Quesadilla: everything measured here was measured on the tortilla

A quesadilla is a tortilla with melted cheese, and the research under that name is research on the tortilla. The lime cooking that turns maize into masa carries the strongest numbers. In 40 healthy adults in Soweto assigned to eat deliberately mouldy maize, nixtamalization cut fumonisin B1 and B2 by 95 percent and zearalenone by 89 percent, with the reductions measured in maize porridge rather than in tortillas. In the same 40 people the urinary markers told another story, and fumonisin B1, zearalenone and its metabolites came out no different between the nixtamalized and the control group (p > 0.05). That intervention was short and the background diet was already high in maize, so unchanged urine may be reading other sources. Minerals behave the way maize makes them behave. Ten healthy Mexican women aged 21 to 51 absorbed about the same share of the zinc from corn tortilla whether it was fortified or not, 0.35 plus or minus 0.07 unfortified against 0.36 and 0.37 for two fortificants (SEM), from single test meals. The quantity of zinc they took up was still significantly lower from the plain tortilla, so the share of a dose and the amount absorbed are two separate readings. Elemental iron added to corn masa flour reached a geometric mean bioavailability of 3.8 percent (range 2.7 to 5.3) in 24 children aged 5 to 7 years, and disodium EDTA lifted it to 5.1 percent at P = 0.18, which is no lift. The isotope particles were 15 micrometres across, finer than commercial elemental iron powder, so a real fortified tortilla may deliver less.

What your body absorbs

• Fortifying corn tortilla with 20 mg/kg zinc as zinc oxide gave the same fractional zinc absorption as zinc sulfate and as unfortified tortilla, about 0.35 to 0.37 of the dose in adult women. — 10 healthy adult women, randomised double-blind crossover, single test meals in two phases (n = 10) Evidence B source
  Fractional zinc absorption 0.35 +/- 0.07 unfortified, 0.36 +/- 0.05 zinc oxide, 0.37 +/- 0.07 zinc sulfate (SEM), no difference between treatments
• In the same 10 women the total zinc taken up from plain corn tortilla was significantly lower than from tortilla fortified with 20 mg/kg of zinc, even though the share of the dose absorbed stayed at about 0.35 either way. — 10 healthy women aged 21 to 51 years, staff or students of a Mexican nutrition institute, latin square meal sequence (n = 10) Evidence B source
  Significantly less zinc absorbed from unfortified tortilla than from either fortified tortilla, with the two fortificants similar to each other
• Elemental iron added to corn masa flour reached only 3.8 percent bioavailability in children aged 5 to 7 years, and disodium EDTA did not significantly raise it. — two groups of 12 children aged 5 to 7 years fed labelled tortillas, blood sampled after 14 days (n = 24) Evidence B source
  Geometric mean bioavailability 3.8 percent (range 2.7 to 5.3); with disodium EDTA 5.1 percent (2.8 to 9.2), P = 0.18

What cooking and storage change

• Phytate in maize holds back the calcium that the lime cooking of tortillas adds: women absorbed 0.50 of the calcium from low-phytate maize tortillas against 0.35 from ordinary maize. — 5 healthy adult women, two test meals of about 140 g tortillas one month apart, calcium isotopes (n = 5) Evidence C source
  Fractional calcium absorption 0.50 +/- 0.03 from low-phytate maize versus 0.35 +/- 0.07 from wild-type maize, P = 0.003
• Nixtamalization, the alkaline cooking that turns maize into masa for tortillas, cut fumonisin B1 and B2 by 95 percent and zearalenone by 89 percent in visibly mouldy maize. — 40 healthy adults in an informal settlement in Soweto, South Africa, randomly assigned to control or mouldy nixtamalized maize (n = 40) Evidence B source
  Fumonisin B1 minus 95 percent, fumonisin B2 minus 95 percent, zearalenone minus 89 percent in the maize; fumonisin B3 and deoxynivalenol down to undetectable

What it does to your health

• Replacing 30 percent of the refined flour in tortillas with soy flour lowered blood glucose 90 to 120 minutes after the meal in adults with overweight or obesity. — 17 adults with overweight or obesity, repeated measures, tortilla matrix eaten by 10 of them at 0, 10 and 30 percent soy flour (n = 17) Evidence B source
  Lower plasma glucose at 90 to 120 minutes for tortillas (p = 0.0009); glucose area under the curve lower for breads (p = 0.03) and arepas (p = 0.04); insulin, hunger and satiety unchanged
• Among Mexican adolescents the better breakfasts drew their extra protein and calcium from eggs, milk, cheese and lime treated tortilla, the same pairing a quesadilla is built on. — 230 Mexican freshmen aged about 18 years, two 24 hour recalls, breakfast quality index tertiles (n = 230) Evidence C source
  Highest breakfast quality tertile had greater protein (p = 0.007) and calcium (p = 0.050) intake; no anthropometric differences between tertiles

Safety, limits and interactions

• A preservative overdose in flour tortillas made 721 people ill in Finnish schools in 2023, with calcium propionate measured above 24000 mg/kg against a legal maximum of 2000 mg/kg. — 721 pupils and staff in 17 schools of one Finnish municipality, questionnaire-based retrospective cohort (n = 721) Evidence C source
  Adjusted odds ratio 3.3 (95% CI 1.4 to 7.4) for eating the tortillas, odds not risk; 45 percent of cases fell ill during or within 30 minutes of lunch
• Each extra maize tortilla a day went with 2.0 percent higher blood levels of an aflatoxin adduct in Mexican adults, and tortillas from homemade masa carried the strongest link. — 915 adults aged 40 years and over in south and eastern Mexico, 2018 to 2019, median maize intake 307 g a day (n = 915) Evidence C source
  Per 30 g of maize, AFB1-lysine plus 2.1 percent (95% CI 0.9 to 3.4); per tortilla plus 2.0 percent (95% CI 0.6 to 3.4); homemade masa tortilla plus 2.8 percent (95% CI 1.1 to 4.6)

What people believe that the data does not support

• The belief that American corn tortillas now carry folic acid does not hold: of 43 corn masa and tortilla products photographed in 28 states, three masa flours had it and no tortilla did. — 132 product photographs of 43 unique corn masa flour or corn tortilla products from 28 US states, January 2019 (n = 43 products) Evidence C source
  3 of 43 products fortified, all of them masa flour; zero of the tortilla products fortified

Who this works differently for

• When folic acid actually added to Mexican tortillas and bread was measured, up to 12 percent of younger children were taking in more than the tolerable upper intake level, while 9 to 33 percent of women of childbearing age still fell below the average requirement. — national 24 hour recall data, Mexican National Health and Nutrition Survey 2012, recalculated with measured folic acid in tortillas and bakery bread (n = national survey sample) Evidence C source
  9 to 33 percent of women of childbearing age below the EAR; up to 12 percent of younger children above the UL
• Red blood cell folate in Hispanic women of childbearing age in the United States was 963 nmol/L against 1043 in white women before corn masa fortification was allowed, and it showed no improvement afterwards. — 8 studies, 20123 Hispanic women of reproductive age in the United States, before and after voluntary fortification of corn masa flour (n = 20123) Evidence C source
  RBC folate 963 versus 1043 nmol/L before fortification with no post-fortification improvement; neural tube defect rate 7.5 versus 7.1 per 10000 live births

What is still unknown

• Although nixtamalization removed most of the mycotoxin from the maize, urinary markers of exposure in the same 40 adults did not differ between the nixtamalized and the control group. — 40 healthy adults, urine analysed for fumonisin B1, zearalenone and its metabolites after eating either maize (n = 40) Evidence B source
  No significant difference between groups for urinary fumonisin B1, zearalenone, alpha and beta zearalenol (p > 0.05); deoxynivalenol and tenuazonic acid unaffected, detected in over 90 percent of samples
• The authors of that review graded their own evidence on folic acid intake and birth defects in this population as low to very low across every outcome. — 8 studies, 20123 Hispanic women of reproductive age in the United States (n = 20123) Evidence C source
  GRADE certainty low to very low for all outcomes

The bottom line

Cheese on lime treated tortilla does show up in the data, as an association and nothing more. Among 230 Mexican freshmen with two 24 hour recalls, the third with the highest breakfast quality took in more protein (p = 0.007) and more calcium (p = 0.050), drawn mostly from eggs, milk, nixtamalized tortilla, cheese and processed meats. That was a cross sectional study with a locally built index. Replacing 30 percent of the refined flour with soy flour lowered plasma glucose 90 to 120 minutes after a tortilla meal in 17 adults with overweight or obesity (p = 0.0009), from single meals. That reads a glucose curve over two hours and no health outcome. The cautions on this page come from the maize side. In 2023, 721 pupils and staff in 17 schools of one Finnish municipality fell ill after flour tortillas in which calcium propionate was measured above 24000 mg/kg against a legal maximum of 2000 mg/kg. Eating those tortillas carried an adjusted odds ratio of 3.3 (95% CI 1.4 to 7.4), which is odds and not risk. The investigators call that cause likely rather than proven, because the manufacturer found no production fault and only three samples held the high concentration. In 915 Mexican adults aged 40 and over, each extra tortilla a day went with a 2.0 percent higher blood aflatoxin adduct (95% CI 0.6 to 3.4). That comes from cross sectional data with self reported intake and a Mexican maize supply whose contamination differs from other countries. Folic acid cuts both ways at once. When the amount actually present in Mexican tortillas and bakery bread was assayed and put back through national survey data, up to 12 percent of younger children came out above the tolerable upper intake level. In the same recalculation 9 to 33 percent of women of childbearing age stayed below the average requirement, with tortilla values standing in for other corn masa foods. If you buy corn tortillas in the United States expecting folic acid, 3 of 43 photographed corn masa and tortilla products carried it in January 2019, and all three were flours. None of the tortilla products had it, in a crowdsourced sample of shelves across 28 states. Red blood cell folate in Hispanic women of reproductive age was 963 nmol/L against 1043 nmol/L in white women before voluntary corn masa fortification and showed no improvement after it, across 8 studies and 20123 women. The authors of that review graded their own evidence low to very low on every outcome, which is the ceiling on every folate figure here. So a corn tortilla is not a folic acid source to count on before or during pregnancy: none of the 43 photographed tortilla products carried it, and the women most likely to rely on it showed no rise in red blood cell folate after voluntary fortification was allowed. We have no USDA composition entry for quesadilla in this cohort, so this page carries no number for the cheese, the calcium or the energy in one.

Sources

1. ques-daily-r1-01 · randomised controlled 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 2026-09-24
2. ques-daily-r1-02 · randomised controlled trial
   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 2026-09-24
3. ques-daily-r1-03 · randomised 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).
   J Nutr, 2004 · checked 2026-09-24
4. ques-daily-r1-04 · clinical trial, not randomised
   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 2026-09-24
5. ques-daily-r1-05 · randomised controlled trial
   Nixtamalization achieved a reduction in fumonisin B3 and deoxynivalenol (DON) to unquantifiable or undetectable levels in maize, while reducing fumonisin B1 (FB1), fumonisin B2, and zearalenone (ZEN) by 95%, 95%, and 89%, respectively.
   Toxins (Basel), 2025 · checked 2026-09-24
6. ques-daily-r1-13 · randomised controlled trial
   Compared with the control condition, 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).
   Nutrients, 2026 · checked 2026-09-24
7. ques-daily-r1-14 · 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 2026-09-24
8. ques-daily-r1-07 · outbreak investigation, retrospective cohort
   In a questionnaire-based retrospective cohort study, consumption of flour tortillas and vegetable filling served at lunch were statistically associated with illness (adjusted odds ratio (aOR) = 3.3; 95% confidence interval (CI): 1.4-7.4 for the tortillas and aOR = 1.5; 95% CI: 1.1-2.1 for the filling).
   Euro Surveill, 2026 · checked 2026-09-24
9. ques-daily-r1-08 · cross-sectional study
   After multivariable adjustment, for every 30 g of maize consumed (1 tortilla equivalent), circulating AFB1-lys incremented by 2.1% [95% confidence interval (CI): 0.9%, 3.4%].
   Am J Clin Nutr, 2025 · checked 2026-09-24
10. ques-daily-r1-10 · prevalence survey of 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.
    Birth Defects Res, 2019 · checked 2026-09-24
11. ques-daily-r1-09 · nutrition survey analysis
    Despite accounting for FA-fortified staple foods, 9-33% of women of childbearing age still have intake below the EAR, whereas up to 12% of younger children have intake above the UL.
    Am J Clin Nutr, 2019 · checked 2026-09-24
12. ques-daily-r1-11 · systematic review of observational studies
    RBC folate concentrations were lower among Hispanic women compared to NHW women pre-voluntary fortification (963 nmol per liter (nmol/L) versus 1043 nmol/L) but showed no improvement post-fortification.
    BMC Public Health, 2025 · checked 2026-09-24
13. ques-daily-r1-06 · randomised controlled trial
    Biomarker analysis revealed that after consumption of either control or nixtamalized maize, urinary levels of FB1, ZEN, and its metabolites
    Toxins (Basel), 2025 · checked 2026-09-24
14. ques-daily-r1-12 · systematic review of observational studies
    The certainty of evidence, assessed using the Grading of Recommendations, Assessment, Development, and Evaluations framework, ranged from low to very low across outcomes.
    BMC Public Health, 2025 · checked 2026-09-24