Estrogen in Meat, Dairy, & Eggs

Recent observed feminization of aquatic animals has raised concerns about estrogenic compounds in water supplies and the potential for these chemicals to reach drinking water. While much attention has been focused on the environmental impacts of xenoestrogens, the endocrine-disrupting industrial pollutants, relatively little research has examined the ecological consequences of environmental loading of actual estrogens. This is somewhat surprising, given that the potency of some estrogens can be thousands of times more estrogenic than typical endocrine-disrupting chemicals.

Estradiol, for example, is at least 10,000 times more potent than most xenoestrogens, and dietary exposure to natural sex steroids (in meat, dairy, and eggs) is therefore highly relevant in the discussion of the impact of estrogens on human development and health. And chicken estrogen is identical to human estrogen—they’re identical molecules. So it doesn’t matter if it ends up in our drinking supply from women taking birth control pills excreting it in their urine, or cows excreting it into their milk. The source doesn’t matter; the quantity does.

And a child’s exposure to estrogens in drinking water is about 150 times lower than exposure from cow’s milk, so our day-to-day estrogen exposure levels are more likely determined by whether or not we happen to eat dairy products that day.

Human urine is often cited as the main source of natural and synthetic estrogens in the aquatic environment, but the level of estrogen even in the urine of heavy meateaters, who have significantly higher levels, pales in comparison to the estrogens excreted by the farm animals themselves. Pig, sheep, cattle, and chickens produce literally tons of estrogen every year.

Women may excrete 16 mcg every day, but farm animals may release 10 times more, or in the case of pregnant cows, thousands of times more. Animal waste may contribute an estimated 90% of total estrogens in the environment. Five gallons of runoff water contaminated with chicken manure may contain a birth control pill’s worth of estrogen.

Estrogen levels in poultry litter are so high that when farmers feed chicken manure to their animals to save on feed costs, it may trigger premature development. Poultry manure has among the highest hormone content, quadruple the total estrogens, and nine times more 17 beta-estradiol, the most potent estrogen, which can be considered a complete carcinogen, as it exerts both tumor-initiating and tumor-promoting effects.

Who cares, though? From a human health standpoint, do we really care about feminized fish, or the appearance of intersex cockroaches? The problem is that the hormones get into our food supply. Endogenous steroid hormones in foods of animal origin are unavoidable as they occur naturally in these products.

It’s not a matter of injected hormones, which are banned in places like Europe in order to protect consumers’ health. They are part of animal metabolism, and so as a matter of fact, all foodstuffs of animal origin contain steroid hormones, and the presence of hormones in food has been connected with several human health problems, which we’ll look into next.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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