Nature's defensive wisdom: Plant lectins, physiologically active factors, and the evolutionary secrets of breast milk

Originally, substances in plant seeds that can cause red blood cell aggregation were collectively called phytohemagglutinins. However, the same substances have been found in many organisms besides seeds, so all such substances are now called phytohemagglutinins. Some phytohemagglutinins have cellular stimulating activity, activating the immune system and thus inhibiting cancer cells, yeast, and bacteria. Phytohemagglutinins in sword beans, PHA in lentils, and PWN in American burdock are known to have such effects.

In addition, phytohemagglutinins with this effect are also found in the tissues of soybeans, potatoes, and sunflowers. These substances include vitamin A and lysophosphatidylcholine. Vitamin A is partially oxidized in the body, acting on macrophages and T lymphocytes in the form of aldehydes and acids, thereby enhancing the body's defense capabilities. Lecithin loses a fatty acid to become lysophosphatidylcholine. Lysophosphatidylcholine, even at low concentrations, can stimulate macrophages and promote antibody production, thereby improving the body's defense capabilities.

Recently, milk, including breast milk and cow's milk, has been re-evaluated from a scientific perspective. Breast milk and cow's milk are considered complete foods for infants and calves, respectively. Infants can grow solely on breast milk. Breast milk contains not only nutrients but also all the "functions" and "information" necessary for healthy infant growth, thus it is highly valued as a treasure trove of physiologically active substances and functional food ingredients. Assistant Professor Masao Iwamori of the Faculty of Medicine at the University of Tokyo has studied the composition of gangliosides in breast milk.

Recent findings reveal a regular pattern in the types of gangliosides during lactation. Gangliosides are glycolipids, found in higher concentrations in the brain. The majority of gangliosides in breast milk are GD₃ and GM₃. According to Masao Iwamori's research, at the beginning of lactation, 100% of the gangliosides in breast milk are GD₃; subsequently, GD₃ decreases while GM₃ increases, reaching almost 100% GM₃ by day 60 of lactation. Furthermore, this change is unrelated to the mother's age or childbirth experience.

Gangliosides are substances closely related to brain development and memory formation, making the variation in their ratio with developmental stages an extremely interesting phenomenon. Gangliosides are just one example of the physiologically active substances in milk (breast milk and cow's milk); they also contain hormones, growth factors, enzymes, and many other physiologically active substances, with nearly a hundred different enzymes alone. In addition, there are many potential factors, mainly products of casein breakdown in milk. The presence of morphine-like substances in milk may be related to infant sleep.

Breast milk contains a wide variety of physiologically active substances, but their roles in an infant's body are not yet fully understood. Assistant Professor Shuichi Uenogawa of the Faculty of Agriculture at the University of Tokyo says, "The location and function of the physiologically active substances in breast milk are currently being studied worldwide, but infants are not simply fed milk for energy."