Everybody knows that if one uses morphine, one is slow and apathetic. Simply because morphine is an opioid substance. 

The only reason why we, and other animals, are sensitive to such substances, is because our body and brain contain receptors for opioid peptides. Why ?

When we have to flee from danger but are wounded, we have to be able to run away anyway. Therefore the body produces opioid peptides to ease the pain, when necessary. These opioid peptides are called endorphins. Marathon-runners know the action of these endorphins as 'runner’s high' ; it enables them to go on even when exhausted. Without the proper receptors, these endorphins (and anesthetics !!) don’t work.

Besides drugs and endorphins, opioid-receptors in the brain are susceptible to some other opioid substances: those that are absorbed through consuming food. This happens because far from all peptides are entirely decomposed into single amino acids in the digestive tract. (1) Also, most opioid peptides are hard to decompose. (2)

But why do some foods contain opioid peptides? And what foods?

Milk

Milk is always, always mother's milk, meant for the suckling. We decided to consider mothers' milk from cows, goats, sheep, camels, or from whatever other animal as food for human beings, but by nature this, of course, it isn't true. Human-like beings have existed for 2 to 3 million years, and man did not start to drink mothers' milk from other animals until at the most 0.01 million years ago. For over 99% of our existence, we did not regard cow's milk as food for human beings.

Why do we so now ?

Economics

When humans migrated to areas where less fruits could be found, it was necessary to find other foods. Economically, it appeared to be more efficient to repeatedly take milk from the cattle than to slaughter them for meat. Where the least fruits could be found (Northern Europe), humans best adapted to consuming cow’s milk; people of colour are far more allergic to cow’s milk-proteins and/or –lactose than white people.

But why does milk contain opiod peptides?

From womb to breast milk
The human head is relatively big, and that's why human infants come out to the world too early ; in comparison to other primates gestation length should be 21 months instead of 9. But by then the baby's head would be far too big to pass the pelvis. That's why human infants actually aren't ready for the outside world; they can't even walk !!

Suckling is a compensation for being born too early. Through mother’s milk the baby receives all kind of messenger-substances. These messenger-substances stimulate development and functioning of different organs, including the brain. (see this site) Therefore, children that have been nursed are generally smarter than those that haven't. (see this site) And because mother’s milk is that important, it contains substances that have to make sure the baby wants to drink lots of milk all the time ;

Opioid peptides in Milk

Besides a non-opioid peptide stimulating appetite (3), milk by nature contains different opioid peptides, hidden in milk-proteins such as caseïn, lactalbumin, beta-lactaglobulin and lactoferrin.

Milk-opioid peptides are : beta-casomorphins (4) , alpha-caseïn exorphins, casoxins, beta-casorphins, alpha-lactorphins, beta-lactorphins and lactaferroxins. (5)

Absorption

After having consumed a milk-product, it is digested in the digestive tract. Milk-proteins are decomposed by enzymes into normal peptides, opioid peptides and amino acids. To make sure the baby absorbs as much complete opioid peptides and growth factors, milk also contains substances (lactose, substance P) enhancing permeability of the intestinal mucus. (6) And to prevent the decomposition of the peptides, these peptides are relatively indigestible. (7)

These opioid peptides cause physical dependence in the young, to make sure it wants to drink lots of mother’s milk. Also, it makes the young sleep enough. (8) Of course, these opioids can also cause constipation. (9)

Unfortunately, adult milk-consumers also absorb those opioid peptides.

Because food-manufacturers want us to be physically dependent to the food they sell, you can find milk- and wheat-proteins in lots of different food-products. Even some meat-products contain milk- and / or wheat-proteins.

>> Information from 'Zombie Food' - www.13.waisays.com