Seven Vital Correlations Between Different Blood Types and Health

When it comes to medical emergencies and donating blood, it's important to know your blood type. But do you know the health risks and benefits associated with your blood type? While scientists have been interested in the relationship between blood type and health for years, recent research has provided major breakthroughs, indicating that your blood type is a key influence in multiple aspects of your health and well being. Studies across the world have found a strong correlation between different blood types and everything from infertility to increased heart disease. For example, people with type O might have a reduced risk for cancer, however, studies show they are also more vulnerable to norovirus.

While none of the studies are conclusive about cause and effect, they do further emphasize the importance of knowing your blood type. You can't change your blood type, but being aware of certain risks can help you to stay vigilant. So how does it all work?

What's In a Blood Type?

There are four different blood types -- A, B, AB and O. The average adult has about 4-6 liters of blood circulating through his or her body. However, blood is just the name for what is actually a grouping of smaller cells. Your blood is comprised of red blood cells, which work to transport oxygen and remove carbon dioxide, white blood cells, which fight infections, platelets, which help the blood to clot, and plasma, which contains salt and other proteins.

Your blood type is purely genetic and is determined by microscopic substances, called blood type antigens, that live on the surface of your red blood cells. The different letters associated with different blood types indicate the type of antigen that lives on your red blood cells. For example, if you have A antigens present, then you're type A. If you have A and B antigens, then you're type AB. Type O is unique in that it has no antigens. When mixed with other blood types, type O simply takes on the antigens of the other blood type, which is why it is known as the universal donor. While type O is the most common blood type, type AB is the most rare, occurring in only about four percent of the population.

Your blood is present in almost every part of your body, meaning so are your blood type antigens. Because of this, they influence how your body reacts to everything from stress to digestion.

7 Ways Blood Type Affects Your Health

1. Blood Clots

At Risk: Type AB

In a recent study conducted in Denmark, scientists analyzed about 66,000 people over more than 30 years to explore the relationship between blood type and deep-vein thrombosis (DVT), or blood clots that form in your lower legs and can travel to your lungs, heart or even brain to become life threatening. Researchers found that people with type AB had a 4 percent higher risk of DVT than people with type O.

This may seem like a small amount, but when analyzing the data further, researchers found that people with blood type AB, who presented no other risk factors, made up about 20 percent of the blood clots. Compare this to other risk factors such as being overweight, which accounted for 16 percent, and smoking, which accounted for only 6 percent, and it makes blood type AB the most important risk factor for DVT in the general population.

2. Cognitive Issues

At Risk: Type AB

More bad news for type AB. Scientists at the University of Vermont studied over 30,000 people and found that people with blood type AB are 82 percent more likely to develop thinking and memory issues that can lead to dementia than people with other blood types. This was even after taking race, gender and geography into account. Older people with type AB were specifically more likely to have problems learning or recalling lists of items.

Coauthor and leader of the study Mary Cushman, MD suggested that this could be tied to the issues of blood clotting discussed earlier, as these vascular conditions can affect brain function. However, the researchers also hypothesized that it could be related to different blood types ability to stick to one another or to blood vessel walls, which can also affect brain function.

3. Fertility

At Risk: Type O

While age is still the most important risk factor when considering fertility problems, multiple studies have found a correlation between a woman's blood type and the reproductive system. One study by researchers at Yale University and New York's Albert Einstein College of Medicine found that women with blood type O are twice as likely to have a lower egg count and poorer egg quality than others.

The study, which followed more than 560 women undertaking fertility treatment, also found that women with blood type A were better protected against diminishing egg counts over time. The researchers measured the level of reproductive hormone FSH in the women and adjusted for other fertility factors, such as age and BMI. Women with blood type O were more likely to have higher levels of FSH, indicating a low ovarian reserve.

4. Gastric Cancer

At Risk: Type AB and A

The hits keep coming for type AB. A study performed by Sweden's Karolinska Institute found that people with blood type AB are roughly 26 percent more likely to contract stomach cancer than people with type B or O. People with type A are 20 percent more likely than people with type B or O. The study followed over a million people for a 35 year period and found that people with type A or AB are also more vulnerable to the risks of other factors such as smoking and alcohol use.

Lead researcher, Gustaf Edgren, MD, PhD, believes this is due to a bacteria called H. pylori, which resides in the gut of roughly two-thirds of the world's population. Edgren believes that people with type A or AB are more susceptible to the bacteria, and a heightened immune system reaction could lead to a stronger risk of stomach cancer.

5. Heart Disease

At Risk: Type AB, A, and B

According to research by the Harvard School of Public Health, people with blood type O are less at risk for heart disease than those with different blood types. On the flip side, people with blood type AB have a 23 percent increased risk for heart disease, while type B have 11 percent and type A 5 percent increased risk. Researchers believe this could be due to the correlation between blood type AB and blood clots, as well as, higher rates of inflammation that have also been linked to type AB and B blood types.

The study analyzed more than 77,000 people over two decades and posited that type O's good fortune may be associated with a specific chemical that it contains, which boosts blood flow and helps to prevent clots.

6. Pancreatic Cancer

At Risk: Type AB, A, and B

More good news for type O's comes through research from the Journal of the National Cancer Institute. The study found that people with blood type O are 37 percent less likely to develop pancreatic cancer than those with different blood types. As with the link to stomach cancer, researchers believe this could be due to the gut bacteria H. pylori. The study found that blood type antigens A and B actually help the bacteria to thrive. Because people with type O carry no antigens, they have a reduced risk for the bacteria growing.

7. Stress

At Risk: Type A & O

Among other things, your blood type antigens determine how much of the stress hormone cortisol is released. This means that blood type controls how people react to stress. For example, people with blood type A naturally release higher levels of cortisol and also produce more in response to stressful situations than other blood types. Where as, on the other hand, people with blood type O may produce less cortisol than type A, but they are prone to overproducing adrenaline during times of stress, creating a "fight or flight" reaction. This makes it more difficult for type O's to clear the cortisol from their system.

Because of this, how you handle stress is incredibly important. When it comes to exercise, people with blood type A should steer toward low-intensity, calming activities such as yoga or Tai Chi. Because of their high levels of adrenaline, people with type O benefit more from high-intensity exercise such as running or kick-boxing.

While it's clear that your blood type can play a part in disease risk, or even protection, the best advice is to continue living a healthy lifestyle.

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