our 50’s look at nutrition still argues that to counter a lack of calcium in the diet we should increase consumption of cow's milk. However, statistics show that the countries that drink the most cow's milk also have the highest rates of osteoporosis - a common marker of calcium deficiency - so clearly cow’s milk is more a part of the problem than the solution.
And anyway, the same people that harp on about cow's milk being a great source of calcium, also tote that beef is a great source of protein. But hang on, here, where are the cows getting all this protein and calcium from ? Obviously their plant diet must have sufficient doses of each.
And if you would like to counter - quite rightly - that we are not cows, then let’s go ask the monkeys the same question. Where do our closest relatives - with virtually the same gut as us - get all their protein (they are proposed to be 7 to 10 times stronger than humans) and all their calcium (ever seen an ape using crutches or a toothbrush ?) - clearly, the plant kingdom has it covered.
But worse than not needing cow’s milk for our calcium intake, it actually costs us calcium
We are quite distant from cows – especially in digestive capacity. In order to be a grass specialist, cows have evolved enormous stomachs and a digestive capacity to match, needed to break down grass’ super-tough cellulose content. With such a huge stomach, a large body is needed to carry it around, and therefore a massive stream of amino acids is required in order to build and maintain all those muscle cells, and huge amounts of calcium are required to build the bone structures to hold it all up.
And to get a calf up to size, those key nutritions are needed in huge amounts - thus the composition of cow’s milk is relatively high in both protein and calcium - as advertised. The key factor in this story is the shape of the gut that is receiving these key components.
Evolution has primed a calf for such import, and the nutrients are held in compounds that the calf stomach can make use of. A human baby has a wildly different structure, and subsequent set of nutritional requirements. Human milk is very sugar-rich and relatively protein poor - pointing to the most importance of feeding and growing the developing brain at that time. This is quite different from the high protein, low sugar blend in cow's milk concerned with putting on muscle mass.
To be clear here, the first two to three days of human breast milk does contain a relatively high protein content, due to all these immunological starter materials, but then it massively tails off. Correspondingly, a human baby's stomach remains quite passive for this time because the immunological proteins have evolved in such a way to allow them to enter the baby's body without digestion. After this stage it starts to move towards the trait of an adult's stomach which becomes very acidic in response to proteins, so as to aid their digestion into amino acids that get used outside of the gut. All mammals share this early stage of conveying the mother’s immunological information through her milk, educating the young gut and immune system of the young.
So, it does follow that a cow’s milk supply will be high in calcium - to build the bones of the newborn calf at such a speed that it can carry such a specialist stomach in such a huge body. However, the high calcium content in cow's milk is mostly bound within a very tough and sticky protein called casein.
This tough material was once used industrially as a paint thickener and as an ingredient in glue. There is only one class of enzymes which can break down casein which is rennin, and after the first few days of life, human production of this key protein-digesting enzyme declines. Thus, past this point, humans cannot break down casein and access much of the calcium in cow's milk.
The Protein & Calcium Connection
Whenever a protein-dense food source is put into the gut, the stomach will react with peptides and hydrochloric acid in order to begin the digestion of these tough compounds. This resulting acidity will damage the small intestine - as it is not protected in the same way that the stomach is - and to avoid this, the liver will produce bile of equal and opposite alkalinity, secreted where the two meet, happily neutralising the digestive pH..
The main element used to make alkaline bile is calcium. So the more protein-dense the meal, the more calcium is used in its digestion. However, much of the protein-rich food sources In an ape’s diet are nuts and seeds, which are also calcium-rich, so their digestion will reveal plenty of calcium and replenish stocks lost in digesting the proteins.
When cow's milk enters the human stomach, the water is first drawn out to leave the dense, proteinous and fatty material open to the stomach acids secreted in digestive response. However, most of the calcium in cows milk is held in casein - which we simply do not have the chemistry to get into, so it passes through the intestines without releasing much of its calcium content. However, the liver will release lots of its calcium-rich alkaline bile in order to protect the intestines - thus we have a consequent calcium loss from cow’s milk.
This understanding starts to tie up the seeming contradictions between the countries with highest cow’s milk consumption and their skyrocketing incidence of calcium deficient markers.
However, it is true that there are many other materials in cow's milk that can be beneficial in the diet, such as the fat-soluble vitamins, minerals and useful fats that they contain.
Sheep and Goat (and camel, and rat, and dog, and badger, and…)
We can diversify our view of cow’s milk by starting to consider other animals’ milks - the most obvious being goat and sheep.
They are not grass specialists - kept in fields of grass for our convenience, and so their gut shape is a step closer to our own, and therefore the resulting milk is more tolerable to us monkey guts..
Organic - better : grass-fed - of course : free-range : please - unpasteurised : der ! - local : always best
But there are many other concerns to consider, too. Modern farming practices, like feeding cows cheaper grain rather than grass, are cited as a reason for a general decline in the health of cattle (and likewise the quality of their milk), plus the use of growth hormones in milk producing cattle - depending on your country’s legislation on such things - which now produce an average of 38 pints per day in the UK, and 52 pints in the US, figures which have more than doubled in the past 40 years. If they were producing just enough to feed their calves, as nature intended, this would be about 3 or 4 litres a day !
Therefore, animal welfare issues are rife around this industry, especially regarding impregnation routines. As lactation lasts around ten months, the cow is simultaneously pregnant and lactating for six to eight months during each calving cycle.
In the last ten years many alternatives to cow’s milk have become popular - to degrees that massively vary over time. For, it seems, the concern with our milk supply, is more about our addiction to a white fluid that stays stable in a hot drink, than anything to do with its actual composition.
And anything that we consume from a carton with such hourly gusto is going to cause us problems. Therefore we will continue to spiral through the options of various animal milks, grain milks, beans milks, nut milks, etc. until we come to rest on the reality that cartons are the problem !
All that said, it seems the only real inertia that the dairy industry has is the massive economic force that it wields.
Much like the wheat industry. The fishing industry. The arms industry. The phone industry.
No one can actually justify their practices, their mess or their ethics, so we just don’t look.
And that approach allows us consume ever-growing quantities of their products, and then blaming others for the ecological ramifications.
But these days of ignorance are numbered, so put the kettle on quick.
A number of scientific studies have concluded that consuming cow's milk actually costs the body calcium - here’s a good one if you can tolerate the language - "Metabolism of dietary protein causes increased urinary excretion of calcium." (American Journal of Epidemiology 1994;139). "Osteoporosis is caused by a number of things, one of the most important being too much dietary protein." Science 1986;233(4763).
“Countries with the highest rates of osteoporosis, such as the United States, England, and Sweden, consume the most milk. China and Japan, where people eat much less protein and dairy food, have low rates of osteoporosis." (Nutrition Action Healthletter, June, 1993).
The main study for this was conducted over a period of 20 years, on more than 10,000 men and women across parts of Sweden. The researchers concluded that a high milk intake, in both sexes, is associated with a slightly earlier death, and lower bone density, along with higher levels of oxidative stress and inflammatory conditions
Critics of this study point to the fortification of Sweden's milk with vitamin A – known to reduce calcium stocks, thus influencing fracture risks, but even those critics concede that fracture risks generally rise from the intake of milk through a problematic type of sugar found in cow's milk.
One way or another, we find that milk is not all it is cracked up to be.
Karl Michaëlsson, Alicja Wolk, Sophie Langenskiöld, Samar Basu, Eva Warensjö Lemming, Håkan Melhus, Liisa Byberg, ‘Milk intake and risk of mortality and fractures in women and men: cohort studies’ (British Medical Journal, http://www.bmj.com/content/349/bmj.g6015).