Tortillas: the calcium is real and the trials are tiny

Every feeding trial on this page is small, from 5 people to 24. The firmest thing in them is a mechanism measured with isotopes. Lime treatment, the nixtamalization that turns maize into masa, puts calcium into a corn tortilla, and phytate in the maize holds a good part of it back. In 5 healthy women eating a 140 g tortilla meal, fractional calcium absorption was 0.35 from ordinary maize and 0.50 from an experimental low-phytate maize (p = 0.003). That second maize is a research hybrid rather than anything on a shelf. Zinc works differently. In 10 Mexican women the fraction absorbed from corn tortilla was 0.35 plain, 0.36 with zinc oxide and 0.37 with zinc sulfate at 20 mg/kg, and adding 30 or 60 mg/kg of iron changed none of it. Fortifying did raise the total zinc those women absorbed, since fortified tortilla holds more zinc to begin with, and 70 to 80 percent of them started with plasma zinc below 70 ug/dL.

The numbers, per 100 g

What a real portion looks like

• Among 197 Mexican 18-year-old breakfast eaters, those in the top breakfast quality tertile took in more protein and calcium, and lime-treated nixtamalized tortilla was one of the main sources alongside eggs, milk and cheese. — 230 Mexican university freshmen aged 18.5, 197 breakfast eaters, two 24-h recalls (n = 230) Evidence C source
  Higher protein (p = 0.007) and calcium (p = 0.050) intake in the highest breakfast quality tertile; no anthropometric differences
• Fifty grams of tortilla chips took about 488 chews and 350 seconds in the mouth, the most of 35 savoury foods tested in 15 adults, against 27 chews for mashed potato. — 15 adults, 35 savoury foods at 50 g each over 5 sessions, video-recorded (n = 15) Evidence B source
  488 chews and 350 s oral exposure per 50 g of tortilla chips versus 27 chews for mashed potatoes and 27 s for canned tomatoes; chewing rate about 1 chew/s

What your body absorbs

• In 10 Mexican women, fractional zinc absorption from corn tortilla was 0.35 unfortified, 0.36 with zinc oxide and 0.37 with zinc sulfate at 20 mg/kg, and adding 30 or 60 mg/kg iron did not change it. — 10 adult women per phase, aged 21 to 51, Mexico City, stable isotope method (n = 10 per phase) Evidence B source
  Fractional zinc absorption 0.35 ± 0.07 (unfortified), 0.36 ± 0.05 (ZnO), 0.37 ± 0.07 (ZnSO4); with 0, 30, 60 mg/kg iron: 0.32, 0.33, 0.32, absorbed 4.8, 4.5, 4.8 mg/day
• In the same zinc trial, 70% to 80% of the 10 women per phase had plasma zinc below 70 ug/dL at baseline, and they absorbed less total zinc from plain tortilla than from tortilla fortified at 20 mg/kg. — 10 healthy women per phase, aged 21 to 51, Mexico City, no zinc supplements for 6 months (n = 10 per phase) Evidence B source
  Plasma zinc below 70 ug/dL in 70% (phase 1) and 80% (phase 2); less zinc absorbed from unfortified tortilla than from either fortified tortilla
• Calcium absorption from a 140 g tortilla meal rose from 0.35 to 0.50 in 5 women when the maize had about 60% less phytate, so phytate, only modestly reduced by nixtamalization, limits the calcium that lime treatment adds. — 5 healthy adult women, two test meals one month apart, dual-isotope method (n = 5) Evidence B source
  Fractional calcium absorption 0.50 ± 0.03 from low-phytate maize tortillas versus 0.35 ± 0.07 from wild-type maize (p = 0.003)
• Only 3.8% of hydrogen-reduced elemental iron added to corn masa tortillas was absorbed by children aged 5 to 7, and adding EDTA raised it to a non-significant 5.1%. — two groups of 12 Mexican children aged 5 to 7 years, stable isotope, 14-day follow-up (n = 24) Evidence B source
  Geometric mean bioavailability 3.8% (range 1 SD 2.7 to 5.3); with Na2EDTA 5.1% (2.8 to 9.2), p = 0.18

What cooking and storage change

• Replacing 30% of the refined flour in tortillas with soy flour lowered plasma glucose at 90 to 120 minutes after the meal. That was the 10 adults with overweight or obesity who took the tortilla arm of a 17-person crossover, and insulin and hunger ratings did not change. — 17 adults with overweight or obesity, tortilla arm n = 10, randomized repeated-measures crossover, single meals (n = 17) Evidence B source
  Lower plasma glucose at 90 to 120 min for tortillas with 30% soy flour (p = 0.0009); no difference in insulin, hunger or satiety; product liking maintained
• Barley tortillas with 11.6 g of beta-glucan per 50 g of available carbohydrate gave a lower glucose and insulin response than tortillas with 4.5 g in 12 healthy adults, while amylose and insoluble fibre content made no difference. — 12 healthy adults, six visits each, double-blind randomized crossover (n = 12) Evidence B source
  Lower postprandial glucose and insulin with high beta-glucan (11.6 g) versus low beta-glucan (4.5 g) tortillas; higher GLP-1 AUC with high insoluble fibre (19.6 g vs 7.4 g)
• Two 28 g servings a day of tortilla chips fried in oil carrying 1.5 g of heat-modified free phytosterols cut plasma cholesterol by 10% and LDL by 15% over 4 weeks in 7 adults, with HDL unchanged. Tortilla chips as sold were not tested. — 7 adults, two 4-week crossover periods (n = 7) Evidence B source
  Plasma cholesterol down 10%, LDL cholesterol down 15%, HDL unchanged, with 1.5 g/d phytosterols delivered in tortilla chips

What it does to your health

• A 250 kcal mid-morning snack of tortilla chips raised glucose and insulin more than the same calories from pecans in 20 adults with overweight or obesity, while appetite ratings and lunch intake did not differ. — 20 adults with overweight or obesity, standardized breakfast then snack, randomized crossover (n = 20) Evidence B source
  Higher glucose and insulin after tortilla chips; higher free fatty acids, triglycerides, PYY and GLP-1 after pecans; no difference in VAS appetite or energy intake at lunch

Safety, limits and interactions

• Among 915 Mexican adults aged 40 and over, each maize tortilla eaten per day was associated with 2.0% higher circulating aflatoxin B1-lysine, and the link was driven by tortillas made from homemade masa (2.8% per tortilla). — 915 adults aged 40 or older, south and eastern Mexico, 2018 to 2019, food frequency questionnaire and serum AFB1-lysine (n = 915) Evidence C source
  2.0% (95% CI 0.6% to 3.4%) higher AFB1-lys per maize tortilla per day; 2.8% (1.1% to 4.6%) for homemade masa tortilla; minimal for store-bought masa or maize flour
• In a 2023 Finnish school outbreak of 721 cases, flour tortillas carrying more than 24,000 mg/kg of the preservative calcium propionate, over ten times the EU limit of 2,000 mg/kg, were the likely cause of rapid gastrointestinal symptoms. — 721 ill individuals in 17 schools in one Finnish municipality, August 2023, questionnaire-based retrospective cohort (n = 721) Evidence C source
  Adjusted OR 3.3 (95% CI 1.4 to 7.4) for tortilla consumption; calcium propionate above 24,000 mg/kg in three samples versus a regulatory maximum of 2,000 mg/kg

What people believe that the data does not support

• Three years after the FDA allowed folic acid in corn masa flour, a 2019 survey of 43 corn masa and corn tortilla products across 28 US states found folic acid in only three masa flours and in no corn tortilla at all. — 132 product photos from 28 US states via a social media campaign, 43 unique corn masa flour or corn tortilla products, January 2019 (n = 43 products) Evidence C source
  3 of 43 products fortified with folic acid, all masa flours; 0 corn tortilla products fortified
• US regulation permits, but does not require, folic acid in corn masa flour, capped at 0.7 mg of folic acid per pound of flour, which is why the folate on a corn tortilla label depends on the brand. — corn masa flour sold in the United States Evidence E source
  Voluntary addition allowed at up to 0.7 mg folic acid per pound of corn masa flour (21 CFR 172.345(i))
• WHO recommends fortifying maize flour and corn meal with iron and with folic acid, for children, women and neural tube defect prevention, and grades the evidence behind both recommendations as very low quality. — populations where maize flour and corn meal are staples, particularly children and women Evidence E source
  Iron fortification recommended to prevent iron deficiency; folic acid fortification recommended to reduce neural tube defects; both on very low-quality evidence

The bottom line

What is mixed into the dough moves the glucose curve more than the tortilla does. Swapping 30 percent of the refined flour for soy flour lowered plasma glucose at 90 to 120 minutes after a single meal (p = 0.0009), in a crossover trial of 17 adults with overweight or obesity, 10 of whom took the tortilla arm. Insulin, hunger and fullness ratings were the same. Tortillas made of barley flour with 11.6 g of beta-glucan per 50 g of available carbohydrate produced a lower glucose and insulin response than the same tortillas with 4.5 g, in 12 healthy adults. Amylose and insoluble fibre made no difference there. Neither product is the corn or wheat tortilla in a supermarket packet, and both trials measured one meal and stopped. Tortilla chips are a separate food and they behave like one. A 250 kcal mid-morning snack of chips raised glucose and insulin more than 250 kcal of pecans in 20 adults with overweight or obesity, while appetite ratings and what they ate at lunch did not differ. Chips were also the hardest work in the mouth of 35 savoury foods tested on 15 adults, at about 488 chews and 350 seconds per 50 g, against 27 chews for mashed potato. That study recorded chewing, not what anyone ate afterwards. In a third trial 7 adults ate two 28 g servings a day of tortilla chips fried in oil carrying 1.5 g of heat-modified free phytosterols, and over four weeks their plasma cholesterol fell 10 percent and LDL 15 percent, with HDL unchanged. Seven people, a laboratory-made chip, and the phytosterols were the active part. Chips as sold were never in that trial. The folate on a corn tortilla is a question about the brand. US rules have permitted folic acid in corn masa flour since 2016, up to 0.7 mg per pound, and they do not require it. A crowd-sourced survey in January 2019 collected 43 unique corn masa flour and corn tortilla products from 28 states and found folic acid in three masa flours and in none of the tortillas. That was a convenience sample seven years ago, and a shelf today may look different. WHO recommends fortifying maize flour and corn meal with iron and with folic acid, and grades the evidence behind both recommendations as very low quality. That recommendation is aimed at industrial flour and at preventing neural tube defects, and the survey above means a corn tortilla cannot be counted on to carry folic acid at all. Iron added to a tortilla is not a formality either. In 24 Mexican children aged 5 to 7, 3.8 percent of the hydrogen-reduced elemental iron in corn masa tortillas was absorbed, and adding EDTA lifted that to 5.1 percent, which did not reach significance (p = 0.18). Two cautions sit here, and both are about how a tortilla was made. Among 915 Mexican adults aged 40 and over, each maize tortilla eaten per day went with 2.0 percent higher circulating aflatoxin B1-lysine (CI 0.6 to 3.4 percent), and the association sat with tortillas from homemade masa at 2.8 percent per tortilla, while store-bought masa and maize flour showed minimal amounts. That is a cross-sectional study with self-reported intake in the Mexican maize supply, and it measured an exposure marker rather than liver disease. In August 2023, 721 people across 17 schools of one Finnish municipality fell ill quickly after school meals, and eating the flour tortilla carried an adjusted odds ratio of 3.3 (CI 1.4 to 7.4). Three tortilla samples held more than 24,000 mg/kg of calcium propionate against an EU limit of 2,000 mg/kg. That was one production period at one manufacturer. On the other side, among 197 Mexican 18-year-olds who ate breakfast, those in the top third for breakfast quality took in more protein and calcium, and nixtamalized tortilla was one of the main sources alongside eggs, milk and cheese. That is one campus and two days of recall. What this page cannot give you is a number for what is in a tortilla, because no card here carries the composition of one, and the USDA retention tables have no tortilla entry, so the cost of reheating is unmeasured. We found nothing on medicines and nothing on children beyond the iron absorption trial above. On pregnancy the page carries only the WHO fortification recommendation, which is about industrial flour rather than about tortillas as sold. It carries no card on allergens either, so on the wheat, barley and soy flours that appear in the trials above it has nothing to tell you.

Sources

1. tort-c1-14 · cross-sectional study
   breakfasters in the highest BQI tertile had significantly greater intakes of protein (p = 0.007) and calcium (p = 0.050), primarily derived from eggs, milk, lime-treated (nixtamalized) tortilla, cheese, and processed meats.
   Appetite, 2026 · checked 2026-09-23
2. tort-c1-15 · randomized within-subjects trial
   Average number of chews for 50 g of food varied from 27 for mashed potatoes to 488 for tortilla chips. Oral exposure time was highly correlated with the total number of chews, and varied from 27 s for canned tomatoes to 350 s for tortilla chips.
   Appetite, 2013 · checked 2026-09-23
3. tort-c1-03 · randomized crossover trial
   The mean (+/- SEM) fractional zinc absorption from unfortified tortilla, tortilla fortified with zinc oxide, and tortilla fortified with zinc sulfate did not differ among treatments: 0.35 +/- 0.07, 0.36 +/- 0.05, and 0.37 +/- 0.07, respectively.
   Food Nutr Bull, 2012 · checked 2026-09-23
4. tort-c1-04 · randomized crossover trial
   The prevalence of plasma zinc levels < 70 μg/dL was 70% in the first phase of the study and 80% in the second phase, and 67% of women had erythrocyte zinc < 12 μg/mL in both phases of the study...The subjects absorbed significantly less zinc with CT than with fortified tortillas, and absorption from both fortified tortillas (CT + ZnO and CT + ZnSO4) was similar.
   Food Nutr Bull, 2012 · checked 2026-09-23
5. tort-c1-05 · clinical crossover trial
   Bioavailability of calcium is, however, compromised by phytate, which is present in large quantities in maize kernels and is only modestly reduced by nixtamalization...Mean fractional absorption of calcium from tortillas prepared from the low-phytate maize (0.50 +/- 0.03) was significantly (P = 0.003) greater than that from tortillas prepared from the control maize (0.35 +/- 0.07).
   Am J Clin Nutr, 2005 · checked 2026-09-23
6. tort-c1-06 · randomized controlled trial
   When normalized to 40% absorption of the reference dose, the geometric mean (+/-range 1 SD) bioavailability of reduced iron in tortilla was 3.8% (2.7-5.3). The addition of Na(2)EDTA, tended to increase it (P = 0.18) to 5.1% (2.8-9.2).
   J Nutr, 2004 · checked 2026-09-23
7. tort-c1-01 · randomized crossover trial
   substituting 30% of refined flour with soy flour significantly reduced the area under the concentration-time curve for postprandial glucose for breads (p = 0.03) and arepas (p = 0.04), and reduced plasma glucose concentrations at 90-120 min for tortillas (p = 0.0009). In contrast, postprandial insulin concentrations and subjective hunger and satiety ratings did not differ across substitution levels or food matrices (all p > 0.05).
   Nutrients, 2026 · checked 2026-09-23
8. tort-c1-02 · randomized crossover trial
   Amylose and insoluble fibre content did not alter postprandial glucose and insulin, but high-β-glucan tortillas elicited a lower glucose and insulin response as compared to the low-β-glucan tortillas.
   Br J Nutr, 2015 · checked 2026-09-23
9. tort-c1-10 · randomized crossover trial
   subjects (n = 7) consumed two 28-g servings of tortilla chips fried in oil with or without phytosterols that provided 0 or 1.5 g/d for 4-wk periods in a crossover design (Expt. 3). During consumption of the phytosterol-enriched chips, significant reductions in plasma cholesterol (10%) and LDL cholesterol (15%) were achieved without affecting HDL-C.
   J Nutr, 2004 · checked 2026-09-23
10. tort-c1-09 · randomized crossover trial
    VAS ratings, energy, food intake and macronutrient composition did not differ between treatment conditions, but glucose and insulin were significantly more elevated after tortilla chips.
    Nutrients, 2024 · checked 2026-09-23
11. tort-c1-07 · cross-sectional study
    For every maize tortilla consumed, the concentration of circulating AFB1-lys was 2.0% (95% CI: 0.6%, 3.4%) higher. The corresponding estimate for homemade masa tortilla was 2.8% (95% CI: 1.1%, 4.6%). The magnitude of the estimates for tortillas made from store-purchased masa or bought in a tortilleria and those made from store-bought maize flour was minimal.
    Am J Clin Nutr, 2025 · checked 2026-09-23
12. tort-c1-08 · retrospective cohort study
    In three samples from tortillas produced during a limited production period, high concentrations of calcium propionate (E 282) were measured (> 24,000 mg/kg), exceeding the regulatory maximum limit of 2,000 mg/kg.
    Euro Surveill, 2026 · checked 2026-09-23
13. tort-c1-11 · prevalence survey
    People from 28 states shared photos of 132 products, including 43 unique corn masa flour or corn tortilla products. Of those, only three corn masa flour products included folic acid: (a) Maseca Instant White (4.4 lb bag); (b) Masa Brosa Instant; and (c) Masa Brosa Instant Blue. None of the corn tortilla products were fortified.
    Birth Defects Res, 2019 · checked 2026-09-23
14. tort-c1-12 · regulation
    Folic acid may be added to corn masa flour at a level not to exceed 0.7 milligrams of folic acid per pound of corn masa flour.
    21 CFR 172.345 Folic acid (folacin), eCFR, current · checked 2026-09-23
15. tort-c1-13 · agency guideline
    Fortification of maize flour and corn meal with iron is recommended to prevent iron deficiency in populations, particularly vulnerable groups such as children and women (very low-quality evidence).2 •• Fortification of maize flour and corn meal with folic acid is recommended to reduce the risk of occurrence of births with neural tube defects (very low-quality evidence).
    WHO guideline: Fortification of maize flour and corn meal with vitamins and minerals, 2016 · checked 2026-09-23