Of these, water does not matter, while lactose and butter fat are at best useless for nutrition and at worst harmful.
Casein and whey protein are the useful components of milk, which you can get separated from the undesirable components as milk protein concentrate (i.e. casein + whey protein) or whey protein concentrate (where butter fat has been removed by centrifugation, then water and lactose have been removed by ultrafiltration and drying).
Some years ago there where some scary claims that "casein causes cancer", but I have read the original claims and all the studies on which they were based, so I could determine that the claims were bogus, because they were based on invalid inferences from the results of otherwise very important studies, which were unjustly blemished by these sensational claims.
The real conclusions of those studies did not contain any information whatsoever about whether casein is good or bad, and their main correct conclusion was that certain kinds of malnutrition have protective effects against cancer. This is not at all surprising, because malnutrition behaves like a mild form of chemotherapy, i.e. it is much more harmful for cancerous cells than it is for normal cells. Unfortunately malnutrition also has bad health effects, so it is not an acceptable solution for avoiding cancer, but a compromise must be made between the risk of cancer and not eating enough essential nutrients.
If health were the only criterion, it would be better to avoid any milk-based products except milk or whey protein concentrates.
However milk and various dairy products, like cream and butter, are irreplaceable for obtaining the best taste in various dishes. I have experimented a lot with replacing dairy with various vegetable milks. While the results were decent, they were never as good as with real milk-based products (and they were also more expensive than with real milk). Still, it is better if such tasty dairy-based food is eaten only infrequently. Eating dairy daily is without doubt a bad habit.
> while lactose and butter fat are at best useless for nutrition and at worst harmful.
They carry energy, and thus are useful. They would only become harmful if you would produce so much that our bodies, adopted for scarcity, were presented with an excess amount of it over longer periods. And you wouldn't build a society and industry around that kind of production, right? Right?
They carry energy in forms that can cause problems when they represent a too large fraction of the daily energy intake. Moreover, energy from vegetable products like maize, rice, wheat or high-oleic sunflower oil is many, many times cheaper, while also having much less health risks. So eating dairy for getting energy makes absolutely no sense.
Energy as carbohydrates should consist mostly of glucose (preferably as starch, for slower digestion). Half of lactose is galactose, which like fructose cannot be used directly, but it must be converted by the liver, which may be overwhelmed when too much is ingested.
There are studies that have concluded that galactose, when eaten in excess or when the liver is worse at converting it, can lead to eye cataract. While this is not certain, based on personal anecdotes I believe that this is true, because all of the people whom I know, and who had been eating a lot of dairy for a long time, eventually have developed eye cataracts in their old age.
Energy as fat should consist mostly of oleic acid (the main component of storage fat in humans). While the effect of high daily intakes of saturated fatty acids is still debated, the overwhelming evidence is that they are harmful.
From personal experience I believe this to be true. Until about 5 years ago, I had been eating large quantities of dairy products every day. Then I have been diagnosed with incipient atherosclerosis, which scared me. Examining my habits, I could not identify any other cause, except the high consumption of dairy. Based on this assumption, I have completely changed the composition of fat that I am eating daily. Now more than 90% of my daily intake of fats comes from a mixture of oils chosen such as to have adequate proportions of oleic acid, linoleic acid, DHA & EPA and liposoluble vitamins.
About one year after this change from dairy to healthy fats, all symptoms of atherosclerosis have disappeared and there were also other very noticeable improvements in my cardiovascular health.
So now I am pretty much convinced that the fat from dairy products is harmful, at least in excessive quantities. I do not believe that eating once a week something containing milk, cheese, whipped cream or butter can cause any problems, but eating such food every day, most likely will be bad.
Of these, water does not matter, while lactose and butter fat are at best useless for nutrition and at worst harmful.
Casein and whey protein are the useful components of milk, which you can get separated from the undesirable components as milk protein concentrate (i.e. casein + whey protein) or whey protein concentrate (where butter fat has been removed by centrifugation, then water and lactose have been removed by ultrafiltration and drying).
Some years ago there where some scary claims that "casein causes cancer", but I have read the original claims and all the studies on which they were based, so I could determine that the claims were bogus, because they were based on invalid inferences from the results of otherwise very important studies, which were unjustly blemished by these sensational claims.
The real conclusions of those studies did not contain any information whatsoever about whether casein is good or bad, and their main correct conclusion was that certain kinds of malnutrition have protective effects against cancer. This is not at all surprising, because malnutrition behaves like a mild form of chemotherapy, i.e. it is much more harmful for cancerous cells than it is for normal cells. Unfortunately malnutrition also has bad health effects, so it is not an acceptable solution for avoiding cancer, but a compromise must be made between the risk of cancer and not eating enough essential nutrients.
If health were the only criterion, it would be better to avoid any milk-based products except milk or whey protein concentrates.
However milk and various dairy products, like cream and butter, are irreplaceable for obtaining the best taste in various dishes. I have experimented a lot with replacing dairy with various vegetable milks. While the results were decent, they were never as good as with real milk-based products (and they were also more expensive than with real milk). Still, it is better if such tasty dairy-based food is eaten only infrequently. Eating dairy daily is without doubt a bad habit.