Does the Blood-Type Diet Support the Body Long Term?

A friend of mine recently bought a book on eating according to blood type and was genuinely excited to follow it. She felt hopeful, like she had finally found something that would tell her exactly what to eat and what to avoid.

I understood that feeling immediately. When you are trying to feel better in your body, clarity feels like relief, and structure can feel like safety.

The concept behind this diet is headed in the right direction, because diet should not be one size fits all, despite what influencers often claim online. That much, I agree with.

The blood-type diet came from a genuine desire to personalize nutrition. People were following generalized dietary advice and still struggling and the idea that something as personal as blood type could offer clarity made sense at the time.

What I couldn’t bring myself to articulate to my friend in that moment is where the framework starts to feel off. She was excited, and sometimes excitement deserves to exist without being immediately analyzed.

When someone finally feels hopeful about their health, the last thing they need is their momentum interrupted. So I listened, held space, and saved the deeper reflection for later.

I'm all for personalization because that's 100% holistic. The issue is that our blood type never changes so it shouldn't be used as the main decision maker. The internal environment of our body, which is referred to as the terrain, changes.

Our digestion shifts under stress. Our tolerance changes with sleep, illness, hormones, pregnancy, postpartum, grief, climate, and life stage. You see what I mean?

Some aspects of the body respond within hours or days, like digestion, hydration, or nervous system reactivity.

Other patterns take weeks, months, or even years to shift, especially when they involve hormones, immunity, or long-standing tissue depletion.

What matters is that terrain is responsive. It changes in conversation with what we consume, how we live, and what the body is being asked to adapt to.

I study the body through a terrain-based lens, which means I pay close attention to patterns rather than diagnoses or labels, that part is a doctor’s role. I look at whether organ systems are dry or damp, tense or lax, sluggish or overreactive, inflamed or depleted.

In conventional medicine, patterns are often considered too broad or preliminary to focus on, yet they form the foundation of health. Long before disease names appear, the body expresses itself through patterns.

Blood types exist primarily for medical and biological reasons, not because they dictate how you should eat. Blood types are based on specific antigens on red blood cells. These antigens help the immune system distinguish “self” from “non-self.” That’s their job and it's important job.

Your blood type can also tell doctors which blood you can safely receive. And yes, some blood types are associated with slightly higher or lower risks for certain conditions, like clotting tendencies or susceptibility to specific infections.

These are correlations, not instructions for how to live or eat. Eating in a way that supports your terrain is what helps reduce risk, because what you eat directly influences your overall health including circulation and inflammation.

What blood type doesn't do is regulate digestion, determine enzyme production, dictate nutrient needs, reflect hydration, inflammation, or nervous system tone, or adapt to stress, illness, or life stage.

Two people with the same blood type can eat the same meal and have completely opposite reactions because their internal terrain is different. Blood type does not tell you why a food helps or harms you in a given moment. Terrain does.

And with diets like these, foods are now labeled as good or bad, without any explanation of how they interact with the body on a physiological level.

With these diets, there is no discussion of whether a food is drying or moistening, stimulating or stabilizing, tonifying or relaxing. These are the physiological effects that get overlooked.

This is traditional wisdom that's being swept under the rug. Part of the reason these effects are overlooked is because they haven’t been explored in modern research yet.

So what do these physiological effects actually mean?

If you consume something and it leads to a bowel movement, increased sweating, or more frequent urination, whatever you consumed, whether it’s a food, a drug, or a herb, is having a drying effect, because fluids are leaving the body. That’s a simple example, but it illustrates the point.

The environment can do the same thing. Sun exposure, for instance, increases sweating. In response, we naturally reach for something hydrating. This is terrain matching in its most basic and intuitive form, responding to what the body is experiencing.

Without understanding how a food interacts with the terrain, eating turns into rule-following rather than a relationship with your own body.

The same food can help one person and harm another. It can support you at one time and irritate you at a different time because seasons and environment matter too when it comes to diet.

It all depends on your current terrain, particularly the terrain of your digestive system, nervous system, and circulatory system.

For example, If digestion is slow, the nervous system is on edge, and circulation is weak, people tend to pile on stimulants to get through the day but it tends to backfire.

Supporting that combination of terrain patterns looks like warmth, meaning cooked foods and warm meals, easy-to-digest foods, and calming the system through steady meals, gentle flavors, and avoiding overstimulation rather than pushing the body harder.

See how simple that sounds? Nothing too complicated. Certain lifestyle choices can also be calming, warming and easy-going. A warm shower is a warming lifestyle choice.

Instead of asking, “What should my blood type eat?” I believe a more useful question is, “How is my body doing right now?”

It is responding with the options it has. When we shift our focus to internal patterns, food stops being moralized and starts becoming supportive.