Cornmeal: the label and the mill decide what you get

A Cochrane review could not tell whether fortifying maize flour or corn meal with iron and other micronutrients lowers anemia. The risk ratio was 0.90 (95% CI 0.58 to 1.40) in 2 studies of 1027 children and women, with very low certainty, and no trial tested iron alone. A second Cochrane review found one study of 38 pregnant women in which folic acid-fortified maize porridge raised red cell folate by 239 nmol/L, also very low certainty, and no trial reported neural tube defects. What is in your bag depends on one word on the label. Enriched corn meal in the US must carry 140 micrograms of folic acid per 3.5 oz (100 g) since 1998, while plain or stone-ground cornmeal may carry none. Milling sets much of the rest. Across 15 USDA records, magnesium runs from 32 to 133 mg per 3.5 oz (100 g) and fiber from 3.9 to 10.4 g, mostly because degermed meal loses the germ and bran that whole-grain and Navajo blue meal keep.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Enriched corn meal in the US must carry 140 mcg folic acid per 3.5 oz (100 g) since 1998, while corn masa flour may carry up to 154 mcg per 3.5 oz (100 g) only voluntarily since 2016. — US grain products Evidence E source
  140 mcg/100 g mandatory in enriched corn meal; up to 154 mcg/100 g voluntary in masa
• Magnesium in cornmeal ranges from 32 to 133 mg per 3.5 oz (100 g) across 15 USDA records and fiber from 3.9 to 10.4 g, while the UK table gives sifted cornmeal 44 mg magnesium. — USDA SR Legacy cornmeal records (15, degermed to whole grain and Navajo blue); CoFID 2021 Cornmeal, sifted (n = 16 records) Evidence E source
  Magnesium 32-133 mg/100 g (USDA), 44 mg (CoFID); fiber 3.9-10.4 g (USDA), NSP 2.2 g (CoFID)

What a real portion looks like

• In the US dietary survey a cup of cooked cornmeal mush weighs 8.5 oz (240 g), and one ounce of dry cornmeal cooks up to about 6.7 oz (190 g) of mush. — FNDDS Cornmeal mush, no added fat (56201516) Evidence E source
  1 cup cooked 240 g; 1 oz dry yields 190 g; 1 cup dry yields 955 g

What your body absorbs

• In a Cochrane review, pregnant women given folic acid-fortified maize porridge had red cell folate 239 nmol/L higher than without it, from one study of 38 women. — pregnant women who received folic acid-fortified maize porridge (n = 38) Evidence A source
  Erythrocyte folate MD 238.90 nmol/L (95% CI 149.40-328.40); very low certainty
• In Kenyan children aged 24-36 months, a plain maize-based meal delivered only 0.14 mg of absorbed zinc, 2.6 times less than the same meal with whole house crickets. — children aged 24-36 months old in Kenya (n = 28-29 per arm) Evidence B source
  Absorbed zinc 0.14 mg (95% CI 0.11-0.16) from low-enriched maize meal vs 0.36 mg (0.30-0.43) with crickets
• Breaking down phytic acid with the enzyme phytase, at the meal or during preparation, raised zinc absorption from zinc-fortified maize porridge by more than 80% in young adults. — young adults consuming maize or sorghum porridges fortified with 2 mg zinc Evidence C source
  Fractional zinc absorption +>80% with phytase (P < 0.001)

What it does to your health

• A Cochrane review found it uncertain whether iron-fortified maize flour or corn meal lowers anemia: risk ratio 0.90 (0.58 to 1.40) in 2 studies of 1027 people, with very low certainty. — children aged 2 to 11.9 years and women (n = 1027) Evidence A source
  Anemia RR 0.90 (95% CI 0.58-1.40); iron deficiency RR 0.75 (0.49-1.15); very low certainty
• In a randomized trial in 14 healthy adults, stiff porridge made from refined maize flour had a glycemic index of 74.7 and from whole maize flour 71.4, both in the high range. — Fourteen healthy participants with mean age of 25 years (n = 14) Evidence B source
  GI refined maize ugali 74.7 ± 6.5; whole maize ugali 71.4 ± 5.1 (high GI ≥70)

Safety, limits and interactions

• In a randomized study with 40 adults in Soweto, lime-cooking (nixtamalization) of visibly moldy maize cut fumonisin B1 by 95% and zearalenone by 89%. — Forty adult healthy volunteers from an informal settlement in Kliptown, Soweto (South Africa) (n = 40) Evidence B source
  FB1 -95%, FB2 -95%, ZEN -89% in maize; urinary biomarkers similar to control maize
• Among Mexican American women on the Texas-Mexico border, fumonisins, the mold toxins of maize, emerged as a novel risk factor for neural tube defects in a population short of folic acid. — Mexican American women living on the Texas-Mexico border Evidence C source
  Fumonisins identified as a novel putative risk factor (no size in abstract)
• FDA guidance recommends at most 2 ppm total fumonisins in degermed corn meal and 4 ppm in whole or partially degermed corn meal. — US human foods Evidence E source
  Degermed corn meal 2 ppm; whole or partially degermed corn meal 4 ppm

What people believe that the data does not support

• Across 21 human studies, whole grain corn products high in bran were linked to better blood lipids and glucose, while refined corn products were linked to less favorable metabolic outcomes. — Twenty-one studies were included (n = 21 studies) Evidence C source
  Qualitative: whole grain, bran-rich corn favorable; refined corn less favorable

What is still unknown

• Where maize is the staple, niacin deficiency persists: in postwar Angola 29.4% of 723 women and 6.0% of 690 children had low urinary niacin metabolites. — 723 women aged 15-49 y and 690 children aged 6-59 mo (n = 1413) Evidence C source
  Low niacin metabolite excretion: women 29.4%, children 6.0%
• The USDA retention table has no row for cornmeal: its cereal group lists flour and meal, pasta and rice methods, so vitamin losses when cooking cornmeal cannot be read from it. — USDA Table of Nutrient Retention Factors Release 6, group Cereal Grains and Pasta Evidence E source
  No cornmeal-specific factor; 14 group rows describe other goods

The bottom line

Cooked as a stiff porridge, cornmeal counts as a high glycemic food. In a randomized trial in 14 healthy adults in Tanzania, eaten in 50 g carbohydrate portions, ugali from refined maize flour had a glycemic index of 74.7 and from whole maize flour 71.4. Both sit above the high threshold of 70. A scoping review of 21 human studies linked whole grain corn products rich in bran with better blood lipids and glucose, and refined corn with less favorable outcomes. It had no pooled estimate and did not grade bias. A cup of cooked cornmeal mush weighs 8.5 oz (240 g) in the US dietary survey, and one ounce of dry meal cooks up to about 190 g. Maize meals give little zinc to the body. In Kenyan children aged 24 to 36 months, a single maize-based test meal delivered 0.14 mg of absorbed zinc, 2.6 times less than the same meal with whole crickets. In five small non-randomized absorption studies in young adults eating zinc-fortified maize porridge, breaking down phytic acid with the enzyme phytase raised zinc absorption by more than 80 percent. Where maize is the staple, niacin can run short. In postwar Angola 29.4 percent of 723 women and 6.0 percent of 690 children had low niacin metabolites, a survey that reflects poverty and the whole diet rather than cornmeal alone. The caution with maize is mold. FDA guidance, which is advisory, sets at most 2 ppm of fumonisins for degermed corn meal and 4 ppm for whole or partly degermed meal. Among Mexican American women on the Texas border who were short of folic acid, a case-control study flagged fumonisins as a possible risk factor for neural tube defects, with no size given. In 40 adults in Soweto, lime-cooking visibly moldy maize cut fumonisin B1 in the grain by 95 percent, and urine markers ended level with those from clean maize. The US rule that adds folic acid to enriched corn meal was set to reduce the risk of neural tube defects, and it covers only meal labeled enriched. The label matters for wheat too: one of the USDA self-rising cornmeal records has wheat flour added. The USDA retention table has no row for cornmeal, so vitamin loss in the pot is unknown.

Sources

1. cml-daily-r1-10 · fact sheet
   In January 1998, the U.S. Food and Drug Administration (FDA) began requiring manufacturers to add 140 mcg folic acid/100 g to enriched breads, cereals, flours, corn meals, pastas, rice, and other grain products [13] to reduce the risk of neural tube defects (NTDs)...In April 2016, FDA approved the voluntary addition of up to 154 mcg folic acid/100 g to corn masa flour [15].
   NIH Office of Dietary Supplements, Folate fact sheet for health professionals · checked 2026-09-29
2. cml-daily-r1-12 · food composition dataset
   USDA SR Legacy cornmeal, 15 records: magnesium 32-133 MG, fiber 3.9-10.4 G, vitamin B6 0.182-0.593 MG per 100 g (max: Cornmeal, blue (Navajo), FDC 167628); CoFID 2021 11-011 Cornmeal, sifted: Magnesium 44 mg, NSP 2.2 g, Iron 1.30 mg, Niacin 1.0 mg
   USDA FoodData Central SR Legacy (15 cornmeal records, reference FDC 167628); CoFID 2021 code 11-011 · checked 2026-09-29
3. cml-daily-r1-13 · food portion dataset
   Cornmeal mush, no added fat, FNDDS 56201516: 1 cup, cooked 240 g; 1 cup, dry, yields 955 g; 1 strip or slice 50 g; 1 oz, dry, yields 190 g
   USDA FNDDS portion weights, code 56201516 (fdc_id 2708374) · checked 2026-09-29
4. cml-daily-r1-02 · Cochrane review
   Folate status: pregnant women who received folic acid-fortified maize porridge had significantly higher erythrocyte folate concentrations (mean difference (MD) 238.90 nmol/L, 95% CI 149.40 to 328.40); 1 study, 38 participants; very low-certainty evidence)
   Cochrane Database Syst Rev, 2019 · checked 2026-09-29
5. cml-daily-r1-05 · RCT
   We found that AZ from meals with whole crickets (geometric mean: 0.36 mg; 95%CI: 0.30, 0.43) was 2.6 times higher than from low-enriched maize meals (0.14 mg; 0.11, 0.16; P < 0.001), while it was not different from low-chitin cricket flour meals.
   Nat Commun, 2025 · checked 2026-09-29
6. cml-daily-r1-06 · clinical trial
   Adding phytase to the maize porridge immediately before consumption or using phytase for dephytinization during meal preparation both increased FAZ by >80% (both P < 0.001).
   J Nutr, 2014 · checked 2026-09-29
7. cml-daily-r1-01 · Cochrane review
   Compared to unfortified maize flour, it is uncertain whether fortifying maize flour or corn meal with iron and other vitamins and minerals has any effect on anaemia (risk ratio (RR) 0.90, 95% confidence interval (CI) 0.58 to 1.40; 2 studies; 1027 participants; ... or on the risk of iron deficiency (RR 0.75, 95% CI 0.49 to 1.15; 2 studies; 1102 participants; very low-certainty evidence)
   Cochrane Database Syst Rev, 2018 · checked 2026-09-29
8. cml-daily-r1-03 · RCT
   The GI (mean ± standard error) of IBR was the highest (87.8 ± 6.8) followed by RMU (74.7 ± 6.5) and WMU (71.4 ± 5.1).
   J Food Sci, 2019 · checked 2026-09-29
9. cml-daily-r1-04 · RCT
   Forty adult healthy volunteers from an informal settlement in Kliptown, Soweto (South Africa), were randomly assigned to consume control maize or visibly moldy maize subjected to nixtamalization. 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 2026-09-29
10. cml-daily-r1-07 · case-control
    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 2026-09-29
11. cml-daily-r1-11 · regulatory guidance
    Degermed dry milled corn products (e.g., flaking grits, corn grits, corn meal, corn flour with fat content of < 2.25%, dry weight basis)...2 parts per million (ppm)...Whole or partially degermed dry milled corn products (e.g., flaking grits, corn grits, corn meal, corn flour with fat content of > 2.25 %, dry weight basis)...4 ppm
    FDA, Guidance for Industry: Fumonisin Levels in Human Foods and Animal Feeds · checked 2026-09-29
12. cml-daily-r1-09 · scoping review
    Twenty-one studies were included, investigating a wide range of health outcomes, including metabolic markers, growth metrics in infants, and risk of chronic diseases such as type 2 diabetes, obesity, and hypercholesterolemia. Findings indicated that whole grain corn products, particularly those high in fiber-rich corn bran, were associated with favorable effects on blood lipid and glycemic profiles.
    J Nutr, 2025 · checked 2026-09-29
13. cml-daily-r1-08 · cross-sectional
    Excretion of niacin metabolites was low in 29.4% of the women and 6.0% of the children, and the creatinine-adjusted concentrations were significantly lower in the women than in the children (P < 0.001, t test).
    Am J Clin Nutr, 2007 · checked 2026-09-29
14. cml-daily-r1-14 · dataset gap
    USDA-RETN-R6 group Cereal Grains and Pasta (20): 14 methods (FLOUR/MEAL, PASTA, RICE), none named cornmeal
    USDA Table of Nutrient Retention Factors, Release 6, 2007 · checked 2026-09-29