Researchers Reveal Which Blood Group Has the Lowest Cancer Risk
Research links blood type O with lower risks of several cancers. Discover what scientists found, which cancers show the strongest link, and what it means.
Your blood type is something you probably learned once and rarely thought about again.
A, B, AB, or O.
Maybe you know whether you’re positive or negative. Maybe you don’t.
But researchers have spent years asking an intriguing question:
Could your blood type influence your risk of developing certain cancers?
The answer appears to be more complicated than a simple yes or no.
Studies examining hundreds of thousands of people have found associations between the ABO blood groups and the risk of several cancers. Among the most consistent findings, people with blood type O have tended to show lower risks of certain cancers compared with people with non-O blood types.
That doesn’t mean blood type O prevents cancer.
It doesn’t mean someone with type A, B, or AB will develop cancer.
And it certainly doesn’t mean your blood type determines your overall health.
Instead, researchers are uncovering a fascinating association that may help scientists better understand how genetics, inflammation, immunity, and cancer biology interact.
So which blood group appears to have the lowest cancer risk?
Type O is the leading answer in the research—but there’s a lot more to the story.
The Short Answer: Blood Type O Shows the Lowest Risk in Several Studies
The four major ABO blood groups are:
- Type A
- Type B
- Type AB
- Type O
A large systematic review and meta-analysis examined 89 studies involving more than 100,000 cancer cases.
Researchers found that, overall, blood group O was associated with a lower cancer risk compared with non-O blood groups.
The strongest associations appeared for several specific cancers, including gastric and pancreatic cancer.
In the analysis, blood type O was associated with approximately:
- 16% lower odds of gastric cancer
- 25% lower odds of pancreatic cancer
- 11% lower odds of colorectal cancer
- 10% lower odds of breast cancer
The same analysis found associations involving several other cancer types as well.
But there’s an important scientific distinction:
An association is not the same thing as proof that blood type causes or prevents cancer.
Your blood group is only one small piece of an enormously complicated cancer-risk puzzle.
Why Are Researchers Interested in Blood Type?
At first, it may seem strange that blood type could have anything to do with cancer.
After all, ABO blood groups are mainly discussed in the context of blood transfusions.
But ABO blood-group antigens aren’t limited to red blood cells.
Related molecules are found on the surfaces of various cells and tissues throughout the body.
Researchers have therefore investigated whether these biological differences might influence processes involved in disease.
Possible explanations being studied include:
- Inflammation
- Immune-system interactions
- Cell adhesion
- Blood-clotting pathways
- Interactions between cells and microorganisms
- Tumor-cell behavior
Scientists don’t yet have one definitive explanation for all of the observed associations.
That’s important.
A headline saying that one blood type “causes” or “prevents” cancer would go far beyond what the research establishes.
The Pancreatic Cancer Connection Is Particularly Interesting
One of the strongest and most widely discussed associations involves pancreatic cancer.
In a major study published in the Journal of the National Cancer Institute, researchers examined two large populations.
Compared with people who had blood type O, people with:
- Type A
- Type B
- Type AB
had higher rates of pancreatic cancer.
The adjusted hazard ratios were approximately:
- A: 1.32
- B: 1.72
- AB: 1.51
compared with type O.
That means the researchers observed a statistically significant association between non-O blood groups and pancreatic cancer.
It does not mean that having B blood makes pancreatic cancer inevitable.
Far from it.
Cancer develops through a complex combination of genetic, environmental, behavioral, and biological factors.
Blood type is only one possible piece of that picture.
What Did the Large Meta-Analysis Find?
The systematic review provides a broader view because it combined results from many studies.
Researchers analyzed data from 89 eligible studies involving 100,554 cancer cases across 30 cancer sites.
Overall, type O was associated with lower cancer odds compared with non-O blood groups.
The researchers also found that type A was associated with higher risk for several cancers, including:
- Gastric cancer
- Pancreatic cancer
- Breast cancer
- Ovarian cancer
- Nasopharyngeal cancer
Meanwhile, type O was associated with lower risk for several of those cancer types.
This is one reason researchers continue studying ABO blood groups.
The pattern isn’t limited to one cancer.
But that doesn’t mean the same relationship applies equally to every cancer.
Does Blood Type O Protect You From Cancer?
No.
This is perhaps the most important point in the entire article.
Having blood type O does not make you immune to cancer.
People with type O can and do develop cancer.
A lower statistical risk is not the same as zero risk.
Imagine two groups of people.
If one group has a 20% lower relative risk for a particular condition, that doesn’t mean nobody in that group develops it.
It means that, at the population level, the condition occurred less often in that group under the conditions studied.
Individual risk can be dramatically different from population averages.
That’s why you shouldn’t use your blood type as a reason to skip cancer screening or ignore symptoms.
What Does “Lower Risk” Actually Mean?
This phrase is frequently misunderstood.
Suppose researchers find that people with blood type O have a lower relative risk of a particular cancer than people with non-O blood types.
That doesn’t tell you that type O is a shield.
It tells you that researchers observed a statistical difference between groups.
Your actual cancer risk depends on many other factors.
These can include:
- Age
- Family history
- Inherited genetic mutations
- Tobacco exposure
- Alcohol consumption
- Obesity
- Physical activity
- Diet
- Certain infections
- Environmental exposures
- Previous medical conditions
For some cancers, these established risk factors are much more important than ABO blood type.
Blood Type A and Cancer Risk
If type O appears to have a lower risk for certain cancers, what about type A?
Research has repeatedly found associations between blood type A and increased risk for certain cancers.
The systematic review found higher odds of:
- Gastric cancer
- Pancreatic cancer
- Breast cancer
- Ovarian cancer
- Nasopharyngeal cancer
among people with blood type A compared with relevant comparison groups.
A large cohort study involving more than 339,000 people also found that blood type A was associated with higher stomach-cancer incidence and mortality compared with type O.
But again, this needs to be interpreted correctly.
Blood type A is not a diagnosis or a prediction.
Most people with type A blood will not develop these cancers.
What About Blood Type B?
Blood type B has also been associated with cancer risk in some research.
The relationship appears particularly interesting for pancreatic cancer.
In the large prospective study mentioned earlier, blood type B had the highest observed hazard ratio among the four ABO groups for pancreatic cancer compared with type O.
A separate cohort study involving 339,432 people also found an association between non-O blood types and pancreatic cancer, with type B reaching statistical significance in that analysis.
But researchers aren’t saying that blood type B directly causes pancreatic cancer.
The biological explanation remains an area of investigation.
And What About AB?
Blood type AB is less common than A, B, or O in the United States.
Research has also found associations between AB blood and certain cancer outcomes.
In the large pancreatic cancer study, people with type AB had a higher pancreatic cancer risk than those with type O.
However, because AB is less common, some studies have fewer participants with this blood type.
That can make statistical estimates less precise.
It’s another reason not to turn population research into a personal prediction.
Why Might Blood Type Affect Cancer Risk?
Scientists have proposed several possibilities.
1. Inflammation
Chronic inflammation can contribute to the development of several diseases, including some cancers.
Researchers are investigating whether ABO-related biological differences influence inflammatory pathways.
2. Cell adhesion
Cancer cells need to interact with surrounding tissues.
Changes in cell-surface molecules may potentially affect how cells attach, migrate, or communicate.
3. Immune response
Blood-group antigens can interact with biological systems involved in immunity.
Researchers are studying whether these differences affect how the body responds to abnormal cells.
4. Blood clotting
Some ABO blood groups are associated with differences in clotting-related proteins.
Cancer and blood clotting are biologically connected, although the relationship between ABO type and cancer is considerably more complicated than simply saying one type “clots more.”
5. Infection
Some infections are known to contribute to cancer.
Researchers have explored whether blood-group differences influence how certain microorganisms interact with human cells.
These mechanisms are areas of scientific research—not settled explanations.
The Stomach Cancer Connection
The stomach is another area where the ABO relationship has attracted attention.
The large meta-analysis found that blood type O was associated with lower odds of gastric cancer, while type A was associated with increased risk.
A separate cohort study of more than 339,000 people found that type A was associated with a 38% higher stomach-cancer incidence compared with type O in that population.
Why might this happen?
One possibility involves the complex interaction between blood-group antigens, the stomach lining, inflammation, and infections such as Helicobacter pylori.
But researchers are still investigating exactly how these factors interact.
Your Blood Type Isn’t the Same as Your Cancer Risk Profile
This distinction is crucial.
Imagine two people.
Person One
Blood type O.
But they smoke heavily, have a strong family history of cancer, rarely exercise, and have other established risk factors.
Person Two
Blood type A.
They don’t smoke, maintain a healthy weight, exercise regularly, follow recommended cancer-screening guidelines, and have no major inherited cancer-risk syndrome.
It would be a mistake to conclude that Person One is automatically “safer” simply because of blood type.
Real-world cancer risk is far more complicated.
The Biggest Mistake: Treating Blood Type Like a Health Score
Your blood type isn’t a grade.
It isn’t:
O = healthy
A = unhealthy
B = dangerous
AB = high risk
That’s not how the research works.
Each blood group has biological characteristics.
Those characteristics may influence susceptibility to particular diseases.
But no ABO group is universally “best.”
A blood type associated with lower risk for one condition may have different associations with another health outcome.
Medicine rarely works in simple categories.
Does Your Rh Factor Matter?
When Americans talk about blood type, they often mean something like:
A+
O−
B+
The “+” or “−” refers to the Rh factor, which is separate from the ABO group.
Most of the cancer research discussed in this article focuses on the ABO system.
That means you shouldn’t assume that being O-negative automatically provides a greater cancer advantage than O-positive.
The available research does not establish a simple “best blood type” ranking based on the positive or negative designation.
Can You Change Your Blood Type?
No.
Your ABO blood group is genetically determined.
You cannot change it through:
- Diet
- Exercise
- Supplements
- Detoxes
- Fasting
- Vitamins
- Weight loss
And you shouldn’t try.
The useful question isn’t:
“How can I change my blood type?”
It’s:
“What can I do to reduce the cancer risks I can actually influence?”
That’s where your attention is much better spent.
What Cancer Risks Can You Actually Influence?
This is where the science becomes more practical.
Although you cannot choose your blood type, many cancer-risk factors are modifiable.
Don’t smoke
Tobacco exposure is one of the most important preventable causes of cancer.
If you smoke, quitting can substantially improve your long-term health.
Limit alcohol
Alcohol consumption is associated with increased risk of several cancers.
Less is generally better for cancer prevention.
Maintain a healthy weight
Excess body weight is associated with increased risk for multiple cancers.
Stay physically active
Regular physical activity is linked with lower risk of several cancers.
Eat a balanced diet
Focus on a varied eating pattern that includes vegetables, fruits, whole grains, legumes, and other nutrient-dense foods.
Follow recommended screening guidelines
Screening can help detect certain cancers early, sometimes before symptoms appear.
These strategies have far more practical value than worrying about whether your blood type is A, B, AB, or O.
Should People With Type A Blood Get Extra Cancer Screening?
Not simply because they have type A blood.
At present, blood type alone isn’t a reason to start ordering specialized cancer tests outside established screening recommendations.
Your screening schedule should be based on factors such as:
- Age
- Sex
- Family history
- Personal medical history
- Genetic risk
- Smoking history
- Other established risk factors
If you have a strong family history of a particular cancer, talk with a healthcare professional about whether genetic counseling or earlier screening is appropriate.
What About Pancreatic Cancer Screening?
This is an especially important distinction.
The association between non-O blood types and pancreatic cancer has attracted significant scientific attention.
But that doesn’t mean people with A, B, or AB blood should routinely undergo pancreatic scans.
Pancreatic cancer screening is not recommended for the general average-risk population simply because of ABO blood type.
Research continues into better ways of identifying people who may benefit from earlier detection.
Could Blood Type Eventually Help Personalize Cancer Prevention?
Possibly.
This is one of the more interesting future possibilities.
If researchers can determine exactly how ABO-related biology influences cancer development, blood type might eventually become one component of a broader risk model.
Imagine a future risk assessment that combines:
- Genetics
- Family history
- Age
- Lifestyle
- Environmental exposures
- Medical history
- Blood type
- Other biological markers
That could potentially provide a much more individualized picture of risk.
But we’re not at the point where blood type alone can determine who should receive special cancer screening.
What Recent Research Is Really Telling Us
The most responsible interpretation isn’t:
“Scientists discovered the blood type that can’t get cancer.”
They didn’t.
A more accurate interpretation is:
Researchers have identified reproducible statistical associations between ABO blood groups and the risk of several cancers, with blood group O generally showing lower risk for some cancers compared with non-O groups.
That’s scientifically interesting.
It may eventually help researchers understand cancer biology.
But it isn’t a personal prediction tool.
Common Myths About Blood Type and Cancer
Myth #1: Type O people don’t get cancer
Reality: People with type O can develop every major type of cancer.
A lower statistical risk is not immunity.
Myth #2: Type A means you’ll get cancer
Reality: Type A is associated with higher risk for certain cancers in some studies, but most people with type A blood will not develop those cancers.
Myth #3: Blood type is the biggest cancer-risk factor
Reality: Cancer risk is influenced by numerous genetic, environmental, and lifestyle factors. Blood type is only one potential contributor.
Myth #4: You need different screening because of your blood type
Reality: ABO blood type alone isn’t generally used to determine standard cancer-screening schedules.
Myth #5: O-negative is the “cancer-proof” blood type
Reality: Research primarily concerns the ABO groups, and no blood type makes a person immune to cancer.
A Simple Way to Think About the Research
Think of cancer risk like a giant puzzle.
Your blood type is one small piece.
Other pieces include:
Genetics + age + environment + lifestyle + infections + family history + chance + biological changes
No single piece tells you what the entire picture will look like.
That’s why the discovery is scientifically interesting without being something to fear—or celebrate excessively.
What If You Don’t Know Your Blood Type?
There’s no reason to panic.
Your blood type is useful information for medical care, but you don’t need to know it to follow standard cancer-prevention recommendations.
If you’re curious, your blood type may be documented in certain medical records or determined through appropriate blood testing.
Blood donors can also receive information about their blood type depending on the donation organization and circumstances.
But don’t order unnecessary testing solely because you’re worried that your blood type determines your cancer risk.
Frequently Asked Questions
Which blood type has the lowest cancer risk?
Among the ABO blood groups, type O has generally been associated with lower risk of several cancers compared with non-O blood groups, particularly gastric and pancreatic cancer. However, type O does not prevent cancer.
Does blood type O protect against cancer?
No. Research shows statistical associations between type O and lower risk for certain cancers, but people with type O can still develop cancer.
Which blood type has the highest cancer risk?
There isn’t one blood type that has the highest risk for every cancer. Type A has been associated with increased risk of several cancers, while non-O groups have been associated with higher pancreatic-cancer risk in some studies.
Is blood type A linked to stomach cancer?
Yes. Multiple studies have found an association between type A and higher gastric-cancer risk compared with type O. A large cohort study also found higher stomach-cancer incidence and mortality among people with type A.
Does blood type affect pancreatic cancer risk?
Research has consistently found an association between ABO blood type and pancreatic cancer risk, with non-O groups generally showing higher risk than type O. The biological reason for this association is still being investigated.
Should people with type A blood worry about cancer?
No. Having type A blood does not mean you will develop cancer. It is simply one biological characteristic that has been statistically associated with differences in risk for certain cancers.
Can you lower cancer risk if you have a higher-risk blood type?
You cannot change your ABO blood type, but you can address many established cancer-risk factors. Avoiding tobacco, limiting alcohol, staying physically active, maintaining a healthy weight, and following recommended screening guidelines are more practical steps.
Does O-negative have a lower cancer risk than O-positive?
The cancer research discussed here primarily concerns the ABO groups rather than a simple O-negative versus O-positive comparison. You should not assume that the Rh-negative designation provides additional cancer protection.
Does blood type determine your overall health?
No. Blood type is only one biological characteristic. It does not determine whether someone will be healthy or unhealthy.
Should blood type determine cancer screening?
Not by itself. Standard screening decisions are generally based on factors such as age, personal and family history, genetics, and other established risks rather than ABO blood type alone.
So, which blood group appears to have the lowest cancer risk?
Type O.
Research involving large populations and a substantial body of published studies has found that people with type O generally have lower rates of several cancers than people with non-O blood types, with particularly notable associations involving pancreatic and gastric cancers.
But don’t misunderstand what that means.
Type O isn’t a cancer shield.
Type A doesn’t mean cancer is inevitable.
Type B doesn’t mean you should be frightened.
And AB doesn’t mean you’re destined for poor health.
These are statistical relationships—not predictions about individual people.
The most useful takeaway is actually broader.
Researchers are learning that seemingly simple biological characteristics can influence disease in subtle ways. Understanding those connections may eventually help scientists develop better risk models, prevention strategies, and treatments.
For now, however, your blood type shouldn’t determine how you live your life.
Know your family history. Don’t smoke. Stay active. Maintain a healthy weight. Limit alcohol. Follow appropriate cancer-screening recommendations. And pay attention to persistent changes in your health.
Those actions can do far more for your long-term health than worrying about whether your blood type is the “right” one.
Your blood type may influence your statistical risk.
It does not determine your destiny.