Corn as a vegetable: what the maize studies can and cannot say

The strongest study design on this page is a Cochrane review, and its answer is weak. Teaching maize farmers in Kenya, Zimbabwe and Tanzania to store their harvest against aflatoxin may raise their infants' weight-for-age z-score by 0.57 (95% CI 0.16 to 0.98). That rests on one trial of 249 infants, and the reviewers rate it very low certainty. It is also about maize grain as a staple food. Sweet corn eaten as a vegetable has much thinner evidence. A regular raw ear weighs about 3.7 oz (105 g) and gives about 90 calories, 19.6 g of carbohydrate, 2.1 g of fiber and 676 micrograms of lutein plus zeaxanthin, figures USDA recalculated from 100 g values. We found no study comparing corn head to head with other vegetables. We also found no randomized trial of whole sweet corn, and we could not check how the US dietary guidelines classify it. In one 4-week study, 15 middle-aged adults ate 6.3 oz (180 g) a day of green beans, pumpkin and sweet corn, and serum lutein across the 29 people in both groups rose by 37% with no change in macular pigment. Corn was one of three vegetables there, the abstract does not say the groups were randomized, and the sample was small.

How much is actually in it

• A regular ear of raw sweet corn weighs about 3.7 oz (105 g) and provides about 90 calories, 19.6 g carbohydrate, 2.1 g fiber and 676 ug lutein plus zeaxanthin. — US dietary survey food record Evidence E source
  Per 100 g: 86 calories, 18.7 g carbohydrate, 2 g fiber, 6.8 mg vitamin C, 644 ug lutein + zeaxanthin; 1 cup = 150 g

What your body absorbs

• In a randomized crossover trial in 9 adults, muffins from orange maize for 12 days raised serum beta-cryptoxanthin by 131% (whole grain) and 108% (refined), and zeaxanthin was also highly bioavailable. — 9 adults, mean age 23.4 years, 5 men, with optimal vitamin A status; 12 days per arm (n = 9) Evidence B source
  Serum BCX AUC 1.70 (whole-grain orange) and 1.66 (refined orange) vs -0.06 umol/L*d (white maize), P < 0.003; zeaxanthin AUC 0.94 and 0.96 vs 0.05
• In a cluster randomized trial of 679 Zambian children, eating beta-carotene-rich maize daily for 6 months left serum beta-carotene nearly twice as high as in the control group and raised zeaxanthin and beta-cryptoxanthin. — 679 rural Zambian children, daily biofortified maize for 6 months (n = 679) Evidence B source
  Serum beta-carotene 0.273 vs 0.147 umol/L, p < 0.001; alpha-carotene, beta-cryptoxanthin and zeaxanthin increased (p < 0.001); no change in lutein or lycopene
• A 4-week intervention supplying 1.8 mg lutein a day from vegetables including sweet corn raised serum lutein by 37% across the sample, without a change in macular pigment. — 29 healthy normolipemic adults aged 45 to 65; 15 ate 180 g/day of green beans, pumpkin and sweet corn for 4 weeks (n = 29) Evidence C source
  Serum lutein +37%; lutein/HDL-cholesterol +29% (p = 0.008); macular pigment optical density unchanged

What cooking and storage change

• Nixtamalization, the traditional alkaline cooking of maize, cut fumonisin B1 and B2 by 95% and zearalenone by 89% in visibly moldy maize, leaving exposure comparable to clean maize in a 40-person trial. — 40 healthy adults in Soweto, South Africa, randomly assigned to control maize or nixtamalized moldy maize (n = 40) Evidence B source
  FB1 -95%, FB2 -95%, ZEN -89% in maize; urinary FB1 and ZEN not different from control (p > 0.05)
• By the USDA retention table for vegetables boiled in covering water and drained, about 75% of vitamin C and 65% of folate remain after cooking. — USDA food group Vegetables and Vegetable Products Evidence E source
  Vitamin C 75% retained, folate 65%, thiamin 80%, niacin 85%, potassium 90%

What it does to your health

• A scoping review of 21 human studies linked whole grain corn products rich in corn bran to better blood lipid and glycemic profiles, and refined corn products such as cornflakes to less favorable ones. — 21 human studies comparing corn flour with another grain or no intervention (n = 21 studies) Evidence C source
  Direction only, no pooled effect size
• In a randomized crossover trial in 30 young men, cookies made with 67% high-amylose maize flour lowered cumulative blood glucose AUC by 22% over 200 minutes versus wheat cookies. — 30 healthy men, mean age 22.9, BMI 22.6; single test cookies once a week for 3 weeks (n = 30) Evidence B source
  0 to 120 min glucose AUC 44% lower (high dose); cumulative 0 to 200 min AUC 22% lower (P < 0.05); no effect on food intake

Safety, limits and interactions

• A Cochrane review found that teaching maize farmers post-harvest practices to cut aflatoxin may raise infant weight-for-age z-score by 0.57, on very low-certainty evidence from one trial of 249 infants. — mother-child pairs in rural maize-farming communities in Kenya, Zimbabwe and Tanzania; 3 cluster RCTs, 5 to 9 months (n = 249) Evidence A source
  WAZ +0.57 (95% CI 0.16 to 0.98); underweight -6.7% (95% CI -12.6 to -1.4); very low certainty

What people believe that the data does not support

• The EU did not authorize the claim that a diet rich in vegetables promotes heart health. — — Evidence E source
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Who this works differently for

• In a 2-month randomized feeding trial, orange maize supplied an estimated 11% of recent dietary vitamin A to Zambian children aged 3 to 5. — rural Zambian children aged 3 to 5, subset of a 2-month randomized feeding trial (n = 88) Evidence B source
  11% of recent dietary vitamin A (95% CI 2 to 21%); serum lutein, zeaxanthin and beta-cryptoxanthin higher vs white maize, P < 0.001
• Historical records link pellagra in South Africa, as in Europe and the USA, to poverty and heavy dependence on maize as the staple food. — South African population records, 1897 to 2019 Evidence C source
  Pellagra associated with maize-dependent diets; cases largely gone by 2000, subclinical niacin deficiency not ruled out
• According to the NIH Office of Dietary Supplements, pellagra was once common among poor people in the southern United States and parts of Europe whose limited diets consisted mainly of corn. — people living in poverty with corn-based diets, early 20th century Evidence E source
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• WHO recommends fortifying maize flour and corn meal with iron to prevent iron deficiency, particularly in children and women, on very low-quality evidence. — populations relying on maize flour and corn meal Evidence E source
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The bottom line

The carotenoid trials used biofortified orange maize, a bred variety that differs from ordinary sweet corn. In 9 adults who ate orange maize muffins for 12 days, serum beta-cryptoxanthin rose 131% on whole grain and 108% on refined flour, and zeaxanthin rose too, against white maize. In a cluster randomized trial in 679 rural Zambian children, 6 months of daily beta-carotene-rich maize left serum beta-carotene at 0.273 micromol/L against 0.147 in the control group, with no change in lutein or lycopene. In 88 Zambian children aged 3 to 5, orange maize supplied an estimated 11% (95% CI 2 to 21%) of recent dietary vitamin A, an estimate built on equations from a gerbil study. Cooking changes some numbers. USDA retention factors for vegetables boiled in water and drained keep about 75% of vitamin C and 65% of folate, a factor set for the whole vegetable group in a table dating from 1975. For blood sugar, a scoping review of 21 human studies linked whole grain corn products rich in bran to better lipid and glucose profiles and refined products such as cornflakes to worse ones, with no pooled effect size and no quality rating. In 30 young men, cookies made with a special high-amylose maize flour lowered blood glucose area under the curve by 22% over 200 minutes against wheat cookies, in single test meals. The EU turned down the claim that a diet rich in vegetables promotes heart health. That ruling means the evidence fell short at the time of assessment. It does not show that there is no effect. The cautions on this page concern stored staple maize. In 40 adults in Soweto, nixtamalization, the traditional alkaline cooking of maize, cut fumonisin B1 and B2 by 95% and zearalenone by 89% in visibly moldy grain, and urinary toxin levels matched those of people eating clean maize over the short trial. The abstract gives no figure for aflatoxin, and the trial does not show that moldy grain becomes safe to eat once cooked. Pellagra, the niacin deficiency disease, was linked to poverty and heavy dependence on maize as the staple food in South Africa, Europe and the United States. Cases in South Africa were largely gone by 2000. WHO recommends fortifying maize flour and corn meal with iron, particularly for children and women, and rates its own evidence very low quality. We found no study on corn allergy, and no source on corn with medicines or in pregnancy.

Sources

1. cnv-daily-r3-12 · food composition dataset
   Corn, raw | FNDDS code 75109600 | fdc_id 2709783 | 1 regular ear 64726 = 105 g | 1 cup 10205 = 150 g | per 100 g: Energy 86 kcal, Carbohydrate 18.7 g, Fiber 2 g, Vitamin C 6.8 mg, Lutein + zeaxanthin 644 ug
   USDA FNDDS, Corn, raw, food code 75109600, fdc_id 2709783 · checked 2026-09-28
2. cnv-daily-r3-01 · randomized crossover trial
   After a 7-d washout, 9 adults (mean ± SD age: 23.4 ± 2.3 y; 5 men) were provided with muffins made from BCX-enhanced whole-grain orange maize (WGOM), refined orange maize (ROM), or refined white maize (RWM) for 12 d in a randomized, blinded, crossover study followed by a 7-d washout. ... A greater increase occurred in serum BCX from WGOM muffins (131%) than from ROM muffins (108%) (P ≤ 0.003). Zeaxanthin AUCs were higher for WGOM (0.94 ± 0.33) and ROM (0.96 ± 0.47) than for RWM (0.05 ± 0.12 μmol ⋅ L-1 ⋅ d; P < 0.003).
   Am J Clin Nutr, 2018 · checked 2026-09-28
3. cnv-daily-r3-02 · cluster randomized controlled trial
   We conducted a cluster randomized, controlled feeding trial in rural Zambia to test the impact of daily consumption of biofortified maize over a 6-month period on vitamin A status. ... Data on circulating carotenoids by intervention group in 679 children are reported here. As previously shown, consumption of this β-carotene-rich maize significantly improved serum β-carotene concentrations (0.273 vs. 0.147 μmol/L, p < 0.001, in this subset of children). Here we show significant increases in α-carotene, β-cryptoxanthin, and zeaxanthin (p < 0.001). There was no impact on lutein or lycopene concentrations.
   Eur J Clin Nutr, 2018 · checked 2026-09-28
4. cnv-daily-r3-04 · dietary intervention study
   Twenty-nine healthy normolipemic subjects, aged 45-65 y, consumed 1.8 mg lutein/day supplied from fruits (14 subjects, 500 g/day of oranges, kiwi and avocados) or vegetables (15 subjects, 180 g/day of green beans, pumpkin, and sweet corn) for four weeks. Serum lutein concentration increased by 37%.
   Nutrients, 2021 · checked 2026-09-28
5. cnv-daily-r3-05 · randomized intervention study
   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 2026-09-28
6. cnv-daily-r3-13 · reference dataset
   USDA-RETN-R6:3775 VEG,OTHER,BLD,WATER COVER,DRAINED, group Vegetables and Vegetable Products: vitamin_c_mg 75% retained, folate_total_ug 65%, thiamin_mg 80%, niacin_mg 85%, potassium_mg 90%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, code USDA-RETN-R6:3775 · checked 2026-09-28
7. cnv-daily-r3-10 · 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. Conversely, refined corn products, such as cornflakes and extruded snacks, were linked to less favorable metabolic outcomes, particularly in individuals with metabolic disorders.
   J Nutr, 2025 · checked 2026-09-28
8. cnv-daily-r3-11 · randomized crossover trial
   In a repeated-measures crossover trial, healthy men (n = 30, 22.9 ± 0.6 y, BMI of 22.6 ± 0.3 kg/m(2)) were randomly assigned to consume 1 of 3 cookies once a week for 3 wk. ... Yet despite the higher response following the meal, cumulative AUC (0 to 200 min) was still 22% lower after the high-dose treatment (P < 0.05).
   J Food Sci, 2014 · checked 2026-09-28
9. cnv-daily-r3-06 · Cochrane systematic review
   Maize and groundnuts are prone to aflatoxin contamination, and are the major sources of human exposure to aflatoxins, due to their high intake as staple foods, particularly in low- and middle-income countries (LMICs). ... may improve WAZ in infants from these farmers' households, on average, by 0.57 (95% confidence interval (CI) 0.16 to 0.98; 1 study; 249 participants; very low-certainty evidence), compared to infants from households where the farmers received routine agricultural extension services.
   Cochrane Database Syst Rev, 2020 · checked 2026-09-28
10. cnv-daily-r3-14 · regulatory register entry
    POL-HC-8056 Vegetables (fresh, frozen, canned, bottled, dried, juiced) A diet rich in vegetables promotes heart health. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8056, snapshot 2026-09-21 · checked 2026-09-28
11. cnv-daily-r3-03 · randomized controlled trial
    A random subset of samples from a two-month randomized controlled feeding trial of rural three- to five-year old Zambian children were used to determine the impact of orange maize intake on serum carotenoid concentrations ( n = 88) and 13C-natural abundance in serum retinol ( n = 77). ... Predictions made from equations developed in the aforementioned gerbil study estimated that maize provided 11% (2-21%, 95% confidence interval) of the recent dietary vitamin A to these children.
    Exp Biol Med (Maywood), 2017 · checked 2026-09-28
12. cnv-daily-r3-07 · scoping review
    As in Europe and the USA, pellagra was associated with poverty and an overdependence on maize as staple food.
    Public Health Nutr, 2021 · checked 2026-09-28
13. cnv-daily-r3-08 · agency fact sheet
    Pellagra was not uncommon in the early 20th century among individuals living in poverty in the southern United States and parts of Europe whose limited diets consisted mainly of corn [2,3].
    NIH Office of Dietary Supplements, Niacin Fact Sheet for Health Professionals · checked 2026-09-28
14. cnv-daily-r3-09 · 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).
    WHO guideline: Fortification of maize flour and corn meal with vitamins and minerals, 2016 · checked 2026-09-28