🔍 Summary of findings
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Several large analyses (systematic reviews + cohort studies) found that people with blood group O tend to have a lower risk of some cancers compared with non-O blood groups (A, B, AB). For example, one meta-analysis concluded:
“Blood group A is associated with increased risk of cancer, and blood group O is associated with decreased risk of cancer.” PMC+3PubMed+3WebMD+3
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For specific cancers:
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Gastric (stomach) cancer: Blood group A and AB showed higher risk compared to O. BioMed Central+1
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Pancreatic cancer: Non-O blood types (i.e., A, B, AB) had higher risk compared to O in some studies. PMC+2news.cancerconnect.com+2
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Some studies found that types B or AB may have lower risk for certain cancers when compared with A, but the overall picture remains inconsistent. E.g., one study in Chinese men found blood type B had a significantly lower risk for gastrointestinal cancers compared to A. PLOS
✅ Which blood group appears to have the lowest cancer risk according to evidence?
Based on the available data: Blood group O is generally associated with the lowest risk of many (but not all) cancers, compared with A, B, or AB.
⚠️ Important caveats and limitations
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The risk differences are relatively small. For example, an odds ratio for gastric cancer with group A vs O might be around ~1.19 (so ~19% higher risk) in one meta-analysis. BioMed Central+1
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These are associations, not proofs of causation. Many confounding factors exist (diet, infections like H. pylori, smoking, genetics).
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The strength of the association varies by cancer type, population, geography, and study design. Some studies found no significant association for certain cancers and blood groups. For example: for breast cancer, one large study found no clear association between ABO blood type and breast cancer risk or survival. PMC
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Having blood group O does not mean you’re “safe” from cancer — it simply means your relative risk may be a bit lower (for some cancer types) compared to some non-O groups.
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Screening, healthy lifestyle, genetics, exposures have much stronger impact on cancer risk than blood type alone.
🧠 Take-away for you
If you ask “Which blood group has the lowest cancer risk?” the best answer given current evidence is blood group O.
But importantly: don’t over-interpret this. It’s not a substitute for regular health screening, good lifestyle (no smoking, healthy diet, exercise), and genetic/family risk awareness.
