THE ROLE OF MILK IN HUMAN HEALTH AND NUTRITION
- June 1, 2017
Milk and dairy products have been an integral part of human history for millennia, and are almost universally regarded as a healthy and often necessary part of the human diet.
All mammals, including humans, are dependent on breast milk from their mothers (with the interesting exception of the Dayak fruit bat of South East Asia, where nursing is a male function), for a number of reasons:
This is fairly obvious, but the composition of human breast milk is perfectly suited to support an infant’s development, through an ideal blend of nutrients:
An infant’s immune system is not fully developed at birth, and a crucial role of breast milk is to provide passive immunity from the mother (or father, in the case of the Dayak fruit bat) to the infant. The first few days after birth, the mother produces a specialised type of milk called colostrum, which is loaded with antibodies, growth factors and other immune system boosters that are easily absorbed and digested by the infant. As colostrum gradually changes to mature milk (3-4 days after birth), antibodies continue to be an important part of the total protein content.
Breast milk also contains a host of good bacteria which populate an infant’s digestive tract and help prevent stomach infections, in addition to providing the profound benefits of probiotics to a growing child.
Although milk is clearly essential to our survival for the first few years after birth, its role in adult nutrition remains a debatable topic.
Cow milk, for example, has an excellent nutritional profile for humans, as it provides a high quality source of protein (and forms the basis of delicious products such as butter, cheese and ice cream) – but it may not be necessary or even advisable for a large part of the population. This can be especially true in the context of Indians.
As humans wean off breast milk, an interesting phenomenon occurs. The production of lactase, the enzyme that helps infants survive by breaking down the lactose in the gut, begins to slow down and sometimes even disappear. From an evolutionary standpoint, this wasn’t a problem; prior to the domestication of animals, milk was not an accessible food source after a mother stopped lactating, and lactase was not really needed in order to survive.
A decrease in the production of lactase impairs our ability to break down lactose into simple sugars that can be used as fuel, leaving it in our digestive tract. The bacteria in our digestive tract love lactose, and begin to ferment it, leading to the formation of gases and fatty acids. This leads to symptoms of bloating, heaviness and an upset stomach– the hallmarks of lactose intolerance.
It’s important to understand that lactose tolerance is a spectrum. Some individuals cannot tolerate even a small amount of lactose, while some can (and do) live on a diet with dairy as the primary source of protein. For example, populations from North Europe, who have historically bred cattle, have developed lactase persistence, which is the ability to manufacture sufficient lactase throughout their lives. (An interesting theory posits that lactase persistence fuelled economic benefits, as it allowed populations to maximise returns from cattle by repeatedly obtaining quality nutrients from an animal, instead of just once through its meat.)
A number of interesting studies on Indian populations have shown that while milk and dairy products are ubiquitous in our culture, a huge 60-80% of the Indian population (depending on ethnicity) is unable to properly break down lactose. Studies have tested the ability of North and South Indian populations to digest lactose, and have found that as high as 66% of North Indians and 88% of South Indians had an abnormal Lactose Tolerance Test, where individuals were fed pure lactose and their blood checked for increases in blood sugar, which would be expected if lactose were being broken down into digestible sugars. These individuals also had their genes tested, which corroborated the result that most Indians do not show lactase persistence.
However, smart choices and alternatives do let us reap the benefits of milk and dairy, even if we are sensitive or intolerant to lactose.
Soy, almond and other nut milks
While the taste of these alternatives is distinctly different, they provide a near-identical textural alternative. Soy milk also provides protein and other nutrients in line with milk.
Companies have even started marketing lactose-free milk, which they make by adding lactase directly into the milk. Lactase breaks down the lactose into glucose and galactose, which our bodies can easily absorb.
Fermented dairy products
As we know, bacteria, especially the good kind, love lactose and ferment it as a food source. Because of this, fermented dairy products, such as yogurt and kefir, have very low levels of lactose, as the bacteria in them have used it all up to grow. For example, regular yogurt contains less than 4% lactose in weight, as opposed to the 50% normally contained in milk. Straining the yogurt to remove more of its whey can reduce this even further.
Cheeses also follow this rule; the more a cheese is aged, the lower its lactose content because of the ensuing bacterial growth. Fresh cheeses such as mozzarella and paneer have reasonably high amounts of lactose (3-5% by weight), whereas naturally aged cheeses such as Parmesan and cheddar tend to have very low lactose levels (often under 1% by weight). Keep in mind that processed cheeses normally add back milk to melted cheese, increasing the lactose content dramatically.
From being essential to our survival at the start of our lives, to being a source of gastronomic pleasure for the rest of days, milk definitely deserves a nod this World Milk Day. We’d love to know if you liked this article and would welcome any suggestions at firstname.lastname@example.org!
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