Monday, January 20, 2014

Blood Type Diet Fails Empirical Test: Plant-Based Diet Benefits All Blood Types

In December 2010, I published on this blog my critical evaluation of D'Adamo's blood type diet hypothesis. That post has been viewed more than 20,000 times since then, making it the third most viewed post on this blog.  Adherents of blood type diets who comment on that post have consistently taken their personal experiences as confirmation of the theory, and I have consistently held that the theory is bankrupt.

Well, this month, Wang et al published "ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors" which provides an empirical refutation of the blood type diet theory.   Moreover, this paper provides some additional evidence to support my contention that human physiology is primarily adapted to a plant-based diet, as I have argued in Powered By Plants.
D'Adamo has some explaining to do. Listen carefully with your crap detector full on. 
Image source: Doubleday Publishing.

The researchers ranked each of 1455 people according to their degrees of adherence to each of the four blood type diets (BTDs), as determined by a one-month, Toronto-modified Willet 196-item semi-quantitative food frequency questionnaire (FFQ).  The researchers ranked each individual for degree of adherence to all four BTDs, so each received four scores. The subjects represented four major ethnocultural groups: White (n = 703), East Asians (n = 491), South Asians (n = 155), and others (n = 106).   Data analysis included adjustment for ethnocultural group, age, sex, and energy intake.

The researchers found that adherence to a type-A, i.e. predominantly plant-based, meat- and dairy- restrictive diet had the most body composition and cardiometabolic benefits for all blood types:

“With increasing adherence to the Type-A diet, subjects, regardless of their ABO blood group, had lower BMI, blood pressure, waist circumference, serum total cholesterol, triglycerides, insulin, HOMA-IR, and HOMA-Beta. Adherence to the Type-AB diet was associated with lower blood pressure, serum total cholesterol, triglycerides, insulin, HOMA-IR, and HOMA-Beta. Adherence to the Type-O diet was associated with lower serum triglycerides.”

Notice that only the largely plant-based Type A diet was associated with lower BMI and waist circumference.  Greater adherence to the dairy- and meat-rich type B and O diets was not associated with lower BMI or waist circumference, and the only apparent benefit of adhering closely to the type O animal-based “hunter” diet for any blood group was slightly reduced triglycerides (1.04 mmol/L or 92 mg/dL for the lowest adherence versus 0.91 mmol/L or 81 mg/dL for the highest adherence).

Whole Foods Plant-Based For The Win!

Upon further analysis, the researchers found “that matching the diet with the corresponding blood group was not associated with any additional benefits and may even be associated with some adverse effects.” 

Wang et al made some other comments similar to those I made in my 2010 post:

“Several previous studies have questioned the validity of the ‘Blood-Type’ diets. Based on phylogenetic analysis of human ABO alleles, blood group A has been suggested to be the ancestral human blood group [28], [29], rather than group O as postulated by D'Adamo [1]. As for the claim that certain food items contain lectins incompatible with an individual's ABO blood group, studies to date suggest no ABO-specific agglutination [30]. The absence of scientific evidence was further supported by a recent systematic review [14], which found no study that directly investigated the effects of the ‘Blood-Type’ diet.”

I completely agree with their summary:

“In summary, the present study is the first to test the validity of the ‘Blood-Type’ diet and we showed that adherence to certain diets is associated with some favorable cardiometabolic disease risk profiles. This may explain anecdotal evidence supporting these diets, which are generally prudent diets that reflect healthy eating habits. However, the findings showed that the observed associations were independent of ABO blood group and, therefore, the findings do not support the ‘Blood-Type’ diet hypothesis.”

The blood type diet has always lacked evidential base.  In contrast, as stated by Wang et al:

“The association between the Type-A diet adherence and favorable cardiometabolic risk profile is not surprising considering this diet's emphasis on high consumption of fruits and vegetables, and low consumption of meat products, which is similar to a dietary pattern that has been recommended by various health agencies because of its association with a lower risk of cardiovascular diseases [19], [20], [21], [22], [23].”

This study supports my position that whole foods plant-based diets best match human nutritional physiology and provide the most health benefits, while also providing more evidence casting doubt on claims that low-carbohydrate, animal-based diets fit human health and fitness requirements.  I will consider including this research in future editions of Powered By Plants: Natural Selection & Human Nutrition.


Taz Man said...

It's not about temporary fad diets. It's about adopting healthy and sustainable eating habits.

Sherry Patterson said...

Well said and well supported. Fad diets and gimmicks do not work, but a whole-food, plant-based diet does. It has now been scientifically proven that the Blood-Type diet and the Paleo diet are unsound and unhealthy. But, at the same time, there is solid evidence that a plant-based diet is nature's most perfect remedy for human health.

Sherry Patterson