Naan bread: every trial used a different flatbread

No trial has fed anybody commercial naan. What exists is a handful of small randomised trials on South Asian flatbreads, chapatis and breads made from an atta mix, which are unleavened and have neither the yogurt nor the tandoor. They agree on one thing. What happens to blood glucose after a flatbread depends on what goes into the dough, and most additions do nothing. In 38 normal-weight adults, 10 fibre and legume combinations were tested in 100 g of a commercial high-fibre atta mix. Three of them cut the glucose response by 30 percent or more: 6 g of guar gum, 4 g of konjac mannan, and 15 g of chickpea flour with 2 or 4 g of guar gum (p less than 0.01). No other combination differed from the control. These were single meals in healthy people, and the doses that worked are large enough to change the dough and the taste.

The numbers, per 100 g

How much is actually in it

• Wheat flour is fortified with folic acid in more than 80 countries, and a Cochrane review found that not one of its randomised trials measured neural tube defects, leaving a single non-randomised study reporting a risk ratio of 0.32 on low-certainty evidence. — 10 studies of folic acid fortification of wheat or maize flour, including 5 randomised trials with 1,182 participants, 3 non-randomised studies with 1,181 participants and 8,037 live births, and 2 interrupted time series (n = 10 studies) Evidence C source
  Total neural tube defects risk ratio 0.32 (95% CI 0.21 to 0.48) in one non-randomised study of 8,037 births, graded low-certainty, with no randomised trial reporting the outcome at all

What your body absorbs

• Adding soluble fibre to a wheat flatbread barely slowed how fast glucose was absorbed in 12 healthy men. With 15% chickpea flour and 4% guar gum, the time to half absorption did not change, the rate of glucose appearing from the meal fell 11%, and the glucose made by the liver fell 64%. — 12 healthy men eating three 13C-labelled flatbread meals in randomised crossover order, control or control with 15% chickpea flour plus 2% or 4% guar gum (n = 12) Evidence B source
  No significant change in time to 50% absorption, and with 4% guar gum the 4-hour area under the curve fell 11% for exogenous glucose appearance, 14% for total appearance, 14% for disposal and 64% for endogenous glucose production

What it does to your health

• In 38 adults eating South Asian flatbreads, only some fibre additions worked. Cutting the blood glucose response by at least 30% took 6 g of guar gum, 4 g of konjac mannan, or 15 g of chickpea flour with guar gum, and the other combinations did nothing. — 38 normal-weight adults testing 10 fibre and legume flour combinations in 100 g of a commercial high-fibre flatbread flour mix, in a balanced incomplete block design (n = 38) Evidence B source
  Postprandial glucose reduced by 30% or more with 6 g guar gum, 4 g konjac mannan, or 15 g chickpea flour plus 2 or 4 g guar gum, p less than 0.01, with no significant change for other combinations
• Working 4 to 8 g of barley beta-glucan into chapatis dropped their glycaemic index from 54 to 30 and 29 in 8 healthy adults, a fall of 43% to 47%. — 8 healthy adults, 3 men and 5 women aged 26 to 50 with body mass index under 30, eating chapatis with 0, 2, 4, 6 or 8 g of high-molecular-weight barley beta-glucan on separate occasions (n = 8) Evidence B source
  Glycaemic index 30 with 4 g and 29 with 8 g against 54 without beta-glucan, a 43% to 47% reduction, with blood glucose lower at 45 and 60 minutes
• Replacing 7.5% of the flour in chapattis with sprouted fenugreek lowered both the glucose and the insulin response in 18 healthy adults aged 18 to 25. — 18 healthy adults aged 18 to 25 with body mass index 21 to 22.5, eating chapattis with 7.5% sprouted fenugreek or white flour control in randomised crossover order (n = 18) Evidence B source
  Postprandial glucose and insulin both significantly lower than control at p less than 0.05, with blood sampled at 0, 30, 60 and 120 minutes

Safety, limits and interactions

• Among 103 pregnant women in Sindh, Pakistan, how often they ate chapati was one of the food habits linked to higher lead in their blood at delivery (beta 0.20, p less than 0.001). — 103 pregnant women in urban Karachi and rural Gambat whose blood lead was measured at delivery and whose diet was captured by questionnaire and three-day duplicate food portions (n = 103) Evidence C source
  Chapati beta 0.20 (p less than 0.001) for maternal blood lead, alongside boiled rice 0.35, cooked root vegetables 0.16 and fried savoury items 0.15, reported at a 90% confidence interval

The bottom line

Two more trials point the same way and give the numbers. Working 4 to 8 g of high- molecular-weight barley beta-glucan into chapatis pulled their glycaemic index from 54 down to 30 and 29 in 8 healthy adults aged 26 to 50. That is a fall of 43 to 47 percent, and eight people carry every one of those values. Replacing 7.5 percent of the flour with sprouted fenugreek lowered both glucose and insulin after the meal in 18 lean adults aged 18 to 25, at p less than 0.05. The authors call it a pilot, and the abstract never says by how much. How the fibre works is stranger than the label suggests. In 12 healthy men eating 13C-labelled flatbreads, chickpea flour with 4 percent guar gum left the time to half absorption unchanged, and the rate of meal glucose appearing in the blood fell only 11 percent over 4 hours. The 2 percent dose of guar gum moved those numbers less. What fell was the glucose made by the liver, by 64 percent. So a flatbread with fibre in it is not mainly a slower bread, and if you are counting on fibre to spread the absorption of a meal out over hours, that is not what this trial measured happening. Twelve young men and one meal each. What the flour carries depends on where it was milled. Wheat flour is fortified with folic acid in more than 80 countries, and a Cochrane review of that policy found that none of its randomised trials measured neural tube defects at all. The one figure available, a risk ratio of 0.32 (95% CI 0.21 to 0.48) across 8,037 births, comes from a single non-randomised study the reviewers graded low-certainty. The practical meaning is narrow. The B vitamin figures in the USDA table on this page describe flour fortified under United States rules, and the same bread baked from unfortified flour elsewhere is a different set of numbers. The one safety signal found for this class of bread is about lead and comes from one country. Among 103 pregnant women in Karachi and rural Gambat whose blood lead was measured at delivery, how often they ate chapati was positively associated with that lead (beta 0.20, p less than 0.001), reported at a 90 percent confidence interval rather than 95. Boiled rice carried a larger coefficient, 0.35. That is local contamination picked up in processing, packaging and storage, not a property of flatbread, and it says nothing about naan sold in a British or American shop. Beyond that study we found nothing on allergy, nothing on interactions with medicines, and nothing specific to pregnancy for this bread. The absence of those cautions here means nobody has published them where we looked, which is a different statement from safety. One more practical point sits in the USDA survey data rather than in any study: a piece counted as a quarter of a 10-inch naan weighs 44 g, so a whole one is four of the portions any table describes.

Sources

1. naan-r1-06 · systematic review
   Neural tube defects: none of the included RCTs reported neural tube defects as an outcome. In one non-RCT, wheat flour fortified with folic acid and other micronutrients was associated with significantly lower occurrence of total neural tube defects, spina bifida, and encephalocoele, but not anencephaly, compared to unfortified flour (total neural tube defects risk ratio (RR) 0.32, 95% confidence interval (CI) 0.21 to 0.48; 1 study, 8037 births; low-certainty evidence).
   Cochrane Database Syst Rev, 2019 · checked 2026-09-24
2. naan-r1-01 · randomised crossover trial
   In a randomised cross-over design, twelve healthy males consumed each of three different 13C-enriched meals: control flatbreads (C), or C incorporating 15 % CPF with either 2 % (GG2) or 4 % (GG4) GG...Compared with C, GG2 and GG4 had no significant effect on T 50 %abs. However, GG4 significantly reduced 4-h AUC values for RaE, RaT, RdT and EGP, by 11, 14, 14 and 64 %, respectively, whereas GG2 showed minor effects.
   Br J Nutr, 2017 · checked 2026-09-24
3. naan-r1-02 · randomised controlled trial
   Using a balanced incomplete block design, we tested the inclusion of guar gum (GG), konjac mannan (KM) and chickpea flour (CPF) in 10 combinations (2/4/6 g GG; 2/4 g KM; 15 g CPF, and 10 or 15 g CPF plus 2 or 4 g GG) in 100 g total of a control commercial high-fibre flatbread flour mix ("atta") on PPG in 38 normal-weight adults...Flatbreads with 6 g GG, 4 g KM, and 15 g CPF plus 2 or 4 g GG reduced PPG ≥30 % (p < 0.01), while no other combinations differed significantly from the control.
   Eur J Nutr, 2017 · checked 2026-09-24
4. naan-r1-03 · randomised crossover trial
   In a randomized, single-blind, controlled crossover trial, 8 healthy human subjects (3 men, 5 women; aged 26-50 years; body mass index, <30 kg/m(2)) consumed unleavened Indian flatbreads called chapatis containing high-molecular-weight barley beta-glucan at doses of 0, 2, 4, 6, and 8 g on different occasions...The glycemic index (GI) values of chapatis with 4 and 8 g beta-glucan were 43% to 47% lower (GI, 30 and 29, respectively) compared with chapatis without beta-glucan (GI, 54).
   Nutr Res, 2009 · checked 2026-09-24
5. naan-r1-04 · randomised crossover trial
   Eighteen healthy participants (18-25 years; BMI 21-22.5 kg/m2) consumed chapattis containing 7.5% sprouted fenugreek or white flour as a control in a randomized crossover design...Fenugreek-supplemented chapattis significantly reduced postprandial glucose and insulin responses (p < 0.05) compared with control.
   Nutrients, 2026 · checked 2026-09-24
6. naan-r1-05 · cross-sectional study
   A total of 103 venous blood samples (Karachi = 63 and Gambat = 40) of pregnant women were measured for blood Pb levels at the time of delivery...With 90% confidence interval, chapati (local flat bread) (β=0.20, p<0.001), boiled rice (β=0.35, p<0.001), cooked root vegetables (β= 0.16, p=0.03), fried savory items (β=0.15, p=0.03), sweet snacks (β=0.13, p=0.08) were positively associated with elevated mother blood Pb levels.
   J Ayub Med Coll Abbottabad, 2021 · checked 2026-09-24