Is there estrogen in milk and should it be a concern?
There is actually estrogen present in milk, because some of the cow’s estrogen is transferred into the milk. Since estrogen is a fat-loving molecule (not as fat-loving as testosterone and DHT) it’s mainly found in the fat of milk. So whole milk contains more estrogen than low fat or skim milk.
Estrogen can be found in 16 known different forms, with the 4 we’re going to focus on being estrone (E1), estriol (E3), estradiol (E2) and estrone-sulfate (E1-S).
Is the amount of estrogen in milk even worrisome?
Estrone concentrations averaged 2.9, 4.2, 5.7, 7.9, 20.4, 54.1 pg/mL, and 118.9 pg/g in skim, 1%, 2%, and whole milks, half-and-half, cream, and butter samples, respectively. 17Beta-estradiol concentrations averaged 0.4, 0.6, 0.9, 1.1, 1.9, 6.0 pg/mL, and 15.8 pg/g in skim, 1%, 2%, whole milks, half-and-half, cream, and butter samples, respectively. The amount of fat in milk significantly affected E(1) and E(2) concentrations in milk. Organic and conventional dairy products did not have substantially different concentrations of E(1) and E(2). Compared with information cited in the literature, concentrations of E(1) and E(2) in bovine milk are small relative to endogenous production rates of E(1) and E(2) in humans.Reference
Likewise, using the overall mean concentration for E2 in milk, the mean E2 mass in 237 mL (8 fluid ounces) of raw whole milk was 330 pg (0.33ng). The quantity of E2 in whole milk, therefore, is low and is unlikely to pose a health risk for humans.Reference
As you can see, the amount of estrogen varies a lot between different samples (1.32-7.9ng/L), yet, none of the samples have high enough amounts for it to be a concern. More on that a bit later.
Although the most potent endogenous estrogens – E1 and E2 – are present in the milk, the main estrogen present in milk is estrone sulfate (E1-S) (R).
The oral bioactivity of free 17β-estradiol and estrone is actually quite low, but estrone-S as a main conjugate in milk, has a relatively high oral bioactivity (R).
It is suggested that during milk ingestion, only about 2–5% of milk estrogens enter the systemic circulation, which is low (R).
Other hormones in milk
Estrogen is not the only hormone found in milk, but also other hormones, such as androgens, thyroid hormones, IGF-1, progesterone, prolactin, etc. Most of them don’t have a potent effect on the body but can have some effect. For example, chronic milk consumption can increase IGF-1 and DHT by a small amount. But this doesn’t mean milk is bad. In comparison, insulin resistance is several-fold stronger at boost IGF-1 than milk consumption is.
The concentrations of hormones (ng/mL) in cow’s milk is as follows (R):
|Prolacin||15.4 ± 1||radio immunoassay||(17)|
|IGF-1||4 ± 1||radio immunoassay||(17)|
|PGE2||2.4 ± 0.3||radio immunoassay||(36)|
|PGF2α||2 ± 0.5||radio immunoassay||(39)|
|TXB2||1 ± 0.5||radio immunoassay||(39)|
|Corticosteroids||14 ± 4||competitive protein binding(CPB) assay||(44)|
|Testosterone||0.09 ± 0.03||radio immunoassay||(53)|
|5α-esteroids||3 ± 1||radio immunoassay||(54)|
|Progesterone||12 ± 2||radio immunoassay||(64)|
|Esteriol||0.027 ± 0.01||HPLC||(94)|
Progesterone concentrations are significantly correlated to increasing fat content of milk and progesterone are the main estrogen antagonist in the body (R).
Here is another table from the same study to show the ratio of progesterone to estrogen (R).
How much estrogen from milk is safe?
Here I’m going to quote a couple of papers on the amounts and effects of estrogen in humans.
Macrina et al. (20) suggested that no harmful health effect could be expected if daily intake of estrogens is less than 540 ng/day what would represent about 1% of daily production in segment of population with the lowest estrogen production (prepubertal boys).Reference
As seen from the estrogen content from different milk samples above (1.32-7.9ng/L), you’ll have to consume between 409 and 68L of whole milk daily to get about 540ng of estrogen daily, which is still considered to be a safe amount. This makes it almost impossible to consume enough milk for estrogen to go too high.
There are also many animal studies showing that milk consumption has no effect on circulating estrogen levels or affects testosterone, fertility, weight and size of reproductive organs, etc (R).
The milk has to be spiked with estrogen at >100 fold of natural levels found in milk before it starts having an effect on the animals.
Therefore, although there are physiological differences between mice and humans, considering the safety margin of more than 100-fold (perhaps even 1000-fold), it is plausible to conclude that endogenous estrogens from milk do not pose a risk for reproductive health. (R)Reference
This paper concluded that the quantity of active estrogens in dairy products is too low to demonstrate biological activity (R).
In fact, this study even found an association between increasing dairy food and nutrient intakes and decreasing estradiol concentrations (R).
In our bodies, our naturally produced (or ingested estrogen) is conjugated with a glucuronic acid in the liver, which makes it more water soluble and easy to excrete from the body. It is this easily detoxed form that’s mostly present in milk.
However, the issue comes in when the body reactivates estrogen. There are enzymes called beta-glucuronidases that remove the glucuronic acid from estrogen, thus allowing it to be re-absorbed. This is a major reason why people experience a continual estrogenic burden…which is because the body can’t detox it.
So estrone-sulfate from milk is better absorbed than E1 or E2, but can be easily detoxed, unless…glucuronidase activity is elevated. Then you might experience estrogenic side effects from the milk.
Any alternatives to cows milk?
Goats milk is the most common alternative to cows milk, although there are also sheeps milk, buffalo milk, camels milk, etc, all of which are good options.
Goat’s milk is significantly lower in estrogen than cows milk. From this paper.
A lower combined concentration of E(1) and E(2) was found in goat milk than in any of the cow milk products tested (R). Regular whole (14.45 pg/mL) and regular 2% (13.58 pg/mL) cow milks contain the highest concentrations of unconjugated E1. Goat milk contains the lowest concentration of biologically active E1 (1.45 pg/mL). The concentration of E1 in goat milk was more than 3-fold less than that found in any of the other milk products tested. The highest concentrations of biologically active E2 were found in organic (6.00 pg/mL) and regular whole (5.84 pg/mL) cow milks. Whereas goat milk contained 1.82 pg/mL, the lowest unconjugated E2 levels were found in organic nonfat (0.48 pg/mL) and regular nonfat (0.63 pg/mL) milks.Reference
If you’re concerned about the very low amounts of estrogen in cow’s milk, then you can switch to goat’s milk. Goat’s milk is also much easier digested than A1 cow’s milk, since it’s a A2 protein source.
As always, thanks so much for reading my article. Let me know in the comments below if you have any questions. And if you found this article to be insightful and helpful please like and share so this information can help others as well.
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