"D'Adamo theorizes that the basis for such differences is our reactions to certain food proteins called lectins. Lectins are common in plant foods, especially grains and beans, and may be involved in food allergies and some immune disorders. But there is no convincing evidence for any interactions between lectins and the molecules that determine blood type."

"Yet some people swear the blood type diet has worked for them. There's a reason for that. Making changes in how we eat is not easy. To follow any prescribed dietary program with rules and restrictions represents a significant commitment of mental energy toward self-improvement. That alone can lead to a greater sense of well-being and better health. But if you want to eat a better diet, I recommend you rely on information grounded in nutritional science."

Dr. Weil is a well-known holistic doctor and author of numerous books on diet. In a short article on the AARP online magazine, Dr. Weil again argues that the Blood Type Diet should 'be sacked.'

Jettisoning his previous criticisms, including the rather odd observation that animals have blood types and yet don’t follow the Blood Type Diet, Dr. Weil instead now offers his opinions on the lack of association between lectins and blood types. Dr. Weil's claim that there are no proven relationships between lectins and the molecules that determine blood type was apparently taken from an incorrect assertion that often finds its way onto the Wikipedia entry on the Blood Type Diet. This is hardly a hard-science resource.

In fact, blood group specificity is listed as one of the nine major factors influencing glycosylation in the gut (glycosylation is the process of manufacturing the sugar molecules that lectins bind with). Other factors include diet, age, animal species, disease and bacterial population. (Trends in Glycoscience and Glytcotechnology; 8:149-165)

Dr. Weil is apparently still ignorant of the secretory differences (digestive enzymes, etc.) between the blood groups, perhaps the most significant reason behind the need for the tailoring nutritional needs to these genetic markers.[1]

Despite his efforts to position himself as the arbiter of that which is 'good' about alternative medicine, Dr. Weil is clearly capable of speaking out of both sides of his mouth. In a reply one of his own critics (Arnold S. Relman, editor-in-chief emeritus of the New England Journal of Medicine)[2], he writes:

"I don't think you can have it both ways; you can't demand evidence, and then when evidence comes in that contradicts your preconceptions, say you aren't going to look at it."

"First, I would ask Dr. Relman please to strike the word 'anecdote' from his medical vocabulary. It is offensive and trivializes important information. If he wants to call the case reports I have published 'uncontrolled clinical observations,' I will not object. Scientific method starts with raw observation, proceeds to hypothesis and then to experiment."

"In my experience-- I consider experience to be one valuable source of data--many patients use alternative methods because they find that they work. And if a patient has tried a method and found that it works, that patient needs no further proof, does not need to read the reports of a randomized, double-blind, controlled trial in a medical journal to be convinced of the efficacy of treatment."

Dr. Weil is clearly ill-informed and should have consulted the work of William Boyd, who first wrote of the blood type specificity of lectins more than a half centry ago[3] or reviewed the research of Martin Nachbar[4] from the 1980's before making such claims, since he is essentially just plain wrong.  A trip to MEDLINE might have might have also proved helpful.[5], [6], [7]

• Did not contact Dr. D'Adamo prior to article
• Searching MEDLINE for terms "ABO", "Blood", "Groups" and 'Lectins" yields 687 published studies[9]
• A search on MEDLINE shows that Dr. Weil has not published any peer-review articles on nutrition and genetics.

Both Henry Lindlahr and Benedict Lust died in their early 60's. A  recent study of 1200 people who reached the century mark between 1932 and 1952 showed only four were vegetarians. At some point in time, naturopathic medicine, and in some peoples' minds health itself, became strongly associated with a vegetarian diet.  Some individuals within my own profession suggest that I had abandoned the core of naturopathic medicine by advocating good quality meat for individuals of certain blood types.

Getting stuck in a belief system can be a tough place to dwell. Often a good question to ask is, "what does the evidence show?"  Naturopathic medicine developed from the water cure movement of Europe. Theodor Hahn is credited as being the first of the pioneers of this water cure movement to integrate vegetarian dietetic principles. He was convinced that a meat-free diet would prolong life. In fact he was so convinced of the value of a vegetarian diet that he spent a great deal of his professional life writing books and pamphlets on the subject and was the editor of a magazine called The Vegetarian. 

He died of colon cancer at the age of 59. 

Perhaps his diet some how extended his life and he would have died at an even younger age had he not been a vegetarian. This at least is a quite common argument I have heard repeated by supporters of a vegetarian diet when one of their proponents dies an early death.  Ultimately there is no answer, but it is ironic that the person responsible for integrating a vegetarian diet into what would become naturopathic medicine died so young of colon cancer.

According to Drs. McMahon and Williams, Henry Lindlahr, the  founder of "Scientific Naturopathy" in the United States, "was completely committed to vegetarian diet."  Actually, the opposite is true. In fact it has been stated that Lindlahr often incurred the wrath of militant vegetarians by suggesting that "properly prepared and combined vegetables and meats could be more wholesome than certain bad vegetarian combinations." He wrote that it was not his intention "to make a fetish of vegetarianism." Clearly he was not the strict proponent of this diet that these critics would like to believe.

Dr. D'Adamo is far from the only naturopath advocating a hunter gatherer-type diet for some people. The work of Dr. Ron Schmid, ND in his books Native Nutrition and Traditional Foods Are Your Best Medicine constitute some of the best writings by an ND on the subject. 

There may be a repair mechanism that helps heal the intestinal lining from lectin damage, but that does not constitute an effective argument for their wholesale consumption.  Put another way,  our skin would also eventually heal if we sliced it open with a kitchen knife, but that is not a good reason to cut yourself.

The lectin ricin  is from the castor bean, Ricinis communis, not botulism toxin (as McMahon and Williams state above). Botulism is actually a bacterial toxin, not a lectin, from the Clostridium botuliinum. The rest of the review is a hodgepodge of assertions, with many technical errors, and  leaves us no purposeful way to respond. 

Is it too much to expect a critic with an agenda to be possess a rudimentary level of knowledge in the field they purport to criticize?

• Did not contact Dr. D'Adamo prior to article
• Dr. McMahon passed away on February 13, 2008

• Did not contact Dr. D'Adamo prior to article

• Did not contact Dr. D'Adamo prior to article

• The Editors of Time-Life Books
• Ralph W Moss
• Robert C Atkins, MD
• Barry Sears
• Larry Dossey, MD
• John Robbins
  
• Andrew Weil, MD
• Joseph Pizzorno, ND
• Deepak Chopra, MD
• Herbert Benson, MD

• Did not contact Dr. D'Adamo prior to article