Originally featured in the August 2014 issue of IHCAN magazine.
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Less well-appreciated than gluten, the carbohydrate-binding proteins lectins may be just as much a potential threat to health, says Louise Carder, BSc Nutr Med, PgDip, mIFM
Evolutionists are well aware of bottlenecks that face species from time to time. In this current period of human history, chronic diseases such as autoimmune conditions are proving to be the scourge – and possibly bottleneck – of our lifetime. Not only can they affect our ability to reproduce, but they also affect our quality of life and our mortality rates.
According to the National Institute of Environmental Health Sciences (NIEHS), up to 23.5 million Americans have been diagnosed with one of more than the 80 known auto-Immune diseases.(1) By comparison, cancer affects up to 9 million and heart disease up to 22 million. However, the American Autoimmune Related Diseases Association claims that the figure for autoimmune conditions could be closer to 50 million, as only those conditions for which epidemiological studies have been undertaken are included in the NIEHS figures.(2) Many cardiovascular conditions could also be autoimmune in their origin, so it is entirely likely that autoimmune conditions are in fact already the leading cause of death in the Western world.
But what of the causes of auto-immunity? Well certainly genes provide the fertile ground for the development of autoimmune conditions, but it is our environment that delivers the triggers. In the case of nutritional factors, the negative impact on human health of the anti-nutrient gluten is now well-mapped territory. Less well mapped, but emerging to be potentially just as insidious, is the impact of a class of carbohydrate-binding proteins found widely in the natural world. Common in foods we consume on a daily basis and often components of the foundation foods of many IHCAN nutrition programmes, lectins are becoming of increasing interest to scientists for their anti-nutrient effects.
Lectins have four key anti-nutrient effects in humans:
• Acute poisoning.
• Damage to the Gastro-intestinal tract and other organs.
• Precipitation of immune system reactivity.
It is their impact on immune system reactivity and in particular their participation in the steps that lead to auto-immunity that will be the focus of my keynote presentation at the IHCAN Conference on September 13.
This presentation will identify key lectin groups, explore their autoimmune impacts and consider the most current functional tests that will allow us to incorporate knowledge of lectins into our therapeutic programmes. By looking beyond gluten and considering lectins, we are adding to the picture of how anti-nutrients in our diets are contributing to a wider decline in human health.
But what is it about lectins that makes them so damaging? To answer this we can look to the derivation of their name. The word lectin comes from the Latin word legere, which means to select or choose. Lectins, as carbohydrate binding proteins, really do selectively choose where they are going to bind. Stillmark first discovered lectins in 1888 while he was working with castor bean extracts, finding that this binding ability allowed lectins to agglutinate red blood cells.(3) In 1891 Ehrlich began his lectin immunological research (4), but it wasn’t until 1945 that Boyd found lectins could be blood type specific (5). So from the outset scientists have been aware that lectins are able to mediate their surroundings, from a single red blood cell to influencing our immune systems.
Studies on lectins are being published all the time and across the journal spectrum, and links with specific autoimmune conditions have been suggested, in particular with coeliac disease, IgA nephropathy and Type 1 diabetes.(6,7,8) The link with auto-immunity comes from the ability of lectins to play a part in destruction of the mucosal lining of the digestive tract, the inhibition of repair mechanisms, and then the ability to enter systemic circulation and also facilitate passage of other molecules, too, thereby eliciting an immune response.(9) Such an immune response then drives inflammatory processes further inhibiting healing.
While some autoimmune conditions are linked with viruses, such as Proteus mirabilis and rheumatoid arthritis (10), and Coxsackie virus and type 1 diabetes (11), it may well be that the involvement of lectins in the development of intestinal permeability assists with the presentation of the virus to the immune system, as well as facilitating an autoimmune response based on molecular mimicry.
Wheat germ agglutinin (WGA) is perhaps the most studied of the grain lectins and has been found to enter systemic circulation and bind (in vitro) to an exhaustive list of tissues.(12) Human studies have found WGA antibodies in coeliac patients.(13). Testing for antibodies, for example, to WGA is something that the presentation will also cover.
So, having established that lectins can be detrimental to human health, there are different therapeutic dietary options available. Diets such as the Paleo or Stone Age are increasingly popular and provide useful resources for practitioners wanting to add low-lectin foods to a therapeutic programme. For those that want to go one stage further, then choosing foods according to one’s blood type is also possible. We know lectins have an effect on different blood types, and work by naturopathic physician Dr Peter D’Adamo, ND, in particular focuses on this.(14)
The lectin story is an extremely complex one, as lectin content in food is hard to measure and effects are so varied. In the context of auto-immunity the picture is much clearer, and shows why lectins must now be considered within the anti-nutrient group of foods that are contributing to the triggers that lead to autoimmunity and therefore may be the latest bottleneck to face our species.
3. Peumans WJ, Van Damme EJM Plant lectins: versatile proteins with important perspectives in biotechnology. Biotech & Gen Eng Rev 1998, 15.
4. Sharon N, Lis H. Lectins. (Springer, 1993).
5. Sharon N, Lis H. Lectins. (Springer, 1993).
6. Falth-Magnusson K, Magnusson K-E. Elevated levels of serum antibodies to the lectin wheat germ agglutinin in celiac children lend support to the gluten-lectin theory of celiac disease. Pediatr Allergy Immunol 1995, 6: 98-102.
7. Amore A et al. Functional consequences of the binding of gliadin to cultured rat mesangial cells. Am J Kidney Dis 1994, 23: 290-301.
8. Atkinson MA, Mclaren NK. The pathogenesis of insulin-dependent diabetes mellitus. N Engl J Med 1994, 331:1428-36.
9. Cordain L. Cereal grains: humanity’s double-edged sword. World Rev Nutr Diet 1999, 84,19-73.
10. Wilson C et al. Shared amino acid sequences between major histocompatibility complex class II glycoproteins, type XVI collagen and Proteus mirabilis in rheumatoid arthritis. Ann Rheum Dis 1995, 54: 216-20.
11. Laitinen OH et al. Coxsackievirus B1 is associated with induction of β-cell autoimmunity that portends type 1 diabetes. Diabetes. 2014, 63 (2): 446-55.
12. Freed DLJ. Lectins in food: their importance in health and disease. J Nutr Med 1991, 2:45-64.
13. Falth-Magnusson K, Magnusson K-E. Elevated levels of serum antibodies to the lectin wheat germ agglutinin in celiac children lend support to the gluten-lectin theory of celiac disease. Pediatr Allergy Immunol 1995, 6:98-102.