Are There More Hormones in Whole Milk?

Recently, we received a reader question about the levels of hormones in whole milk. The question asked, “Regarding steroid hormones, are they found in the fatty portion of dairy products? If so, would the levels be highest in fatty dairy products, such as whipping cream, when compared to fat free skim milk?”

To answer this question, we reached out to Dr. Ann Macrina, a research and teaching associate and dairy expert, at Penn State.

Dr. Ann Macrina:

In general, higher fat dairy products contain a higher concentration of steroid hormones. However, the exact distribution between the fat and non-fat fractions really depends on the particular steroid hormone. Some steroids are more lipiphilic (more likely to combine with fat) than others.

Approximately 55% of estrone, one form of estrogen, is found in the fat fraction of milk with the remainder in the non-fat fraction.

Estradiol, another form of estrogen, and progesterone are more lipiphilic than estrone, and a greater proportion would associate with the fat fraction of milk.

But, keep in mind that the overall quantity of steroid hormones in dairy products, even high-fat dairy products, is much lower than the amounts produced naturally by the body.

For example, butter is ~80% fat, and one serving contains 1.9 nanograms (billionth of a gram) of estrogen.

One 8-oz glass of whole milk contains 2.2 nanograms of estrogen.

One 8-oz glass of skim milk contains 0.8 nanograms.

The human body produces 54,000 nanograms (prepubertal boy) to 630,000 nanograms (woman) of estrogen per day.