Bacon: two rashers a day, and the evidence is graded high

Most diet and disease associations are graded weak. This one is not. An umbrella review scored 153 pooled associations and found only a handful worth calling high quality, and bacon at two slices a day, tracking with roughly double the rate of type 2 diabetes, was among them. Processed meat more generally gets 37 percent more diabetes per 50 grams a day, and in a separate umbrella review 72 percent more stomach cancer and 17 percent more colorectal cancer at the same dose. None of it is randomised, and two rashers every day is a substantial habit that travels with other habits.

The numbers, per 100 g

What a real portion looks like

• Two rashers of bacon a day went with roughly double the rate of type 2 diabetes, and that estimate was graded high quality. — 53 publications giving 153 adjusted summary hazard ratios across dietary behaviours, food groups, beverages, macronutrients and micronutrients (n = 153 pooled associations) Evidence C source
  Quality of evidence was high for higher type 2 diabetes incidence with red meat (1.17 per 100 g/day, 1.08-1.26), processed meat (1.37 per 50 g/day, 1.22-1.54), bacon (2.07 per two slices/day, 1.40-3.05) and sugar-sweetened beverages (1.26 per serving/day); also high for lower incidence with whole grains and cereal fibre

What your body absorbs

• Smoked meat leaves a chemical signature in urine within two hours, which is how researchers can finally tell bacon from ham in a study. — 12 volunteers in the intervention, eating bacon, salami and hot dog plus two control foods, and 474 subjects from the EPIC cross-sectional study (n = 12 in the trial, 474 in the cohort) Evidence B source
  Syringol and four derivatives were characteristic of digests of smoked meat products; as sulfate esters in urine they rose at 2 and 12 hours after eating hot dog or bacon, and were positively associated with recent and habitual smoked meat consumption in the EPIC samples

What cooking and storage change

• Nitrite-cured meat and plain fresh red meat produced the same amount of nitroso compounds in the gut. — 12 people in the first study (six male, six female) and 16 in the second (5 male, 11 female) (n = 28 across two studies) Evidence B source
  Faecal nitroso compounds were low on vegetarian diets (2.6 and 3.5 units) and high on both meat diets, with no difference between preserved and fresh meat (175 against 185 nmol/g, p = 0.75); the composition differed, with fresh meat giving more nitrosyl iron (78% against 54%) and preserved meat more nitrosothiols and other compounds; DNA breaks did not differ, though preserved meat gave more oxidised pyrimidines

What it does to your health

• Fifty grams a day of processed meat tracked with 72 percent more stomach cancer and 17 percent more bowel cancer. — 34 articles covering 54 meta-analyses (n = 54 meta-analyses) Evidence C source
  Processed meat was associated with higher risk of several cancers, cardiovascular disease, metabolic disorders and all-cause mortality; per 50 g a day, gastric cancer +72%, colorectal cancer +17%, prostate cancer +4%

What is still unknown

• At the stage before bowel cancer, processed meat tracked with polyps and not with adenomas. — 31 observational studies (n = 31 studies) Evidence C source
  Red meat was linked to colorectal adenomas (RR 1.13, 1.05-1.21), polyps (1.73, 1.02-2.94) and distal colon adenomas (1.19, 1.02-1.40); processed meat was linked to polyps (1.65, 1.05-2.61) but not adenomas (1.14, 0.93-1.41); seafood was inversely linked to adenomas (0.74, 0.58-0.94)
• For stomach cancer the association held in case-control studies and vanished in the cohorts. — 12 cohort and 30 case-control studies (n = 42 studies) Evidence C source
  Red meat RR 1.45 (1.22-1.73) and processed meat 1.45 (1.26-1.65) overall; bacon specifically 1.37 (1.17-1.61), beef 1.28, ham 1.44, sausage 1.33; by design, red meat gave 1.63 (1.33-1.99) in case-control studies and 1.02 (0.90-1.17) in cohorts

The bottom line

Two things complicate the simple story. When the gastric cancer question was split by study design, the association held in case-control studies and disappeared entirely in the prospective cohorts. And when nitrite-cured meat was compared against plain fresh red meat in a controlled feeding study, the nitroso compounds in the gut came out the same, which points at the haem in red meat rather than at curing specifically. Two notes for anyone reading further. Our own USDA reference record for bacon is a soy-based meatless product, so the composition table on most pages is unreliable. And there is a Danish paper about fried bacon and parsley sauce in footballers that is a Christmas joke, not a source.

Sources

1. bcn-dr-01 · umbrella review of meta-analyses of prospective observational studies
   Quality of evidence was also high for the association for increased incidence of type 2 diabetes with higher intake of red meat (for an increment of 100 g/day, 1.17 (1.08 to 1.26)), processed meat (for an increment of 50 g/day, 1.37 (1.22 to 1.54)), bacon (per two slices/day, 2.07 (1.40 to 3.05)), and sugar sweetened beverages (for an increase of one serving/day, 1.26 (1.11 to 1.43)).
   BMJ, 2019 · checked 2026-09-22
2. bcn-dr-06 · randomised crossover metabolomics study with cross-sectional validation
   The same compounds present as sulfate esters in urine increased at 2 and 12 h after consumption of smoked meat products (hot dog, bacon) in the intervention study.
   Am J Clin Nutr, 2019 · checked 2026-09-22
3. bcn-dr-05 · controlled feeding studies
   Faecal NOC concentrations on VEG diets were low (2.6 and 3.5 mmol/g) but significantly higher on meat diets (PM 175 +/- 19 nmol/g versus RM 185 +/- 22 nmol/g; P = 0.75).
   Carcinogenesis, 2009 · checked 2026-09-22
4. bcn-dr-02 · umbrella review of systematic reviews and meta-analyses
   Dose-response analysis revealed that an increase in PM consumption of 50 g/day was associated with a 72% higher risk of gastric cancer, 17% higher risk of colorectal cancer, 4% higher risk of prostate cancer
   Front Public Health, 2026 · checked 2026-09-22
5. bcn-dr-03 · meta-analysis of observational studies
   Processed meat consumption was correlated with increased colorectal polyp risk (1.65; 1.05, 2.61) but not colorectal adenoma risk (1.14; 0.93, 1.41).
   Nutr Rev, 2026 · checked 2026-09-22
6. bcn-dr-04 · meta-analysis of observational studies
   When conducted by study design, the association was significant in case-control studies (RR: 1.63, 95% CI: 1.33-1.99) but not in cohort studies (RR: 1.02, 95% CI: 0.90-1.17) for red meat.
   PLoS One, 2013 · checked 2026-09-22