net acid load.

[lyn64]

I'm a bit confused about the notion that a net acid load diet necessarily eventually results in buffering from bones, possibly eventually leading towards osteoporosis. I realize that both intra cellular and extracellular(blood) ph is very tightly controlled and that the concept of alkaline/acid blood fluctuations in response to various food metabolic ash residue is complete hogwash.

But given that the fine tuning of ph homeostasis does indeed require buffering from something, the whole idea of bone calcium being used as an acidity buffer seems a bit silly anyway doesn't it? I mean excess acidity is either peed out or (in the very short term) just breathed out (carbon dioxide).

Perhaps it will help the discussion if we just consider the overwhelmingly net acid load diet of traditionally living Inuit. Why are their bones so healthy with such an net acidifying diet? I know Cordain (et al) did try to argue otherwise , but apparently his research methods were a bit shonky.

Lyn

[Gabriel Guzman]

The link between osteoporosis and 'excess' protein in the diet has been tried for years to the point that some people already take is as a cause and effect situation.

Yes, protein increases the net acid load and it gets buffered by bones leaching calcium. That part is true and holds. What doesn't hold is that it necessarily leads to osteoporosis. The problem arises when there is not enough calcium coming in the diet. If that happens, then there is no way to balance the calcium used to buffer the acid load. Fortunately for us, when calcium levels are low, a signal is triggered that increases calcium absorption in the intestine.

There may be a misconception with respect to the amount of calcium in the Inuit diet. Although it is tempting to think that since the access to vegetables is very limited then the Inuit necessarily have an overwhelming net acid load due to the high intake of protein, without anything to buffer it, a closer look at their typical foods tells a different story. Inuit consume fish but not only the meaty part. In fact, fish head, skin and bones are also consume and those are rich sources of calcium in their diet. Their intake of protein, contrary to what's commonly assume, although higher than the USDA recommended intake, is also high in fat (both saturated and insaturated), so it is a misconception to think that Inuit consume excessive amounts of protein alone. With respect to access to vegetables, there is access to them, not the kind of vegetables one has in mind when one thinks of food. Although not a large portion of their diet, in the tundra there are small , bright purple flowers that are ate when bloomed.

Back to calcium consumption, however, it is interesting to note that Inuit may not be the right population to compare to, in terms of calcium intake. A study published in the Canadian Medical Association Journal in 2003 compared Inuit children with white children. Inuit children from the North of Canada have an average calcium intake of ~20 mg/day, which is consider far too low compared to the guidelines for North American children (~800 mg/day). At a glance, this would present a paradox. That comparison between Inuit and white children, however, showed a preponderance of a certain Vitamin D receptor genotype among Inuit children and the comparison also suggested a more efficient calcium absorption by Inuit children. There are reports that show that when Inuit adopt a more southern-like diet with access to calcium-fortified foods (milk, cheese, orange juice, bread, etc.), they become susceptible to nephrolithiasis or nephrocalcinosis, supporting the hypothesis of a genetic adaptation to lower calcium intake. If somebody decides that Inuit children consume too little calcium and subject them to 'standard intakes', or introduces foods with more calcium than what they really need and are genetically adapted to, they'd be doing them more harm than benefit.

The take home message is that calcium intake is relative to a population and is difficult to compare if a population has adapted to a lower consumption. Not too long ago, I read a Letter to the Editor, sent by a Canadian researcher to the American Journal of Clinical Nutrition criticizing another author because he proposed that calcium intakes were far too high, are sometimes hard to ensure and haven't showed a decrease in bone fracture. The Canadian research defended the standard guidelines for Calcium intake by writing that the references used by the other researcher were not valid and used the following arguments:

Hegsted’s statement that recommended calcium intakes are
now so high that it is difficult, if not impossible, to devise practical diets that meet these recommendations is also puzzling. How about the Food Guide Pyramid or Canada’s Food Guide? Three daily servings of milk products—for example, an 236-mL (8-oz) glass of skim milk with breakfast, lunch, and dinner— with a balanced diet yields ~1200 mg Ca. (My italics)

The fact that long-standing recommendations to increase calcium intakes appear to have had little or no effect on the prevalence of osteoporosis or fractures in the United States in no way proves that the recommendations are invalid, anymore than increasing levels of obesity in the United States prove that the long-standing recommendations to reduce fat intake are invalid.

Hardly a sound argument if the basis of comparison is the long-standing recommendations to reduce fat intake to prevent obesity.

For us, who have access to vegetables, the problem is not how much protein are we eating, thinking that there is a huge acid net load. The problem is how much grains are we eating, which are more acidic and provide more net acid load than proteins. When the diet provide plenty of green vegetables (which produce a net alkaline load), the buffer capacity is enhanced and doesn't depend on calcium leaching only, which happens all the time anyway. The key factore are, then, enough green vegetables (for a net alkaline load), enough protein, which is also needed for bone formation (not just calcium as the media makes it look like), and enough calcium from the diet to balance the calcium that will be leached out from the bones.

[lyn64]

Really interesting. Thanks for such a detailed reply Gabriel. I was wondering if you could clarify the 'buffering' bit... a bit?



Protein increases the net acid load and it gets buffered by bones leaching calcium. That part is true and holds.

But why does 'net acid load' have to be 'buffered' by anything, let alone adequate dietary calcium? Don't the lungs and the kidneys just excrete excess acid. This whole 'buffering' concept seems to ignore how powerful these two organs are at getting rid of excess acidity. Without them, I can well understand how the body would have to 'buffer' this low pH. But aren't lungs and kidneys expressly designed to be able to cope with far more excess acidity than even a pure muscle meat dietary intake would produce? So well designed in fact, that the kidneys even reabsorb bicarbonate to ensure maximum efficiency at just getting rid of excess acid. Saying that, I realize that getting enough potassium as well as sodium is essential for this acid excretory function of lungs and kidneys to work properly without creating long term problems for the kidneys.

Lyn

[Gabriel Guzman]

Really interesting. Thanks for such a detailed reply Gabriel. I was wondering if you could clarify the 'buffering' bit... a bit?

...why does 'net acid load' have to be 'buffered' by anything, let alone adequate dietary calcium?

Actually, why not? This is one example of how important redundant systems are for the survival of a spieces. Mammals have a number of redundant systems that are triggered seemingly to accomplish the same thing, but it is the existence of such redundancy that guarantees successful adaptation and function.


Don't the lungs and the kidneys just excrete excess acid. This whole 'buffering' concept seems to ignore how powerful these two organs are at getting rid of excess acidity. Without them, I can well understand how the body would have to 'buffer' this low pH. But aren't lungs and kidneys expressly designed to be able to cope with far more excess acidity than even a pure muscle meat dietary intake would produce? So well designed in fact, that the kidneys even reabsorb bicarbonate to ensure maximum efficiency at just getting rid of excess acid. Saying that, I realize that getting enough potassium as well as sodium is essential for this acid excretory function of lungs and kidneys to work properly without creating long term problems for the kidneys.

Lyn

Yes, the lungs and kidneys are also designed to deal with excess acid. In fact, because we are open systems, when there is an increase in acidity resulting from metabolic processes that constantly generate CO2, the release of CO2 is what maintains the acidity constant (pH). However, there is also other buffer systems called nonbicarbonate buffers, which are predominantly intracellular and make up about one thirds of the total buffer capacity of the blood; the bicarbonate buffer, which is the one you described, accounts for the other two thirds. Without the kidneys, the lungs couldn't cope with the bicarbonate concentration, which changes primarily due to increaes in carbonic acid concentration, so renal excretion of hydrogen ions is necessary.

Contrary to the open system buffers (lungs and kidneys), noncarbonic buffers opperate as closed systems (predominantly intracellular). Hemoblobin, for example, is one of those noncarbonic buffers in the blood.

Perhaps to understand the two buffering systems (carbonc and noncarbonic), it's easy to think that


A primary change in CO2 is a respiratory disturbance in the acid-base balance
A primary change in bicarbonate is a nonrespiratory or metabolic disturbance of the acid-base balance.


Metabolic disturbances can be either acidic (metabolic acidosis) or alkaline (metabolic alkalosis). Renal failure to excrete the normal acid load, ingestion of acid, excess endogenous production of acid as seen in diabetes and true starvation (ketoacidosis), anaerobic prodcution of lactic acid (incomplete oxidation of carbohdyrate), all those induce metabolic acidosis (pH is low, and there is low concentration of bicarbonate). Metabolic alkalosis, on the other hand, may rise from inake of alkaline substances, loss of hydrogen ions from vomiting or from increase renal excretion of hydrogen in potassium deficiency. In this type of imbalance respiratory compensation is limited.

So, when we talk about buffering systems, especially those that deal with metabolic activity, rather than just respiratory disturbances, we need more than lungs and kidneys to keep an appropriate buffering capacity in the blood and a constant pH.

What does all that have to do with calcium anyway? Well, when we eat and diggest food, they ultimately must report to the kidney as either acid or base. When the diet yields a net acid load, the acid must be buffered by the alkaline stores of base in the body. Here is where Calcium enters the picture. Calcium salts in the bones represent the largest store of alkaline base in the body and amay be depleted and eliminated in the urine when the diet produces a net acid load. I say may be depleted because it doesn't necessarily follow that a net acid load depletes calcium stores (the bone) if enough calcium is provided by the diet and absorbed in the intestine.

Because protein metabolism increases the net acid load, diets that are higher in protein are immediately branded as 'calcium leaching' diets and therefore increase the risk of osteoporosis. Bone health depends more on acid-base balance than the actual amount of calcium one takes. An to keep a good balance between the calcium we lose and the calcium we retain, besides making sure we have an adequate dietary intake, we need to make sure that our acid-base balance leans on the net basic load instead of net acid load. The only instance in which a diet higher in protein can actually induce a net acid lad all the time, therefore making it unhealthy, is when there is also a restriction in green vegetables and fruits, which are all good producers of base load. When the diet is also balanced from that point of view, calcium is not lost and used for neutralization of acid load.

On a side note, here is a list of the highest acid-producing foods (in that order):


hard cheeses
cereal grains
salted foods
meats
legumes

[lyn64]

... when we eat and diggest food, they ultimately must report to the kidney as either acid or base. When the diet yields a net acid load, the acid must be buffered by the alkaline stores of base in the body.

This is what I can't understand. Given that when food is eaten and digested it must report to the kidney as acid or base, if it is base as in say protein digestion, can't the kidneys just excrete the excess acid (with the help of potassium) without any need for 'buffering'? Buffering would surely only be necessary if the excess acidity had to be dealt with 'within' the body, rather than just merely peed out. In other words, buffering seems to be only necessary if we are a closed system. But we're not, urine pH can vary enormously in a healthy individual and be highly acid in the context of , say, a high muscle protein, only moderate calcium intake long term diet.

Perhaps I'm just not understanding what 'buffering' actually means. Correct me if I'm wrong but I was under the impression that an acid becomes less acidic the more alkali it is mixed with, i.e. the acid is 'buffered' by the alkali.


The kidneys work by sensing lowered pH in the blood delivered by the portal vein, reabsorb whatever bicarbonate is available, extract the acid, and fill your bladder with this excess acid. What's 'buffering' got to do with any of this? I can understand that if the kidneys just had to adjust blood pH to its very narrow 'normal' range and recirculate it without 'losing' the excess (i.e. losing it from the body altogether- in urine), the excess acidity would obviously need to be 'buffered' by on board alkali (perhaps bone or dietary calcium salts)

But humans pee several times a day and it's always more or less acid. This is a 'net' acid loss from the body. So can't this net acid loss account for any 'net acid load' produced by diet?

Sorry I'm being so dense about this. Many thanks for your patience:) .

Lyn.

[Gabriel Guzman]

Buffering is required all the time precisely to avoid excess but when there is, then there are ways to get rid of it. So, is not so much that the kidneys work only when is needed but all the time.

As to why they work that way? That may be more a philosophical question than a physiological one... I'm used to think of redundant systems as ways evolution made sure we can cope and adapt, though that answer may not satisfactory either.

Buffering means exactly what you said... another word is 'neutralization', which means counteract acidic ions with alkaline ones (crude explanation but perhaps effective). There are ions being produced all the time, both acidic and alkaline and any disturbances must be kept in check.

Acidic ions are added to the system all the time, for example from metabolism (hydorchloric acid, lactic acid, keto acids, sulfuric acids, etc.), or they can be removed fro mthe blood by excretion of hydrogen ions by the kidney. Basic or alkaline ions can also be added to the system, for example from metabolism of vegetables, which produce salts of weak acids. For respiratory buffers, the concentration of CO2 can be changed, for example by a change in CO2 production in metabolism, or in CO2 expiration in the lungs. When the concentration of CO2 drops the pH rises and vice versa. The concentration of bicarbonate can also change, primarily due to its excretion by the kidneys or during episodes of diarrhea; when bicarbonate drops so does the pH and vice versa.

Just because the kidneys are the ultimate organ where 'acidity' or 'alkalinity' is reported, doesn't mean they're the only organ who can work on neutralizing either acid or base.

Perhaps your confusion comes from underestimating the elegance of the body's buffering systems and to what extent they must work all the time due to the accumulation of protons (hydrogen ions), which In most individuals, the source of net acid load is from the metabolism of protein (when its consumption exceeds 60g/day) and long chain fats (when they are more than 20% of calories in the diet). That means that we're pretty much generating large amounts of protons that accumulate and must be neutralized by matching buffering elements from the body. The kidneys cannot do that on their own.

The body routinely buffers acidic substances carbonate, with a corresponding loss of mineral (sodium and potassium if reserves permit and then a corresponding loss of calcium and magnesium along with other minerals, as available). For its excretion, net acid excess must be buffered with alkaline agents derived from the diet. That means that our buffering capacity for net acid excess is diet-dependent. Moreover, the body can neutralie a large but finite amount of daily acid. If neutralizing agents are not provided in the diet, that is when there is not enough net alkaline-producing food in the diet (vegetables), very little of the fixed acids can be buffered without going into tissue alkaline reserves. Essentially, all excess acids must be buffered at the expense of bone and body buffering reserves, independent of what the kidney does.

Regarding the acidity of urine... In a pH balanced body, urine is slightly acidic in the morning with pH between 6.5-7, and becomes more alkaline (pH 7.5-8) during the night because there is no food or beverage being consume. During the day, it tends to be more acidic due to food and beverge consumption that can increase the amount of protons. Again, the apparent variation is not intrinsic of the buffering system but diet-dependent.

The kidneys can't and shouldn't handle acidic pH lower than 6 in the urine (never under pH 5) to avoid substantial damage to the genitourinary tract . For example, the pH of a Coke with phosphoric acid is 2.8 to 3.2. To achieve a urinary pH of 5, which is not nearly close to a healthy lower range of pH 6, a 12 oz. (330mL) can of Coke would have to be diluted 100 fold, resulting in 100 liters of urine or a corresponding amount of buffer must be drawn from the body to neutralize the excess acid. So, it's not enough with just making uring to get rid of the excess acid. In fact, as you said, buffering is dealth 'whithin' the body and not just peed out.

As to whether we are open or closed systems, at least as far as buffering mechanisms is concerned, respiratory buffers operate as an open system whereas nonrespiratory buffers operate more like closed systems.

[Nean]

"Regarding the acidity of urine... In a pH balanced body, urine is slightly acidic in the morning with pH between 6.5-7, and becomes more alkaline (pH 7.5-8) during the night because there is no food or beverage being consume. During the day, it tends to be more acidic due to food and beverge consumption that can increase the amount of protons. Again, the apparent variation is not intrinsic of the buffering system but diet-dependent."

So... back to our intermittent fasting experiment. Is that change in pH balance when fasting part of 'fasting allows the body to rest'? Meaning not having to do as much acid buffering?

[Gabriel Guzman]

I don't think the body actually 'rests', if just that the abundance of protons is lower than the abundance of basic ions. There's buffering going on, only this time to maintain the pH from becoming too alkaline. However, depending on the fast itself, if there is protein breakdown, then the story goes again as discussed with acidic ions. The body is design to be 'alkaline' but metabolism is almost always acidic. I suppose that during fasting, without food or beverage being ingested, the body draws on it's own alkaline sources to buffer any acid being produced but maybe not as much as if the diet itself is mainly acidic in nature (i.e. with limited amounts of absence of vegetables).

[Nean]

'fasting allows the body to rest' being a populist, unscientific explaination of the benefits of fasting.... so, was that a qualified yep?;)

[Gabriel Guzman]

Nope ;) The body never rests. I think your quote refers to 'resting from buffering excess acid' (if taken within the context of acid-base balance). It may also mean that it rests from doing diggestion (which is true). The quote is so 'open' that can be interpreted in so many reasons. Those who swear by IF will probably take it as a positive thing. Those who don't agree with IF will interpret that there isn't such 'resting' as the body is hard at work to get its energy from other sources.

I prefer to think that maybe during IF, some aspects of metabolism are favoured over others and buffering excess acid is decrease. That doesn't mean that maintaining buffer capacity is dormant, but the effort is shifted to maintaining an alkaline environment, more preferable than an acidic one.

As I said in another post, IF is still an 'uncharted territory' and we can speculate forever about what exactly happens and argue against or in favour. I'm inclined to think that it is not necessarily the IF period what matters but the type of food during the refeeding time what makes the difference between IF being beneficial or not. However, resting? The only time I use that word is when there is a reasonable period between vigorous exercise, and it applies only to muscle workout because the body is anythnig but resting during that time.

Those words get very confusing when used losely... rest, equilibrium... a dead body is at rest and pretty much in some kind of equilibrium, in the sense that its chemical reactions don't change anymore towards the production and consumption of something! So.. we don't want our bodies to be totally at 'rest' and definitely not at 'equilibrium'! ;) But we could use some more 'balance'!

[lyn64]

The kidneys can't and shouldn't handle acidic pH lower than 6 in the urine (never under pH 5) to avoid substantial damage to the genitourinary tract . For example, the pH of a Coke with phosphoric acid is 2.8 to 3.2. To achieve a urinary pH of 5, which is not nearly close to a healthy lower range of pH 6, a 12 oz. (330mL) can of Coke would have to be diluted 100 fold, resulting in 100 liters of urine or a corresponding amount of buffer must be drawn from the body to neutralize the excess acid. So, it's not enough with just making uring to get rid of the excess acid. In fact, as you said, buffering is dealth 'whithin' the body and not just peed out.


Thanks Gabriel. The 'Coke' example finally cleared it up for me - I think:) . So you are saying that the net acidity generated by metabolism of adequate dietary protein cannot be dealt with by 'excretion' mechanisms (urine, respiratory carbonic acid) ALONE but always require a certain amount of internal buffering from alkaline reserves AS WELL? Hardly independently redundant systems at all, wouldn't you say? Rather entirely complementary. Concievably then, the excretion mechanism of dealing with metabolic acidity is 'redundant' insofar as the 'internal buffering by alkaline reserves' could function to maintain pH homeostasis without any exretion at all. But the converse - that the excretion could do it all without any help from internal buffering - is not true. I.e. serious damage to the uro- genitary tract would result.

So you could concievably just take potassium bicarbonate supplements with a high net acid load diet and everything would be hunky dory in terms of pH homeostasis without needing either a particulary high dietary calcium intake or risking bone demineralization for acidity buffering purposes? Assuming of course that you thought that the phytochemical benefits of high vegetation intake were vastly overstated (which I personally do - mainly because I think all vegetation also comes with a similarly huge raft of ANTINUTRIENTS [but that of course, is another story:p])

I seem to remember Dr. Mary Dan hypothesized about alkaline drinking water coupled with low sodium paleo intakes doing just that (dealing perfectly adequately with high net acid load paleo diets) in one of her blog entries about pH homeostasis.

You mentioned that hard cheese was a net metabolic acid load star. Is that because it is so high in Sodium? Or is it something intrinsic about the concentrated casein itself? Also doesn't the high calcium in cheese mitigate the acid load? Could you have a crack at explaining why sodium intake contributes to net acid load and potassium mitigates it?

Lyn

[laughingW]

I seem to remember Dr. Mary Dan hypothesized about alkaline drinking water coupled with low sodium paleo intakes doing just that (dealing perfectly adequately with high net acid load paleo diets) in one of her blog entries about pH homeostasis.

I was just listening to that interview where Jay Wortman, the Canadian low carb guy who works with Inuits (First Nations), was saying that some of the water they cooked with was lightly brackish from having been sea water into ice into cooking water. Hm. It's about 50 minutes into the interview.

[Gabriel Guzman]

Thanks Gabriel. The 'Coke' example finally cleared it up for me - I think:) . So you are saying that the net acidity generated by metabolism of adequate dietary protein cannot be dealt with by 'excretion' mechanisms (urine, respiratory carbonic acid) ALONE but always require a certain amount of internal buffering from alkaline reserves AS WELL? Hardly independently redundant systems at all, wouldn't you say? Rather entirely complementary. Concievably then, the excretion mechanism of dealing with metabolic acidity is 'redundant' insofar as the 'internal buffering by alkaline reserves' could function to maintain pH homeostasis without any exretion at all. But the converse - that the excretion could do it all without any help from internal buffering - is not true. I.e. serious damage to the uro- genitary tract would result.[\quote]

:thumbsup: A cyberslice of Boston Cream Coconut cake for you!!

[quote]
So you could concievably just take potassium bicarbonate supplements with a high net acid load diet and everything would be hunky dory in terms of pH homeostasis without needing either a particulary high dietary calcium intake or risking bone demineralization for acidity buffering purposes? Assuming of course that you thought that the phytochemical benefits of high vegetation intake were vastly overstated (which I personally do - mainly because I think all vegetation also comes with a similarly huge raft of ANTINUTRIENTS [but that of course, is another story:p])

I wouldn't speculate on that until I see something written about it (which maybe there is, I just haven't done a search on that). The first thing that comes to mind is that a supplement may or not provide what's really needed. What if it's too much? What if potassium gets out of balance too? We all know that are the risks of supplementation... too much in a pill may not be what we need.


I seem to remember Dr. Mary Dan hypothesized about alkaline drinking water coupled with low sodium paleo intakes doing just that (dealing perfectly adequately with high net acid load paleo diets) in one of her blog entries about pH homeostasis.

But even paleo diets included some roots, shoots and gathered greens that would help the system as well.


You mentioned that hard cheese was a net metabolic acid load star. Is that because it is so high in Sodium? Or is it something intrinsic about the concentrated casein itself? Also doesn't the high calcium in cheese mitigate the acid load? Could you have a crack at explaining why sodium intake contributes to net acid load and potassium mitigates it?

Lyn

I'm not sure is the sodium content (you can have cheeses that are not high in sodium) My guess is the sulfur content in the proteins. As for the amount of calcium, it may not be enough compared to the amount of sulfur in the protein but that would be speculation of my part.

[lyn64]

Mmmm... cybercake; Sooo L.C.






The first thing that comes to mind is that a supplement may or not provide what's really needed. What if it's too much? What if potassium gets out of balance too? We all know that are the risks of supplementation... too much in a pill may not be what we need.



But even paleo diets included some roots, shoots and gathered greens that would help the system as well.



I'm not sure is the sodium content (you can have cheeses that are not high in sodium) My guess is the sulfur content in the proteins. As for the amount of calcium, it may not be enough compared to the amount of sulfur in the protein but that would be speculation of my part.


So why isn't the high potassium intake from lots of dietary vegetation also a potential overdose of alkalinity? I take your point that there may be other factors in dietary vegetation that are beneficial to human health. But in terms of the alkalizing factor, potassium bicarbonate would do the job wouldn't it? I mean isn't it fairly well established exactly how much alkalizing ions are required to buffer a particular acid load from dietary intake? For that matter, is pure starch (or glucose) acidifying too. By which I mean to ask if all dietary sources of either energy or tissue building are metabolically acidifying? I realize of course that there are other constituents in many carbohydrate containing foods that are alkalizing. But I'm referring only to the carbohydrate itself. Or is it only fat and protein that are acidifying?

I was also hoping you could address the subject of why dietary sodium exacerbates metabolic acidity and dietary potassium mitigates it. Sodium itself is not acidic is it?

Lyn

[Gabriel Guzman]

What makes you think that there is necessarily 'high' potassium intake in vegetables? Compared to what? The problem between naturally ocurring substances and commercial supplements is that the amounts are different and supplements don't have the rest of components found in the whole foods themselves.

As to why salty foods are more acidic, I don't know the answer to that yet. It may not be sodium itself but the foods in which it is contained, and my guess is that it is not natural foods what the source that measured acidity in salty foods used in the determination. After all, it is sodium what's used in the food industry, rather than potassium (for example), to add salty flavor to foods.