Here are 10 myth-busting reasons to consider milk from a different point of view.
Milk is Not an Essential Part of the Human Diet

Humans are the only species that drinks milk into adulthood. We are also the only species that drinks the milk of another species. Milk is only an essential dietary requirement for baby mammals, who should even then only be consuming the milk of their own species. Humans between two and five years old no longer require milk in any form, and have in fact lost the ability to digest it properly.
Cows' Milk is the Perfect Food for Calves, and Only Calves

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Every mammal produces milk specifically designed for the babies of that particular species and no other. It is necessary for a calf to increase its weight tenfold during the first year of its life, and its mother's milk provides all the vitamins, minerals, proteins, and fats required for this level of growth. Human babies do not increase their weight by anything like this ratio in the first year of life - 70lb one-year-olds are hardly a common occurrence! Cows' milk contains far more protein and fat than a human, particularly a human baby, requires.
Milk's complex structure requires a more extensive digestive system than that of a human, again making it a wholly unsuitable food for us.
Milk Consumption has Many Adverse Side Effects in Humans

Milk is not designed to be broken down by the human digestive system. It can therefore lead to gastrointestinal problems such as bloating, stomach cramps, and wind. It also increases mucus formation, leading to catarrh, chronic coughs, and sinus blockage. It is interesting to note that the human body produces excess mucus as an allergic response.
There is also a worrying link with certain types of cancer, due to the hormones given to non-organic dairy cows in order to encourage excess milk production. These hormones are present in the milk from these cows, and are therefore consumed by whomever drinks it.
Milk Can Actually Contribute to Bone Depletion, Rather than Preventing it

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High levels of protein in the diet upset the body's natural pH levels, making the body more acidic. This potentially dangerous side effect is countered by the body's wonderful ability to maintain a safe balance. However, in order to balance the pH and raise it to a safe level of alkalinity once more, the body needs calcium. When faced with this crisis, calcium stores (i.e. the bones) are raided in order to reduce the acidity. This calcium cannot be reabsorbed, and is later excreted by the kidneys.
Milk contains high levels of acidic animal protein. Combined with the average modern diet, the consumption of dairy products results in high levels of protein, which therefore causes a depletion of the body's calcium stores. Eating less protein (and therefore consuming fewer dairy products) is a vital step to reducing the likelihood of bone depletion.
It is also interesting to note that the highest levels of dairy consumption occur in the Western world, which also has the highest number of osteoporosis sufferers. Very few, if any, dairy products are consumed in Eastern countries such as China and Japan, which also happen to have the world's lowest rates of osteoporosis. So claims that dairy products are essential for combating this disease would not seem to be held up by these examples.
Milk is a Highly Inefficient Source
of Calcium

Despite all the constant claims that dairy products are an essential source of vital calcium, and should therefore be consumed regularly and in particular fed to our growing children, milk is actually a terrible source of dietary calcium. While it is true that milk contains high levels of calcium, it is a little-known fact that this calcium is in a form that is indigestible to the human body.
The calcium in milk is bonded to casein, a protein. In order to digest this calcium, it must be separated from the casein using two bodily enzymes: rennin and lactase. Baby mammals produce these enzymes so that they can digest their mother's milk properly, but once they reach an age where milk should no longer be a part of their diet, their bodies stop producing these now obsolete enzymes.
Humans over the age of three years old no longer produce rennin at all, and 75% of people stop producing lactase as well. Without these enzymes, the calcium cannot be separated from the protein, and is therefore useless to the human body. Nearly all of milk's supposedly wonderful source of calcium is actually excreted in urine, having done the body no good whatsoever.
There is Plenty of Calcium to be Found in a Balanced Diet, Without the Need for Dairy Products