Lectins are proteins abundant in the virus, bacteria, animal and plant kingdom, which bind reversibly to specific sugar structures (for most references and background see [
48,
49]). Different classes of plants, such as mono- and dicotyledonous, have different classes of lectins with differing biochemical properties, and there is a subclass of lectins only found in grasses like cereals. Many plant lectins are thought to play a role in the plants defence against being eaten. Accordingly, plant lectins have an obvious preference for binding to sugar structures of animal, fungal or microbial origin, and are usually at highest concentrations in plant parts essential for reproductive success such as seed germs. The intensively studied lectin wheat germ agglutinin (WGA), which protects against insects and fungi [
49], is present in wheat seed in both the germ and the gluten part of endosperm [
50]. Peptides behaving in a lectin-like manner have also been obtained upon cleavage of gliadin in gluten [
51]. Sourdough lactic acid bacteria hydrolyse gliadin peptides and inhibit their lectin-like behaviour [
52], which perhaps explains some of the unexplained health effects of probiotics [
53]. White flour consumed by humans contains a high proportion of gluten and has agglutinating activity suggestive of lectins [
54‐
57]. Thus, lectins are present in our food, they are heat-stable and resistant to breakdown in the gastrointestinal tract, they bind to the surface epithelium of the digestive tract and they can lead to anti-nutritional, mild allergic or other subclinical effects in humans and animals [
48,
49]. Lectins can also be transported through the gut wall into the blood circulation, where they directly influence peripheral tissues and body metabolism through the binding to glycosylated structures, such as the insulin receptor, the epidermal growth factor receptor and the interleukin 2 receptor [
57‐
65]. WGA have effects on activation of the epidermal growth factor receptor [
61], mitogenesis [
66], agglutination of red blood cells [
48], activation of platelets and cell adhesion molecules [
67] and vascular permeability [
68‐
70]. WGA also have several effects related to autoimmunity, allergy and inflammation [
57,
71]. WGA binds to several types of mammalian cells including pancreatic duct epithelial cells [
72], prostatic cancer cells [
73], arterial macrophages and smooth muscle cells [
74,
75], glomerular capillary walls, mesangial cells and tubules of human kidney [
59]. Human serum contains antibodies against WGA and lectins of soybean and peanut [
76]. Hence, lectins have sufficient properties to affect the leptin system indirectly, through effects on metabolism central to the proper function of the leptin system, and possibly also directly through interaction with leptin or the leptin receptor. The intriguing possibility of a direct interaction between lectin and the leptin system is worth some additional comments.