No single blood type is definitively “the healthiest,” but type O consistently comes out ahead across the largest body of research. People with type O blood have lower rates of heart disease, reduced risk of several cancers, and appear to be less susceptible to certain infections. That said, the differences are modest, and your blood type is far less important to your health than your diet, exercise habits, and other lifestyle factors.
Type O and Heart Disease Risk
The clearest health advantage for type O blood shows up in cardiovascular research. A meta-analysis published in Arteriosclerosis, Thrombosis, and Vascular Biology found that people with non-O blood types (A, B, or AB) have an 11% higher risk of coronary heart disease compared to those with type O. Among non-O types, AB carried the highest risk at 23% above type O, followed by B at 15% and A at 6%.
The reason comes down to clotting. Your blood type influences how much of certain clotting proteins circulate in your bloodstream. People with type O have roughly 25% to 30% lower levels of von Willebrand factor, a protein that helps blood clot, compared to those with type B or AB. They also have lower levels of Factor VIII, another key clotting protein, at about 77% of the levels seen in type B individuals. Lower clotting activity means fewer dangerous clots forming inside arteries, which translates to fewer heart attacks and a lower risk of deep vein thrombosis and pulmonary embolism.
That same trait has a downside: people with type O blood tend to bleed more easily and may experience heavier bleeding during surgery or after injury.
Cancer Risk Varies by Type
Pancreatic cancer research reveals some of the starkest differences between blood types. Compared to type O, the odds of developing pancreatic cancer are 38% higher for type A, 47% higher for type AB, and 53% higher for type B. In raw numbers from one large consortium study, incidence rates were 28.9 cases per 100,000 people per year for type O versus 44.5 per 100,000 for type B. Pancreatic cancer is still rare overall, so even the higher-risk groups face a small absolute chance, but the relative gap is notable.
Genetics within each blood type matter too. Someone who inherited the B gene from both parents (BB genotype) had a 142% higher risk of pancreatic cancer compared to someone with two O genes. People who inherited B from just one parent (BO genotype) had a smaller but still significant 45% increase.
Infectious Disease Protection
Type O blood appears to offer some protection against infectious diseases, most notably malaria and COVID-19. In regions where malaria is common, type O has long been recognized as protective against severe illness. The mechanism involves “rosetting,” a process where infected red blood cells clump together with uninfected ones. Type O red blood cells resist this clumping more effectively, which reduces the parasite’s ability to cause life-threatening complications.
During the COVID-19 pandemic, a similar pattern emerged. Studies found that people with type A blood were more likely to become infected and more likely to develop severe respiratory failure. Type O individuals were less susceptible to infection and less likely to progress to severe disease. Part of the explanation may involve clotting again: patients with type A and AB blood showed elevated levels of D-dimer, a marker of blood clot activity linked to the dangerous inflammatory response seen in severe COVID cases.
Type 2 Diabetes and Metabolic Health
Blood type also plays a small role in diabetes risk. In a large study of women, those with type B blood were 21% more likely to develop type 2 diabetes than those with type O. Type A carried a 10% increase, while type AB showed a 17% increase, though that last finding didn’t reach statistical significance. When researchers factored in Rh status (positive or negative), the numbers shifted further: B-positive women were 35% more likely to develop type 2 diabetes than O-negative women, and A-negative women were 22% more likely.
These are meaningful differences at the population level, but they’re dwarfed by lifestyle factors like body weight, physical activity, and diet quality.
Cognitive Health and Dementia
The relationship between blood type and brain health is more complicated. A study published in Frontiers in Neurology found that men with type AB blood had a 34% higher risk of Alzheimer’s disease. This risk jumped to 75% in men who also carried one copy of the APOE e4 gene, the strongest known genetic risk factor for Alzheimer’s. Interestingly, men with two copies of the APOE e4 gene and type AB blood actually had a lower risk of dementia, though this finding came from a small sample.
Type AB blood was also associated with higher levels of white matter damage in the brain, which can contribute to cognitive decline over time. These findings suggest AB may be the least favorable type for brain aging, though the research is still evolving.
Longevity and Type B
If type O wins on heart disease and cancer risk, type B may have a surprising edge in longevity. A Japanese study compared blood type distribution among 269 centenarians (people over 100) with over 7,000 controls from the same region. Type B was significantly overrepresented among centenarians at 29.4%, compared to 21.9% in the general population. Types A and O were slightly less common among the longest-lived group.
This doesn’t necessarily mean type B causes longer life. Japan has a specific disease burden and dietary pattern that may interact with blood type differently than in other populations. But it’s a reminder that no single blood type dominates every health category.
Fertility Differences
For women concerned about reproductive health, blood type may have a small connection to ovarian reserve, the supply of eggs available for fertilization. A study of Chinese women found that type O was associated with a lower risk of diminished ovarian reserve, while types B and AB were linked to higher risk. Women with the B antigen on their red blood cells were more likely to have elevated FSH levels, a hormonal marker that signals a shrinking egg supply.
The Blood Type Diet Is Not Supported
If your search led you to the idea that eating specific foods for your blood type can improve your health, the evidence doesn’t back it up. A 2013 systematic review found zero studies supporting the blood type diet. A follow-up study in 2014 showed that people on blood-type diets did see some improvements in cholesterol and blood pressure, but those benefits had nothing to do with their actual blood type. A 2021 study of people on a low-fat vegan diet confirmed the same: metabolic improvements were unrelated to blood type. The diets may work for some people, but not for the reasons their proponents claim.
Putting It in Perspective
Type O blood carries the most consistent advantages across heart disease, cancer, and infection risk. Type AB tends to fare the worst in those same categories. Types A and B fall somewhere in the middle, with each carrying its own specific vulnerabilities. But the overall contribution of blood type to disease risk is small. Only about 6% of coronary heart disease cases in the population are attributable to having a non-O blood type. The rest comes down to factors you can control.
Your blood type is fixed at birth and unchangeable, which makes it a poor target for health anxiety. Knowing you’re type A or AB might give you one more reason to stay on top of cardiovascular screening or keep your weight in a healthy range, but it shouldn’t change the fundamental playbook: eat well, move often, don’t smoke, and manage stress. Those choices will always matter more than the antigens on your red blood cells.