Wheat flour: what the fortification adds and what raw flour risks

Plain wheat flour matters for health mostly because of what countries put into it. A Cochrane meta-analysis of 5 trials with 2315 people aged two and over found that iron-fortified wheat flour may cut the risk of anemia by 27 percent (risk ratio 0.73, 95% CI 0.55 to 0.97), and the reviewers rated that evidence low certainty. Folic acid is the other half of the story. Across 30 before and after studies from countries that made grain fortification mandatory, serum folate rose by 15.0 nmol/L (95% CI 9.4 to 20.5). Those are pre-post comparisons with high heterogeneity, and none of them is a randomized trial. The bag in your kitchen shows the gap. US enriched all-purpose flour lists 5.62 mg iron and 160 ug folate per 3.5 oz (100 g), averaged over 6 samples. UK plain white flour in the national table lists 1.94 mg iron and 16 ug folate per 3.5 oz (100 g).

The numbers, per 3.5 oz (100 g)

How much is actually in it

• US enriched all-purpose flour carries about 0.94 mg thiamin, 160 ug folate and 5.6 mg iron per 3.5 oz (100 g), with a 6-sample spread of up to 62%. — USDA Foundation Foods, Flour, wheat, all-purpose, enriched, bleached (FDC 789890) (n = 6 samples) Evidence E source
  Thiamin 0.939 mg (0.785-1.09), folate 160 ug (122-222), iron 5.62 mg (5.01-6.35), niacin 6.74 mg (5.88-8.81), protein 10.9 g per 3.5 oz (100 g)
• UK plain white flour lists 0.28 mg thiamin, 16 ug folate and 1.94 mg iron per 3.5 oz (100 g), far below US enriched flour because the UK adds no folic acid yet. — CoFID 2021, Flour, wheat, white, plain, soft (11-886) Evidence E source
  352 calories, 9.1 g protein, 4.0 g AOAC fiber, thiamin 0.28 mg, folate 16 ug, iron 1.94 mg, calcium 96 mg per 3.5 oz (100 g)

What your body absorbs

• In a crossover RCT in Haitian mothers and children, iron from bread made with NaFeEDTA-fortified flour was absorbed about 40% better than from ferrous fumarate. — 22 healthy mother-child pairs in Haiti, wheat flour bread rolls with stable iron isotopes (n = 44) Evidence B source
  Iron absorption 13.06% vs 9.24% in mothers, 12.99% vs 9.26% in children (P<0.05)
• In a cluster RCT in rural Pakistan, zinc-biofortified wheat flour raised zinc intake by 1.5 mg a day in adolescent girls but did not change plasma zinc. — 517 adolescent girls aged 10-16, households given flour for 25 weeks (n = 517) Evidence B source
  Zinc intake +1.5 mg/day; plasma zinc 641.6 vs 643.8 ug/L (p = 0.455)
• In a 16-week RCT on 45 adults, wheat rolls with 400 ug folic acid a day raised plasma folate by 23 nmol/L versus unfortified rolls. — 45 healthy men and women aged 18-45, fortified wheat rolls for 16 weeks (n = 45) Evidence B source
  Plasma folate +23 nmol/L (95% CI 12 to 34) with folic acid rolls vs placebo; same with microencapsulated L-5-MTHF

What cooking and storage change

• Baking fortified wheat rolls destroyed 20-25% of the added folic acid, while frozen storage for 90 days caused no significant loss. — folic acid-fortified wheat breakfast rolls analyzed by HPLC Evidence D source
  20-25% folic acid lost in baking; roll size affected retention; stable 90 days at -20 C

What it does to your health

• In a Cochrane review, iron-fortified wheat flour may cut the risk of anemia by about 27% in people aged two and over (5 trials, 2315 participants, low certainty). — general population aged 2 years and above, 5 trials, 2315 participants, 3 to 24 months (n = 2315) Evidence A source
  Anemia RR 0.73 (95% CI 0.55 to 0.97), low-certainty evidence
• A meta-analysis of 30 studies found mandatory folic acid fortification of flour and grains raised serum folate by about 15 nmol/L and cut folate deficiency sharply. — populations in countries with mandatory grain fortification, pre vs post data, 30 articles (n = 30 studies) Evidence C source
  Serum/plasma folate +15.0 nmol/L (95% CI 9.4 to 20.5); deficiency prevalence ratio 0.08 (95% CI 0.03 to 0.23)
• In an RCT on 80 adults, 4 weeks of bread and biscuits from refined high-amylose wheat raised fecal butyrate by 38% compared with regular refined wheat. — 80 healthy adults, 160 g bread and 75 g biscuits a day for 4 weeks (n = 80) Evidence B source
  Fecal butyrate excretion 38% higher with refined high-amylose wheat vs refined low-amylose (P < 0.05)

Safety, limits and interactions

• In a 2022 French STEC outbreak with 59 cases, 50 with hemolytic uremic syndrome, bacteria from pizza dough and flour matched the patients' strains. — 59 cases of STEC O26:H11 or O103:H2 in France, 50 with HUS, 2 deaths (n = 59) Evidence C source
  OR 116.0 (95% CI 26.8-501.9) for eating the implicated pizzas

What people believe that the data does not support

• In a 2019 FDA survey of 2,171 US adults, 35% had tasted or eaten something with uncooked flour in the past year. — 2171 US adults, national probability survey, 2019 (n = 2171) Evidence C source
  35% ate raw flour in the previous 12 months

Who this works differently for

• In a 12-week trial on 29 women, one folic acid-fortified wheat roll a day raised red cell folate by 20% at the lower dose. — 29 healthy women, one fortified roll a day (about 166 or 355 ug folic acid) for 12 weeks (n = 29) Evidence B source
  Erythrocyte folate +20% (p < 0.05) and serum folate +30% (p < 0.001) in the lower-dose group
• WHO recommends fortifying wheat flour with folic acid to lower the risk of neural tube defects in pregnancies. — women of reproductive age, populations eating industrially milled wheat flour Evidence E source
  Strong recommendation, low and very low certainty of evidence

The bottom line

The form of iron changes how much of it you absorb. In a crossover trial in 22 healthy mother and child pairs in Haiti, one meal of bread rolls made with NaFeEDTA-fortified flour gave about 13 percent iron absorption against about 9 percent from ferrous fumarate. Zinc is less clear. In a cluster randomized trial of 517 girls aged 10 to 16 in rural Pakistan, 25 weeks of zinc-biofortified flour added 1.5 mg of zinc a day to their intake, and plasma zinc did not change (641.6 against 643.8 ug/L). The authors note that plasma zinc is an insensitive marker, so the trial cannot say whether the extra zinc reached the body. Folic acid added at baking still counts. In a 16 week randomized trial on 45 healthy adults aged 18 to 45, rolls carrying 400 ug of folic acid a day raised plasma folate by 23 nmol/L (95% CI 12 to 34) against unfortified rolls. In one laboratory analysis, baking destroyed 20 to 25 percent of the folic acid added to a single recipe of rolls, and 90 days in the freezer caused no significant further loss. A special wheat bred for more amylose is a separate product from ordinary flour. It was tested for 4 weeks in 80 healthy adults eating 5.6 oz (160 g) of bread and 2.6 oz (75 g) of biscuits a day. The refined high-amylose version raised fecal butyrate by 38 percent over regular refined wheat, as a secondary outcome with total fecal short chain fatty acids unchanged. Who should be careful. Raw flour is not a ready to eat food. In a 2022 French outbreak, 59 people fell ill with a toxin-producing E. coli, 50 developed kidney failure and 2 died, and bacteria from the flour and pizza dough matched the patients, in a single outbreak case-control study (odds ratio 116, 95% CI 26.8 to 501.9). In a 2019 FDA survey of 2171 US adults, 35 percent said they had tasted or eaten something with uncooked flour in the past year. Do not eat raw dough or batter, and do not let children do it. For women who may become pregnant, WHO strongly recommends fortifying wheat flour with folic acid to lower the risk of neural tube defects, on low and very low certainty evidence. We found no card on wheat allergy, celiac disease, kidney disease or drug interactions for flour itself.

Sources

1. whf-r8-08 · reference dataset
   Flour, wheat, all-purpose, enriched, bleached: Thiamin 0.939 mg (range 0.785-1.09, 6 samples) · Folate, total 160.0 ug (122.0-222.0) · Iron 5.62 mg (5.01-6.35) · Niacin 6.74 mg (5.88-8.81) · Protein 10.9 g
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-30
2. whf-r8-09 · reference dataset
   CoFID 11-886 Flour, wheat, white, plain, soft: Energy 352 kcal · Protein 9.1 g · AOAC fibre 4.0 g · Thiamin 0.28 mg · Folate 16 ug · Iron 1.94 mg · Calcium 96 mg
   CoFID 2021, Public Health England / OGL v3.0 · checked 2026-09-30
3. whf-r8-03 · randomized crossover trial
   In conclusion, in Haitian women and children, Fe absorption from NaFeEDTA was 40 % higher than from FeFum, and the combination FeFum+NaFeEDTA did not significantly increase Fe absorption compared with FeFum alone.
   Br J Nutr, 2017 · checked 2026-09-30
4. whf-r8-04 · cluster randomized trial
   Consumption of the zinc-biofortified flour resulted in a moderate increase in intakes of zinc (1.5 mg/day) and iron (1.2 mg/day). This had no significant effect on PZC (control 641.6 ± 95.3 µg/L vs. intervention 643.8 ± 106.2 µg/L; p = 0.455)
   Nutrients, 2022 · checked 2026-09-30
5. whf-r8-13 · randomized controlled trial
   Likewise, the mean plasma folate was 23 (12, 34) and 23 (12, 34) nmol/L higher in the L-5-MTHF (P < 0.001) and folic acid wheat roll (P < 0.001) groups, respectively, than in the placebo group.
   J Nutr, 2013 · checked 2026-09-30
6. whf-r8-07 · in vitro food analysis
   The baking procedure resulted in 20-25 % loss of fortified folic acid in the rolls used in the present study. The size of the rolls affected the retention of folic acid during baking. No significant loss was seen in folic acid concentration in the rolls during the intervention period.
   Eur J Nutr, 2002 · checked 2026-09-30
7. whf-r8-01 · Cochrane meta-analysis
   Iron-fortified wheat flour with or without other micronutrients added versus wheat flour (no added iron) with the same other micronutrients added may reduce by 27% the risk of anaemia in populations (risk ratio (RR) 0.73, 95% confidence interval (CI) 0.55 to 0.97; 5 studies, 2315 participants; low-certainty evidence).
   Cochrane Database Syst Rev, 2021 · checked 2026-09-30
8. whf-r8-02 · meta-analysis
   For serum/plasma folate concentrations, the MDM across all studies was 15.0 nmol/L (95% CI: 9.4, 20.5). For serum/plasma folate insufficiency and deficiency, the mPR estimates were 0.17 (95% CI: 0.08, 0.37) and 0.08 (95% CI: 0.03, 0.23), respectively.
   J Nutr, 2026 · checked 2026-09-30
9. whf-r8-05 · randomized controlled trial
   At 4 wk, the HAW-R group had 38% higher fecal butyrate excretion than the LAW-R group (P < 0.05)
   J Nutr, 2022 · checked 2026-09-30
10. whf-r8-11 · case-control outbreak study
    Isolates from pizza dough and flour samples were indistinguishable from the clinical outbreak strains.
    Euro Surveill, 2026 · checked 2026-09-30
11. whf-r8-10 · cross-sectional survey
    Thirty-five percent of consumers reported having tasted or eaten something with uncooked flour in it in the previous 12 months.
    J Food Prot, 2022 · checked 2026-09-30
12. whf-r8-06 · randomized trial
    After 90 days of intervention, an increase of 20 % (p < 0.05) was observed. At day 0, mean serum folate concentrations were 16.9 +/- 4.3 nmol/L. The mean serum folate concentrations increased by 30 % (p < 0.001) after 90 days.
    Eur J Nutr, 2002 · checked 2026-09-30
13. whf-r8-12 · guideline
    Fortification of wheat flour with folic acid is recommended as a public health strategy to reduce the risk of occurrence of pregnancies affected by neural tube defects among women of reproductive age and to improve folate status in populations (strong recommendation, low and very low certainty of evidence).
    WHO Guideline: Fortification of Wheat Flour with Vitamins and Minerals as a Public Health Strategy, 2022 · checked 2026-09-30