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Sunday, February 13, 2011

Does protein leach calcium from the bones? Yes, but only if it is plant protein

The idea that protein leaches calcium from the bones has been around for a while. It is related to the notion that protein, especially from animal foods, increases blood acidity. The body then uses its main reservoir of calcium, the bones, to reduce blood acidity. Chris Masterjohn does not agree with this idea. This post generally supports Chris’s view, and adds a twist to it, related to plant protein consumption.

The “eat-meat-lose-bone” idea has apparently become popular due to the position taken by Loren Cordain on the topic. Dr. Cordain has also made several important and invaluable contributions to our understanding of the diets of our Paleolithic ancestors. He has argued in his book, The Paleo Diet, and elsewhere (see, e.g., here) that to counter the acid load of protein one should eat fruits and vegetables. The latter are believed to have an alkaline load.

If the idea that protein leaches calcium from the bones is correct, one would expect to see a negative association between protein consumption and bone mineral density (BMD). This negative association should be particularly strong in people aged 50 and older, who are more vulnerable to BMD losses.

As it turns out, this idea appears to be correct only for plant protein. Animal protein seems to be associated with an increase in BMD, at least according to a study by Promislow et al. (2002). The study shows that there is a positive multivariate association between animal protein consumption and BMD; an association that becomes negative when plant protein consumption is considered.

The study focused on 572 women and 388 men aged 55–92 years living in Rancho Bernardo, California. Food frequency questionnaires were administered in the 1988–1992 period, and BMD was measured 4 years later. The bar chart below shows the approximate increases in BMD (in g/cm^2) for each 15 g/d increment in protein intake.


The authors reported increments in BMD for different increments of protein (15 and 5 g/d), so the results above are adjusted somewhat from the original values reported in the article. Keeping that in mind, the increment in BMD for men due to animal protein was not statistically significant (P=0.20). That is the smallest bar on the left.

Does protein leach calcium from the bones? Based on this study, the reasonable answers to this question are yes for plant protein, and no for animal protein. For animal protein, it seems to be quite the opposite.

Even more interesting, calcium intake did not seem to be much of a factor. BMD gains due to animal protein seemed to converge to similar values whether calcium intake was high, medium or low. The convergence occurred as animal protein intake increased, and the point of convergence was between 85-90 g/d of animal protein intake.

And high calcium intakes did not seem to protect those whose plant protein consumption was high.

The authors do not discuss specific foods, but one can guess the main plant protein that those folks likely consumed. It was likely gluten from wheat products.

Are the associations above due to: (a) the folks eating animal protein consuming more fruits and vegetables than the folks eating plant protein; or (b) something inherent to animal foods that stimulates an increase in the absorption of dietary calcium, even in small amounts?

This question cannot be answered based on this study; it should have controlled for fruit and vegetable consumption for that.

But if I were to bet, I would bet on (b).

Reference

Promislow, J.H.E., Goodman-Gruen, D., Slymen, D.J., & Barrett-Connor, E. (2002). Protein consumption and bone mineral density in the elderly. American Journal of Epidemiology, 155(7), 636–644.

59 comments:

Joe said...

Hi Ned, the reason for animal protein's affect on bone may be due to it's effect on the Sex Hormone Binding Globulin (SHBG) and the free androgen index.

Protein has been shown to lower SHBG and so increase the amount of free testosterone which has an anabolic affect on bone.

This study shows examines the relationship
"In contrast, serum SHBG level was significantly higher (+42.2%), whereas free androgen index was lower (-24.8%) in patients with primary or secondary osteoporosis."
http://cat.inist.fr/?aModele=afficheN&cpsidt=1137619


So it has a positive effect on bone despite it's acidity which causes bicarbonaturia.

This doesn't mean we shouldn't be concerned about acidosis as it is bad for thyroid levels, stimulates cortisol secretion, causes panic attacks and has been linked to many diseases.

Stargazey said...

Thanks for this, Ned. The idea that bone is sacrificed to maintain blood pH goes against everything I've learned. Why should the body use up bone when carbon dioxide is freely available to use as a buffer?

It amazes me that even the Heart Scan Blog promotes this idea. At first Dr. Davis was saying that the blood pH was changed by eating meat (hello sudden death) but at least he has now changed that to saying it's the urinary pH.

Nigel Kinbrum said...

"...something inherent to animal foods that stimulates an increase in the absorption of dietary calcium, even in small amounts?"
In addition to what Joe said, there's also Vitamin D3 & K2 in animal produce. D3 increases Ca absorption & K2 directs Ca towards bones.

David said...

Ned take a look at the abstract for "Acid diet (high-meat protein) effects on calcium metabolism and bone health" in Current Opinion in Clinical Nutrition & Metabolic Care:
November 2010 - Volume 13 - Issue 6 - p 698–702

Doug said...

Hi

I don't have the study in front of me but have it at home, but it was an isotope study lasting 10 days since these are hugely expensive. The subjects were given all food, beverage and even distilled water to drink to account for all sources of calcium and minerals as much as possible. This study found that the increase in urinary calcium from higher protein diets was because there was an increase in intestinal absorption of calcium and the calcium was traced back to intake not from the bone turnover (per isotopes kinetics)...

aryaman said...

This blog is applied reductionism and the fact of the author's liking for meat...science thereby gets blurred.

Jeanne said...

God, I wish I could remember half the stuff I read well enough for it to be a help. But a while back I was looking up this issue, and apparently, there is an amino acid that also acts like a buffer in the body. Gluta-... something or other. I can't remember! *weeps* But it's an amino acid that is available in much greater amounts in meat than in plant protein.

I remember reading about it and thinking "Whoa! So everything I've read from the vegetarian camp about animal protein is B.S.!"

Oh Lord, you're quoting research based on questionnaires. Not the most reliable way to gather dietary information. (I've done a few online surveys in my time.) This study is a good starting point for further research, but I wouldn't take it as final word. No matter how much I want to. Hahaha.

Jeanne said...

OK I just tried searching on this, and maybe it's glutamine. Here's the entry about it on Wikipedia.

http://en.wikipedia.org/wiki/Glutamine

Wow, that would explain why cat urine has so much ammonia in it. They are obligate carnivores.

Wikipedia says there are plant sources of this amino acid. I don't know how they compare to animal sources but I would guess there's less present, since plant foods are generally lower in protein in the first place.

Here's another source, not real great, but a decent starting point:

http://www.healthvitaminsguide.com/aminoacids/glutamine-and-glutamic-acid.htm

But the fun part is, your body *makes* glutamine. It's not an essential amino acid unless your body is under certain types of stress. So it would seem to me that we don't need to do as much as we think we need to do to maintain proper acid/alkaline balance in the body. The body's already got that all sorted out; a/a balance is just another excuse, as far as I'm concerned, to tell people not to eat meat. Who needs to listen to that sort of nonsense? Not me.

Alex said...

Back when I was predominantly vegetarian, I would overeat, partly due to excess carbs making me voraciously hungry a couple hours later and partly from just not feeling nourished. I can eat loads of protein from soy and beans and never feel the deep satiety I get from meat, which makes me believe that vegetable proteins aren't as well assimilated or somehow don't nourish the body as well. As I understand it, there's a strong correlation between inadequate dietary protein and bone loss, and my guess is that "plant protein leaches calcium from the bones" is really a function of protein deficiency due to plant protein being poorly assimilated. But, again, this is just a guess.

Anonymous said...

gluten? I was thinking soy...

Rev. Doc Lowrey said...

I certainly agree that this is weak research for lack of controls, self-reporting and small sample size.

It may be true that the author had a pro-meat bias (think cold-fusion).

Our knowledge is constantly evolving, but one point seems to still be true - that protein molecules are generally too large to pass through the intestine and certainly too large to enter a cell where they presumably would do the damage under consideration.

Protein must be broken down into it's amino acid components and then re-assembled in the cell to again make the protein needed by that cell.

It seems to me that excess protein that makes it into the interstitial fluids would have little impact on bone degradation.

More likely it is a lack of calcium in small enough particle size from the diet (which generally is only assured from a plant source) that causes the body to rob the bones of calcium.

As over 70% of body metabolic processes require calcium, there is an unending demand for this mineral by all cells and it must come from somewhere.

The statement defining this article seems illogical to me. There are many other factors that may be considered especially considering the myriad chemicals and acids in meat that are not mentioned as considerations in this study. (a fault of most studies is what they leave out of their research)

Regarding not feeling full or getting hungry too soon after a non-meat meal - I believe that the complexity of meat (it's our most difficult to digest non-mineral food) keeps it in the system longer and promotes a feeling of fullness. Also, less of the meat is actually digested (unless you run it through the blender before eating) and so there is more solid matter in the gut, promoting a feeling of fullness. (also warmth and energy)

A good question might be if it is good to feel "full" at all. It is reported that feeling less than "full" is dramatically beneficial.

It also helps your pants fit better.

The source of your minerals especially, since your body can not break the ionic bonds to make usable size particles is a serious issue that most health product manufacturers pay little to no attention to, making most supplements worthless and in some cases very dangerous.

Dr. Lowrey

David Isaak said...

Interesting, but raises a huge number of questions and answers none.

It's obvious to me that we need better resolution on the "plant" side of these observations. Is it mostly wheat? Is it, as Anon suggests, soy? (I rather doubt it, actually. I lived in Rancho Bernardo for several years, and still own a house there, and "alternative" foods aren't exactly popular or easy to find there.)

But I think that where we really need some increased fidelity is on "animal protein. It's curious to me that people seem to leap from "animal protein" immediately to "meat." In an elderly population, I think that a largish fraction of animal protein is quite likely dairy and eggs.

I don't know all that many 80-year-olds who still have a voracious appetite for steak. And many elderly people I know make a point of keeping up their intake of dairy precisely for the calcium.

I doubt that calcium per se is that useful, but the vitamin K2 in cheeses is a bone-builder, and Rancho Bernardo is one of the sunniest places I've ever lived, so Vitamin D levels are probably above the norm.

Is the meat? I doubt it. But, as you note, we need far more resolution within the "plant" category, and I think the "animal" category might show very different results if meat and dairy were distinguished. In fact, I think "plant proteins" and "animal proteins" are rather silly categories in the first place.

Anonymous said...

When you consider food chain it makes sense that we eat plant eating animals. Animals eat the plants that contain nutrients, minerals ect. and then we get it from them when we eat the animal. Seems a logical path since you don't see lions munching on wheat and soy when the antalope aren't around.

Paul Jaminet said...

Hi Ned,

It seems more likely that animal proteins are innocuous, and plant proteins are toxic.

Especially if the plant proteins in question are gluten! There are many mechanisms by which wheat proteins can interfere with bone density ... not least by their interference with vitamin D.

Best, Paul

Ned Kock said...

Hi everybody. I posted this from the airport in Brussels, before starting a 17-h trip back to Texas. So I am still a bit dazed by the trip.

The comments above are great! I welcome views pro and con anything I write here.

Of course any study has weaknesses, and we always need more research to clarify certain issues. Using food questionnaires is a bit of problem. There are some stats that can be used to reassure readers (e.g., use of multiple redundant questions, combined with factor analysis). I don’t think the authors used these.

Having said that, one interesting thing about this study is that it has quite a lot of citations to it. Many are from studies that employed completely different methods, and still reached fairly consistent conclusions.

The reduced link below is for a Google Scholar search, showing several of the citations:

http://bit.ly/dKdmFa

This type of citation pattern is one of my criteria for choosing a study as a basis for a blog post.

No citation bias here. At least I try not to be biased!

Anne said...

Really interesting post for me Nick as, among other things, I have osteoporosis (I'm in my mid 50's). I eat a Paleo diet with a high animal protein intake and I have sometimes worried about the effect of this on calcium and bone mineral density. I have blood tests every few months and my urea level always comes back marked high by the lab and this is due to my high protein diet. My doc isn't concerned because my creatinine levels are normal, but I've sometimes wondered. I take heart from your post.

Jack C said...

Ned

In my opinion it is the fat soluble vitamins A, D and K2 that are the cause of the increased bone density associated with increased intake of animal protein. Generally, intake of animals fats is proportional to the intake of animal protein and the intake of fat soluble vitamins. (Example found in data from pubmed 19124480)

It is not a matter of increased absorption of calcium, but a matter of increased synthesis osteocalcin, which requires vitamins A and D, and the activation of osteocalcin by vitamin K2. Activation of osteocalcin is required to put calcium where it belongs in teeth and bones and prevent it from accumulating in soft tissues where it does not belong.

Note that osteoporosis is associated with increased calcification of arteries.

It is not surprising that calcium intake made little difference as calcium deficiency is not widespread. Deficiency of vitamin K2, however, is common, and the amount of K2 required to maintain a given level of activated osteocalcin increases with age.(PMID 16469998)

Jack C said...

I must add that while intake of fat and associated fat soluble vitamins is generally proportional to protein intake, that is not always the case. Popular high protein, low fat diets such as the 'new' Atkins diet and the South Beach diet may cause vitamin A deficiency due to reduced fat intake (and therefore reduced vitamin A intake) and increased utilization of vitamin A in the digestion of protein. Lack of vitamin A resulting from a diet high in animal protein and low in fat can therefore cause vitamin A deficiency which results in osteoporosis due to reduced osteocalcin synthesis.

In the western world the primary source of the vitamin K2 that is needed for activation of osteocalcin, and thus prevention of osteoporosis and calcification of arteries, is dairy (about 75%), mostly from fermented cheese. Those who think that it is "unpaleo" to eat dairy are missing out on a good source of vitamin K2.

Ned Kock said...

Hi Joe. Thanks for the link. It is an interesting theory, but we need to keep in mind that the highest gain in BMD was in women.

Ned Kock said...

Hi Stargazey. My understanding is that protein in general leads to an acid load, which is reflected in a slight increase in blood acidity. That increase triggers the body’s homeostatic response via the kidneys. So Dr. Davis may not have been too far off track.

Protein from animal foods seems to have “something” that increases bone absorption. Good candidates for this “something” are the fat-soluble vitamins, but we need more research to be sure.

Fat soluble vitamins are present in plant foods as well, but they need dietary fat to be absorbed. In fact, vitamin E is abundant in seeds but hard to find elsewhere, including meat.

Ned Kock said...

Hi Nigel. Those vitamins (D and K2) are hard to find in food (with exceptions, like aged raw milk cheese for K2), so we are left with the possible explanation that the fat in animal foods helps absorb them. This makes sense, but the underlying idea would be that the animal fat is the key.

Another idea that may support your point strongly is that animal fat stores more fat-soluble vitamins than the nutrient data sources (e.g., Nutritiondata.com) lead us to believe. This needs more research, but makes sense, since animals are supposed to store those vitamins in their body fat. What may end up happening is that the fat isolation process needed to identify nutrients ends up destroying a proportion of them.

Ned Kock said...

Hi David and Doug. That finding seems to support what I said on the post: an increase in acidity, but better absorption more than compensating for the greater acid load.

Ned Kock said...

Hi Jeanne. Glutamine it indeed special; it is also the most abundant amino acid in muscle:

http://bit.ly/92mkxX

It is quite possible that glutamine has something to do with the findings discussed in the post.

The main dietary sources of glutamine are by far animal foods in general – not only meat, but eggs and dairy as well.

So even if it is nonessential, its levels are likely to be more elevated in those who consume animal products.

Ned Kock said...

Hi Alex. Poor absorption may be the reason, but we would have to assume that the poor absorption extends to calcium as well. It is quite possible, as glutamine (mentioned by Jeanne) seems to promote proper gut integrity.

Ned Kock said...

Hi Rev. Actually there is a lot of research suggesting that protein in general has an acid load on the body. What this study and others (including the isotope study mentioned by David and Doug) suggest is that animal foods somehow lead to increased absorption of calcium.

Ned Kock said...

Hi Anon(1) and David. I am assuming the main plant protein may be wheat because wheat products are much more widely available than soy products, and much cheaper.

Ned Kock said...

Hi Anon(2). That line of reasoning makes a lot of sense. And has the advantage of being simple, which is one of the reasons I like it.

Ned Kock said...

Hi Anne. Thanks for stopping by and sharing. Always good to talk with your doctor, and discuss what you see here and elsewhere. These types of population-based findings are a good starting point for dietary decisions, but everybody’s body is different – not even identical twins have the same exact body responses to dietary nutrients.

Ned Kock said...

Hi Jack. Osteocalcin indeed is an interesting protein. It also stimulates the secretion of insulin, which some like to demonize even though it seems to play a role in BMD maintenance/increase. Even more interesting, osteocalcin stimulates the secretion of adiponectin, which in turn increases insulin sensitivity, leading to a cascade of effects.

Ned Kock said...

Hi Paul. Thanks for stopping by and for your comment.

Indeed, the findings here may very well be explained by a neutral effect of animal protein and a negative effect of plant protein, particularly gluten. Plant proteins are also implicated in colorectal cancer, being associated with increases in it (on a multivariate basis). Animal proteins seem to be protective:

http://bit.ly/bKkv0C

Having said that, the analysis summarized in this post goes somewhat against the idea that animal protein is neutral. The reason is that the analysis included animal and plant protein as competing independent variables, so the positive effect of animal protein is after controlling for any correlation between it and plant protein.

In other words, the positive effect of animal protein that is reported exists regardless of plant protein intake. A univariate analysis would have led to a much stronger (but possibly illusory) effect of animal protein.

Ned Kock said...

Let me also mention one possibility that I don’t think has been brought directly by any comment above. It is possible that a high animal protein intake is associated with more non-exercise physical activity (and maybe even more voluntary exercise). The reason is that in most people excess protein is oxidized, with minimal amounts stored as fat, leading to an increase in activity (and also, incidentally, in NEAT):

http://bit.ly/9Fjn0p

Since animal protein is generally of better quality than plant protein, it would lead to a greater amino acid release on a gram-adjusted basis. The resultiing higher levels of activity may account for the increase in BMD, as a compensatory adaptation by the body.

David Isaak said...

Jack C said: "In the western world the primary source of the vitamin K2 that is needed for activation of osteocalcin, and thus prevention of osteoporosis and calcification of arteries, is dairy (about 75%), mostly from fermented cheese."

Exactly. Which is why I have problems with adding together dairy and meat under the heading "animal protein." I think it may obscure a much stronger effect of high dairy intake.

Daniel said...

This has become very intense! How many comments are there here??? I only googled protein and all I have found so far is really intense articles.

Stargazey said...

Here's the reference, Ned: Homegrown osteoporosis prevention and reversal

Animal products are acidic, vegetables and fruits are alkaline. Put them together and you should obtain a slightly net alkaline body pH that preserves bone health. Throw grains like wheat, carbonated soft drinks, or other acids into the mix and you shift the pH balance towards net acid. This powerfully erodes bone.

A pH below 7.0 (net acid) is incompatible with human life.

Ned Kock said...

Hi Stargazey.

Yes, I was thinking more in terms of variations in the 7.35-7.45 range triggering the responses.

Indeed, the "alkalinizing diet" advice is completely incompatible with the data summarized in this post.

I wouldn't go for the advice on supplements either. The one on "strength training" is a good one, for both men and women.

Ned Kock said...

Dr. Davis’s comments on calcium are fairly compatible with this post.

Ned Kock said...

David, here is my take regarding dairy in this study. In the study summarized in this post, calcium intake can be seen as an (imperfect) surrogate measure for dairy intake, simply because dairy is likely to have been a major source of calcium. This would be true even if the participants were taking calcium supplements, as long as they were taking the supplements more or less uniformly (a confounder).

In this sense, the conclusion that calcium intake didn’t matter can be seen as partially supporting the conclusion that dairy intake didn’t matter. Note that this is not the same as saying that dairy is not as good a contributor of animal protein as meat is.

In other words, dairy’s contribution to the BMD effect that we observed may have been accounted for, even if not fully, by the variable animal protein. But the protein could have also come from meat. Both meat and dairy usually come with animal fat, unless the meat and/or dairy are particularly low fat (another possible confounder). That again shifts the importance to animal fat.

But I do agree that it would be good to have different types of animal foods entered into the analysis separately. If the above were true, a simple test of redundancy would tell us whether two or more variables should be grouped.

Jack C said...

Ned,

In your response to David you stated that the fact that calcium intake can be seen as an imperfect surrogate for calcium intake partially supports the conclusion that dairy intake doesn't matter (with respect to bone density).

While this is true, your conclusion is greatly weakened by the fact that 25(OH)D status appears to be the dominant predictor ob BMD relative to calcium intake. Among men and women, BMD increases with higher vitamin D status through almost the entire natural range of serum vitamin D, whereas calcium influences BMD only in those with very low calcium intake (lowest quartile: men and women) or women with low vitamin D status (less than 20 ng/ml.) (PMID 19113911)Calcium intake therefore effects BMD for a much smaller percentage of the population than does vitamin D status. Dairy fat therefore may play a larger role in BMD than your premise suggests.

The adverse effect of some plant proteins on vitamin D that was pointed out by Paul seems likely to be the reason for the reduction of BMD caused by plant protein.

Ned Kock said...

Good point Jack, but then we get to my response to Paul, which refers to animal and plant protein being independent variables in the multivariate analysis. The coefficients are calculated controlling for each other’s effects, as well as the effects of any other variables added to the model as independent variables.

David Isaak said...

I just think "animal" and "plant" are kind of silly categories.

They seem almost medieval, and the only reason I think peope are obsessed with them isn't because they have a great deal of scientific merit.

For example, say "plant fats" and many people will think "corn oil, canola oil, safflower oil." But what about cocounut oil, palm oil...?

I can easily imagine someone studying the effect of plant fats on some health marker. But I ihave no idea what it would be telling me without higher resolution.

Ned Kock said...

I agree David. My approach is usually to take as much as I can from flawed studies, and triangulate that with what I get from other studies, hopefully forming a big picture that is less flawed.

Nearly all studies have some flaws, including the ones that I do myself.

Of course I also enjoy the debate with knowledgeable folks like you, and many other readers of this blog; some of whom are also awesome bloggers.

Since we are on the subject, let me raise another issue that is open to debate. It is related to the animal version plant fat issue. I believe that animal fat is generally healthier than plant fat. So getting those two categories only in a research study gives me something, not much, to work with.

One reason is the fat-soluble vitamin content of fat coming from animals, which is technically not the macronutrient fat. SFAs and MUFAs from plants are, generally speaking, not in the same league as SFAs and MUFAs from animals.

Joe said...

Hi again Ned,

"It is an interesting theory, but we need to keep in mind that the highest gain in BMD was in women."

Low estrogen is also associated with osteoporosis. Circulating SHBG influences the bioavailability of estrogen too, protein lowers SHBG providing more free estrogen to have its anabolic affect on bone.

"The reason is that in most people excess protein is oxidized, with minimal amounts stored as fat, leading to an increase in activity (and also, incidentally, in NEAT):"

Also gluconeogenesis. Any excess protein in a meal will be converted by the liver into glucose in the blood with a correlating increase in insulin secretion. People on high protein diets have been shown to secrete significantly more insulin than people on other diets when insulin is measured over 24hrs

Joe said...

Sorry, scrap that last comment about protein and insulin, it doesn't seem to be consistently true

http://jap.physiology.org/content/85/3/935/F3.large.jpg

Ned Kock said...

Hi Joe. I suspect that gluconeogenesis is minimal when glycogen stores are full, because the fate of glucose in those cases will typically be oxidation or conversion to fat via de novo lipogenesis.

The latter should be less common for healthy folks eating natural foods … but anything goes when your hunger regulation is messed up by industrial junk.

When glycogen stores are depleted, the glucose from gluconeogenesis will be grabbed by the liver and/or muscle to replenish their glycogen stores. Some will be oxidized, and practically none will become fat.

Does glycogenesis involve insulin? Sure.

Healthy insulin levels found in long-lived people are not zero.

Very low insulin levels are found in type 1 diabetics, and they are not good. Otherwise type 1 diabetics would live to 150 years of age, and everybody would want to become a type 1 diabetic.

Ned Kock said...

In the comment above I was referring to gluconeogenesis based on dietary protein.

Joe said...

"Very low insulin levels are found in type 1 diabetics, and they are not good. Otherwise type 1 diabetics would live to 150 years of age, and everybody would want to become a type 1 diabetic."

Reminds me of Cynthia Kenyon's views on insulin, apologies for the daily mail.
http://www.dailymail.co.uk/health/article-1323758/Can-cutting-Carbohydrates-diet-make-live-longer.html

"When glycogen stores are depleted, the glucose from gluconeogenesis will be grabbed by the liver and/or muscle to replenish their glycogen stores. Some will be oxidized, and practically none will become fat."

This might explain why people on high protein diets secrete more insulin in response to glucose.
http://www.ncbi.nlm.nih.gov/pubmed/8923841

They do have more gloconeogenesis however
"Hepatic glucose output was significantly increased in individuals with HP intake [HP IDDM, 14.8 +/- 0.6 vs. NP IDDM, 12.7 +/- 0.7 (P < 0.01); HP control, 12.2 +/- 0.5 vs. NP control, 10.9 +/- 0.5 (P < 0.01 mumol/kg.min)."

Ned Kock said...
This comment has been removed by the author.
Jack C said...

Hi Ned,
In your post you asked "are the associations above due to --- (b) something inherent in animal foods that stimulates an increase in absorption of dietary calcium, even in small amounts?"

Vitamin K2 appears to be one such something (in rats anyway) according to a study (PMID 16261991) which found that "vitamin K (K2)supplementation promoted the reduction of urinary calcium excretion and retarded the abnormal elevation of serum PTH level in rats fed a low calcium diet, and stimulated intestinal calcium absorption in rats fed a normal calcium diet."

It seems reasonable that in humans as well, vitamin K2 and vitamin D would have an additive effect on intestinal calcium absorption in rats fed a normal calcium diet, and vitamin K2 would reduce calcium excretion in those on a calcium deficient diet.

Rats differ from humans in that they readily convert K1 to K2 whereas humans do not, so when rats grow old they suffer from only mild arterial calcification.

In my comment on Feb 15 I was somewhat inaccurate when I said that "in the western world 75% of vitamin K2 intake came from dairy" for that estimate was based on intake data from Rotterdam and Heidelberg where cheese and butter consumption is higher and meat consumption lower than in the U.S.

In the U.S., dairy sources, excluding butter which has little calcium, probably account for about 25% of animal fat intake and 50% of vitamin K2 intake.

While other constituents of animal foods may also stimulate increased calcium absorption, it seems quite likely that vitamin K2 does so and may be a major reason for the decreased bone loss observed in those with high animal protein intake.

You commented on Feb 16 in response to my post "Osteocalcin --also stimulates the secretion of adiponectin--" Indeed, it has been found that serum adiponectin levels are associated with osteolcalcin levels. A recent study )PMID 15699258) found that low plasma adiponectin levels are associated with progression of coronary artery calcification independently of other cardiovascular risk factors, a finding which is consistent with increased artery calcification that results from vitamin K2 deficiency. Another study (PMID 18593824) found a significant negative association between total adiponectin and intake of refined cereals. Since arterial calcification is associated with osteoporosis, these studies show that refined cereals result in bone loss.

Joe said...

Hi Ned, thanks for the interesting comments

"In the Linn et al. study the response to the high protein appears to have been “bad” only in the diabetic participants."

T Linn also did a study on normoglycemic people too with similar results

"Results. Glucose-stimulated insulin secretion was increased in the high protein group (516 ± 45 pmol/l vs 305 ± 32, p = 0.012) due to reduced glucose threshold of the endocrine beta cells (4.2 ± 0.5 mmol/l vs 4.9 ± 0.3, p = 0.031). Endogeneous glucose output was increased by 12 % (p = 0.009) at 40 pmol/l plasma insulin in the high protein group,"
http://www.springerlink.com/content/eqwkrc1f97gjf2et/

"In normoglycemic folks insulin will lead to protein responses, with numbers approaching those to natural carb-rich foods (http://bit.ly/grde0g)."

The trouble with this study is it only tracked insulin and blood glucose for 120 mins after eating and didn't track long term high protein diets. The more protein you eat the longer it takes to digest, larger portions will take alot longer than 120 mins to digest.

I remember reading a study of long term high protein diets showing they had consistently higher blood sugar and insulin secretion than normal protein diets although as hard as I try I can't find it again.

I very much like being on a high protein diet as I love eating it but I wonder why societies which primarily live off animal derived foods only eat around ~20% protein. The herders living on the mongolian steppes apparently do so and the Inuit living on cariboo apparently discard alot of protein or give it to their animals.

There's also an anecdote I heard from a prison warden saying that if you want a prisoner to die quickly, feed him alot of protein. These are all off the top of my head anecdotes which feed my curiosity though, I may be wrong.

Eye Creams said...
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Jack said...
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Ned Kock said...

Two (quite original) spam comments above deleted.

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M & M said...

Bones=protein=collagen I
www.mcponline.org/content/early/2011/05/23/mcp.M110.006718.abstract

no Cu and Mg :)
Biochemistry bones of which are composed

Anonymous said...

Bone mineral density can be high in the absence of sufficient calcium for healthy bones.

Ned Kock said...

Thanks for the links Joe. In the Linn et al. study the response to the high protein appears to have been “bad” only in the diabetic participants. It looks like the researchers employed a 4-group design, with 2x2 conditions. And the problem with those folks seemed to me mainly due to the insulin-to-glucagon ratio.

In normoglycemic folks protein will lead to insulin responses, with numbers approaching those to natural carb-rich foods (http://bit.ly/grde0g). Typically in those folks there will be no glucose response to protein, as the pancreas’ alpha cells secrete glucagon to counterbalance the effect of insulin (secreted by beta cells), and avoid hypoglycemia.

My general impression is that diabetes is not an insulin-only condition; it is a much more complex metabolic disorder. Its main cause may well be inflammation, leading to impaired fat metabolism and ultimately destruction of beta cells (http://bit.ly/9B3Nsr).

Anonymous said...

Dear Ned,

Whats your opinion about high protien diets leading to higher levels of uric acid in the blood-which of course would lead to furthur complications..?

viagra online said...

I have heard this idea about if it is possible that protein can leach calcium from the bones, and I wish I could remember what I read, but I can't right now :S

Alma Mott review blog said...

Now, as you age, you lose bone, and you don’t make enough bone to keep pace with what you have lost. Bones become thin with age and vulnerable to fractures. The bone deterioration process picks up pace after you cross 50 years.

You may be impacted by osteoporosis, which can be very painful. It can even deform the body and prevent you from doing your daily tasks. Even sneezing, coughing , pulling, pushing, etc., can lead to fractures.