In 1996 Peter D’Adamo, a naturopathic physician, published a book in which he described how people could be healthier, live longer, and achieve their ideal weight by eating according to their blood type. One’s choice of condiments, spices, and even exercise should depend on one’s blood type. Soon, the book was a best seller and people everywhere were finding out their blood type, revising their grocery lists, and changing how they ate, exercised, and thought about their health.
Here are some of the recommendations according to the “Eat Right for Your Type” diet:
Those with type O blood should choose high-protein foods and eat lots of meat, vegetables, fish, and fruit but limit grains, beans, and legumes. To lose weight, seafood, kelp, red meat, broccoli, spinach, and olive oil are best; wheat, corn, and dairy are to be avoided.
Those with type A blood should choose fruit, vegetables, tofu, seafood, turkey, and whole grains but avoid meat. For weight loss, seafood, vegetables, pineapple, olive oil, and soy are best; dairy, wheat, corn, and kidney beans should be avoided.
Those with type B blood should pick a diverse diet including meat, fruit, dairy, seafood, and grains. To lose weight, type B individuals should choose green vegetables, eggs, liver, and licorice tea but avoid chicken, corn, peanuts, and wheat.
Those with type AB blood should eat dairy, tofu, lamb, fish, grains, fruit, and vegetables. For weight loss, tofu, seafood, green vegetables, and kelp are best but chicken, corn, buckwheat, and kidney beans should be avoided.
As mentioned, the recommendations for the blood type diets extend well beyond food choices. For example, people with type O blood are advised to choose high-intensity aerobic exercise and take supplements for their sensitive stomachs, while those with type A blood should choose low-intensity activities and include meditation as part of their routine.
But does it work?
High-quality studies about the blood type diet had not been published in peer-reviewed medical literature. Even now, a search in the medical literature for the author’s name reveals no research pertaining to this diet. Studies published in 2013 and 2014 about the blood type diets are worth noting. The 2013 study analyzed the world’s medical literature and found no studies demonstrating benefit from a blood type diet. The 2014 study found that while people following any of the blood type diets had some improvement in certain cardiometabolic risk factors (such as cholesterol or blood pressure), those improvements were unrelated to blood type.
Does it make any sense?
The theory behind this diet is that blood type is closely tied to our ability to digest certain types of foods, so that the proper diet will improve digestion, help maintain ideal body weight, increase energy levels, and prevent disease, including cancer and cardiovascular disease.
Put an end to diet disappointment with Harvard Medical School's Ultimate Guide to
Weight Loss
Click to get access to exclusive content.
Type O was said to be the original “ancestral” blood type of the earliest humans who were hunter-gatherers, with diets that were high in animal protein. Group A was said to evolve when humans began to farm and had more vegetarian diets. Group B blood types were said to arise among nomadic tribes who consumed a lot of dairy products. And since Group AB blood was supposed to have evolved from the intermingling of people with types A and B blood, type AB recommendations were intermediate between those for people with types A and B blood.
Each of these theories has been challenged. For example, there is evidence that type A was actually the first blood group to evolve in humans, not type O. In addition, there is no proven connection between blood type and digestion. So, in addition to a lack of evidence that the diet works, serious questions remain about why it should work in the first place.
So, what’s the downside?
It’s a fair question, especially since some improvements were seen in people who adopted certain blood type diets (see link above). Eating based on your blood type requires you to know your blood type and then follow a restrictive diet. Personal preferences might be a problem: a vegetarian with type O blood may struggle to stay on the assigned diet, and people who love red meat may be disappointed to learn they have type A blood. Recommended supplements are not cheap; neither are the recommended organic foods. And if you have certain health conditions, such as high cholesterol or diabetes, a nutritionist can make better evidence-based recommendations for you than those determined by your blood type.
Now what?
Advocates of blood type diets may say that while the ideal study has not yet been performed, the absence of evidence doesn’t prove they’re ineffective. And there’s also no proof that these diets are harmful. So, my guess is that interest in the blood type diets will not disappear any time soon. But there’s a reason that bookstores have rows and rows of books on diet, each claiming to be highly effective if not the best. We simply don’t know which diet is best for each individual person. And even if we did, sticking to any single diet is often challenging.
Though it seems Americans don’t agree on much, screening for cancer is an exception. Who wouldn’t support preventing or identifying cancer at an early, more treatable stage, when the alternative is pain, toxic therapies, and a shortened life? That may be why people get confused when news headlines don’t reinforce a “just do it” message. A recent example of the disconnect between public perception and medical evidence is screening for prostate cancer using the prostate-specific antigen (PSA) test. The United States Preventive Services Task Force (USPSTF), a non-governmental expert panel that produces guidelines for primary care providers, proposed new recommendations saying doctors should only order the PSA test for older men after discussing its pros and cons and eliciting preferences for screening.
Screening for prostate cancer with the PSA test: The backstory
To understand the new draft recommendation requires a brief history of this test. Introduced in the 1980s as a way to follow patients already diagnosed with prostate cancer, it began to be used to screen for new cancers. Given that the PSA is an easy blood test to perform, it was quickly adopted — without waiting for evidence that it actually worked. For many years, the USPSTF said there wasn’t enough information to recommend for or against the PSA test.
That changed in 2012 when the USPSTF released a controversial recommendation against screening. It was based in part on a large US study showing no decrease in prostate cancer deaths among men screened using the PSA test. The recommendation also reflected concern about the test causing a surge in prostate cancer diagnoses, many of which were small, low-risk cancers being treated with surgery or radiation — treatments with common side effects.
I was uncomfortable with this “don’t screen” recommendation and am happy about the proposed change. Here’s why: while the US screening trial was negative, another large study in European men showed a small decrease in prostate cancer deaths after more than 10 years of follow-up. Moreover, specialists had devised new strategies to avoid overtreating low-risk cancers.
Having a conversation about screening with the PSA test
I discuss the pros and cons of the PSA test with my patients and ask about their personal preferences for screening. I tell them that while screening can reduce death due to prostate cancer by 20%, the “bang for the buck” is small. It takes screening of over 1,000 men to prevent one death. I also highlight that the benefit of screening is years off, but the risks of treatment — impotence, incontinence, and bowel problems — occur right away.
I also emphasize the PSA test isn’t very accurate. There can be anxiety due to false positive results, meaning further testing shows no cancer. I mention the potential for diagnosing a low-risk cancer where the treatment may be worse than the disease, and that following them closely without treatment may be preferable. How much a man wants to know something like this can differ — some view it as useful information, others see it as an endless source of worry.
Finally, I share my own perspective. As a medical student in the late 1980s learning about the PSA test, my grandfather was dying from prostate cancer. He was an otherwise healthy man who had many good years left, and I wondered if the PSA test could have helped him. Because of this family history, I have decided to have the PSA test. But I’m also unsure what I would do if I didn’t have that history. The small potential for benefit must be weighed versus the risk of false positives or of finding a low-risk tumor that may never cause harm. I can see how two men without risk factors for prostate cancer could make different decisions.
So, I think the USPSTF got it right. This is a decision best made by a well-informed patient in collaboration with his doctor. The challenge in implementing this is practical: the short time I have with each patient. I could save time by simply ordering the test without a discussion. But in my role as health advisor, I need to be able to not only say when I think we should or should not do something, but also when there is a choice. And when there isn’t one right decision for everyone, my patient is the best person to make the choice that’s right for him. I can state my personal preference, but need to highlight why that may not be the right answer for him. Ever wonder what it would be like to be able to look at people’s entire adult lives? Not asking older people to remember, but starting with them as teenagers and tracking their health and well-being until they die? We’ve been lucky enough to do this for the past 78 years, starting in the late 1930s and early ‘40s with a group of men who agreed to be part of one of the longest studies of adult life ever done.
The Harvard Study of Adult Development has tracked the lives of 724 men from the time they were teenagers into old age — 268 Harvard College sophomores, and 456 boys from Boston’s inner city. Using questionnaires, interviews, medical records, and scans of blood and brains, we’ve monitored their physical and mental health, work lives, friendships, and romances.
Here are five of the big lessons we’ve learned about what contributes to a good life.
Lesson 1: Happy childhoods matter
Having warm relationships with parents in childhood predicts that you will have warmer and more secure relationships with those closest to you in adulthood. We found that warm childhoods reached across decades to predict more secure relationships with spouses at age 80. A close relationship with at least one sibling in childhood predicts that people are less likely to become depressed by age 50. And warmer childhood relationships predict better physical health in adulthood all the way into old age.
Lesson 2: Fostering the welfare of the next generation can ease the sting of difficult childhoods
People who grow up in difficult childhood environments (chaotic families, economic uncertainty) grow old less happily than those who have more fortunate childhoods. But by the time these people reach middle age (ages 50 to 65), those who mentor the next generation — guiding younger adults at home or at work — are happier and better adjusted than those who do not. The kind of maturation needed to nurture younger people also seems to reduce some of the sting of growing up disadvantaged.
Lesson 3: Coping effectively with stress has lifelong benefits
We all have habitual ways of managing stress and relieving anxiety. Some people tend to ignore uncomfortable facts, while others tend to face difficult issues and deal with what is unpleasant. For example, someone who is angry at his boss might “forget about it” but start missing important work deadlines. Alternatively, he might find a way to take up his concerns directly with that boss. We found that the people who cope with stress by engaging more directly with reality rather than pushing it away have better relationships with others. This coping style makes it easier for others to deal with them, which in turn makes people want to help them. They end up having better relationships and more social support, and this predicts healthier aging in your 60s and 70s. People who use these more adaptive coping mechanisms in middle age also end up with brains that stay sharper longer.
Lesson 4: Breaking bad habits earlier in life makes a difference
Watching people’s smoking habits across adulthood, those who quit earlier are less likely to develop lung disease as they grow old. They are also more likely to live longer than people who do not quit smoking or who quit later in life. Our findings differ from some studies that find no change in risk of disease and death once you’re tobacco-free for 15 years or more. Getting off the couch and starting to exercise earlier in life predicts that you’ll stay healthy longer in life, that your brain will stay sharper, and even that your immune system will be stronger.
Lesson 5: Time with others makes us happier
Looking back on their lives, people most often report their time with others as the most meaningful part of life, and what they’re proudest of. Time with other people makes us happier on a day-to-day basis, and time with a close partner buffers us against the mood dips that come with increased physical pain.
Here are some of the recommendations according to the “Eat Right for Your Type” diet:
Those with type O blood should choose high-protein foods and eat lots of meat, vegetables, fish, and fruit but limit grains, beans, and legumes. To lose weight, seafood, kelp, red meat, broccoli, spinach, and olive oil are best; wheat, corn, and dairy are to be avoided.
Those with type A blood should choose fruit, vegetables, tofu, seafood, turkey, and whole grains but avoid meat. For weight loss, seafood, vegetables, pineapple, olive oil, and soy are best; dairy, wheat, corn, and kidney beans should be avoided.
Those with type B blood should pick a diverse diet including meat, fruit, dairy, seafood, and grains. To lose weight, type B individuals should choose green vegetables, eggs, liver, and licorice tea but avoid chicken, corn, peanuts, and wheat.
Those with type AB blood should eat dairy, tofu, lamb, fish, grains, fruit, and vegetables. For weight loss, tofu, seafood, green vegetables, and kelp are best but chicken, corn, buckwheat, and kidney beans should be avoided.
As mentioned, the recommendations for the blood type diets extend well beyond food choices. For example, people with type O blood are advised to choose high-intensity aerobic exercise and take supplements for their sensitive stomachs, while those with type A blood should choose low-intensity activities and include meditation as part of their routine.
But does it work?
High-quality studies about the blood type diet had not been published in peer-reviewed medical literature. Even now, a search in the medical literature for the author’s name reveals no research pertaining to this diet. Studies published in 2013 and 2014 about the blood type diets are worth noting. The 2013 study analyzed the world’s medical literature and found no studies demonstrating benefit from a blood type diet. The 2014 study found that while people following any of the blood type diets had some improvement in certain cardiometabolic risk factors (such as cholesterol or blood pressure), those improvements were unrelated to blood type.
Does it make any sense?
The theory behind this diet is that blood type is closely tied to our ability to digest certain types of foods, so that the proper diet will improve digestion, help maintain ideal body weight, increase energy levels, and prevent disease, including cancer and cardiovascular disease.
Put an end to diet disappointment with Harvard Medical School's Ultimate Guide to
Weight Loss
Click to get access to exclusive content.
Type O was said to be the original “ancestral” blood type of the earliest humans who were hunter-gatherers, with diets that were high in animal protein. Group A was said to evolve when humans began to farm and had more vegetarian diets. Group B blood types were said to arise among nomadic tribes who consumed a lot of dairy products. And since Group AB blood was supposed to have evolved from the intermingling of people with types A and B blood, type AB recommendations were intermediate between those for people with types A and B blood.
Each of these theories has been challenged. For example, there is evidence that type A was actually the first blood group to evolve in humans, not type O. In addition, there is no proven connection between blood type and digestion. So, in addition to a lack of evidence that the diet works, serious questions remain about why it should work in the first place.
So, what’s the downside?
It’s a fair question, especially since some improvements were seen in people who adopted certain blood type diets (see link above). Eating based on your blood type requires you to know your blood type and then follow a restrictive diet. Personal preferences might be a problem: a vegetarian with type O blood may struggle to stay on the assigned diet, and people who love red meat may be disappointed to learn they have type A blood. Recommended supplements are not cheap; neither are the recommended organic foods. And if you have certain health conditions, such as high cholesterol or diabetes, a nutritionist can make better evidence-based recommendations for you than those determined by your blood type.
Now what?
Advocates of blood type diets may say that while the ideal study has not yet been performed, the absence of evidence doesn’t prove they’re ineffective. And there’s also no proof that these diets are harmful. So, my guess is that interest in the blood type diets will not disappear any time soon. But there’s a reason that bookstores have rows and rows of books on diet, each claiming to be highly effective if not the best. We simply don’t know which diet is best for each individual person. And even if we did, sticking to any single diet is often challenging.
Though it seems Americans don’t agree on much, screening for cancer is an exception. Who wouldn’t support preventing or identifying cancer at an early, more treatable stage, when the alternative is pain, toxic therapies, and a shortened life? That may be why people get confused when news headlines don’t reinforce a “just do it” message. A recent example of the disconnect between public perception and medical evidence is screening for prostate cancer using the prostate-specific antigen (PSA) test. The United States Preventive Services Task Force (USPSTF), a non-governmental expert panel that produces guidelines for primary care providers, proposed new recommendations saying doctors should only order the PSA test for older men after discussing its pros and cons and eliciting preferences for screening.
Screening for prostate cancer with the PSA test: The backstory
To understand the new draft recommendation requires a brief history of this test. Introduced in the 1980s as a way to follow patients already diagnosed with prostate cancer, it began to be used to screen for new cancers. Given that the PSA is an easy blood test to perform, it was quickly adopted — without waiting for evidence that it actually worked. For many years, the USPSTF said there wasn’t enough information to recommend for or against the PSA test.
That changed in 2012 when the USPSTF released a controversial recommendation against screening. It was based in part on a large US study showing no decrease in prostate cancer deaths among men screened using the PSA test. The recommendation also reflected concern about the test causing a surge in prostate cancer diagnoses, many of which were small, low-risk cancers being treated with surgery or radiation — treatments with common side effects.
I was uncomfortable with this “don’t screen” recommendation and am happy about the proposed change. Here’s why: while the US screening trial was negative, another large study in European men showed a small decrease in prostate cancer deaths after more than 10 years of follow-up. Moreover, specialists had devised new strategies to avoid overtreating low-risk cancers.
Having a conversation about screening with the PSA test
I discuss the pros and cons of the PSA test with my patients and ask about their personal preferences for screening. I tell them that while screening can reduce death due to prostate cancer by 20%, the “bang for the buck” is small. It takes screening of over 1,000 men to prevent one death. I also highlight that the benefit of screening is years off, but the risks of treatment — impotence, incontinence, and bowel problems — occur right away.
I also emphasize the PSA test isn’t very accurate. There can be anxiety due to false positive results, meaning further testing shows no cancer. I mention the potential for diagnosing a low-risk cancer where the treatment may be worse than the disease, and that following them closely without treatment may be preferable. How much a man wants to know something like this can differ — some view it as useful information, others see it as an endless source of worry.
Finally, I share my own perspective. As a medical student in the late 1980s learning about the PSA test, my grandfather was dying from prostate cancer. He was an otherwise healthy man who had many good years left, and I wondered if the PSA test could have helped him. Because of this family history, I have decided to have the PSA test. But I’m also unsure what I would do if I didn’t have that history. The small potential for benefit must be weighed versus the risk of false positives or of finding a low-risk tumor that may never cause harm. I can see how two men without risk factors for prostate cancer could make different decisions.
So, I think the USPSTF got it right. This is a decision best made by a well-informed patient in collaboration with his doctor. The challenge in implementing this is practical: the short time I have with each patient. I could save time by simply ordering the test without a discussion. But in my role as health advisor, I need to be able to not only say when I think we should or should not do something, but also when there is a choice. And when there isn’t one right decision for everyone, my patient is the best person to make the choice that’s right for him. I can state my personal preference, but need to highlight why that may not be the right answer for him. Ever wonder what it would be like to be able to look at people’s entire adult lives? Not asking older people to remember, but starting with them as teenagers and tracking their health and well-being until they die? We’ve been lucky enough to do this for the past 78 years, starting in the late 1930s and early ‘40s with a group of men who agreed to be part of one of the longest studies of adult life ever done.
The Harvard Study of Adult Development has tracked the lives of 724 men from the time they were teenagers into old age — 268 Harvard College sophomores, and 456 boys from Boston’s inner city. Using questionnaires, interviews, medical records, and scans of blood and brains, we’ve monitored their physical and mental health, work lives, friendships, and romances.
Here are five of the big lessons we’ve learned about what contributes to a good life.
Lesson 1: Happy childhoods matter
Having warm relationships with parents in childhood predicts that you will have warmer and more secure relationships with those closest to you in adulthood. We found that warm childhoods reached across decades to predict more secure relationships with spouses at age 80. A close relationship with at least one sibling in childhood predicts that people are less likely to become depressed by age 50. And warmer childhood relationships predict better physical health in adulthood all the way into old age.
Lesson 2: Fostering the welfare of the next generation can ease the sting of difficult childhoods
People who grow up in difficult childhood environments (chaotic families, economic uncertainty) grow old less happily than those who have more fortunate childhoods. But by the time these people reach middle age (ages 50 to 65), those who mentor the next generation — guiding younger adults at home or at work — are happier and better adjusted than those who do not. The kind of maturation needed to nurture younger people also seems to reduce some of the sting of growing up disadvantaged.
Lesson 3: Coping effectively with stress has lifelong benefits
We all have habitual ways of managing stress and relieving anxiety. Some people tend to ignore uncomfortable facts, while others tend to face difficult issues and deal with what is unpleasant. For example, someone who is angry at his boss might “forget about it” but start missing important work deadlines. Alternatively, he might find a way to take up his concerns directly with that boss. We found that the people who cope with stress by engaging more directly with reality rather than pushing it away have better relationships with others. This coping style makes it easier for others to deal with them, which in turn makes people want to help them. They end up having better relationships and more social support, and this predicts healthier aging in your 60s and 70s. People who use these more adaptive coping mechanisms in middle age also end up with brains that stay sharper longer.
Lesson 4: Breaking bad habits earlier in life makes a difference
Watching people’s smoking habits across adulthood, those who quit earlier are less likely to develop lung disease as they grow old. They are also more likely to live longer than people who do not quit smoking or who quit later in life. Our findings differ from some studies that find no change in risk of disease and death once you’re tobacco-free for 15 years or more. Getting off the couch and starting to exercise earlier in life predicts that you’ll stay healthy longer in life, that your brain will stay sharper, and even that your immune system will be stronger.
Lesson 5: Time with others makes us happier
Looking back on their lives, people most often report their time with others as the most meaningful part of life, and what they’re proudest of. Time with other people makes us happier on a day-to-day basis, and time with a close partner buffers us against the mood dips that come with increased physical pain.
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