Should Pregnant Women Avoid Cow’s Milk?

Foods of animal origin in general naturally contain hormones, but cow’s milk may be of particular concern. The hormones naturally found even in organic cow’s milk may have played a role in studies that found a relationship between dairy products and human illnesses, such as acne, certain cancers and male reproductive disorders. Milk consumption has also been associated with an increased risk of early puberty in girls and endometrial cancer in postmenopausal women, but “hormonal levels in food could be particularly dangerous in the case of vulnerable populations, such as young children or pregnant women. To this critical population, even a small hormonal intake could lead to major changes in the metabolism.”

If you check out my video Why Do Vegan Women Have 5x Fewer Twins, you can see that children are highly sensitive to sex steroids. Because their levels of sex steroids are very low, even a small variation would account for a major change in the total activity of the involved hormone. Because no lower threshold for estrogenic action has been established, caution should be taken to avoid unnecessary exposure of fetuses and children to exogenous sex steroids, even at very low levels.

In the AMA’s Pediatrics Journal, the Chair of Boston Children’s Hospital’s Obesity Prevention Center along with the chair of Harvard’s nutrition department questioned dairy industry recommendations that children should drink three glasses of milk a day. Dairy milk evolved to promote the growth of grazing animals at high risk for predation when small, so they needed to put on a few hundred pounds quickly in the first few months of life.

The consequences of lifetime human exposure to such growth factors in milk have not been well studied. They wrote:

“Milk consumption increases serum concentrations of insulin-like growth factor 1, which is linked to prostate and other cancers. In addition, modern industrial methods maintain dairy cows in active milk production throughout their pregnancies, resulting in a milk supply with high levels of reproductive hormones.”

Pregnant cows excrete significantly higher levels of sex steroids into their milk than non-pregnant cows. The subsequent consumption of such dairy products from pregnancy results in additional consumer exposure. And it’s not just dairy. Although dairy products are an important source of hormones, other products of animal origin must be considered as well. All edible tissues of animal origin contain estrogen. This may explain why, in a study of over a thousand women eating plant-based diets, vegan women have a twinning rate that is one fifth that of vegetarians and omnivores.

Twin pregnancies are risky pregnancies, with much higher complication rates. Many parents and physicians underestimate the negative consequences of multiple pregnancy, but women with a multiple pregnancy face greater risks for themselves and their infants. Twin babies may be ten times more likely to die at birth. To avoid these complications, the research team writes, “women attempting conception should avoid milk and dairy products.”

Minimizing dairy, our nation’s #1 source of saturated fat may be a good idea for dads too: Dairy Estrogen and Male Fertility.

What about the endocrine-disrupting xenoestrogens–how do they compare with the natural hormones in our food supply? That was the topic of my video Estrogen in Meat, Dairy, and Eggs.

Then once they’re born, best to stick to human milk:

Then as young children, dairy can sometimes cause another problem: Childhood Constipation and Cow’s Milk

Here’s a selection of other pregnancy-related videos:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2013: Uprooting the Leading Causes of Death, More Than an Apple a Day, 2014: From Table to Able: Combating Disabling Diseases with Food, 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

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Estrogen in Animal Products

Estrogen hormones can be thousands of times more estrogenic than typical endocrine-disrupting chemicals. 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 the same molecule. 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.

If you check out my video Estrogen in Meat, Dairy, and Eggs, you can see that 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 meat-eaters, who have significantly higher levels, pales in comparison to the estrogen excreted by the farm animals themselves. Pig, sheep, cattle, and chickens produce literally tons of estrogen every year.

Women may excrete 16 mg every day, but farm animals may release ten 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 and a “complete” carcinogen, as it exerts both tumor initiating and tumor promoting effects.

From a human health standpoint, do we really care about feminized fish, or the appearance of “intersex roaches”? The problem is that the hormones get into the food supply. Endogenous steroid hormones in food 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. Sex steroid hormones are part of animal metabolism, and so all foodstuffs of animal origin contain these hormones, which have been connected with several human health problems. (See Why Do Vegan Women Have 5x Fewer Twins?)

What effects might these female hormones have on men? See Dairy Estrogen and Male Fertility.

The implications of this relatively new practice of milking cows even when they’re pregnant is further explored in:

More on xenoestrogens in:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2013: Uprooting the Leading Causes of Death, More Than an Apple a Day, 2014: From Table to Able: Combating Disabling Diseases with Food, 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

Image Credit: BruceBlaus

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What to Eat and What to Avoid to Protect Against Kidney Cancer

58,000 Americans are diagnosed with kidney cancer every year, and 13,000 die. And the numbers have been rising. Approximately 4 percent of cases are hereditary, but what about the other 96 percent? Historically, the only accepted risk factor has been tobacco use, but cigarette smoking has been declining. So, what’s going on?

Nitrosamines are one of the most potent carcinogens in cigarette smoke. One hot dog has as many nitrosamines and nitrosamides as five cigarettes. And these carcinogens are also found in fresh meat as well: beef, chicken, and pork. So, even though smoking rates have dropped, perhaps the rise in kidney cancer over the last few decades may have something to do with meat consumption. But would kidney cancer just be related to the processed meats like bacon, sausage, hot dogs, and cold cuts that have nitrate and nitrite additives, or fresh meat as well?

The NIH-AARP study featured in my video Can Diet Protect Against Kidney Cancer? is the largest prospective study on diet and health ever performed—about 500,000 men and women followed for nine years. In addition to examining nitrate and nitrite intake from processed meat, they also looked at intake from other sources such as fresh meat, eggs, and dairy. Nitrite from all animal sources, not just processed meats, was associated with an increased risk of kidney cancer. The researchers found no associations with nitrate or nitrite intake from plant sources.

When meat producers advertise their bacon or lunch meat as “uncured,” this means no nitrites or nitrates added. But if you look at the small print, you’ll see something like “except for celery juice.” That’s just a sneaky way to add nitrites. Processed meat producers ferment the nitrates in celery to create nitrites, then add it to the meat: a practice even the industry admits “may be viewed as incorrect at best or deceptive at worst.”

But that same fermentation of nitrates to nitrites can happen thanks to bacteria on our tongue when we eat vegetables. So, why are nitrates and nitrites from vegetables on our tongue harmless, but nitrates and nitrites from vegetables in meat linked to cancer? The actual carcinogens are not nitrites, but nitrosamines and nitrosamides. In our stomach, to turn nitrites into nitros-amines, and nitros-amides, we need amines and amides, which are concentrated in animal products. And vitamin C and other antioxidants in plant foods block the formation of these carcinogens in our stomach. That’s why we can safely benefit from the nitrates in vegetables without the cancer risk. In fact, some of the highest nitrate vegetables, like arugula, kale, and collards, are associated with decreased risk of kidney cancer. The more plants, it appears, the better.

Plant-based diets and fiber-rich diets are recommended to prevent cancer, as well as chronic conditions associated with kidney cancer, such as obesity, high blood pressure, and diabetes. It’s like sodium intake and kidney cancer. Sodium intake increases kidney disease risk, but that’s not just because sodium intake increases blood pressure. It appears the salt is associated with increased cancer risk even independently of hypertension. What about plant-based diets? Turns out the protective association remains even in people who are not obese and have normal blood pressure. So overall, plant-based and fiber-rich diets appear to do both: decrease cancer risk directly and indirectly.

I briefly address kidney health in Preventing Kidney Failure Through Diet and Treating Kidney Failure Through Diet, but have a whole series of more in-depth videos dealing with various kidney issues.

More on the fascinating nitrate story, involving improving athletic performance and blood flow with nitrate-rich vegetables:

More on carcinogens caused by cooking meat in videos like:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2013: Uprooting the Leading Causes of Death, More Than an Apple a Day, 2014: From Table to Able: Combating Disabling Diseases with Food, 2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

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