); and 17.7 μg/dL for the high-concentration group (95% CI, 15.6 μg/dL to 19.9 μg/dL).
    JAMA Pediatr, 2016 · checked 2026-09-30
13. fsc-daily-r5-12 · Randomized controlled trial
    In intent-to-treat analysis, women's baseline-adjusted endline eTDP (mean; 95% CI) was higher among women in the low (259; 245-274 nmol/L) and high (257; 237-276 nmol/L) groups compared with control (184; 169-198 nmol/L; P < .001); low and high groups did not differ (P = .83).
    J Pediatr, 2017 · checked 2026-09-30