Study analysis · PLoS ONE · 2015
Eating bacon every day could raise your colon cancer risk by 36%—but steak might actually lower it.
Processed meats like bacon and hot dogs are linked to higher cancer risk over time, while unprocessed red meat like steak isn’t—and might even seem protective because it’s eaten by healthier people.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study watched a big group of people for many years to see who got colon cancer and what they ate. It found that people who ate more processed meat (like bacon or hot dogs) were more likely to get cancer in the lower part of the colon. But because it didn’t randomly assign people to eat different things, we can’t say for sure that the meat caused the cancer — just that they’re linked.
What’s the bottom line?
Scientists looked at whether eating different kinds of red meat affects the chance of getting colon cancer, and where in the colon the cancer might form.
How strong is this study?
This is a well-done study with lots of people followed for a long time, and it asked about their diet many times. That makes the results more trustworthy than smaller or shorter studies. But since it only observed people’s habits instead of testing changes, there could still be other reasons behind the patterns they saw.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
38 / 100
- Randomizationnot randomized
- Blindingnot blinded
- Control groupno control group
- Sample size (n=134497)+20/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an observational cohort study; while it adjusts for multiple confounders, it cannot control for all unmeasured or residual confounding factors. Therefore, it cannot prove that processed meat causes colorectal cancer.
Key takeaways
- 01
Eating one serving of processed meat (like bacon or hot dogs) every day was linked to 36% higher chance of cancer in the lower part of the colon.
- 02
Eating unprocessed red meat (like steak) was linked to 25% lower risk in that same area, but this might be because those people ate healthier overall.
- 03
The type and timing of meat matter: processed meat over many years increases risk, while unprocessed meat doesn't seem to raise risk and may appear protective due to other healthy habits.
Surprising findings
- Unprocessed red meat was linked to *lower* risk of distal colon cancerThis contradicts the widespread belief that all red meat is bad. It suggests that when you control for healthy behaviors, unprocessed meat doesn’t act like a carcinogen.
- Recent processed meat intake didn’t affect cancer riskMost assume that current diet directly impacts current cancer risk. But here, only long-term (4–8+ years) consumption mattered—recent habits showed no link.
Practical takeaways
Limit daily bacon, hot dogs, and deli meats to reduce long-term colon cancer risk.
This study shows association, not causation, and was done in health professionals who may have different lifestyles.
high confidenceDon’t panic about steak or roast beef—this study found no strong evidence they increase colorectal cancer risk.
The apparent benefit may come from other healthy habits, not the meat itself.
medium confidenceFocus on long-term dietary patterns, not short-term changes, for cancer prevention.
Cancer develops over decades, so last year’s diet won’t tell your full story.
high confidenceWhy this study matters
Processed Meat = Higher Cancer Risk (But Only Over Time)
Every daily serving of processed red meat (like bacon or hot dogs) was linked to a 36% higher risk of distal colon cancer. But this only applied to long-term consumption—eating it recently didn’t matter, suggesting it takes 4–8 years for damage to build up.
This shows that your diet habits over decades matter more than what you ate last month, which changes how we think about prevention.
Steak Might *Lower* Cancer Risk? (Here’s the Catch)
People who ate more unprocessed red meat had a 25% lower risk of distal colon cancer. But this likely isn’t the meat itself—it’s because those people also ate more fiber, took supplements, and had healthier diets overall.
It reveals how misleading nutrition studies can be: healthy eaters look healthier, even if one of their habits (like eating steak) isn’t the cause.
Not All Colon Cancer Is the Same
Processed meat was linked to cancer in the lower (distal) colon, but not the upper (proximal) colon or rectum. This suggests different parts of the colon respond differently to diet.
Most people think of 'colon cancer' as one disease—this shows it’s multiple conditions with different causes.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists looked at whether eating different kinds of red meat affects the chance of getting colon cancer, and where in the colon the cancer might form.
Research results
Eating one serving of processed meat (like bacon or hot dogs) every day was linked to 36% higher chance of cancer in the lower part of the colon. Eating unprocessed red meat (like steak) was linked to 25% lower risk in that same area, but this might be because those people ate healthier overall.
What this means - more context
The type and timing of meat matter: processed meat over many years increases risk, while unprocessed meat doesn't seem to raise risk and may appear protective due to other healthy habits.
The study aimed to examine the associations between processed and unprocessed red meat consumption and colorectal cancer risk, specifically by tumor location (proximal colon, distal colon, rectum) and timing of consumption in relation to cancer development.
In two large prospective cohorts of US health professionals, higher intake of processed red meat was associated with increased risk of colorectal cancer, particularly distal colon cancer, with a 36% higher risk per daily serving. This association required a latency period of at least 4–8 years, suggesting long-term exposure is critical. In contrast, unprocessed red meat was inversely associated with distal colon cancer (25% lower risk per serving), though this may reflect residual confounding by healthy diet patterns. No association was found between processed meat and proximal colon or rectal cancers, and recent consumption of processed meat was not linked to distal cancer risk.
Methods Used
The study analyzed data from the Nurses’ Health Study (87,108 women, 1980–2010) and Health Professionals Follow-up Study (47,389 men, 1986–2010), using repeated food-frequency questionnaires to assess dietary intake every 4 years. Cox proportional hazards models were used to estimate hazard ratios for colorectal cancer by subsite, adjusted for multiple covariates, with results pooled via random-effects meta-analysis.
Main Finding
Processed red meat intake was associated with a 15% increased risk of overall colorectal cancer (HR = 1.15, 95% CI: 1.01–1.32) and a 36% increased risk of distal colon cancer (HR = 1.36, 95% CI: 1.09–1.69) per daily serving. Unprocessed red meat was associated with a 25% lower risk of distal colon cancer (HR = 0.75, 95% CI: 0.68–0.82), but a weak, non-significant increase in proximal colon cancer (HR = 1.14, 95% CI: 0.92–1.40). Recent processed meat intake showed no association with distal cancer.
Confidence Level
The study has high methodological rigor due to its large sample size, long follow-up (up to 30 years), repeated dietary assessments, and adjustment for key confounders. However, as an observational study, residual confounding and measurement error in dietary recall remain limitations.
Study Flags
Red Flags
- •Residual confounding possible (e.g., unmeasured lifestyle factors)
- •Dietary intake self-reported via food frequency questionnaires
- •Findings in health professionals may not generalize to general population
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Unprocessed red meat was linked to *lower* risk of distal colon cancer
This contradicts the widespread belief that all red meat is bad. It suggests that when you control for healthy behaviors, unprocessed meat doesn’t act like a carcinogen.
Practical Takeaways
Limit daily bacon, hot dogs, and deli meats to reduce long-term colon cancer risk.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study watched a big group of people for many years to see who got colon cancer and what they ate. It found that people who ate more processed meat (like bacon or hot dogs) were more likely to get cancer in the lower part of the colon. But because it didn’t randomly assign people to eat different things, we can’t say for sure that the meat caused the cancer — just that they’re linked.
Strengths
- Large sample size (n = 134,497)
- Long follow-up period (up to 30 years)
- Repeated dietary assessments using validated food frequency questionnaires
Weaknesses
- Observational design susceptible to residual confounding
- Dietary data based on self-report with potential measurement error
- Lack of data on meat cooking methods and mutagen exposure
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists looked at whether eating different kinds of red meat affects the chance of getting colon cancer, and where in the colon the cancer might form.
Research results
Eating one serving of processed meat (like bacon or hot dogs) every day was linked to 36% higher chance of cancer in the lower part of the colon. Eating unprocessed red meat (like steak) was linked to 25% lower risk in that same area, but this might be because those people ate healthier overall.
What this means - more context
The type and timing of meat matter: processed meat over many years increases risk, while unprocessed meat doesn't seem to raise risk and may appear protective due to other healthy habits.
The study aimed to examine the associations between processed and unprocessed red meat consumption and colorectal cancer risk, specifically by tumor location (proximal colon, distal colon, rectum) and timing of consumption in relation to cancer development.
In two large prospective cohorts of US health professionals, higher intake of processed red meat was associated with increased risk of colorectal cancer, particularly distal colon cancer, with a 36% higher risk per daily serving. This association required a latency period of at least 4–8 years, suggesting long-term exposure is critical. In contrast, unprocessed red meat was inversely associated with distal colon cancer (25% lower risk per serving), though this may reflect residual confounding by healthy diet patterns. No association was found between processed meat and proximal colon or rectal cancers, and recent consumption of processed meat was not linked to distal cancer risk.
Methods Used
The study analyzed data from the Nurses’ Health Study (87,108 women, 1980–2010) and Health Professionals Follow-up Study (47,389 men, 1986–2010), using repeated food-frequency questionnaires to assess dietary intake every 4 years. Cox proportional hazards models were used to estimate hazard ratios for colorectal cancer by subsite, adjusted for multiple covariates, with results pooled via random-effects meta-analysis.
Main Finding
Processed red meat intake was associated with a 15% increased risk of overall colorectal cancer (HR = 1.15, 95% CI: 1.01–1.32) and a 36% increased risk of distal colon cancer (HR = 1.36, 95% CI: 1.09–1.69) per daily serving. Unprocessed red meat was associated with a 25% lower risk of distal colon cancer (HR = 0.75, 95% CI: 0.68–0.82), but a weak, non-significant increase in proximal colon cancer (HR = 1.14, 95% CI: 0.92–1.40). Recent processed meat intake showed no association with distal cancer.
Confidence Level
The study has high methodological rigor due to its large sample size, long follow-up (up to 30 years), repeated dietary assessments, and adjustment for key confounders. However, as an observational study, residual confounding and measurement error in dietary recall remain limitations.
Study Flags
Red Flags
- •Residual confounding possible (e.g., unmeasured lifestyle factors)
- •Dietary intake self-reported via food frequency questionnaires
- •Findings in health professionals may not generalize to general population
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Unprocessed red meat was linked to *lower* risk of distal colon cancer
This contradicts the widespread belief that all red meat is bad. It suggests that when you control for healthy behaviors, unprocessed meat doesn’t act like a carcinogen.
Practical Takeaways
Limit daily bacon, hot dogs, and deli meats to reduce long-term colon cancer risk.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study watched a big group of people for many years to see who got colon cancer and what they ate. It found that people who ate more processed meat (like bacon or hot dogs) were more likely to get cancer in the lower part of the colon. But because it didn’t randomly assign people to eat different things, we can’t say for sure that the meat caused the cancer — just that they’re linked.
Strengths
- Large sample size (n = 134,497)
- Long follow-up period (up to 30 years)
- Repeated dietary assessments using validated food frequency questionnaires
Weaknesses
- Observational design susceptible to residual confounding
- Dietary data based on self-report with potential measurement error
- Lack of data on meat cooking methods and mutagen exposure
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
This is a well-done study with lots of people followed for a long time, and it asked about their diet many times. That makes the results more trustworthy than smaller or shorter studies. But since it only observed people’s habits instead of testing changes, there could still be other reasons behind the patterns they saw.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
38 / 100
- Randomizationnot randomized
- Blindingnot blinded
- Control groupno control group
- Sample size (n=134497)+20/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 552 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an observational cohort study; while it adjusts for multiple confounders, it cannot control for all unmeasured or residual confounding factors. Therefore, it cannot prove that processed meat causes colorectal cancer.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from Thomas DeLauer cite this study, drawing 1 claim from it.
- Conflicting evidence
Evidence points in both directions — no clear conclusion yet.
Evidence
Authored by
12 researchersIf this is your work, this is how we attribute it on Fit Body Science. Adam Bernstein is listed as the lead author.