Milk does a body good?

Random thought: 

Everyone always says that when you have a cold you shouldn't drink milk because it causes more mucus production.  Is this true?

The main protein in milk is casein.  There are several different forms of casein (alpha, beta, kappa).  There are more than one type of each of these as well.  For example, there's something like 13 different genetic variations of beta-casein, the head honchos being A1 beta-casein and A2 beta-casein.  According to this Woodford guy, all cows used to express the gene to produce A2 beta-casein in their milk.  Somewhere along the line, there was a natural genetic mutation, particularly cows of European origin, that caused cows to start to produce A1 beta-casein.  Why A2 came before A1 I have no idea.  It sounds like most of the cows in the US are of European origin, producing A2 (Don't judge me; I'm not a cow expert).  It's times like these I wish I was back at WVU, so I could just walk down the hall and ask the animal science people.

Anyways, when humans drink milk, their digestive enzymes like pepsin, elastase, and peptidase break down proteins so they can be absorbed in the intestines.  One of the breakdown products of A1 beta-casein is beta-casomorphin 7, abbreviated BCM7.  BCM7 can increase MUC5AC production.  What exactly is MUC5AC?  It's a mucin gene, in the respiratory tract.  What's a mucin?  According to an online dictionary, it's any of a class of glycoproteins found in saliva, gastric juice, etc., that form viscous solutions and act as lubricants or protectants on external and internal surfaces of the body.  Soooo, MUC5AC is a gene that stimulates mucus secretions in the respiratory tract.

So in theory, if milk does cause mucus, this is how it would work:

Is there a direct cause and effect?  It's hard to tell.  Most of the researchers say it's hard to determine because so many people have their own beliefs milk and mucus.  The studies I've found are small, and it looks like participants of those studies think their saliva is thicker after drinking milk.  That makes sense, it does seem to leave a coating in the mouth; however, that doesn't necessarily mean it's mucus, just sticky saliva.  "The possibility that milk consumption increases the viscosity or "thickness" of mucus could be explained by the fact that consumption of an emulsion such as milk can lead to droplet floculation after mixing with saliva. This aggregation affects the mouth feel and other sensory aspects and the sensation may be mistaken for mucus."  There was another study that weighed tissues of people with colds after they drank milk, and apparently, drinking milk does not increase symptoms of the common cold lol.  "In healthy adult volunteers challenged with the common cold virus, milk intake was not associated with an increase in symptoms of congestion or nasal secretion weight."

Conducting my Internet research pretty much led me to believe there are a ton of milk haters in the world.  I read random pieces of research, the beginning to that Woodford's guy Milk is the devil book, proposed hypotheses, and even some guy's biology paper (weird, I know, it was somehow published in google scholar).  As a "health care professional," I have always advocated for milk because of it's nutrient density.  Milk has calcium, potassium, vitamin A, and vitamin D USDA food composition tables.  Completely eliminating milk from your diet could impact your intake of these vitamins and minerals.  Obviously, cutting out milk for a short period of time while you have a cold shouldn't cause too many problems, but it might not reduce the amount of snot you make. 

Random side note:  It looks like there's a lot of research going on to see if the A1 beta-casein and BCM7 are related to heart disease, Type I DM, and even Autism.  Not only is BCM7 involved in mucus production, but it may also be an opiate, an addictive opiate at that.  That's what they were talking about in Fast Food Nation when that guy talked about quesomorphins in cheese making it addictive.  Apparently, because cheese is processed it contains more A1 beta-casein than regular milk.  So, should we not be consuming milk at all???  Have we all been drastically misinformed??  Is there some kind of milk conspiracy my grandpa will be telling me about next time I go visit? Creepy, but that's a horse of a different color.