JC Every food that we eat contains hormones and cow milk is no exception.
However, we need to examine whether the types or concentrations of hormones in milk and other dairy products are sufficient to have a biological impact on human health.
In countries (such as the US) which permit the use of bovine growth hormone (recombinant bovine somatotropin or rbST) in dairy cattle, there is no measurable increase in the concentration of rbST within the milk of supplemented cows and somatotropin itself is a bovine-specific protein hormone.
Hormones that are bovine-specific do not have biological effects in other species as we lack the appropriate receptors for the hormone to bind to – effectively we don’t have a cellular “lock” the hormone “key” will fit.
Moreover, when we consume protein hormones they are broken down within the digestive system into their component amino acids (the reason why insulin has to be injected) and therefore have no biological effect. Milk contains steroid hormones such as oestrogen and progesterone, which, unlike protein hormones, aren’t broken down in the gastrointestinal tract.
Many anti-dairy groups try to correlate global trends in childhood obesity, reduced age at puberty, and diabetes or cancer incidence to consumption of these hormones through dairy foods, despite scientific evidence to the contrary.
We can’t dismiss consumer concerns about hormones, but when we put them into context, we can help to alleviate them
Jude Capper, livestock sustainability consultant
Furthermore, milk consumption has declined per capita over time – if we could correlate dairy hormone intake with health issues we would expect to see a decline rather than an increase over the past decades.
It is crucial to note the concentration of steroid hormones within dairy products are low – for example, ice-cream contains 611 nanograms of oestrogen.
If we put it into context and compare to the contraceptive pill, which contains ~35,000 nanograms of oestrogen, the average woman would have to eat 5.7kg of ice-cream every day to equal the same amount of oestrogen as she gets from one pill.
We can’t dismiss consumer concerns about hormones, but when we put them into context, we can help to alleviate them.