Breast milk is a marvel of nature — but that doesn’t mean adults should drink it to prevent disease
A woman’s claim that she extended her father’s life by more than a year by feeding him expressed milk has led many to ask whether human milk can really delay the growth of cancer. The gold standard nutrition for infants, human milk is not, however, a replacement for conventional medicine in the treatment of adult diseases.
Human milk is perfectly composed for babies, including both nutrient and bioactive components that promote growth and development. Official guidance in the UK recommends exclusive human milk feeding for the first six months of life. Continued breastfeeding for one to two years or longer is then endorsed by various organisations, including the WHO.
The composition of human milk varies. Research shows that it changes within feeds, across the day, across lactation, and between different women. This variability benefits the infant as they grow and develop.
The first fluid produced after delivery is colostrum. It is produced in low quantities and is rich in compounds that boost the immune system (such as leukocytes, secretory immunoglobulin A, and lactoferrin), as well as others that support growth and development (like epidermal growth factor). However, colostrum is relatively low in lactose, potassium, and calcium, leading researchers to conclude its function is not primarily to provide nutrition.
Within days the composition changes, lactose increases, marking the production of what many call “transitional milk”. This change in the milk can be delayed if the baby is delivered preterm or if the mother has a metabolic condition or is obese.
Across the next few weeks, milk production increases rapidly. This is to support the changing nutritional and developmental needs of the growing infant. Within a month to six weeks, the milk becomes fully mature.
Mature milk provides around 65 to 70 calories per 100g, which come from about 4g of fat, 7g of carbohydrate, and 1g of protein. But this composition is constantly changing. The variation in calories is primarily due to differences in fat content. Fat content is significantly lower at night and morning compared with afternoon or evening milk. It also varies within the feed itself. Milk at the end of the feed has higher levels than the initial flow.
The composition of milk also varies with maternal diet, especially the amount and type of fatty acid. Many women in developed countries aren’t getting enough fatty acid – important for infant brain development – in their diet and this affects the composition of their breast milk. For example, low levels of docosahexaenoic acid (DHA) – an omega 3 fatty acid – consumed by North American mothers translates to low levels in their milk. This has led some researchers to suggest that mothers should take appropriate supplements.
More than just nutrition
But human milk doesn’t just contain nutrition; it contains a variety of compounds with medicinal qualities that are important for the baby’s survival. These “growth factors” are numerous and have wide-ranging effects. For instance, epidermal growth factor is important for the development and repair of the gastrointestinal tract. Insulin-like growth factors are critical in stimulating growth and development, with high levels of some linked to neural, and cochlea development in the ear. There are many growth factors, and they affect many important functions, including the development of the blood vessels, metabolism, intestinal system, nervous system, and endocrine (hormone) system.
Human milk also has important immune impacts, protecting against inflammation and infection. Oligosaccharides (a carbohydrate) encourage the growth of organisms that plays an essential role in early bacterial colonisation of the intestine which have important impacts on gut health and general well-being in later life, while also reducing vulnerability to some pathogens, such as noroviruses.
Not for sharing
Containing a variety of white blood cells, human milk stimulates the development of the infant immune system while providing protection from germs. Research reveals that such transmission, however, opens up the potential for infection with HIV, syphilis, hepatitis and herpes, among other viruses, which can pass along with these cells.
This viral transmission, along with the risk of contamination with bacteria and toxins, creates a need for careful management of milk sharing and selling. The nutrient and bioactive compounds are affected by the mother’s consumption of food, drink, medicines and illicit drugs. The presence of toxins and contaminants are introduced by a mother’s environmental exposure, as well as during expression and storage of the milk. Expressing and pasteurising milk changes its composition which can reduce or even eliminate some bioactive components.
Such impacts make oversight crucial for babies fed with another mother’s milk, but also mean a careful approach is needed by those adults who think human milk might hold medicinal value. While a liquid gold, awareness of the risks as well as the benefits of human milk is crucial, both for adult and infant consumers.