Grits: what maize studies say about your bowl

Almost none of the science on this page was done on grits. Search for grits in the research and you find a single allergy case report. Everything else here was measured on other forms of maize: a stiff Tanzanian porridge called ugali, Mexican tortillas, and home-grown maize in rural South Africa. Grits are coarsely ground maize, so these are the nearest studies we have, and each point below says which food was actually tested. We also have no USDA record for grits in this cohort, which is why there is no nutrient table here. The number closest to your bowl is a glycaemic index, a score for how fast a food raises blood sugar compared with pure glucose. In 14 healthy adults, porridge from refined milled maize flour scored 74.7, in the high range, and the whole maize version scored 71.4, also in the high range. The study gave each score a margin of error, plus or minus 6.5 and 5.1, so the gap between the two sits inside that error and this test does not show whole maize doing better. Nobody has run that test on American grits.

What your body absorbs

• In 5 women, calcium absorption from tortillas made with low-phytate nixtamalized maize was 50% versus 35% from ordinary maize. — 5 healthy adult women, two test meals of about 140 g tortillas one month apart (n = 5) Evidence C source
  Fractional calcium absorption 0.50 vs 0.35 (P = 0.003)

What cooking and storage change

• Nixtamalization of visibly mouldy maize cut fumonisin B1 in the maize by 95% and zearalenone by 89%, in a trial with 40 adults in Soweto. It did not test grits or show that mouldy maize is safe to eat. — 40 healthy adults in Kliptown, Soweto, randomised to control maize or nixtamalized mouldy maize (n = 40) Evidence B source
  FB1 and FB2 -95%, ZEN -89% in maize, urinary biomarkers similar to control maize
• Hand-sorting and washing home-grown maize cut fumonisin exposure by 62% among 22 women in a South African farming community. Store-bought grits were not studied. — 22 women in a subsistence maize-farming community in Centane, South Africa (n = 22) Evidence C source
  Fumonisin in maize -84%, in porridge -65%, exposure -62%

What it does to your health

• In 14 healthy adults, Tanzanian ugali, a porridge made from refined milled maize flour, had a glycaemic index of 74.7, in the high range. This is not a measurement of grits. — 14 healthy participants, mean age 25, 50 g available carbohydrate portions of Tanzanian ugali, not grits (n = 14) Evidence B source
  GI refined maize ugali 74.7 (SE 6.5), whole maize ugali 71.4 (SE 5.1), whole grain pilaf 58.9. Refined and whole maize ugali both in the high range, gap within the error

Safety, limits and interactions

• A case report describes a 71-year-old man with no known food allergy who had anaphylaxis after a meal of grits and shrimp. — 1 man, 71 years old (n = 1) Evidence D source
  Single case, cause identified later by the authors

Who this works differently for

• A review of South African records from 1897 to 2019 linked pellagra to poverty and overdependence on maize as a staple. — South African population, historical records 1897-2019 Evidence C source
  Association described, no effect size

The bottom line

If you eat grits, the fair working assumption from that porridge result is a fast carbohydrate food, until someone measures grits themselves. Some grits, sold as hominy grits, are made from maize soaked in lime, a process called nixtamalization. None of the lime or toxin studies below tested grits, and none of them can tell you whether the pack in your cupboard was made this way. In a randomised trial with 40 adults in Soweto, lime treatment of visibly mouldy maize cut fumonisin B1 by 95 percent and zearalenone by 89 percent. Both are toxins made by moulds that grow on maize. In a smaller study of 22 women farming their own maize in South Africa, hand sorting and washing the grain cut their fumonisin exposure by 62 percent. That study had no comparison group. Both measured how much toxin reached people, and neither followed anyone long enough to count illness. Both also used visibly mouldy or home-grown maize in South African communities. We have no measurement of toxin levels in grits bought from a shop. And the Soweto trial does not show that mouldy grain is safe to eat once it has been treated with lime. It measured the toxin left in the grain and toxin markers in urine, which were similar to those of people eating the control maize. For calcium, the grain itself gets in the way. In 5 women, tortillas from a low phytate maize let the body absorb 50 percent of their calcium, against 35 percent from ordinary maize. Phytate is a compound in the grain that holds on to minerals. Five people and tortillas, so read it as a direction and nothing firmer. A review of South African records from 1897 to 2019 tied pellagra, a deficiency disease, to poverty and to leaning on maize as the main food. That is history from diets with little else in them. It says nothing about grits as one part of a varied week, and we found no study comparing how much niacin the body gets from hominy grits against plain grits. On safety our evidence is thin. The one record is a 71 year old man with no known food allergy who went into anaphylaxis after a meal of grits and shrimp. The authors later found the cause, and the abstract we read does not name it, so this case cannot tell you whether grits were the trigger. We have no upper limit, no drug interaction and no data on pregnancy, children or kidney disease for grits. That is a gap in what has been studied, and it is no proof that everyone is safe.

Sources

1. grt-b2-03 · clinical trial
   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
2. grt-b2-02 · 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. ... while reducing fumonisin B1 (FB1), fumonisin B2, and zearalenone (ZEN) by 95%, 95%, and 89%, respectively.
   Toxins (Basel), 2025 · checked 2026-09-23
3. grt-b2-04 · clinical trial
   The customised hand-sorting and washing procedures reduced fumonisin contamination in the maize and porridge by 84 and 65%, respectively. The intervention reduced fumonisin exposure by 62% to 2.55 (1.94-3.35) µg kg(-1) body weight day(-1).
   Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2010 · checked 2026-09-23
4. grt-b2-01 · 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 2026-09-23
5. grt-b2-06 · case report
   We present a 71-year-old man with no history of food allergy or atopy who presented to the emergency room and then our allergy clinic for evaluation after suffering anaphylaxis after a meal of grits and shrimp.
   Allergy Asthma Proc, 2012 · checked 2026-09-23
6. grt-b2-05 · 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 2026-09-23