Hemolytic anemia is caused by a mutation in the gene encoding glucose-6-phosphate dehydrogenase (G6PD). This gene is important for all the cells in your body because it is used in metabolism, but it is critically important for red blood cells because it converts NAP+ to NADPH. In addition to other functions, NADPH is used by cells to convert reactive oxygen species (ROS) into a less reactive and less dangerous molecule.

ROS are present everywhere, but are especially prevalent in the blood where oxygen and CO₂ are being exchanged. With a less efficient G6PD enzyme, red blood cells are less protected against ROS, and can be rapidly degraded if something in the environment triggers even more ROS to be produced.

Most individuals with G6PD deficiency are asymptomatic, meaning that they may not even be aware that they carry a mutation in this enzyme. However, some individuals are especially sensitive to the chemicals present in fava beans, and so they may develop anemia after eating them or being exposed to their pollen (this syndrome is called "favism"). Fava beans have higher concentrations of two chemicals - er digestion, vicine and convicine are converted into molecules that create ROS. Thus, a higher concentration of ROS than usual appears in the blood, and a person with G6PD will experience hemolytic anemia, in which the unprotected blood cells are lysed (to cause dissolution or destruction of cells by lysins)more rapidly than the body can produce them.

Good question! While most people can eat fava beans without any problems, people who have a G6PD deficiency can develop hemolytic anemia from them. G6PD is an enzyme that helps red blood cells and protects them from harm. Without it, the red blood cells in your body would break apart more often and can be harmed by other substances.

Fava beans contain two substances (vicine and convicinem) that can hurt red blood cells. In people with low levels of G6PD, there isn’t enough G6PD to protect the cells from these substances and they hurt the red blood cells. This causes the immune system to remove the red blood cells and leads to anemia. Sometimes the amount of these substances in the fava beans is high enough to cause the immune system to remove red blood cells faster than the body can make more, which is called hemolytic anemia.

Luckily, most people have enough G6PD to be able to eat fava beans without any issues.