Antibodies come in contact with microbes that reside in the large intestine as the chemicals are ingested as tablets and their absorption starts in the intestines where the outer coating of the tablets is dissolved.
As the concentration of antibodies is particularly high in the intestines, the microbes in the large intestine are affected in a very adverse manner by the antibodies. The result is a rapid reduction in the number of bacteria.
This is not good for our health as a very large number of good bacteria live in the intestines. They help in the digestion of food and in the absorption of many vital nutrients. The good bacteria also keep the number of harmful bacteria in check. The affect of antibodies is a disruption in the process of digestion. Over a prolonged period of time it can lead to deficiency of nutrients like vitamin K and the B vitamins. The chances of infections due to the bad bacteria also go up.
Human cells in the intestines are not destroyed by antibodies as antibodies are substances that selectively interfere in the chemical processes of bacterial cells. As these processes do not take place in human cells in the same way as they do in the target bacteria, the human cells do not suffer any damage.