Tostada shells: fried corn with no study of its own

In a crossover trial in 20 adults with overweight, a 250 calories mid-morning snack of tortilla chips raised blood glucose and insulin more than the same calories of pecans, with appetite and later food intake unchanged. That was a single snack, the abstract gives no effect sizes, and the food was chips. We found no study of tostada shells themselves, so this page borrows from tortillas, chips and the maize they share. USDA lists corn tostada shells at 23.4 g fat and 7.0 g saturated fat per 3.5 oz (100 g), from a single record with no sample spread, and the frying oil and brand will move both numbers. The strongest thing to know about the corn is what lime cooking does to it. In a randomized study of 40 healthy adults in Soweto eating maize porridge, nixtamalization cut fumonisin B1 in the maize by 95%. Their urinary biomarkers still did not differ from those of people eating control maize.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• USDA lists corn tostada shells at 23.4 g fat and 7.0 g saturated fat per 3.5 oz (100 g), from a single record with no sample spread. — USDA SR Legacy record, Tostada shells, corn (n = 1 record) Evidence E source
  Fat 23.38 g/100 g (30% DV); saturated fat 7.011 g (35% DV); thiamin 0.353 mg (29% DV)

What your body absorbs

• In a stable-isotope crossover trial in 10 women, about 35% of the zinc in plain corn tortilla was absorbed, the same as from zinc-fortified tortilla. — 10 healthy adult women per phase, Mexico, single test meals (n = 10) Evidence B source
  Fractional zinc absorption 0.35 unfortified, 0.36 zinc oxide, 0.37 zinc sulfate
• In 5 women, calcium absorption from tortillas made with low-phytate maize was 50% against 35% from ordinary maize. — 5 healthy adult women, about 140 g tortillas per test meal (n = 5) Evidence C source
  Fractional calcium absorption 0.50 vs 0.35 (P = 0.003)
• In children aged 5 to 7, only about 3.8% of reduced iron powder added to corn masa tortillas was absorbed. — children aged 5-7 years, 12 per group, Mexico (n = 24) Evidence B source
  Iron bioavailability 3.8% (2.7-5.3); 5.1% with Na2EDTA (P = 0.18)

What cooking and storage change

• Nixtamalization, the lime cooking used for tortilla masa, cut fumonisin B1 in moldy maize by 95% in a South African intervention study. — 40 healthy adults, Soweto, South Africa, maize porridge (n = 40) Evidence B source
  Fumonisin B1 -95%, fumonisin B2 -95%, zearalenone -89% in maize
• An outbreak of stomach illness at a US prison in 2015 was traced to rancid tortilla chips, with hexanal and peroxide found and no germ detected. — residents and staff of a correctional facility, Wyoming Evidence C source
  Tortilla chips the only food item associated with illness

What it does to your health

• In a crossover trial in 20 adults with overweight, a 250 calories snack of tortilla chips raised blood glucose and insulin more than pecans, with no difference in appetite. — 20 adults with overweight or obesity, single mid-morning snack (n = 20) Evidence B source
  Glucose and insulin significantly higher after tortilla chips; appetite and intake unchanged

Safety, limits and interactions

• Case-control studies on the Texas-Mexico border named fumonisins from maize among new risk factors for neural tube defects in women short of folic acid. — Mexican American women, Texas Neural Tube Defect Project, 1995-2000 Evidence C source
  Fumonisins listed as a novel putative risk factor

What people believe that the data does not support

• A 2019 US survey found none of the corn tortilla products checked were fortified with folic acid, despite FDA allowing it since 2016. — 132 products photographed in 28 US states, 43 unique masa or tortilla products (n = 43 products) Evidence C source
  3 of 43 masa flours fortified; 0 tortilla products

What is still unknown

• A systematic review found only two studies on maternal fumonisin exposure, linking it with neural tube defects and hypertensive emergencies in pregnancy. — 17 epidemiological studies on mycotoxins and pregnancy outcomes (n = 2 studies) Evidence C source
  Association only; evidence limited

The bottom line

There is no US survey portion for a plain tostada shell, so we cannot give you a per-shell figure. Minerals in corn tortillas are absorbed at modest rates. In a stable-isotope crossover trial in 10 Mexican women, about 35% of the zinc in a plain soft corn tortilla was absorbed, the same as from zinc-fortified tortilla, and a fried shell was never tested. In 5 women in a study that was not randomized, calcium absorption was 50% from tortillas made with low-phytate maize against 35% from ordinary maize. In Mexican children aged 5 to 7, only 3.8% (2.7 to 5.3 within one standard deviation) of reduced iron powder added to corn masa tortillas was absorbed, a figure for that added iron and not for the iron the corn already holds. If you assume corn tortillas carry folic acid the way enriched bread does, a 2019 survey says otherwise. Of 43 unique masa and tortilla products photographed across 28 US states, a convenience sample gathered through social media, 3 masa flours had folic acid and no tortilla product did. That matters most in pregnancy. Case-control studies of Mexican American women on the Texas border, a population short of folic acid, named fumonisins from maize among new possible risk factors for neural tube defects. A systematic review found only two studies on maternal fumonisin exposure, linking it with neural tube defects and hypertensive emergencies in pregnancy, and both were observational. Fried corn can also go rancid. A stomach illness outbreak at a Wyoming correctional facility was traced to tortilla chips carrying the rancidity markers hexanal and peroxide, with no germ found in food or stool. That was one outbreak. We found no card on allergy or drug interactions for this food.

Sources

1. tsds-daily-r8-01 · food composition data
   Tostada shells, corn (FDC 167525, SR Legacy, Baked Products): saturated fat 7.011 g per 100 g = 35% DV; fat 23.38 g = 30% DV; thiamin 0.353 mg = 29% DV; Foundation samples 0, CoFID match none
   USDA FoodData Central, SR Legacy 2018, FDC 167525 Tostada shells, corn · checked 2026-10-01
2. tsds-daily-r8-02 · 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 2026-10-01
3. tsds-daily-r8-03 · controlled feeding study
   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 2026-10-01
4. tsds-daily-r8-04 · 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).
   J Nutr, 2004 · checked 2026-10-01
5. tsds-daily-r8-05 · randomized intervention study
   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 2026-10-01
6. tsds-daily-r8-07 · outbreak investigation
   Hexanal and peroxide, markers for rancidity, were detected in tortilla chips and composite food samples from the lunch. No infectious agent was detected in human stool specimens or food samples.
   MMWR Morb Mortal Wkly Rep, 2016 · checked 2026-10-01
7. tsds-daily-r8-06 · 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 2026-10-01
8. tsds-daily-r8-09 · case-control review
   Studies in this folic acid deficit-population also revealed several novel risk factors, namely, diarrhea, stress, fumonisins, and the combination of nitrosatable drug exposure with high nitrate/nitrite intake.
   Birth Defects Res A Clin Mol Teratol, 2012 · checked 2026-10-01
9. tsds-daily-r8-08 · cross-sectional product survey
   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 2026-10-01
10. tsds-daily-r8-10 · systematic review
    Only two studies assessed effects of maternal exposure to Fusarium mycotoxins (e.g., fumonisin) on adverse pregnancy outcomes. These studies found that maternal fumonisin exposure may be associated with hypertensive emergencies in pregnancy and with neural tube defects.
    Mycotoxin Res, 2020 · checked 2026-10-01