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Questions About Lectins

Lectins, Arthritis and Nightshades


I have B type blood and arthritis. Are dairy products and vegetables of the 'nightshade' family, eg. potatoes, still considered a 'beneficial' food. I have been told that these kind of food can aggravate arthritic conditions. Many thanks for your help.


Virtually all the nightshade vegetables (like potatoes and tomatoes) are known to contain lectins. Many lectins are capable of influencing the clinical severity of arthtitis, either by acting to upregulate the inflammatory response or by direct action on the tissues themselves. It is probably this reason above all else that their avoidance is recommended by many health authorities albiet in a very non-specific 'avoid all nightshades' principle.

However there is little evidence that the wholesale avoidance of nightshade vegetables has had a demonstrable effect on arthritis. For example, a check of MEDLINE searching under 'nightshade' and 'arthritis' produced no results, yet many people report improvement when then did avoid nightshades.

This shows the importance of choosing your foods by blood type compatibility: instead of trying to see effects by of food groups on broad poopulation groups we look at patterns of individual foods on specific population groups. You do not need to avoid all foods in the category, just the ones which can be expected to react with your individual chemistry.

The Ask Dr. D'Adamo internet advice column ran from 1996 to 2009, at which time Dr. D'Adamo's teaching and programming responsibilities no longer allowed him to devote time and resources to directly answering visitor questions. However we've recently reorganized this treasure-trove of material and made it again available to his readership. He occasionally posts new entries. These are marked with a NEW tag.

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