Transcript: Dairy Estrogen and Male Fertility
Why is high dietary intake of saturated fat is associated with reduced semen quality? What’s the connection? Well a significant percentage the saturated fat intake in the study was derived from dairy products, and residues of industrial chemicals may bioaccumulate up the food chain into cow fat, and some of these lipophilic chemicals may have hormone-disrupting abilities.
The EPA performed a national survey of persistent, bioaccumulative, and toxic pollutants in the U.S. milk supply. Since milk fat is likely to be among the highest dietary sources of exposure to this pollution, it’s important to understand their levels. They tested milk from all over the country and found a witches brew of chemicals. They estimate that dairy products alone contribute about 30% to 50% of our dioxin exposure. And like dioxin, other toxic pollutants tend to be widely dispersed in the environment, bioaccumulated through the food chain and ultimately result in low-level contamination in most animal fats.
This may explain higher pollutant concentrations in fish eaters. Xenoestrogens like PCBs are associated with the fats of fish or animal flesh and cannot be fully removed by washing and cooking, and so can accumulate in our fat too. Xenoestrogens are chemicals with demasculinizing or feminizing effects, but even in a nonpolluted world animal foods have actual estrogen, not xeno estrogen, but estrogen-estrogens, which are unavoidable constituents in non-vegetarian nutrition. All foodstuff of animal origin contains oestradiol, which is at least 10,000-fold more potent than most xenoestrogens, and dietary exposure—meat, dairy products and eggs—to these natural sex steroids is therefore highly relevant since the hormones in these animals are identical to our own.
Estrogens are also contained in meat and eggs, but the major sources are milk and dairy products. By drinking a glass of milk, a child's intake of estradiol is 4000 times the intake of xenoestrogens, in terms of hormone activity. See, modern genetically-improved dairy cows can lactate throughout their pregnancy; the problem is that that’s when the estrogen levels can jump as much as 30-fold.
Though cheese intake has been associated with lower sperm concentration, dairy food intake has also been associated with abnormal sperm shape and movement, so this suggests that dairy intake may be implicated in direct testicular damage, and not just a potential suppression of sperm production due to the estrogen.
While milk products supply most of our ingested female sex steroids, eggs are a considerable source as well, contributing about as much as meat and fish. I guess this could be expected, as eggs are produced directly in the hens’ ovaries.
Meat may also come hormone-enriched. In the U.S. anabolic sex steroids may be administered to animals for growth promotion, a practice banned in Europe 25 years ago. This study in New York found a progressively lower sperm count associated with processed meat consumption, but similar studies in Europe after the ban found the same thing, so it may not be the implanted hormones, but rather a consequence of other things in meat such as the saturated fat, perhaps through cholesterol. We’ve known for decades that men with high cholesterol levels show abnormalities in their spermiograms, decreased sperm concentration, about a third of the normal sperm movement and half the normal sperm shape. Twenty-five years later we’re finding the same thing. In the largest study to date higher levels of cholesterol in the blood was associated with a significantly lower percentage of normal sperm. Cholesterol was also associated with reductions in semen volume and live sperm count. These results highlight the role of fats in the blood in male fertility, and should be of concern given the rising prevalence of obesity and cholesterol problems. Though a healthier diet may be associated with healthier sperm counts, cholesterol-lowering statin drugs did not seem to help.
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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