Dr. D'Adamo's Rebuttal to Dr. Nadeau's Criticism

Notes on Nadeau's Assertions

Dr. Nadeau make several assertion which are unsupportable by the literature, in particular:

"….but most of us are protected against lectins effect because the glucides of cellular membranes are protected by molecules of sialic acid. Lectins thus cannot bind themselves to them to impact them. Cells become vulnerable to lectins only when the sialic acid protection is removed, for example under the influence of an enzyme (neurominidase) present in some micro-organisms such as the influenza virus and streptococcus. This allows to put forward the hypothesis that lectins might be linked to some disease appearing the following of some infections..."

Dr Nadeau is making a glib assertion that is unsupported by the current body of scientific knowledge. Blood group antigens are terminal to sialic acid residues. By enhancing the effect of the cells surface zeta potential (negative charge) sialic acids serve to project the ABH antigens out from the cell surface, not obscure them.

In addition, the very nature of lectins is their glycoconjugate specificity: ABO specific lectins can be expected to interact with ABO antigens. Sialic acid lectins can be expected to interact with sialic acid residues. The notion that they cross-over is preposterous, since the high molecular specificity of lectins is their very reason for classification (Lectin = Latin Legere = "I choose").

Finally, one of the world's foremost authorities on plant and animal lectins (which respectfully, Dr. Nadeau most certainly is not) list blood group specificity as a prime consideration when analyzing lectin reactions in the gut.

TABLE 1:   Factors influencing membrane glycosylation in the gut (1)
  • Animal species
  • Blood group specificity
  • Age
  • Site in the intestines
  • Diet
  • Bacterial status
  • State of differentiation and maturation
  • Pathology

I can think of no better evidence that blood group specificity is a most important consideration with regard to lectin specificity.

In addition Nadeau neglects the extensive literature conclusively proving that lectins resist proteolytic digestion and can be recovered intact in the feces (2) that they can influence systemic metabolism, activate systemic inflammatory diseases (3) and induce proliferation of colon epithelial cells (4) - facts which are not only closed to dispute, but have their underlying mechanism completely elucidated. (5,6,7).

Multiple studies show that dietary lectins influence the endocrine system of the body by binding to the neuroendocrine cells of the gut and stimulating the secretion of gut peptide hormones into the systemic circulation. (1,8) Alternatively, lectins can be transmitted through the gut wall into the blood circulation and thus may directly influence peripheral tissues and body metabolism by mimicking the effects of endocrine hormones. The organs most often affected are the pancreas, skeletal muscle, liver, kidneys and thymus (9,10).

As a researcher, I can well appreciate the value of healthy skepticism. However I draw the line at criticism that reflects only a lack of natural curiosity.

Peter D'Adamo, ND

  1. Pusztai, A.; and Bardocz, S. Biological Effects of Plant Lectins on the Gastrointestinal Tract: Metabolic Consequences and Applications. Trends Glycosci.Glycotechnol.8:149-165)
  2. Ryder SD, Smith JA, Rhodes JM. Peanut lectin: a mitogen for normal human colonic epithelium and human HT29 colorectal cancer cells. J Natl Cancer Inst. 1992 Sep 16;84(18):1410-6. PMID: 1512792
  3. Yu L, Fernig DG, Smith JA, Milton JD, Rhodes JM. Reversible inhibition of proliferation of epithelial cell lines by Agaricus bisporus (edible mushroom) lectin. Cancer Res. 1993 Oct 1;53(19):4627-32.
  4. Cordain L, Toohey L, Smith MJ, Hickey MS. Related Articles Modulation of immune function by dietary lectins in rheumatoid arthritis. Br J Nutr. 2000 Mar;83(3):207-17. Review.
  5. Haas H, Falcone FH, Schramm G, Haisch K, Gibbs BF, Klaucke J, Poppelmann M, Becker WM, Gabius HJ, Schlaak M.. Dietary lectins can induce in vitro release of IL-4 and IL-13 from human basophils. Eur J Immunol. 1999 Mar;29(3):918-27.
  6. Pusztai, A. (1991) in Plant Lectins, Cambridge, Cambridge University Press
  7. Bardocz, S., Grant, G., Ewen, S.W.B., Duguid, T.J., Brown, D.S., Englyst, K., and Pusztai, A. (1995) Gut, 37, 353-360
  8. Hsu, S.M., and Raine, L. (1982) Am. J. Clin. Pathol. 77, 396-400
  9. de Oliveira, J.T.A., Pusztai, A., and Grant, G. (1988) Nutr. Res. 8, 943-947
  10. Pusztai A. Dietary lectins are metabolic signals for the gut and modulate immune and hormone functions. Eur J Clin Nutr. 1993 Oct;47(10):691-9. Review.