Why Is Milk Consumption Associated with More Bone Fractures?

Why Is Milk Consumption Associated with More Bone Fractures?.jpg

Milk is touted to build strong bones, but a compilation of all the best studies found no association between milk consumption and hip fracture risk, so drinking milk as an adult might not help bones, but what about in adolescence? Harvard researchers decided to put it to the test.

Studies have shown that greater milk consumption during childhood and adolescence contributes to peak bone mass, and is therefore expected to help avoid osteoporosis and bone fractures in later life. But that's not what researchers have found (as you can see in my video Is Milk Good for Our Bones?). Milk consumption during teenage years was not associated with a lower risk of hip fracture, and if anything, milk consumption was associated with a borderline increase in fracture risk in men.

It appears that the extra boost in total body bone mineral density from getting extra calcium is lost within a few years; even if you keep the calcium supplementation up. This suggests a partial explanation for the long-standing enigma that hip fracture rates are highest in populations with the greatest milk consumption. This may be an explanation for why they're not lower, but why would they be higher?

This enigma irked a Swedish research team, puzzled because studies again and again had shown a tendency of a higher risk of fracture with a higher intake of milk. Well, there is a rare birth defect called galactosemia, where babies are born without the enzymes needed to detoxify the galactose found in milk, so they end up with elevated levels of galactose in their blood, which can causes bone loss even as kids. So maybe, the Swedish researchers figured, even in normal people that can detoxify the stuff, it might not be good for the bones to be drinking it every day.

And galactose doesn't just hurt the bones. Galactose is what scientists use to cause premature aging in lab animals--it can shorten their lifespan, cause oxidative stress, inflammation, and brain degeneration--just with the equivalent of like one to two glasses of milk's worth of galactose a day. We're not rats, though. But given the high amount of galactose in milk, recommendations to increase milk intake for prevention of fractures could be a conceivable contradiction. So, the researchers decided to put it to the test, looking at milk intake and mortality as well as fracture risk to test their theory.

A hundred thousand men and women were followed for up to 20 years. Researchers found that milk-drinking women had higher rates of death, more heart disease, and significantly more cancer for each glass of milk. Three glasses a day was associated with nearly twice the risk of premature death, and they had significantly more bone and hip fractures. More milk, more fractures.

Men in a separate study also had a higher rate of death with higher milk consumption, but at least they didn't have higher fracture rates. So, the researchers found a dose dependent higher rate of both mortality and fracture in women, and a higher rate of mortality in men with milk intake, but the opposite for other dairy products like soured milk and yogurt, which would go along with the galactose theory, since bacteria can ferment away some of the lactose. To prove it though, we need a randomized controlled trial to examine the effect of milk intake on mortality and fractures. As the accompanying editorial pointed out, we better find this out soon since milk consumption is on the rise around the world.

What can we do for our bones, then? Weight-bearing exercise such as jumping, weight-lifting, and walking with a weighted vest or backpack may help, along with getting enough calcium (Alkaline Diets, Animal Protein, & Calcium Loss) and vitamin D (Resolving the Vitamin D-Bate). Eating beans (Phytates for the Prevention of Osteoporosis) and avoiding phosphate additives (Phosphate Additives in Meat Purge and Cola) may also help.

Maybe the galactose angle can help explain the findings on prostate cancer (Prostate Cancer and Organic Milk vs. Almond Milk) and Parkinson's disease (Preventing Parkinson's Disease With Diet).

Galactose is a milk sugar. There's also concern about milk proteins (see my casomorphin series) and fats (The Saturated Fat Studies: Buttering Up the Public and Trans Fat in Meat and Dairy) as well as the hormones (Dairy Estrogen and Male Fertility, Estrogen in Meat, Dairy, and Eggs and Why Do Vegan Women Have 5x Fewer Twins?).

Milk might also play a role in diabetes (Does Casein in Milk Trigger Type 1 Diabetes, Does Bovine Insulin in Milk Trigger Type 1 Diabetes?) and breast cancer (Is Bovine Leukemia in Milk Infectious?, The Role of Bovine Leukemia Virus in Breast Cancer, and Industry Response to Bovine Leukemia Virus in Breast Cancer).

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: Sally Plank / Flickr. This image has been modified.

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Why Is Milk Consumption Associated with More Bone Fractures?

Why Is Milk Consumption Associated with More Bone Fractures?.jpg

Milk is touted to build strong bones, but a compilation of all the best studies found no association between milk consumption and hip fracture risk, so drinking milk as an adult might not help bones, but what about in adolescence? Harvard researchers decided to put it to the test.

Studies have shown that greater milk consumption during childhood and adolescence contributes to peak bone mass, and is therefore expected to help avoid osteoporosis and bone fractures in later life. But that's not what researchers have found (as you can see in my video Is Milk Good for Our Bones?). Milk consumption during teenage years was not associated with a lower risk of hip fracture, and if anything, milk consumption was associated with a borderline increase in fracture risk in men.

It appears that the extra boost in total body bone mineral density from getting extra calcium is lost within a few years; even if you keep the calcium supplementation up. This suggests a partial explanation for the long-standing enigma that hip fracture rates are highest in populations with the greatest milk consumption. This may be an explanation for why they're not lower, but why would they be higher?

This enigma irked a Swedish research team, puzzled because studies again and again had shown a tendency of a higher risk of fracture with a higher intake of milk. Well, there is a rare birth defect called galactosemia, where babies are born without the enzymes needed to detoxify the galactose found in milk, so they end up with elevated levels of galactose in their blood, which can causes bone loss even as kids. So maybe, the Swedish researchers figured, even in normal people that can detoxify the stuff, it might not be good for the bones to be drinking it every day.

And galactose doesn't just hurt the bones. Galactose is what scientists use to cause premature aging in lab animals--it can shorten their lifespan, cause oxidative stress, inflammation, and brain degeneration--just with the equivalent of like one to two glasses of milk's worth of galactose a day. We're not rats, though. But given the high amount of galactose in milk, recommendations to increase milk intake for prevention of fractures could be a conceivable contradiction. So, the researchers decided to put it to the test, looking at milk intake and mortality as well as fracture risk to test their theory.

A hundred thousand men and women were followed for up to 20 years. Researchers found that milk-drinking women had higher rates of death, more heart disease, and significantly more cancer for each glass of milk. Three glasses a day was associated with nearly twice the risk of premature death, and they had significantly more bone and hip fractures. More milk, more fractures.

Men in a separate study also had a higher rate of death with higher milk consumption, but at least they didn't have higher fracture rates. So, the researchers found a dose dependent higher rate of both mortality and fracture in women, and a higher rate of mortality in men with milk intake, but the opposite for other dairy products like soured milk and yogurt, which would go along with the galactose theory, since bacteria can ferment away some of the lactose. To prove it though, we need a randomized controlled trial to examine the effect of milk intake on mortality and fractures. As the accompanying editorial pointed out, we better find this out soon since milk consumption is on the rise around the world.

What can we do for our bones, then? Weight-bearing exercise such as jumping, weight-lifting, and walking with a weighted vest or backpack may help, along with getting enough calcium (Alkaline Diets, Animal Protein, & Calcium Loss) and vitamin D (Resolving the Vitamin D-Bate). Eating beans (Phytates for the Prevention of Osteoporosis) and avoiding phosphate additives (Phosphate Additives in Meat Purge and Cola) may also help.

Maybe the galactose angle can help explain the findings on prostate cancer (Prostate Cancer and Organic Milk vs. Almond Milk) and Parkinson's disease (Preventing Parkinson's Disease With Diet).

Galactose is a milk sugar. There's also concern about milk proteins (see my casomorphin series) and fats (The Saturated Fat Studies: Buttering Up the Public and Trans Fat in Meat and Dairy) as well as the hormones (Dairy Estrogen and Male Fertility, Estrogen in Meat, Dairy, and Eggs and Why Do Vegan Women Have 5x Fewer Twins?).

Milk might also play a role in diabetes (Does Casein in Milk Trigger Type 1 Diabetes, Does Bovine Insulin in Milk Trigger Type 1 Diabetes?) and breast cancer (Is Bovine Leukemia in Milk Infectious?, The Role of Bovine Leukemia Virus in Breast Cancer, and Industry Response to Bovine Leukemia Virus in Breast Cancer).

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: Sally Plank / Flickr. This image has been modified.

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Why Smoothies are Better Than Juicing

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Studies such as a recent Harvard School of Public Health investigation found that the consumption of whole fruits is associated with a significantly lower risk of type 2 diabetes, whereas fruit juice consumption is associated with a higher risk, highlighting the dramatic difference between eating whole fruits and drinking fruit juice. Cholesterol serves as another example. If we eat apples, our cholesterol drops. On the other hand, if we drink apple juice, our cholesterol may actually go up a little. Leaving just a little of the fiber behind--as in cloudy apple juice--was found to add back in some of the benefit.

We used to think of fiber as just a bulking agent that helps with bowel regularity. We now know fiber is digestible by our gut bacteria, which make short chain fatty acids (SCFAs) out of it. SCFAs have a number of health promoting effects, such as inhibiting the growth of bad bacteria and increasing mineral absorption. For example, experimentally infused into the rectum of the human body, SCFAs can stimulate calcium absorption, so much so that we can improve the bone mineral density of teenagers just by giving them the fiber naturally found in foods like onions, asparagus, and bananas.

Our good bacteria also uses fiber to maintain normal bowel structure and function, preventing or alleviating diarrhea, stimulating colonic blood flow up to five-fold, and increasing fluid and electrolyte uptake. The major fuel for the cells that line our colon is butyrate, which our good bacteria make from fiber. We feed them, and they feed us right back.

If the only difference between fruit and fruit juice is fiber, why can't the juice industry just add some fiber back to the juice? The reason is because we remove a lot more than fiber when we juice fruits and vegetables. We also lose all the nutrients that are bound to the fiber.

In the 1980's, a study (highlighted in my video, Juicing Removes More Than Just Fiber) found a discrepancy in the amount of fiber in carob using two different methods. A gap of 21.5 percent was identified not as fiber but as nonextractable polyphenols, a class of phytonutrients thought to have an array of health-promoting effects. Some of the effects associated with the intake of dietary fiber in plants may actually be due to the presence of these polyphenols.

Nonextractable polyphenols, usually ignored, are the major part of dietary polyphenols. Most polyphenol phytonutrients in plants are stuck to the fiber. These so-called missing polyphenols make it down to our colon, are liberated by our friendly flora and can then get absorbed into our system. The phytonutrients in fruit and vegetable juice may just be the tip of the iceberg.

For those that like drinking their fruits and vegetables, these findings suggest that smoothies may be preferable. I can imagine people who eat really healthy thinking they get so much fiber from their regular diet that they need not concern themselves with the loss from juicing. But we may be losing more than we think.

For those that like drinking their fruits and vegetables, this suggests smoothies are preferable. I can imagine people who eat really healthy thinking they get so much fiber from their regular diet that they need not concern themselves with the loss from juicing, but they may be losing more than they think.

Why are polyphenol phytonutrients important? See, for example, my video How to Slow Brain Aging by Two Years

Not that fiber isn't important in its own right. Check out:

For more on smoothies, check out:

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: Craig Sunter / Flickr

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How Beans Help Our Bones

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Health authorities from all over the world universally recommend increasing the consumption of whole grains and legumes--beans, split peas, chickpeas, and lentils--for health promotion. But what about the phytates?

Phytate is a naturally occurring compound found in all plant seeds (like beans, grains, and nuts) that over the decades has been maligned as mineral absorption inhibitors. That's why, for example, one hears advice to roast, sprout, or soak your nuts to get rid of the phytates so we can absorb more minerals, like calcium.

The concern about phytates and bone health arose from a series of laboratory experiments performed on puppies published in 1949, which suggested that high phytate diets have a bone softening and anti-calcifying effect. Subsequent studies on rats, in which they fed them the equivalent of ten loaves of bread a day, "confirmed" phytate's status as a so-called anti-nutrient. But more recently, in the light of actual human data, phytate's image has undergone a makeover.

A recent study published in the Journal of Medicinal Food asked a simple question: Do people who avoid high phytate foods--legumes, nuts, and whole grains--have better bone mineral density? No. Those that consumed more high-phytate foods actually had stronger bones, as measured in the heel, spine and hip. The researchers conclude that dietary phytate consumption had protective effects against osteoporosis and that low phytate consumption should actually be what's considered an osteoporosis risk factor.

A follow-up study, measuring phytate levels flowing through women's bodies and following bone mass over time, found the same thing: women with the highest phytate levels had the lowest levels of bone loss in the spine and hip. Those who ate the most phytates were also estimated to have a significantly lower risk of major fracture, and a lower risk of hip fracture specifically.

This is consistent with reports that phytate can inhibit the dissolution of bone similar to anti-osteoporosis drugs like Fosamax. Phytates don't have the side effects, though, such as osteonecrosis (bone death) associated with that class of drugs. People take these drugs to protect their bones, but by doing so may also risk rotting them away (See Phytates for the Prevention of Osteoporosis).

Eating healthy can help us avoid other drugs as well. See, for example:

Beans might not just help our skeleton last longer, but the rest of us as well. See Increased Lifespan From Beans.

How might one boost mineral absorption? See New Mineral Absorption Enhancers Found.

Alkaline Diets, Animal Protein, & Calcium Loss is another surprising video on bone health.

And more on the benefits of phytates can be found in my videos:

-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, and From Table to Able.

Image Credit: Asja Boros / Flickr

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What Do Meat Purge and Cola Have in Common?

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In my video, Treating Kidney Failure Through Diet, I profiled research suggesting that the use of a plant-based diet for patients with kidney failure would be beneficial. An important function of our kidneys is to filter out excess phosphorus from our bloodstream, so a decline in kidney function can lead to the build-up of phosphorus in our bodies. This in turn can cause something called metastatic calcification, where our heart valves and muscles and other parts of the body can buildup mineral deposits, eventually potentially resulting in bad things like skin necrosis, gangrene, and amputations. Therefore, controlling dietary phosphorus intake is the lynchpin of successful prevention of metastatic calcification. While both plant foods and animal foods have phosphorus, our bodies seem better able to handle phosphorus excretion from plants, so a plant-based diet may help protect against this dreadful condition.

However, we're beginning to realize that absorbing too much phosphorus isn't good for anyone, even those with healthy kidneys. Having high levels in our blood has been found to be an independent predictor of heart attacks and mortality in the general population, increasing the risk not only of kidney failure, but also of heart failure, heart attacks, coronary death, and overall death. Dietary intake of phosphate is an important matter not just for persons with kidney disease, but for everybody. It's thought to cause damage to blood vessels, to accelerate the aging process, and even, potentially, to hurt our bones by contributing to osteoporosis via a disruption of hormonal regulation. The estimated average requirement of phosphorus is less than 600 mg a day, but the estimated average intake in the United States is nearly twice that. How do we stay away from too much of the stuff?

In the video, Phosphate Additives in Meat Purge and Cola, we can see the different levels of phosphorus in different foods. It looks like many plant foods have as much phosphorus as many animal foods. So why are plant-based diets so effective in treating kidney failure patients? Because most of the phosphorus in plant foods is found in the form of phytic acid, which we can't digest. Therefore, while plant and animal foods may have similar phosphate contents, the amount that is bioavailable differs. In plant foods, the bioavailability of phosphates is usually less than 50%, while the bioavailability of most animal products is up around 75%.

So when we adjust for how much actually gets into our system, plant foods are significantly better. It's like the absorption of heme and non-heme iron: our bodies can protect themselves from absorbing too much plant-based iron, but can't stop excess muscle and blood-based (heme) iron from animals slipping through the intestinal wall (see my video Risk Associated With Iron Supplements).

The worst kind of phosphorus is in the form of phosphate additives (which are absorbed nearly 100%) that are added, for example, to cola drinks. Why is phosphate added to cola? Without the added phosphate, so many glycotoxins would be produced that the beverage would turn pitch black (see my video on Glycotoxins). Thus, cola drinks owe their brown color to phosphate.

Phosphate additives play an especially important role in the meat industry, where they are used as preservatives for the same reason: to enhance a meat product's color. Just like the dairy industry adds aluminum to cheese, the meat and poultry industries "enhance" their products by injecting them with phosphates. If one looks at meat industry trade journals and can get past all the macabre ads for "head dropping robots for the kill floor," you'll see all ad after ad for injection machines. Why? Because of "increased profitability." Enhanced meats have better color and less "purge."

Purge is a term used to describe the liquid that seeps from flesh as it ages. Many consumers find this unattractive, so the industry views phosphate injection as a win-win. When chicken is injected with phosphates, the "consumer benefits through the perception of enhanced quality," and the processor benefits from increased yield because they just pump it up with water and they sell it by the pound. The problem is that it can boost phosphorus levels in meat nearly 70%, a "real and insidious danger" not only for kidney patients, but for us all.

Another toxic addition to alter the color of meat is arsenic-containing drugs fed directly to chickens (see my video Arsenic in Chicken). Carbon monoxide is used to keep red meat red, anthoxanthins keep salmon pink (Artificial Coloring in Fish) and titanium dioxide is used to whiten processed foods (Titanium Dioxide & Inflammatory Bowel Disease). I'm amazed by the risks the food industry will take to alter food cosmetically (more on this in Artificial Food Colors and ADHD).

There are other harmful additives in soda as well (Is Sodium Benzoate Harmful? and Diet Soda and Preterm Birth).

What else is in poultry purge (chicken "juice")? Find out in my video, Phosphate Additives in Chicken.

-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, and From Table to Able.

Images thanks to Michael Scheltgen / Flickr

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Test to See If Your Diet is Alkaline or Acid Forming

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In my video Alkaline Diets, Animal Protein, and Calcium Loss I presented evidence challenging the notion that our body is buffering the acid formed from our diet with calcium from our bones. How then is our body neutralizing the acid? Maybe with our muscles! Our blood gets more acidic as we age and our kidney function declines, and this may be a reason we lose muscle mass as we get older. As a pair of researchers note: "The modern Western diet based on animal products generates an acid load that may cause a lifespan state of unnoticed and growing metabolic acidosis." This chronic low-level diet-dependent metabolic acidosis might contribute to the progressive shrinking of our muscle mass as we age.

Muscle wasting appears to be an adaptive response to acidosis. When our muscles break down, amino acids are released into the bloodstream. Our liver can then take these amino acids and make something called glutamine, which our kidneys can use to get rid of excess acid. And indeed, in a three year study I profile in my video, Testing Your Diet with Pee and Purple Cabbage, those over age 65 eating alkaline diets were better able to preserve their muscle mass, which the researchers think may be because the alkaline-producing fruits and vegetables helped relieve the mild acidosis that occurs with the ingestion of the standard American diet.

So what should we think about the latest review's question, "Does an alkaline diet benefit health?" If the question is "Does a diet low in meat, eggs, and dairy--all acid-producing--and high in fruits and vegetables with lots of dark green leafies benefit health?" then of course the answer is yes, an alkaline diet benefits health. But if the question is "Does it matter what our 'peeH' is (whether our urine is acid or alkaline) regardless of what actually goes into our mouth?" then the answer is... still yes, but the accepted benefits of having alkaline urine appear limited to two areas: lower risk of kidney stones and better uric acid clearance.

We've known about kidney stones and alkalinity for a while, but the uric acid data is new. Researchers have found that alkalization of the urine is effective for removing uric acid from the body. If you remember from my video Flesh and Fructose, uric acid is bad stuff (potentially increasing one's risk of fatal stroke, heart disease, and death), so clearing more from your system is a good thing.

Those eating plant-based diets appear then to have an advantage in this regard. The average vegetarian diet is alkaline producing, and the average meat-eating diet is acid producing. Even though there are some acid-forming meat-substitutes, like some of the Quorn products, they're not as bad as something like tuna, and they're typically consumed in smaller quantities than meat consumers consume meat. Since the protein in plants is usually accompanied by much more potassium (which is alkalinizing), there is good reason to try to meet protein needs from plant sources. And when researchers actually measure urine pH, those eating strictly plant-based diets have the greatest advantage, with significantly more alkaline urine than omnivores.

How can we tell what our urine pH is? Well we can be all boring and order some pH paper strips to pee on. Or... we can use what everyone should have right now in their crisper, a purple cabbage. Everyone should have a red or purple cabbage in their fridge since it is not only one of the single best nutrition bangs for our buck, but we can also do science with it!

First, either boil some purple cabbage until the water turns deep purple or (a quicker and safer way since there's no hot liquids) blend some raw with water in a blender and strain out the solids. Then what you can do with that royal purple liquid is pour it in the toilet bowl after you urinate. (You can imagine how much fun kids have with this!)

If it stays purple, your urine is acidic and you should eat more dark green leafy vegetables. If the toilet bowl turns pink, your urine is really acidic, so you should definitely eat more dark green leafy vegetables. We're looking for blue. If it turns blue that means your urine is neutral or even basic. If it's sky blue, you should... continue to eat more dark green leafy vegetables. Now I have a low-flow toilet, so there's very little water in the bowel to start with. The effect might not be as dramatic if diluted in a larger quantity of water. For a step-by-step tutorial, see my video Testing Your Diet with Pee & Purple Cabbage.

More bathroom chemistry can be found in Pretty in Pee-nk and Asparagus Pee.

How else can we protect our muscles? We can eat healthy enough to avoid statin drugs (see Statin Muscle Toxicity) and the neurotoxins that can cause movement disorders (Muscle Tremors & Diet).

Cherries may also help lower uric acid levels: Gout Treatment with a Cherry on Top.

Superfood Bargains is the video in which purple cabbage takes the gold, though it was unseated in Biggest Nutrition Bang for Your Buck.

Why do I always go on and on about dark green leafy vegetables? Check out my 58 videos on greens and find out! : )

-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 and More Than an Apple a Day.

Image Credit: your neighborhood librarian / Flickr

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Does Animal Protein Cause Osteoporosis?

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For most of the last century, a prevailing theory within the field of nutrition was that by eating acid-forming foods such as meat, we were, in essence, at risk of peeing our bones down the toilet. And no wonder! Experiments dating back to 1920 showed over and over that if we add meat to our diet we get a big spike in the amount of calcium being lost in the urine.

And this made total sense. We had known since 1912 that meat was acid-forming within the body, and how do we buffer acid? What are in antacid (anti-acid) pills like Tums? Calcium compounds.

Meat and eggs have a lot of sulphur-containing amino acids (two to five times more than grains and beans) that are metabolized into sulphuric acid, which the body buffers with calcium compounds. And where is calcium stored in the body? The skeleton. So the thinking was that every time we ate a steak, our body would pull calcium from our bones, bit by bit, and over time this could lead to osteoporosis. Based on 26 such studies, for every 40 grams of protein we add to our daily diet, we pee out an extra 50 mg of calcium. We only have about two pounds of calcium in our skeleton, so the loss of 50 grams a day would mean losing close to 2% of our bone calcium every year. By the end of the 20th century, there was little doubt that acid-forming diets would dissolve our bones away.

But if we actually look at the studies done on protein intake and bone health, that's not what we find. So, where's the flaw in the logic? Meat leads to acid, which leads to calcium loss, which leads to bone loss, right?

Well, it's uncontroversial that protein results in greater calcium excretion, but we've just been assuming it's coming from the bone--where else could the extra calcium dumped in our urine be coming from but our bones?

One study appeared to solve the mystery. An intrepid group of researchers tried feeding a group of volunteers radioactive calcium and then put them on a high protein diet. What happens when we put people on a high protein diet? The amount of calcium in their urine shoots up, and indeed that's just what happened. But here's the big question, was that extra calcium in their urine radioactive or not? To everyone's surprise, it was radioactive. This meant that the excess calcium in their urine was coming from their diet, not from their bones.

What seemed to be happening is that the excess protein consumption boosted calcium absorption, from down around 19% up to 26%. All of a sudden there was all this extra calcium in the blood, so presumably the kidneys are like "whoa, what are we going to do with it all?" So they dump it into the urine. 90% of the extra calcium in the urine after eating a steak doesn't appear to be coming from our bones but from our diet. We're not sure why protein boosts calcium absorption. Maybe protein increases the solubility of calcium by stimulating stomach acid production? Whatever the reason, there was indeed more calcium lost, but also more calcium gained such that in the end, most of that extra calcium is accounted for. In effect, more calcium is lost in the urine stream, but it may be compensated by less loss of calcium through the fecal stream.

This was repeated with even more extreme diets--an acid-forming five-burgers-a-day-worth-of-animal protein diet that limited fruits and vegetables versus an alkaline diet emphasizing fruits and vegetables. More calcium in the urine on burgers, but significantly greater calcium absorption, such that at the end it was pretty much a wash.

Other studies have also since supported this interpretation. Here's an ingenious one: Feed people a high animal protein diet but add in an alkali salt to neutralize the acid. The old thinking would predict that there would be no calcium loss since there is no excess acid to buffer, but no, even though the acid load was neutralized, there was still the excess urinary calcium, consistent with the radioactive isotope study, challenging the "long-standing dogma that animal protein consumption results in a mild acidosis promoting the increased excretion of calcium."

So if our body isn't buffering the acid formed from our diet with our bones, how is it neutralizing the acid? Maybe with our muscles. Alkaline diets may protect our muscle mass! I cover that in my video Testing Your Diet with Pee and Purple Cabbage.

Now the boost in calcium absorption can only compensate if we're taking enough in. For example, dietary acid load may be associated with lower bone mineral density in those getting under 800mg a day. Plant Protein is Preferable to animal protein for a variety of reasons (tends to have less methionine, is less IGF-1 promoting, etc.), but it's not clear how much of an advantage it has when it comes to bone health.

I previously touched on this topic in my video Is Protein Bad to the Bone? But I promised I'd take a deeper dive, hence my video Alkaline Diets, Meat & Calcium Loss.

-Michael Greger, M.D.

Note to chemistry geeks: Yes, I know it's the calcium salt anions that actually do the buffering (carbonate in Tums and phosphate in bones), but I'm trying my best to simplify for a largely lay audience. I'll make it up to you with some kitchen chemistry (actually bathroom chemistry!) in my Testing Your Diet video.

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 and More Than an Apple a Day.

Image Credit: PD Art / Wikimedia Commons

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