Aidan:

Hello and welcome to the Ideal Nutrition Podcast. My name is Aidan Muir and I am here with my co-host, Leah Higl and this is episode 166 where we are going to be talking about the blood type diet. The idea behind the blood type diet is that people have different nutritional needs based on their blood type. So O, A, B or AB. Whether they are positive or negative matters far less than the overall type for this diet. And to keep this simple, I’m just gonna basically read an explanation of how the blood type diet works based on a description from its creator.

So the description is, you’re born with a certain blood type, the four major blood groups are categorised based on two antigens, A and B, either being present or absent on the surface of your red blood cells. For example, somebody who has both antigens has A, B blood, but somebody with neither of these antigens present has O blood. The claim is that the antigens found in your blood that decide what blood type you are, are also present in other parts of your body, including your digestive tract. That’s what causes the foods you eat to react chemically with your blood type.

The original author suggests that the first humans had type O blood. Since they were hunter-gatherers, they ate fewer carbs and more protein. Those with A blood types are believed to have descended from farmers, which is why this diet encourages more vegetables for this group. And they think B, blood types can digest more fat because they supposedly evolved from nomadic tribes whose diet were very rich in meat and dairy. The claim is that if you eat foods that were more common when your blood type evolved, your body will digest these foods more efficiently.

Leah:

So getting into analysing this specific diet a little bit, it does one thing really well in that it does largely promote nutrient-rich foods that are minimally processed for, so from a health perspective, we know majority of the time, that is something that is going to be beneficial for most people. Although there is quite a bit of talk within the blood type diet around lectins. We have discussed this pretty at length and in-depth with episode 78. So if you want to kind of go down that rabbit hole a little further, I definitely suggest checking that out. We’ll link it in the show notes, along with a blog post I wrote on it as well, discussing the plant paradox diet.

But in general as like a really brief summary is that lectins are kind of like they’re a non-issue. They’re something that is going to be found in a majority of plant-based foods and we know that having a diet rich in plant-based foods is never really going to be an issue regardless of lectin content. So we might go into that like a little bit deeper through research and whatnot but overall lectins not an issue. Everything else will be linked in the show notes for a deeper dive.

Aidan:

Let’s talk about the research. So as far as I’m aware, there’s three major slash relevant studies on this. The first one we talked about was the largest of these studies. So it was a 2014 study with 1,455 participants, which is pretty big for a nutrition study of this time. And they found that most of the blood type diets were associated with better health markers. So that’s a positive start. However, this effect was seen in everybody following the diets or as a broad general, it was seen across the board that people improved. Matching the blood type diets with the corresponding blood group did not change the effect size of any of these associations. So general theme from this study, positive improvements in general, but the blood type didn’t actually matter.

Leah:

In a similar vein, a 2018 study of 973 adults also found improvements in markers of health when following these particular, this particular diet or slash diets. But again, matching the participant’s blood type did not outperform versus if they were in like the quote on quote wrong group. So overall there were improvements found by following blood type diet, whether or not the blood type diet that you were following actually matched your blood type didn’t matter, there was just general improvements across the board. So there was no real correlation there.

Aidan:

And a 2020 study found that 68 participants of different blood types ate a low -fat vegan diet for 16 weeks. And at the end of it, the researchers found no major differences in cardiometabolic changes between any of the groups. Obviously, this is relevant because as mentioned earlier, the type O diet is meant to be high in meat. If there was no difference based on these groups, you it’s just kind of at odds with that overall philosophy. Basically, it’s just kind of indicating that the blood type doesn’t really matter for this type of stuff.

Leah:

So our general interpretation of all of this is that the entire premise of the blood type diet is pretty heavily undermined by this research. So it’s good news to see that there are overall health improvements on average, but that is what you would expect when we have noticeable dietary improvements towards more nutrient dense foods and less minimally processed foods. But the fact there was no clear link between the type of diet and the blood type someone had in terms of their actual outcomes clearly shows it doesn’t really matter.

Aidan:

This has been episode 166 of the Ideal Nutrition Podcast. As always, if you have not already left a rating review, we’d massively appreciate that. I did check the other day and both on Spotify and Apple we do have quite a few reviews now which is awesome and I am extremely grateful for everybody who has been leaving reviews so thank you.