The Blood Type Diet: Is It Really “Precision Nutrition” for Us?

My patients often ask me what their blood type is. From my perspective, we only check this before surgery in case a transfusion is needed. Why do they ask? It’s usually a supplement they saw on social media or the Blood Type Diet.

You may have heard it before:

“If you’re Type O, you should eat more meat.”
“If you’re Type A, you should go mostly vegetarian.”
“Your blood type determines what foods work best for you.”

Now, as many of you know, I’m a strong advocate for precision medicine for African Americans (and wrote a book about it). I believe in tailoring health strategies to our biology and our realities.

But precision only works when it’s grounded in real science.

And when you actually look at the evidence, the Blood Type Diet does not hold up.

What the Blood Type Diet Claims

The diet assigns eating patterns based on your ABO blood group:

• Type O (“the hunter”) → High-protein, meat-heavy, limit grains and beans
• Type A (“the farmer”) → Mostly vegetarian
• Type B → Mixed diet with more dairy
• Type AB → A combination approach

The theory says certain compounds in food — especially something called lectins — react differently depending on your blood type and can cause inflammation or disease if you eat the “wrong” foods.

It sounds scientific.
It sounds personalized.

But sounding scientific and being scientifically validated are two different things.

What the Research Actually Shows

A systematic review published in The American Journal of Clinical Nutrition looked at over 1,000 articles on blood type–based diets. The conclusion?

There were no studies that actually confirmed the main claims of the Blood Type Diet.

In other words, there’s no strong evidence that your ABO blood type determines your ideal nutritional needs.

So why do some people say it works?

Because when people follow these plans, they often:

• Cut back on ultra-processed foods
• Reduce sugar
• Eat more intentionally

And that improves health — no matter what your blood type is.

The 2020–2025 Dietary Guidelines for Americans emphasize overall dietary patterns — not blood type — for improving cardiometabolic health. And the American Heart Association supports evidence-based dietary patterns like DASH and Mediterranean eating for heart protection.

Notice what’s missing? Blood type.

Let’s Talk About Type O — Because That’s Us

Here’s why this matters specifically for our community.

About 50% of African Americans are blood type O.

And the Blood Type Diet tells Type O individuals to:

• Eat more red meat
• Limit grains
• Reduce beans and legumes

Now pause for a moment.

We already know that:

At the same time, strong research shows that:

There is no solid evidence that Type O individuals process grains or beans in a uniquely harmful manner. So encouraging a meat-heavy pattern in a population already facing high heart disease rates is not helpful.

The “Hunter” Story Sounds Good — But It’s Oversimplified

You’ll often hear that Type O is the “original” blood type and represents ancient hunters.

Here’s the reality:

ABO blood groups are ancient and complex. Human diets throughout evolution were diverse — including plant fibers, tubers, seeds, fruits, beans, and wild grains.

Blood type does not encode a specific ancestral diet plan, it determines transfusion compatibility.

Now Let’s Talk About the Supplements

This is where things get interesting.

There are companies selling:

• “Type O Digestive Support”
• “Type A Immune Boost”
• Blood-type-specific multivitamins

There is no scientific evidence that your ABO blood group determines your vitamin or mineral needs (and this is from a person who designed a race-based multivitamin).

Your blood type does not determine which supplements you need.