Hello and welcome to the Nutrition Devapodcast. A show where we take a balanced look at the evidence

surrounding common dietary dilemmas so that you can make informed choices about your own diet.

I'm your host Monica Reinagle and today's topic was suggested by Sophie, who wrote,

What about the hormones in milk? My toddlers drink milk every day, but my friend said

that hormones in milk promote growth in height and potentially of tumors also. Plus,

they are hormonally active, bringing kids into puberty earlier. Is this true? Is organic any

different? What are the alternatives? Well, Sophie, it is true that cow's milk, as well as milk

from other mammals like sheep or goats or even humans, contains various naturally occurring hormones.

And in the case of cow's milk, that includes one called bovine somatotropin.

Dairy cows are sometimes also given a synthetic version of this hormone, RBST, to boost their milk

production. Organic dairy operations do not use RBST, but because all cows produce bovine somatotropin

naturally, organic milk also contains this hormone. In fact, hormone levels are not significantly

higher in milk from RBST treated cows than from non-treated cows. And what's more,

this hormone is not biologically active in humans. So even if it were absorbed from drinking milk,

it wouldn't be expected to have any effect on human health. Another concern has to do with the

presence of a different hormone in milk, one called IGF-1 that stands for insulin-like growth

factor one. Our bodies produce IGF-1, especially when we're kids, because it's critical to proper

growth. Then when we reach adulthood and we stop growing, while we stop growing taller anyway,

levels of IGF-1 tend to decline, but not to zero. This hormone continues to play an important

role throughout our life, helping to preserve bone and muscle tissue, for example.

Now, growth, of course, is a double-edged sword. We want to promote the growth of bones and

muscles, but we certainly don't want to promote the growth of cancer cells or tumors. There is

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