THE FORMATION OF MILK

There is instruction for you in cattle. From the contents of their
bellies, from between the dung and blood, We give you pure milk to
drink, easy for drinkers to swallow. (Qur'an, 16:66)
Say: “Who provides for you from the heavens and earth?” Say:
“Allah. It is certain that one or the other of us, either we
or you, is following guidance or else clearly astray.”
(Qur’an, 34:24)

The basic materials which allow the nourishment of the body come
about as a result of chemical changes in the digestive system. These
digested substances then pass through the wall of the intestine into
the blood stream. Due to the circulation of the blood, the
nutriments reach the relevant organs.
Like the other bodily tissues, the milk glands are nourished by
nutriments brought to them by the blood. The blood therefore plays a
most important role in the collection of nutriments from foodstuffs.
Milk is secreted by the milk glands after all these stages and its
nutritional values are particularly high.
Human beings are unable to directly consume either the half-digested
food in an animal’s stomach or an animal’s blood. Furthermore, the
direct consumption of these or any of their compounds can lead to
severe illness, and even death. Thanks to the exceedingly complex
biological systems He has created, Allah provides clean and healthy
food for human beings from these fluids.
This is because it forms as a result of digested food being carried
by the blood. High-nutrition milk is thus produced from blood, which
cannot be consumed directly, and semi-digested food.
The formation of milk is by itself an enormous creation miracle. And
it is another miracle altogether that such detailed information
about that formation should be contained in the Qur’an.
As we have seen, the information about the biological formation of
milk in Surat an-Nahl 66, is in great accordance with the facts
established by modern science. It is quite clear that such
information, requiring detailed knowledge of mammals' digestive
systems, could not have been known at the time when the Qur'an was
revealed.

from MIRICLES OF THE QUR'AN