The Natural Human Diet

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Our epidemics of dietary disease have prompted a great deal of research into what humans are meant to eat for optimal health. In 1985, an influential article highlighted in my video The Problem With the Paleo Diet Argument was published proposing that our chronic diseases stem from a disconnect between what our bodies ate while evolving during the Stone Age (about 2 million years ago) and what we're stuffing our face with today. The proposal advocated for a return towards a hunter-gatherer type diet of lean meat, fruits, vegetables, and nuts.

It's reasonable to assume our nutritional requirements were established in the prehistoric past. However, the question of which prehistoric past we should emulate remains. Why just the last 2 million? We've been evolving for about 20 million years since our last common great ape ancestor, during which our nutrient requirements and digestive physiology were set down. Therefore our hunter-gatherer days at the tail end probably had little effect. What were we eating for the first 90% of our evolution? What the rest of the great apes ended up eating--95 percent or more plants.

This may explain why we're so susceptible to heart disease. For most of human evolution, cholesterol may have been virtually absent from the diet. No bacon, butter, or trans fats; and massive amounts of fiber, which pulls cholesterol from the body. This could have been a problem since our body needs a certain amount of cholesterol, but our bodies evolve not only to make cholesterol, but also to preserve it and recycle it.

If we think of the human body as a cholesterol-conserving machine, then plop it into the modern world of bacon, eggs, cheese, chicken, pork, and pastry; it's no wonder artery-clogging heart disease is our #1 cause of death. What used to be adaptive for 90% of our evolution--holding on to cholesterol at all costs since we weren't getting much in our diet--is today maladaptive, a liability leading to the clogging of our arteries. Our bodies just can't handle it.

As the editor-in-chief of the American Journal of Cardiology noted 25 years ago, no matter how much fat and cholesterol carnivores eat, they do not develop atherosclerosis. We can feed a dog 500 eggs worth of cholesterol and they just wag their tail; a dog's body is used to eating and getting rid of excess cholesterol. Conversely, within months a fraction of that cholesterol can start clogging the arteries of animals adapted to eating a more plant-based diet.

Even if our bodies were designed by natural selection to eat mostly fruit, greens and seeds for 90% of our evolution, why didn't we better adapt to meat-eating in the last 10%, during the Paleolithic? We've had nearly 2 million years to get used to all that extra saturated fat and cholesterol. If a lifetime of eating like that clogs up nearly everyone's arteries, why didn't the genes of those who got heart attacks die off and get replaced by those that could live to a ripe old age with clean arteries regardless of what they ate? Because most didn't survive into old age.

Most prehistoric peoples didn't live long enough to get heart attacks. When the average life expectancy is 25 years old, then the genes that get passed along are those that can live to reproductive age by any means necessary, and that means not dying of starvation. The more calories in food, the better. Eating lots of bone marrow and brains, human or otherwise, would have a selective advantage (as would discovering a time machine stash of Twinkies for that matter!). If we only have to live long enough to get our kids to puberty to pass along our genes, then we don't have to evolve any protections against the ravages of chronic disease.

To find a population nearly free of chronic disease in old age, we don't have to go back a million years. In the 20th century, networks of missionary hospitals in rural Africa found coronary artery disease virtually absent, and not just heart disease, but high blood pressure, stroke, diabetes, common cancers, and more. In a sense, these populations in rural China and Africa were eating the type of diet we've been eating for 90% of the last 20 million years, a diet almost exclusively of plant foods.

How do we know it was their diet and not something else? In the 25 year update to their original paleo paper, the authors tried to clarify that they did not then and do not now propose that people adopt a particular diet just based on what our ancient ancestors ate. Dietary recommendations must be put to the test. That's why the pioneering research from Pritikin, Ornish, and Esselstyn is so important, showing that plant-based diets can not only stop heart disease but have been proven to reverse it in the majority of patients. Indeed, it's the only diet that ever has.

For more on the absence of Western diseases in plant-based rural populations, see for example:

I've touched on "paleo" diets in the past:

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:

Image Credit: Nathan Rupert / Flickr

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The Natural Human Diet

NF-Nov15 The Problem with the Paleo Diet Argument copy.jpg

Our epidemics of dietary disease have prompted a great deal of research into what humans are meant to eat for optimal health. In 1985, an influential article highlighted in my video The Problem With the Paleo Diet Argument was published proposing that our chronic diseases stem from a disconnect between what our bodies ate while evolving during the Stone Age (about 2 million years ago) and what we're stuffing our face with today. The proposal advocated for a return towards a hunter-gatherer type diet of lean meat, fruits, vegetables, and nuts.

It's reasonable to assume our nutritional requirements were established in the prehistoric past. However, the question of which prehistoric past we should emulate remains. Why just the last 2 million? We've been evolving for about 20 million years since our last common great ape ancestor, during which our nutrient requirements and digestive physiology were set down. Therefore our hunter-gatherer days at the tail end probably had little effect. What were we eating for the first 90% of our evolution? What the rest of the great apes ended up eating--95 percent or more plants.

This may explain why we're so susceptible to heart disease. For most of human evolution, cholesterol may have been virtually absent from the diet. No bacon, butter, or trans fats; and massive amounts of fiber, which pulls cholesterol from the body. This could have been a problem since our body needs a certain amount of cholesterol, but our bodies evolve not only to make cholesterol, but also to preserve it and recycle it.

If we think of the human body as a cholesterol-conserving machine, then plop it into the modern world of bacon, eggs, cheese, chicken, pork, and pastry; it's no wonder artery-clogging heart disease is our #1 cause of death. What used to be adaptive for 90% of our evolution--holding on to cholesterol at all costs since we weren't getting much in our diet--is today maladaptive, a liability leading to the clogging of our arteries. Our bodies just can't handle it.

As the editor-in-chief of the American Journal of Cardiology noted 25 years ago, no matter how much fat and cholesterol carnivores eat, they do not develop atherosclerosis. We can feed a dog 500 eggs worth of cholesterol and they just wag their tail; a dog's body is used to eating and getting rid of excess cholesterol. Conversely, within months a fraction of that cholesterol can start clogging the arteries of animals adapted to eating a more plant-based diet.

Even if our bodies were designed by natural selection to eat mostly fruit, greens and seeds for 90% of our evolution, why didn't we better adapt to meat-eating in the last 10%, during the Paleolithic? We've had nearly 2 million years to get used to all that extra saturated fat and cholesterol. If a lifetime of eating like that clogs up nearly everyone's arteries, why didn't the genes of those who got heart attacks die off and get replaced by those that could live to a ripe old age with clean arteries regardless of what they ate? Because most didn't survive into old age.

Most prehistoric peoples didn't live long enough to get heart attacks. When the average life expectancy is 25 years old, then the genes that get passed along are those that can live to reproductive age by any means necessary, and that means not dying of starvation. The more calories in food, the better. Eating lots of bone marrow and brains, human or otherwise, would have a selective advantage (as would discovering a time machine stash of Twinkies for that matter!). If we only have to live long enough to get our kids to puberty to pass along our genes, then we don't have to evolve any protections against the ravages of chronic disease.

To find a population nearly free of chronic disease in old age, we don't have to go back a million years. In the 20th century, networks of missionary hospitals in rural Africa found coronary artery disease virtually absent, and not just heart disease, but high blood pressure, stroke, diabetes, common cancers, and more. In a sense, these populations in rural China and Africa were eating the type of diet we've been eating for 90% of the last 20 million years, a diet almost exclusively of plant foods.

How do we know it was their diet and not something else? In the 25 year update to their original paleo paper, the authors tried to clarify that they did not then and do not now propose that people adopt a particular diet just based on what our ancient ancestors ate. Dietary recommendations must be put to the test. That's why the pioneering research from Pritikin, Ornish, and Esselstyn is so important, showing that plant-based diets can not only stop heart disease but have been proven to reverse it in the majority of patients. Indeed, it's the only diet that ever has.

For more on the absence of Western diseases in plant-based rural populations, see for example:

I've touched on "paleo" diets in the past:

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:

Image Credit: Nathan Rupert / Flickr

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What About Eating Just a Little Meat?

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As you can see in my video, Plant-Based Diets and Diabetes, we've known for decades that a plant-based diet may be protective against diabetes. Studies going back half a century found that those eating meat one or more days a week had significantly higher rates of diabetes, and the more frequently meat was eaten, the more frequent the disease. And this is after controlling for weight, so even at the same weight, those eating more plant-based had but a fraction of the diabetes rates. If anything, vegetarians should have had more diabetes just because they appear to live so much longer, so they had more time to develop these kinds of chronic diseases; but no, apparently lower rates of death and disease.

Fast forward 50 years to the Adventist-2 study, looking at 89,000 people, and we see a stepwise drop in the rates of diabetes as one eats more and more plant-based, down to a 78% lower prevalence among those eating strictly plant-based. Protection building incrementally as one moved from eating meat daily, to eating meat weekly, to just fish, to no meat, and then to no eggs and dairy either. Followed over time, vegetarian diets were associated with a substantially lower incidence of diabetes, indicating the potential of these diets to stem the current diabetes epidemic.

We see the same step-wise drop in rates of another leading killer, high blood pressure. The greater the proportion of plant foods, the lower the rates of hypertension, and the same with excess body fat. The only dietary group not on average overweight were those eating diets composed exclusively of plant foods, but again there was the same incremental drop with fewer and fewer animal products. This suggests that it's not black and white, not all or nothing, any steps we can make along this spectrum of eating healthier may accrue significant benefits.

What about eating a really healthy diet with just a little meat? Is it better to eat none at all? We have new insight last year from Taiwan. Asian diets in general tend to be lower in meat and higher in plant foods compared with Western diet, but whether a diet completely avoiding meat and fish would further extend the protective effect of a plant-based diet wasn't known, until now.

Traditionally, Asian populations have had low rates of diabetes, but a diabetes epidemic has since emerged, and appears to coincide with increased meat, animal protein, and animal fat consumption, but the Westernization of Asian diets also brought along a lot of fast food and junk, and so these researchers at the national university didn't want to just compare those eating vegetarian to typical meateaters. So, they compared Bhuddist vegetarians to Bhuddist non-vegetarians, eating traditional Asian diets. Even the omnivores were eating a predominantly plant-based diet, consuming little meat and fish, with the women eating the equivalent of about a single serving a week, and men eating a serving every few days. That's just 8% of the meat intake in the U.S., 3% for the women. The question: is it better to eat 3% or 0%?

Again, both groups were eating healthy; zero soda consumption, for example, in any group. Despite the similarities in their diet, and after controlling for weight, family history, exercise, and smoking, the men eating vegetarian had just half the rates of diabetes, and the vegetarian women just a quarter of the rates. So even in a population consuming a really plant-based diet with little meat and fish, true vegetarians who completely avoided animal flesh, while eating more healthy plant foods, have lower odds for prediabetes and diabetes after accounting for other risk factors. They wanted to break it up into vegan versus ovo-lacto like in the Adventist-2 study, but they couldn't because there were no cases at all of diabetes found within the vegan group.

More on preventing and treating this terrible disease:

The reason I keep going back to that Adventist-2 study is that it's not only the biggest study of those eating plant based diets in North America, but the largest such study anywhere anytime. We owe those investigators a great debt (not to mention the 96,741 participants!). One thing I'm happy my tax dollars are going towards (via the National Cancer Institute and National Institutes of Health). More from the Adventists in Caloric Restriction vs. Animal Protein Restriction.

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 Meat, Dairy, and Eggs

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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 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.

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 to Protect Against Kidney Cancer

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

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 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 animal sources, not just processed meats, was associated with an increased risk of kidney cancer, and total intake of nitrate and nitrite from processed meat sources was also associated with kidney cancer risk. The researchers found no associations with nitrate or nitrite intake from plant sources, but nitrates from processed meat was associated with cancer.

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 directly, as well as chronic conditions associated with kidney cancer, such as obesity, high blood pressure and diabetes. It's similar to 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/nitrite story in my 17-part series about improving athletic performance with nitrate-rich vegetables such as beets and arugula. Here are a few short highlights:

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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Paleo Diet May Undermine Benefit of CrossFit Exercise

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Much of the low-carb and paleo reasoning revolves around insulin. To quote a paleo blogger, "carbohydrates increase insulin, the root of all evil when it comes to dieting and health." So the logic follows that because carbs increase insulin, we should stick mostly to meat, which is fat and protein with no carbs, so no increase in insulin, right?

Wrong.

We've known for half a century that if you give someone just a steak: no carbs, no sugar, no starch; their insulin goes up. Carbs make our insulin go up, but so does protein.

In 1997 an insulin index of foods was published, ranking 38 foods to determine which stimulates higher insulin levels. Researchers compared a large apple and all its sugar, a cup of oatmeal packed with carbs, a cup and a half of white flour pasta, a big bun-less burger with no carbs at all, to half of a salmon fillet. As you can see in the graph in my video Paleo Diets May Negate Benefits of Exercise, the meat produced the highest insulin levels.

Researchers only looked at beef and fish, but subsequent data showed that that there's no significant difference between the insulin spike from beef, chicken, or pork--they're all just as high. Thus, protein and fat rich foods may induce substantial insulin secretion. In fact, meat protein causes as much insulin release as pure sugar.

So, based on the insulin logic, if low-carbers and paleo folks really believed insulin to be the root of all evil, then they would be eating big bowls of spaghetti day in and day out before they would ever consume meat.

They are correct in believing that having hyperinsulinemia, high levels of insulin in the blood like type 2 diabetics have, is not a good thing, and may increase cancer risk. But if low-carb and paleo dieters stuck to their own insulin theory, then they would be out telling everyone to start eating plant-based. Vegetarians have significantly lower insulin levels even at the same weight as omnivores. This is true for ovo-lacto-vegetarians, lacto-vegetarians, and vegans. Meat-eaters have up to 50% higher insulin levels.

Researchers from the University of Memphis put a variety of people on a vegan diet (men, women, younger folks, older folks, skinny and fat) and their insulin levels dropped significantly within just three weeks. And then, just by adding egg whites back to their diet, their insulin production rose 60% within four days.

In a study out of MIT, researchers doubled participants' carbohydrate intake, and their insulin levels went down. Why? Because the researchers weren't feeding people jellybeans and sugar cookies, they were feeding people whole, plant foods, lots of whole grains, beans, fruits, and vegetables.

What if we put someone on a very-low carb diet, like an Atkins diet? Low carb advocates such as Dr. Westman assumed that it would lower insulin levels. Dr. Westman is the author of the new Atkins books, after Dr. Atkins died obese with, according to the medical examiner, a history of heart attack, congestive heart failure, and hypertension. But, Dr. Westman was wrong in his assumption. There are no significant drop in insulin levels on very low-carb diets. Instead, there is a significant rise in LDL cholesterol levels, the number one risk factor for our number one killer, heart disease.

Atkins is an easy target though. No matter how many "new" Atkins diets that come out, it's still old news. What about the paleo diet? The paleo movement gets a lot of things right. They tell people to ditch dairy and doughnuts, eat lots of fruits, nuts, and vegetables, and cut out a lot of processed junk food. But a new study published in the International Journal of Exercise Science is pretty concerning. Researchers took young healthy people, put them on a Paleolithic diet along with a CrossFit-based, high-intensity circuit training exercise program.

If you lose enough weight exercising, you can temporarily drop our cholesterol levels no matter what you eat. You can see that with stomach stapling surgery, tuberculosis, chemotherapy, a cocaine habit, etc. Just losing weight by any means can lower cholesterol, which makes the results of the Paleo/Crossfit study all the more troubling. After ten weeks of hardcore workouts and weight loss, the participants' LDL cholesterol still went up. And it was even worse for those who started out the healthiest. Those starting out with excellent LDL's (under 70), had a 20% elevation in LDL cholesterol, and their HDL dropped. Exercise is supposed to boost our good cholesterol, not lower it.

The paleo diet's deleterious impact on blood fats was not only significant, but substantial enough to counteract the improvements commonly seen with improved fitness and body composition. Exercise is supposed to make things better.

On the other hand, if we put people instead on a plant-based diet and a modest exercise program, mostly just walking-based; within three weeks their bad cholesterol can drop 20% and their insulin levels 30%, despite a 75-80% carbohydrate diet, whereas the paleo diets appeared to "negate the positive effects of exercise."

I touched on paleo diets before in Paleolithic Lessons, and I featured a guest blog on the subject: Will The Real Paleo Diet Please Stand Up?

but my favorite paleo videos are probably The Problem With the Paleo Diet Argument and Lose Two Pounds in One Sitting: Taking the Mioscenic Route.

I wrote a book on low carb diets in general (now available free full-text online) and touched on it in Atkins Diet: Trouble Keeping It Up and Low Carb Diets and Coronary Blood Flow.

And if you're thinking, but what about the size of the cholesterol, small and dense versus large and fluffy? Please see my video Does Cholesterol Size Matter?

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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Dietary Estrogens and Male Fertility

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In my video, The Role of Diet in Declining Sperm Counts, I discussed the association between high saturated fat intake and reduced semen quality. But what's the connection? One of the most recent papers on the topic found that a significant percentage of the saturated fat intake in the study was derived from dairy products. Residues of industrial chemicals may bioaccumulate up the food chain into animal fat, and some of these lipophilic (fat-loving) chemicals may have hormone-disrupting abilities.

The U.S. Environmental Protection Agency performed a national survey of persistent, bioaccumulative, and toxic pollutants in the U.S. milk supply (highlighted in my video, Dairy Estrogen and Male Fertility). The EPA team noted that since milk fat is likely to be among the highest dietary sources of exposure to these pollutants, it's important to understand the levels in the dairy supply. The team tested milk from all over the country and found a veritable 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 polychlorinated biphenyls (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 non-polluted world, animal foods also have actual estrogen, which are unavoidable constituents of animal products. All foodstuff of animal origin contains estradiol, which is at least 10,000-fold more potent than most xenoestrogens. Dietary exposure--meat, dairy products and eggs--to these natural sex steroids is therefore highly relevant, as the hormones in these animals are identical to our own.

Estrogens are present 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 4,000 times the intake of xenoestrogens in terms of hormone activity. Modern genetically-improved dairy cows can lactate throughout their pregnancy. The problem is that during pregnancy, estrogen levels can jump as much as 30-fold.

Cheese intake has specifically been associated with lower sperm concentration, whereas dairy food intake in general has been associated with abnormal sperm shape and movement. Lower sperm concentrations by themselves may just represent a potential suppression of sperm production due to higher estrogen levels, but abnormal shape and movement suggests that dairy intake may be implicated in actual direct testicular damage.

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. This could be expected, as eggs are produced directly in the hens' ovaries.

Meat may also contain added hormones. In the U.S. anabolic sex steroids may be administered to animals for growth promotion, a practice banned in Europe twenty-five years ago. A study in New York found progressively lower sperm counts associated with processed meat consumption. However, 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 meat components, such as the saturated fat raising cholesterol levels.

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 blood cholesterol levels were 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. Although a healthier diet may be associated with healthier sperm counts, cholesterol-lowering statin drugs do not seem to help.

What about the phytoestrogens in soy? See The Effect of Soy on Precocious Puberty.

More on hormones in dairy in:

Neurotoxic chemicals in the dairy supply have been blamed for neurological conditions as well. See my video Preventing Parkinson's Disease with Diet.

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Taber Andrew Bain / Flickr

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Plant-Based Diets for Hypertension

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Recently, researchers from Taiwan pitted the herbal tea hibiscus against obesity. They gave hibiscus to overweight individuals and reported that subjects showing reduced body weight. However, after 12 weeks on hibiscus subjects only lost about three pounds, only one and a half pounds over placebo. Hibiscus is clearly no magic fix for obesity.

The purported cholesterol-lowering property of hibiscus tea looked a bit more promising. Some older studies suggested as much as an 8% reduction from drinking two cups a day for a month. When all the studies are put together, though, the results are pretty much a wash. This may be because only about 50% of people respond at all to drinking the equivalent of between two to five cups a day, though those that do may get a respectable 12% drop. That's nothing like the 30% one can get within weeks of eating a healthy, plant-based diet, though.

Hibiscus may really shine in treating high blood pressure, a disease affecting a billion people and killing millions. Up until 2010, there wasn't sufficient high quality research to support the use of hibiscus tea to treat hypertension, but there are now randomized double-blind, placebo-controlled studies where hibiscus tea is compared to artificially colored and flavored water that looks and tastes like hibiscus tea, and the tea lowers blood pressure significantly better.

We're still not sure how it works, but hibiscus appears to boost nitric oxide production, which could help our arteries relax and dilate better. Regardless, an updated review acknowledged that the daily consumption of hibiscus tea may indeed significantly lower blood pressures in people with hypertension.

How does hibiscus compare to other blood pressure interventions? The premier clinical trial when it comes to comprehensive lifestyle modification for blood pressure control is the PREMIER Clinical Trial. Realizing that nine out of ten Americans are going to develop hypertension, researchers from John Hopkins randomized 800 men and women with high blood pressure into one of three groups. One was the control group, the so-called "advice only group," where patients were just told to lose weight, cut down on salt, increase exercise and eat healthier. In the two behavioral intervention groups the researchers got serious. Eighteen face-to-face sessions, groups meetings, food diaries, physical activity records, and calorie and sodium intake monitoring. One intervention group just concentrated on exercise; the other included exercise and diet. Researchers pushed the DASH diet, which is high in fruits and vegetables and low in full-fat dairy products and meat. In six months subjects achieved a 4.3 point drop in systolic blood pressure, compared to the control, slightly better than the lifestyle intervention without the diet.

A few points might not sound like a lot--that's like someone going from a blood pressure of 150 over 90 to a blood pressure of 146 over 90--but on a population scale a five point drop in the total number could result in 14% fewer stroke deaths, 9% fewer fatal heart attacks, and 7% fewer deaths every year overall.

A cup of hibiscus tea with each meal didn't just lower blood pressure by three, four, or five points, but by seven points, from an average of 129 down to 122. In fact, tested head-to-head against a leading blood-pressure drug, Captopril, two cups of strong hibiscus tea every morning (five tea bags for the two cups) was as effective in lowering blood pressure as a starting dose of 25mg of captopril taken twice a day.

So hibiscus tea is as good as drugs, without side-effects, and better than diet and exercise? Well, the lifestyle interventions in the PREMIER study were pretty wimpy. As public health experts noted, the PREMIER study was only asking for 30 minutes of exercise a day, whereas the World Health Organization recommends a minimum of an hour a day.

Diet-wise, the lower the animal fat intake, and the more plant sources of protein the PREMIER participants were eating, the better the diet appeared to work. This may explain why vegetarian diets appear to work even better, and the more plant-based, the lower the prevalence of hypertension.

On the DASH diet, subjects cut down on meat, but were still eating it every day, so would qualify as nonvegetarians in the Adventist 2 study (highlighted in my video Hibiscus Tea vs. Plant-Based Diets for Hypertension) which looked at 89,000 Californians. It found that those who only ate meat on a weekly basis had 23% lower rates of high blood pressure. Those who cut out all meat except fish had 38% lower rates. Those eating no meat at all, vegetarians, have less than half the rate. The vegans--cutting out all animal protein and fat--appeared to have thrown three quarters of their risk for this major killer out the window.

One sees the same kind of step-wise drop in diabetes rates as one's diet gets more and more plant-based, and a drop in excess body weight, such that only those eating completely plant-based diets in the Adventist 2 study fell into the ideal weight category. Could that be why those eating plant-based have such great blood pressure? Maybe it's just because they're so skinny. I've previously shown how those eating plant-based just have a fraction of the diabetes risk even at the same weight. but what about hypertension?

The average American has what's called prehypertension, which means the top number of our blood pressure is between 120 and 139. We don't have hypertension yet, which starts at 140, but we may be well on our way. Compare that to the blood pressure of those eating whole food plant-based diets. In one study, those eating plant-based didn't have blood pressures three points lower, four points lower, or even seen points lower, but 28 points lower. However, the group eating the standard American diet was, on average, overweight with a BMI over 26, still better than most Americans, while the vegans were a trim 21--that's 36 pounds lighter.

Maybe the only reason those eating meat, eggs, dairy, and processed junk had such higher blood pressure was because they were overweight. Maybe the diet per se had nothing to do with it?

To solve that riddle we would have to find a group still eating the standard American diet, but as slim as vegans. To find a group that trim, researchers had to use long-distance endurance athletes, who ate the same crappy American diet, but ran an average of 48 miles per week for 21 years. Anyone who runs almost two marathons a week for 20 years can be as slim as a vegan--no matter what they eat!

How did the endurance runners compare to the couch potato vegans? It appears that if we run an average of about a thousand miles every year our blood pressures can rival some couch potato vegans. That doesn't mean we can't do both, but it may be easier to just eat plants.


Those who've been following my work for years have seen how my videos have evolved. In the past, the hibiscus results may have been the whole article or video. But thanks to everyone's support, I've been able to delegate the logistics to staff and concentrate more on the content creation. This allows me to do deeper dives into the literature to put new findings into better context. The posts are a bit longer, but hopefully they're more useful--let me know what you think!

For such a leading killer, hypertension has not gotten the coverage it deserves on NutritionFacts.org. Here's a few videos, with more to come:

So should we all be drinking hibiscus tea every day? This is the first of a four part series on the latest on hibiscus. Stay tuned for the next three:

For another comparison of those running marathons and those eating plants, see: Arteries of Vegans vs. Runners

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Amy / Flickr

Original Link

How to Treat Prediabetes with Diet

NF-May3 Lifestyle Medicine Is the Standard of Care for Prediabetes.jpeg

For people with prediabetes, lifestyle modification is considered "the cornerstone of diabetes prevention." Diet-wise, this means individuals with prediabetes or diabetes should aim to reduce their intake of excess calories, saturated fat, and trans fat. Too many of us consume a diet with too many solid fats and added sugars. Thankfully the latest dietary guidelines aim to shift consumption towards more plant-based foods.

Lifestyle modification is now the foundation of the American Association of Clinical Endocrinology guidelines, the European Diabetes Association guidelines, and the official standards of care for the American Diabetes Association. Dietary strategies include reducing intake of fat and increasing intake of fiber (meaning unrefined plant foods, including whole grains).

The recommendation to consume more whole grains is based on research showing that eating lots of whole grains is associated with reduced risk of developing type 2 diabetes. New research even suggests that whole grains may protect against prediabetes in the first place.

According to the American Diabetes Association's official standards of care (which you can see in my video Lifestyle Medicine Is the Standard of Care for Prediabetes), dietary recommendations should focus on reducing saturated fat, cholesterol and trans fat intake (meat, dairy, eggs and junk food). Recommendations should also focus on increasing omega 3's, soluble fiber and phytosterols, all three of which can be found together in flax seeds; an efficient, but still uncommon, intervention for prediabetes. In one study, about two tablespoons of ground flax seed a day decreased insulin resistance (the hallmark of the disease).

If the standards of care for all the major diabetes groups say that lifestyle is the preferred treatment for prediabetes because it's safe and highly effective, why don't more doctors do it? Unfortunately, the opportunity to treat this disease naturally is often unrecognized. Only about one in three patients report ever being told about diet or exercise. Possible reasons for not counseling patients include lack of reimbursement, lack of resources, lack of time, and lack of skill.

It may be because doctors aren't getting paid to do it. Why haven't reimbursement policies been modified? One crucial reason may be a failure of leadership in the medical profession and medical education to recognize and respond to the changing nature of disease patterns.

"The inadequacy of clinical education is a consequence of the failure of health care and medical education to adapt to the great transformation of disease from acute to chronic. Chronic disease is now the principal cause of disability, consuming three quarters of our sickness-care system. Why has there been little academic response to the rising prevalence of chronic disease?"

How far behind the times is the medical profession? A report by the Institute of Medicine on medical training concluded that the fundamental approach to medical education "has not changed since 1910."


I hope my work is helping to fill the gap that medical professionals are not getting during training about preventing and treating chronic disease. That's actually how this all started. I would make trips to Countway at the beginning of every month in medical school to read all the new journal issues. I felt I had a duty to my patients to stay on top of the literature. But hey, since I'm doing so much work, might as well share it! So what started as an email newsletter morphed into a medical school speaking tour into a DVD series and then now all online for everyone.

For more on preventing and treating prediabetes/diabetes, see:

For more on lifestyle medicine:

And for insight into the sad state of nutrition in medical training, Doctors Know Less Than They Think About Nutrition and Medical School Nutrition Training.

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Alden Chadwick / Flickr

Original Link

How to Treat Prediabetes with Diet

NF-May3 Lifestyle Medicine Is the Standard of Care for Prediabetes.jpeg

For people with prediabetes, lifestyle modification is considered "the cornerstone of diabetes prevention." Diet-wise, this means individuals with prediabetes or diabetes should aim to reduce their intake of excess calories, saturated fat, and trans fat. Too many of us consume a diet with too many solid fats and added sugars. Thankfully the latest dietary guidelines aim to shift consumption towards more plant-based foods.

Lifestyle modification is now the foundation of the American Association of Clinical Endocrinology guidelines, the European Diabetes Association guidelines, and the official standards of care for the American Diabetes Association. Dietary strategies include reducing intake of fat and increasing intake of fiber (meaning unrefined plant foods, including whole grains).

The recommendation to consume more whole grains is based on research showing that eating lots of whole grains is associated with reduced risk of developing type 2 diabetes. New research even suggests that whole grains may protect against prediabetes in the first place.

According to the American Diabetes Association's official standards of care (which you can see in my video Lifestyle Medicine Is the Standard of Care for Prediabetes), dietary recommendations should focus on reducing saturated fat, cholesterol and trans fat intake (meat, dairy, eggs and junk food). Recommendations should also focus on increasing omega 3's, soluble fiber and phytosterols, all three of which can be found together in flax seeds; an efficient, but still uncommon, intervention for prediabetes. In one study, about two tablespoons of ground flax seed a day decreased insulin resistance (the hallmark of the disease).

If the standards of care for all the major diabetes groups say that lifestyle is the preferred treatment for prediabetes because it's safe and highly effective, why don't more doctors do it? Unfortunately, the opportunity to treat this disease naturally is often unrecognized. Only about one in three patients report ever being told about diet or exercise. Possible reasons for not counseling patients include lack of reimbursement, lack of resources, lack of time, and lack of skill.

It may be because doctors aren't getting paid to do it. Why haven't reimbursement policies been modified? One crucial reason may be a failure of leadership in the medical profession and medical education to recognize and respond to the changing nature of disease patterns.

"The inadequacy of clinical education is a consequence of the failure of health care and medical education to adapt to the great transformation of disease from acute to chronic. Chronic disease is now the principal cause of disability, consuming three quarters of our sickness-care system. Why has there been little academic response to the rising prevalence of chronic disease?"

How far behind the times is the medical profession? A report by the Institute of Medicine on medical training concluded that the fundamental approach to medical education "has not changed since 1910."


I hope my work is helping to fill the gap that medical professionals are not getting during training about preventing and treating chronic disease. That's actually how this all started. I would make trips to Countway at the beginning of every month in medical school to read all the new journal issues. I felt I had a duty to my patients to stay on top of the literature. But hey, since I'm doing so much work, might as well share it! So what started as an email newsletter morphed into a medical school speaking tour into a DVD series and then now all online for everyone.

For more on preventing and treating prediabetes/diabetes, see:

For more on lifestyle medicine:

And for insight into the sad state of nutrition in medical training, Doctors Know Less Than They Think About Nutrition and Medical School Nutrition Training.

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 Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Alden Chadwick / Flickr

Original Link