This new analysis of vegans by Aune et al. (2026) includes the Adventist Health Study 2, the EPIC-Oxford study, and the Oxford Vegetarian Study.
The exception is the breast cancer analysis which also includes Mills et al. 1989, which is the Adventist Health Study (not the Adventist Health Study 2).
"[...]
The summary RRs (95% CIs) for vegans vs. non-vegetarians were 0.77 (0.70–0.85, I2 = 0%, n = 3 [they mean three studies - not three people]) for total cancer, 1.02 (0.71–1.48, I2 = 42%, n = 3) for colorectal cancer, 0.80 (0.64–1.00, I2 = 0%, n = 4) for breast cancer, and 0.87 (0.50–1.49, I2 = 49%, n = 3) for prostate cancer. BMI explained a moderate part of the associations. The strength of evidence [judging the likelihood of causality] for vegetarian diets and total, colorectal, colon and breast cancer was judged as probable, and limited suggestive for stomach, pancreatic, and bladder cancers, melanoma and non-Hodgkin’s lymphoma, and for vegan diets and total cancer and breast cancer was considered limited-suggestive. Vegetarian diets compared to non-vegetarian diets are associated with reduced risk of total cancer and seven specific cancer types, while vegan diets are associated with reduced risk of total and breast cancer. Although further studies are needed to assess the long-term adherence to vegetarian and vegan diets and cancer incidence and across less investigated cancers, these results support recommendations to adopt much more plant-based diets for cancer prevention.
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We therefore conducted a systematic review and meta-analysis to clarify the associations between vegetarian and vegan diets and cancer incidence to provide an up-to-date summary of the evidence across cancer sites.
[...]
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The review question was framed using the PECO(S) elements [25]. Studies of healthy individuals in the general population with no restrictions with regard to age, sex, or pregnancy status (P), who adhered to vegetarian (excluding meat, poultry or fish) and vegan (excluding meat, poultry, fish, eggs, and dairy products) diets (E) vs. non-vegetarian (including meat, poultry, fish, eggs, dairy) diets (C) and were followed up for cancer incidence (O) were eligible for inclusion.
[...]
When estimates were presented without and with BMI adjustment in the same study, estimates without BMI adjustment were prioritized for the main analysis, as there is evidence from randomized trials that vegetarian and vegan diets can help with weight loss [31], and BMI can therefore be considered a mediator.
[...]
We calculated E-values for the association between vegetarian and vegan diets and cancer incidence, to assess the potential impact of unmeasured or uncontrolled confounding.
[...]
The publication from Oxford Vegetarian Study and EPIC-Oxford Study pooled the two studies together.
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Figure 2[..]b shows a summary of the results across cancer sites for [..] vegans vs. non-vegetarians [.].
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Three prospective studies (two risk estimates, two publications, 10,562 cases, 141,115 participants) [12, 15] were included in the analysis of vegan diets and total cancer incidence. The summary RR (95% CI) was 0.77 (0.70–0.85, I2 = 0[0–34]%) for vegans vs. non-vegetarians (Figs. 2b and 6c).
[...]
Three cohort studies (two risk estimates, two publications, 1111 cases, 141,115 participants) [12, 15] were included in the analysis of vegan diets and colorectal cancer. The summary RR (95% CI) was 1.02 (0.71–1.48, I2 = 42[0–89]%) for vegans vs. non-vegetarians (Figs. 2b and 6b).
[...]
Four prospective studies (three risk estimates, three publications, 1821 cases, 118,048 participants) [15, 16, 38] were included in the analysis of vegan diets and breast cancer incidence. The summary RR (95% CI) was 0.80 (0.64–1.00, I2 = 0[0–0]%) for vegans vs. non-vegetarians (Fig. 6c). When using results at age 65 from the Adventist Health Study II, the summary RR was 0.76 (0.63–0.92, I2 = 0[0–41]%).
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Three prospective studies (two risk estimates, two publications, 1676 cases, 43,408 participants) [15, 21] were included in the analysis of vegan diets and prostate cancer risk. The summary RR (95% CI) was 0.87 (0.50–1.49, I2 = 49[0–90]%) for vegans vs. non-vegetarians (Figs. 2b and 6d). When using results at age 65 from the Adventist Health Study II, the summary RR was 0.58 (0.43–0.78, I2 = 0[0–0]%).
[...]
We compared BMI-unadjusted and BMI-adjusted results for the associations between vegetarian and vegan diets and cancer risk and the association between vegetarian diets and total cancer was attenuated from 0.87 (0.84–0.91) to 0.92 (0.87–0.96) and the association between vegan diets and total cancer was attenuated from 0.77 (0.70–0.85) to 0.82 (0.74–0.91) when further adjusted for BMI and similar trends were observed for most individual cancer sites (Supplementary Fig. 13–14).
The studies on vegan diets and cancer appeared to deviate in sensitivity analyses suggesting the results on colorectal and prostate cancer may not have been representative for the overall evidence base (Supplementary text 3).
E-values for vegetarians ranged from 1.39 (lower CI: 1.11) for breast cancer to 3.04 (lower CI: 1.60) for stomach cancer (Supplementary Table 20) and for vegans ranged from 1.81 (lower CI: 1.00) for breast cancer to 1.92 (lower CI: 1.63) for total cancer (Supplementary Table 20).
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Some of the observed associations between vegetarian and vegan diets and cancer risk were slightly stronger when not adjusted for BMI compared to when adjusted for BMI, and suggested differences in baseline adiposity explains [..] 42% of the observed reduction in overall cancer risk among [..] vegans, respectively, however, the proportion explained by BMI differed across cancer sites.
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Heterogeneity was in general low across analyses except for the analysis of [...] vegan diets and colorectal cancer and prostate cancer (Fig. 2), but out of these, subgroup analyses were only possible for vegetarian diets [not vegan diets only] and prostate cancer because of limited data.
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We graded the evidence of a causal relationship between vegan diets and total and breast cancer as limitedsuggestive, while that for colorectal and prostate cancers was graded as limited-no conclusion (Supplementary Table 25). A justification for the evidence grading is provided in Supplementary Table 26.
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[...] vegan diets were associated with a reduced risk of total cancer (23%) and breast cancer (20%), but no association was observed for colorectal and prostate cancer.
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Although we were not able to assess the quality of the vegetarian and vegan diets (e.g. if diets contained more whole plant foods or unhealthier items like refined grains, fast foods and sugary drinks), it seems likely given the results, that the majority may have had a decent diet quality, and the findings are in general consistent with reported food group intakes between diet groups.
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Further and larger studies are needed to further investigate the observed associations, associations across less common and less investigated cancers and associations with vegan diets, which were investigated in a limited number of studies, and in general there were relatively few vegans included across studies. Nevertheless, the findings are largely consistent with current evidence of food groups and cancer risk, suggesting the adoption of much more plant-based diets such as vegetarian and vegan diets could play an important role in cancer prevention.
In conclusion, vegetarian diets were associated with reductions in the relative risk of total cancer (13%), stomach (43%), colorectal (14%), pancreatic (23%), breast (10%), and bladder (21%) cancers, melanoma (21%) and non-Hodgkin’s lymphoma (23%). Vegan diets were associated with a 23% reduction in risk of total cancer and a 20% reduction in breast cancer risk. Although further studies are needed to clarify the associations between vegetarian and vegan diets across less investigated cancer sites, these findings support a beneficial role of vegetarian and vegan diets in cancer prevention and provide further support for recommendations to adopt much more plant-based dietary patterns in the general population.
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Fig. 2 Vegetarian (a) and vegan (b) diets and cancer incidence, summary estimates across cancers
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Fig. 6 Vegan diets and total cancer (a), colorectal cancer (b), breast cancer (c), and prostate cancer (d) incidence
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Supplementary Figure 14. Summary estimates from cohort studies on vegan diets and cancer that reported both BMI-unadjusted and BMI-adjusted results.
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Supplementary text 3. Sensitivity analysis
We repeated the analysis in vegetarians restricted to the studies included in the analysis of vegan diets to check whether studies reporting on vegan diets showed results consistent with the overall results. The summary RRs for vegetarians vs. non-vegetarians when restricted to the studies in the analysis of vegans was 0.88 (95% CI: 0.84-0.92, I2=0%, n=2) for total cancer, 0.90 (95% CI: 0.69-1.17, I2=72.5%, n=2) for colorectal cancer, 0.92 (0.82-1.04, I2=39.4%, n=3) for breast cancer, and 0.94 (95% CI: 0.83-1.06, I2=7.6%, n=2) for prostate cancer, with results being similar for total and breast cancer, while associations were weaker and less clear for colorectal and prostate cancer when compared to the main analysis. This suggests the studies on vegans may not have been representative for the overall evidence base for colorectal and prostate cancer.
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Supplementary Table 20. E-values for the associations between vegetarian and vegan diets and cancer.
|
Vegetarians vs. non-vegetarians |
||
|
Cancer
site |
RR
(95% CI) |
E-value
(lower CI) |
|
Total
cancer |
0.87
(0.84-0.91) |
1.56
(1.43) |
|
Upper
aerodigestive tract cancer |
0.97
(0.73-1.29) |
1.21
(1.00) |
|
Stomach
cancer |
0.55
(0.36-0.86) |
3.04
(1.60) |
|
Colorectal
cancer |
0.86
(0.76-0.97) |
1.60
(1.21) |
|
Colon
cancer |
0.79
(0.67-0.93) |
1.85
(1.36) |
|
Proximal
colon cancer |
0.55
(0.31-0.97) |
3.04
(1.21) |
|
Distal
colon cancer |
0.84
(0.57-1.22) |
1.67
(1.00) |
|
Rectal
cancer |
0.88
(0.70-1.11) |
1.53
(1.00) |
|
Pancreatic
cancer |
0.77
(0.62-0.95) |
1.92
(1.29) |
|
Lung |
0.85
(0.70-1.04) |
1.63
(1.00) |
|
Melanoma |
0.79
(0.66-0.94) |
1.85
(1.32) |
|
Breast
cancer |
0.92
(0.86-0.99) |
1.39
(1.11) |
|
Breast
cancer, premenopausal |
0.97
(0.79-1.19) |
1.21
(1.00) |
|
Breast
cancer, postmenopausal |
0.81
(0.69-0.95) |
1.77
(1.29) |
|
Endometrial
cancer |
0.91
(0.77-1.07) |
1.43
(1.00) |
|
Ovarian
cancer |
0.83
(0.68-1.02) |
1.70
(1.00) |
|
Prostate
cancer |
0.87
(0.57-1.00) |
1.56
(1.00) |
|
Kidney
cancer |
0.85
(0.64-1.11) |
1.63
(1.00) |
|
Bladder
cancer |
0.78
(0.62-0.98) |
1.88
(1.16) |
|
Brain
cancer |
0.99
(0.73-1.34) |
1.11
(1.00) |
|
Non-Hodgkin's
lymphoma |
0.76
(0.63-0.93) |
1.96
(1.36) |
|
Multiple
myeloma |
0.75
(0.32-1.77) |
2.00
(1.00) |
|
Leukemia
|
0.95
(0.74-1.21) |
1.29
(1.00) |
|
Vegans vs. non-vegetarians |
||
|
Total
cancer |
0.77
(0.70-0.85) |
1.92
(1.63) |
|
Colorectal
cancer |
1.02
(0.71-1.48) |
1.16
(1.00) |
|
Breast
cancer |
0.80
(0.64-1.00) |
1.81
(1.00) |
|
Breast
cancer1 |
0.78
(0.64-0.94) |
1.88
(1.32) |
|
Prostate
cancer |
0.87
(0.50-1.49) |
1.56
(1.00) |
|
Prostate
cancer1 |
0.58
(0.43-0.78) |
2.84
(1.88) |
1Using alternative estimates at
younger ages from Adventist Health Study-2.
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Supplemental Table 25. Evidence grading for vegan diets and cancer risk
|
|
Reduced risk |
Increased risk |
|
Convincing |
- |
- |
|
Probable |
- |
- |
|
Limited-suggestive |
Total, breast |
- |
|
Limited - no conclusion |
Colorectal, prostate |
|
"
