Pumpernickel bread: a dense rye loaf with a mixed blood sugar record

Pumpernickel is sold as the slow bread, and the pooled evidence on rye is less tidy than that reputation. A meta-analysis of randomized trials found that whole wheat rye did not significantly lower the post-meal blood glucose area compared with refined rye (-99 mg/dL (-5.5 mmol/L) x min, 95% CI -24.8 to 13.8). It rested on only five rye comparisons made with whole wheat flour, which differs from the intact kernels in pumpernickel. The direct evidence on pumpernickel itself is one small study. In 11 adults with type 2 diabetes eating single test meals, it gave a lower peak blood glucose than white, whole wheat and wholegrain breads, and the abstract reports no effect sizes. On weight, the trials disagree. One 12-week trial in 242 adults with overweight on a calorie-reduced diet found 2.4 lb (1.08 kg) more weight loss with high-fiber rye products than with refined wheat (95% CI 0.36 to 1.80). A newer trial of the same length in 255 adults found 7.1 lb (3.2 kg) against 6.4 lb (2.9 kg), a gap that did not reach significance, though CRP fell by 17% in the rye group. Neither trial used pumpernickel specifically.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• USDA lists pumpernickel bread at 24.5 ug selenium and 134 ug folate per 3.5 oz (100 g), from a single reference record with no sample spread. — — (n = 1 record) Evidence E source
  Selenium 24.5 ug/100 g; folate 134 ug/100 g; copper 0.287 mg/100 g

What a real portion looks like

• A medium slice of pumpernickel is 32 g in USDA survey data and carries about 2.1 g of fiber. — — Evidence E source
  Medium slice 32 g; thin slice 25 g; thick slice 43 g; fiber 6.5 g/100 g

What your body absorbs

• In women eating 7.1 oz (200 g) a day of wholegrain rye bread for 12 weeks, the low-phytate version did not improve iron status, and ferritin fell by 12%. — 102 Swedish females of reproductive age randomized, 55 completed, 12 weeks, 200 g rye bread daily (n = 102) Evidence B source
  Low-phytate group ferritin 32 to 27 ug/L (-12%); body iron 6.9 to 5.4 mg/kg

What cooking and storage change

• A systematic review of 8 human studies found no adequately controlled human trial showing that sourdough fermentation of bread improves iron absorption. — 8 human intervention studies, healthy or iron-deficient participants (n = 8 studies) Evidence C source
  Inconclusive; no adequately controlled human study

What it does to your health

• In a 12-week trial on a calorie-reduced diet, adults eating high-fiber rye products lost 2.4 lb (1.08 kg) more body weight than those eating refined wheat. — 242 adults with overweight or obesity (BMI 27-35), aged 30-70, 12 weeks, hypocaloric diet (n = 242) Evidence B source
  2.4 lb (1.08 kg) more weight loss (95% CI 0.36 to 1.80); CRP 28% lower
• In a crossover trial in adults with overweight, a day of wholegrain rye meals lowered the day-long blood glucose area by 30% compared with refined wheat. — 29 adults with overweight or obesity, aged 30-70, single intervention days (n = 29) Evidence B source
  Day-long glucose iAUC 30% lower (P < 0.001); glycemic variability SD -2.3 mg/dL (-0.13 mmol/L)

Safety, limits and interactions

• Rye contains gluten, so pumpernickel is unsuitable for people with celiac disease, whose treatment is a gluten-free diet. — people with celiac disease Evidence E source
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What people believe that the data does not support

• The EU did not authorize the claim that rye bread stimulates insulin secretion or gives a low insulin response. — — Evidence E source
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• The EU did not authorize the claim that high-fiber sourdough rye bread reduces post-meal blood glucose responses. — — Evidence E source
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Who this works differently for

• In a crossover trial in 11 adults with type 2 diabetes, pumpernickel rye bread gave a lower peak blood glucose than white, whole wheat and wholegrain breads at 50 g available carbohydrate. — 11 fasting adults with type 2 diabetes, single test meals (n = 11) Evidence B source
  Lower peak glucose vs all other breads (P < .01); lower peak insulin vs white and wholegrain (P < .001)

What is still unknown

• A meta-analysis of randomized trials found that whole wheat rye bread did not lower the post-meal blood glucose area compared with refined rye (-99 mg/dL (-5.5 mmol/L) x min, not significant). — randomized trials of whole wheat vs endosperm rye foods, 5 rye comparisons (n = 5 strata) Evidence A source
  -5.5 mmol/L x min (95% CI -24.8 to 13.8), P = 0.576
• A newer 12-week trial found no extra weight loss from wholegrain rye over refined wheat on a calorie-reduced diet (7.1 lb / 3.2 kg vs 6.4 lb (2.9 kg)), though CRP fell by 17% with rye. — 255 adults with overweight or obesity, 229 completed, 12-week hypocaloric diet (n = 255) Evidence B source
  Weight loss 7.1 lb (3.2 kg) rye vs 6.4 lb (2.9 kg) wheat, p = 0.32; CRP -17% in rye group (p = 0.03)

The bottom line

A medium slice weighs 1.1 oz (32 g) in USDA survey data and carries about 2.1 g of fiber, a figure recalculated from 6.5 g per 3.5 oz (100 g). Per 100 g, USDA lists 24.5 ug selenium and 134 ug folate from a single reference record with no sample spread, so read those as one measurement of one loaf. In a crossover trial in 29 adults with overweight, a single day of wholegrain rye meals lowered the day-long glucose area by 30% compared with refined wheat. That was one day of eating, and the trial did not follow anyone longer. The EU assessed the claims that rye bread gives a low insulin response and that high-fiber sourdough rye cuts post-meal glucose, and authorized neither. Iron is the open question. A systematic review of 8 human studies found no adequately controlled human trial showing that sourdough fermentation improves iron absorption from bread. In Swedish women of reproductive age eating 7.1 oz (200 g) of wholegrain rye bread a day for 12 weeks, the 24 in the low-phytate group saw ferritin fall by 12%, from 32 to 27 ug/L. That is a within-group change, in a trial where only 55 of 102 women finished. Rye contains gluten, so pumpernickel is off the menu for anyone with celiac disease, whose treatment is a gluten-free diet. We found no study on pregnancy, children, kidney disease or drug interactions for this bread.

Sources

1. pnkl-daily-r8-11 · food composition data
   Bread, pumpernickel (FDC 174918, SR Legacy, Baked Products): selenium 24.5 ug per 100 g = 45% DV; folate 134 ug = 34% DV; copper 0.287 mg = 32% DV; Foundation samples 0, CoFID match none
   USDA FoodData Central, SR Legacy 2018, FDC 174918 Bread, pumpernickel · checked 2026-10-01
2. pnkl-daily-r8-12 · portion data
   Bread, pumpernickel, FNDDS code 51404010, fdc_id 2707760: 1 small or thin/very thin slice 25 g; 1 medium or regular slice 32 g; 1 large or thick slice 43 g; Fiber, total dietary 6.5 G per 100 g, 2.1 G per medium slice
   USDA FNDDS 2021-2023, food code 51404010 Bread, pumpernickel (FDC 2707760) · checked 2026-10-01
3. pnkl-daily-r8-06 · randomized controlled trial
   In the low-phytate bread group (n = 24) there were significant within-group decreases in both ferritin (mean 12%; from 32 ± 7 to 27 ± 6 μg/L, geometric mean ± SEM, p < 0.018) and total body iron (mean 12%; from 6.9 ± 1.4 to 5.4 ± 1.1 mg/kg, p < 0.035).
   Eur J Nutr, 2019 · checked 2026-10-01
4. pnkl-daily-r8-07 · systematic review
   Despite convincing mechanistic evidence that the sourdough-fermentation process in bread fabrication improves iron bioavailability, through reduction of phytate, no human studies address this research question with the appropriate control and study quality.
   Front Nutr, 2026 · checked 2026-10-01
5. pnkl-daily-r8-03 · randomized controlled trial
   After 12 weeks the participants in the rye group had lost 1.08 kg body weight and 0.54% body fat more than the wheat group (95% confidence interval (CI): 0.36; 1.80, p < 0.01 and 0.05; 1.03, p = 0.03, respectively).
   Clin Nutr ESPEN, 2021 · checked 2026-10-01
6. pnkl-daily-r8-05 · randomized crossover trial
   Day-long glucose incremental area under the curve was 30% (P < 0.001) lower after the rye-based diet, and glycemic variability was measured as SD reduced (-0.13 mmol/L, P = 0.04).
   J Nutr, 2025 · checked 2026-10-01
7. pnkl-daily-r8-08 · clinical guideline
   Celiac disease is an immune-based reaction to dietary gluten (storage protein for wheat, barley, and rye) that primarily affects the small intestine in those with a genetic predisposition and resolves with exclusion of gluten from the diet.
   Am J Gastroenterol, 2013 · checked 2026-10-01
8. pnkl-daily-r8-09 · EU health claim register
   POL-HC-7897 Rye bread -Stimulates insulin secretion. -Low insulin response. Non-authorised
   EU Register on nutrition and health claims, claim POL-HC-7897, snapshot 2026-09-21 · checked 2026-10-01
9. pnkl-daily-r8-10 · EU health claim register
   POL-HC-8470 High-fibre sourdough rye bread Reduction of post-prandial glycaemic responses compared with glucose -/- Non-authorised
   EU Register on nutrition and health claims, claim POL-HC-8470, snapshot 2026-09-21 · checked 2026-10-01
10. pnkl-daily-r8-01 · randomized crossover trial
    Pumpernickel bread resulted in a significantly lower peak glucose (P < .01) than all other breads and a lower peak insulin (P < .001) than white or wholegrain bread. Similar appetite responses were found with all 4 breads.
    Diabetes Educ, 2013 · checked 2026-10-01
11. pnkl-daily-r8-02 · meta-analysis
    The consumption of wholemeal rye, compared with endosperm rye, was not associated with a significant reduction in blood glucose AUC (-5.5 mmol/L ⋅ min; 95% CI: -24.8, 13.8 mmol/L ⋅ min; P = 0.576).
    Am J Clin Nutr, 2018 · checked 2026-10-01
12. pnkl-daily-r8-04 · randomized controlled trial
    Weight loss was 3.2 kg in the rye-group and 2.9 kg in the wheat-group, with no significant difference between groups (p = 0.32).
    Clin Nutr, 2026 · checked 2026-10-01