Normal Blood pH: How Your Body Maintains It
Okay, so let’s look back at Monday’s post on Acidosis and Alkalosis. In my haste to go sit on the beach and stare at the ocean, I gave short shrift to covering how the body actually maintains normal blood pH.
Normal Blood pH
So to quickly recap, the body works hard to maintain a normal blood pH between 7.35 and 7.45, a fairly tight range. And pretty much nothing you do, at least in terms of food, is going to change that. So you can’t really “acidify” or “alkalize” your body. Your body requires a rather tight pH in the blood (and equally tight, though different pH in other systems) in order for your bodily functions to proceed as normal.
If you were to “acidify” or “alkalize” your blood, you’d quickly run into some serious issues, regardless of which way you took it.Basically, the foods you eat are digested and broken down into their components. These metabolites exhibit an acid, base, or neutral pH to the body. When you add them all up, you get the net-acid or net-base load of the overall diet. And then the body has to deal with this acidity or alkalinity to make sure the body stays at the proper pH in all of its various systems, particularly the blood.
Effects On Urine
One of the ways that the body deals with excess acid or base is to pass it off to the urine for excretion. According to this study:
In conclusion, a more alkaline diet, higher fruit and vegetable and lower meat intake were related to more alkaline urine with a magnitude similar to intervention studies. As urine pH relates to dietary acid-base load its use to monitor change in consumption of fruit and vegetables, in individuals, warrants further investigation.
But here’s an interesting observation from Dr. Jarvis, author of Folk Medicine:
By keeping logs, he was able to show that ill health went along with the alkaline urine, while good health went along with acidic.
An interesting observation indeed and, to be fair, I really have no idea what to make of it. Just throwing it out there for discussion. It makes sense though, since urine is typically acidic (5-6 pH).
Effects On CO2 Exhalation
Unbeknowst to me (but knownst to others…name it!), Yael Grauer recently wrote a similar article over at The Performance Menu looking at this exact same issue.
Great minds…She pointed out that the body maintains proper pH in the blood by breathing out either more or less CO2, depending on whether the blood is too acidic or too alkaline. Basically, when your blood is too acidic, your breathing increases to release more CO2. Think about when you exercise…breathing increases due to increased acidity in the blood from the cells doing their thing as much or more than the need for oxygen.
Effects On Bones
Another claim is that the body buffers acidity largely by pulling from its largest reserve of alkaline material – calcium from the bones. Well, Yael’s article pushed me to go out to Pubmed and look for some work by Jane Kerstetter. According to Kerstetter,
We conclude that in rats, as in humans, acute increases in protein intake result in hypercalciuria due to augmented intestinal Ca absorption. BBMV Ca uptake studies suggest that higher protein intake improves Ca absorption, at least in part, by increasing transcellular Ca uptake.
But, it’s not quite so simple. That study shows that meat protein increases calcium uptake from the intestines. That’s not necessarily true of all protein though. In fact, (vegetarians take note) Kerstetter showed that soy protein is detrimental to calcium uptake:
These data indicate that when soy protein is substituted for meat protein, there is an acute decline in dietary calcium bioavailability.
Here is one more from Kerstetter regarding high-protein (which says “high acid” to me) diets and bone health:
The high-protein diet caused a significant reduction in the fraction of urinary calcium of bone origin and a nonsignificant trend toward a reduction in the rate of bone turnover. There were no protein-induced effects on net bone balance. These data directly demonstrate that, at least in the short term, high-protein diets are not detrimental to bone.
Of course, if you aren’t taking in enough calcium, perhaps this is an issue. Perhaps not. I’m guessing that, once again, the body is far smarter than we give it credit for. Maybe the increase in osteoporosis isn’t necessarily due to “an acidic diet,” but the particular types of acidic foods we eat, namely:
- the “healthy” soy protein to replace meat – see above
- lots of grains – contain phytic acid that binds with calcium
- high salt intake – may also bind with calcium
- sugar – depletes vitamins and minerals and has been shown (in rats) to throw off calcium/phosphorus balance
There’s also the severely detrimental effects on bone health of low vitamin D and low magnesium intake, both just as important as calcium for building bone.
It All Adds Up To…
Something I’m still not concerned about. If you’re not eating much in the way of grains, you can likely eat your meat and eat plenty of fruits and vegetables with impunity. You don’t need to calculate acid and base loads like John Berardi mentions in his article Covering Your Nutritional Bases.
As I said in my last article, this is mainly just “eat your vegetables” and anti-meat repackaged, because the people that are talking about it are usually promoting high whole grain diets, another acidic food.
As Yael said:
Don’t worry about meat robbing calcium from your bones. You’ll excrete calcium if your urine is more acidic (with hydrogen ions being secreted to balance the acid load), but your body will be getting it from elsewhere. And even though your urine can become more or less acidic, your blood is going to stay the same. Though eating vegetables is generally a good idea for a variety of reasons, it’s not because minerals are being robbed from the bones. And since it appears that half of the hunter-gatherer diets had high acid-load diets, and none of our caveman buddies had modern diseases, I wouldn’t lose sleep over the possibility.
We really can’t take things out of context, especially when talking about a highly complex biological machine like the human (or any mammalian) body, and expect to be able to distill things down to some excessively simple talking point. If you’re concerned, eat more plant matter. But I maintain that meat, fruit, vegetables, properly-prepared beans and non-glutinous grains (like rice), and some dairy are highly unlikely to harm you or your bones, especially if you’re active (which stimulates bone growth) and you have adequate intake of magnesium and a good vitamin D status.
Any additional thoughts on this matter? Anyone have additional supportive or conflicting evidence that I missed?
About Scott
Scott Kustes loves to cook and loves to eat. He started Real Food University to help you get maximum enjoyment out of the meals that you eat. To find out more about how he has rebelled against the fast food culture and counting calories or carbs, join the Real Food Revolution.
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Sorry about the formatting…Sherman, H.C. & Gettler, A.O., The Balance of acid-forming and base-forming elements in foods, and its relation to ammonia metabolism. 1912. (obtained from http://www.jbc.org)• By the time of publication (1912), it had become generally recognized that not only should the diet supply adequate nutrients for the maintenance of body structure, but also that these elements should be balanced in relation to one another – particularly the relation between acid-forming and base-forming foods.• The problem of analysis based on ash yield upon ignition is identified. While it was relatively easy to quantify the alkaline ash, the acid-forming constituents were lost upon combustion – organic acids and sulphur were most notable. It was assumed that if the ash of a food was neutral, it must have a predominance of acid-forming elements.• Another problem identified was that ash analysis was, until then, used to identify the nutrients extracted from the soil by food crops and not the edible portion that we ingest.• The researchers developed methods to better quantify the calcium, magnesium, sodium, potassium, phosphorous, chlorine, and sulphur in the edible portions of foods based on both 100g and 100 calorie portions. They found that all the meats showed an excess of acid-forming elements, eggs also contained a more acid-forming elements though not so much as meats, grains showed a smaller predominance of acid-forming elements than either meat or eggs, milk showed a slight predominance of bases, and fruits and vegetables had a great predominantly bases. They found that a 100 calorie portion of potato had enough base to neutralize a 100 calorie portion of lean beef.• They experimented with these foods to test how much ammonia was used to neutralize an acid-forming diet and found that only ¼ of the excess acid was neutrailzed and eliminated as ammonia salt.• Another more detailed experiment was conducted and they found that there was an 50% increase in the acidity of the urine. This accounted for a greater proportion of acid than the ammonia elimination.Frassetto, L. et al. Estimation of net endongenous noncarbonic acid production in humans from diet potassium and protein contents. Am J Clin Nutr, 1998;68:576-83.• The normal Western diet yields chronic, low-grade metabolic acidosis that varies based on Net Endogenous Acid Production (NEAP).• Under normal physiological circumstances the NEAP is determined by diet and. This study confirmed that NEAP can be predicted using potassium and protein, the major variables of NEAP. Bicarbonate is formed from the combustion of organic potassium salts (e.g. potassium citrate) in vegetables and fruits. Sulfuric acid is produced from the metabolism of protein.• Aging increases the severity of diet-dependent acidosis independently of diet due to age-related renal insufficiency which reduces the retention of bicarbonate and the excretion of acid.• Metabolic acidosis is: chronic, low-grade (sub-clinical), diet-dependent, age-amplified and may contribute to bone mass decline, osteoporosis, and muscle wasting.• Long-term supplementation with potassium bicarbonate has shown the following anabolic effects in post-menopausal women:o improved calcium and phosphorous balance (see Sebastian et al, 1994)o bone resorption markers decrease (see Sebastian et al, 1994)o nitrogen balance improves (see Frassetto et al, 1997)o serum growth hormone concentrations increase (see Frassetto et al, 1996)• Dietary protein and potassium are major contributors to NEAP and highly variable in the diet and are therefore appropriate measures for assessing the net acid load of the diet. Regression modeling confirmed the relationship.• This study found that most of the predictive ability of the Remer-Manz model of renal net acid excretion (RNAE) resides in the protein and potassium content of the diet. Remer and Manz’s potential renal acid load (PRAL) is likewise highly correlated.Ho-Pham, et al. Veganism, bone mineral density, and body composition: a study in Buddhist nuns. Osteoporosis Int (2009) 20:2087-2093.• Cross-sectional study showed that, although vegans had lower calcium and protein intakes than omnivores, veganism did not alter body composition.o [the results appear to be confirmation of the acid-base diet theory – the ratio of potassium to protein is more important than intake of calcium]Alpern, R. & Sakhaee, K. The Clinical spectrum of chronic metabolic acidosis: Homeostatic mechanisms produce significant morbidity. (Abstract only). Am J Kidney Diseases, 1997;vol20,issue2:291-302.• Definition: Chronic metabolic acidosis is a process whereby an excess of nonvolatile acid load is chronically placed on the body due to excess acid generation or diminished acid removal by normal homeostatic mechanisms.• Two common factors in chronic metabolic acidosis are aging and excessive meat ingestion.• The body’s homeostatic response to the acidosis is very efficient, serum bicarbonate and pH are frequently maintained within normal range. These homeostatic mechanisms themselves lead to their own set of pathological consequences including:o kidney stones – urinary pH is a risk factor in stone formationo bone demineralization – bone as an ion exchange leaches minerals to buffer bloodo muscle protein breakdown – renal ammoniagenesis cannibalizes glutamine from muscle tissueo renal growth• This paper introduces the idea of eubicarbonatemic metabolic acidosis – even in patients with normal serum bicarbonate and pH, it is important to treat the acid load and prevent the pathological homeostatic responses.Remer, T. Influence of Diet on Acid-Base Balance. Seminars in Dialysis – Vol. 13, No. 4, (July – August) 2000 pp. 221-226.• Remer identifies the following factors as having an impact on acid-base balance and allow us to estimate the potential renal acid load (PRAL) of any given food or diet:1. the chemical composition of foods (i.e. their content of protein, chloride, phosphorous, sodium, potassium, calcium, and magnesium)2. the different intestinal absorption rates of these relevant nutrients3. the metabolic generation of sulfate from sulfur-containing amino acids4. the grade of dissociation of phosphorous at the physiological pH of 7.45. the ionic valence of calcium and magnesium• Remer identifies a progression in the acid-ash hypothesis. Sherman & Gettler identified the mineral and acid/base contents of various foods and their experiments allowed for a rough estimation of acid excretion. Since then the pH-dependent dissociation of phosphorous and the endogenous production and excretion of acid was taken into account. More recently, the intestinal absorption rates of the various nutrients have been taken into account.• This paper describes the various physiological aspects of diet-related acid-base balance:o Absorption via intestines. the various nutrients have differing absorption rates, therefore theo Production of hydrogen ions and alkali ions in the liver. sulfuric acid is produced from sulfur-containing amino acids (H2SO4) bicarbonate is produced from the alkali salts of organic acids (e.g. NaHCO3)o Blood – buffered by extracellular fluid buffers and pulmonary respiration. on entering the blood, H2SO4 is buffered by NaHCO3 to form neutral Na2SO4 and carbonic acid (H2CO3) which is eliminated as CO2 by the lungs the lungs maintain blood pH within a narrow range by CO2 exhalation in response to blood bicarbonate level the lungs are incapable of altering H+ concentrationo Renal ion excretion and regeneration of bicarbonate. sodium is reabsorbed in the kidney for the restoration of the circulating bicarbonate pool since the kidney cannot elaborate urine more acidic than pH 4.4, it utilizes ammonia as a buffer for the excretion of the sulfuric acid the ammonia is synthesized in the kidney from glutamine, it forms ammonium ions and the sulfur is excreted as (NH4+)2 SO4 2-• increased protein intake can therefore improve renal acid excretion by increasing urinary ammonium output• at a given acid load, urinary acid excretion increase with protein intake• therefore the renal capacity to excrete excess acid as ammonium is increased with protein intake allowing a mechanism to allow us to handle increased acid load from varying protein intakeFarwell, W. & Taylor, E. Serum bicarbonate, anion gap and insulin resistance in the National Health and Nutrition Examination Survey. Diabetic Medicine 2008. Vol. 25, Issue 7, pp. 798-804.• Anion gap = serum [cations] – [anions] = ( [Na+]+[K+] ) − ( [Cl−]+[HCO3−] ).• Included in the study were 1496 adults without diabetes or other chronic diseases (healthy adults).• Lower bicarbonate and higher anion gap are independently associated with insulin resistance:o Participants in the highest quartile of bicarbonate had fasting insulin 12.76 pmol/L lower than those in the lowest quartile.o Participants in the highest quartile of anion gap had fasting insulin 4.39 pmol/L higher than those in the lowest quartile.Farwell, W. & Taylor, E. Serum anion gap, bicarbonate and biomarkers of inflammation in healthy individuals in a national survey. CMAJ 2009. DOI:10.1503/cmaj.090329.• In vitro data suggest that lower extracellular pH activates the immune system.• 4525 healthy adults without chronic disease or recent infection, and an estimated glomerular filtration rate of less than 60mL per 1.73m were studied.• A higher serum anion gap and lower bicarbonate level were associated with higher levels of inflammatory biomarkers in a healthy sample of the general population:o A higher anion gap and lower bicarbonate level were associated with a higher leukocyte count and higher C-reactive protein level.o Participants in the highest quartile had a leukocyte count that was 1.0 x 109/L higher and a C-reactive protein level that was 10.9 nmol/L higher than those in the lowest quartile of anion gap.o Participants in the lowest quartile had a leukocyte count that was 0.7 x 109/L higher and a C-reactive protein level that was 4.0 nmol/L higher than those in the highest quartile of bicarbonate level.o A higher anion gap and lower bicarbonate level were also associated with a higher platelet count, a larger mean platelet volume and a higher ferritin level.Farwell, W. et al, J. Serum Anion Gap and Blood Pressure in the National Health and Nutrition Examination Survey. Hypertension, J Am Heart Assoc. 2007; 50;320-324.• 5043 adult participants who were not taking antihypertensive medications or diuretics and who denied hypertension, cardiovascular disease, diabetes, and other diseases were studied.• Anion gap is independently associated with higher blood pressure:o Participants in the highest quintile of anion gap had systolic blood pressure 3.73 mm Hg higher than participants in the lowest quintile.o Participants in the highest quintile of bicarbonate had systolic blood pressure 2.73 mm Hg lower than participants in the lowest quintileFrassetto, L. et al. Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate. N Engl J Med 1994;330;1776-81.• In normal subjects, a low level of metabolic acidosis and positive acid balance is typically present and correlated to the amount of endogenous acid produced by the metabolism of foods in ordinary diets abundant in protein.• Bone acts as a reservoir of base (alkali salts of calcium) that can be mobilized for the defense of blood pH and plasma bicarbonate concentration in order to maintain homeostasis. Base mobilized from the skeleton to counteract endogenously produced acid may contribute to the decrease in bone mass that normally occurs with aging.• In vitro studies show that extracellular acid increases the activity of osteoclasts (cells that mediate bone resorption) and inhibit the activity of osteoblasts (cells that mediate bone formation).• In vivo, reductions in extracellular pH and plasma bicarbonate are potent and independent signals for the stimulation of bone resorption and inhibition of bone formation.• This study tested 18 post-menopausal women over 18 days and found that administration of potassium bicarbonate sufficient to neutralize the endogenous acid had the following effects:o Improved calcium and phosphorous balanceo Reduced bone resorptiono Increased rate of bone formation.• Conclusion: Countering the normal diet-related production of endogenous acid with orally administered potassium bicarbonate can attenuate or reverse the loss of bone mass that occurs over the long term in postmenopausal women.Ballmer, P. et al. Chronic Metabolic Acidosis Decreases Albumin Synthesis and Induces Negative Nitrogen Balance in Humans. J Clin Invest. 1995;Vol 95;39-45.• This study demonstrates for the first time in any species that chronic metabolic acidosis decreases albumin synthesis, and induces a state of sustained negative nitrogen balance.• Chronic metabolic acidosis not only increases whole body protein degredation and amino acid oxidation, but has profound negative effects on protein synthesis.• The study determined that mild to moderate chronic metabolic acidosis induces a quantitatively impressive protein degradation in a dose- or severity-dependent way. Therefore demonstrating gradation in chronic metabolic acidosis.• In this study, it was shown for the first time that chronic metabolic acidosis results in a decrease of plasma levels of anabolic hormones IGF-1 (insulin-like growth factor 1), fT4 (free thyroxin) and T3 (tri-iodothyronine) in normal human subjects.
This is an important idea. It affects athletic performance, aging, osteoporosis, muscle wasting, inflammation, insulin resistance, blood pressure…Try not to get bogged down in the vegans’ arguments about meat. It’s not about that. (I am an avowed carnivore myself.)
Remember: ‘acid-FORMING’ foods rather than ‘acidic’ foods.Sorry to be such a pain on your blog… But I hate to see misinformation go out there.
There’s an old phrase often used in spiritual and religious circumstances, “Hidden in plain sight.”The more time (now one year) I spend studying our bodies, nutrition, especially of the paleo vs. CW camps, the more I’m struck about the role of grains, especially soy. All the scientists and doctors keep trying to treat a long list of ailments, both minor and major, with the commonality of eating grains (or large amounts of sugar.) It is such a given that we are supposed to eat, what, 60% of our calories from carbs, mostly grains, that few are seeing that dietary devil “hidden in plain sight.”When I virtually stopped eating wheat a year ago my toenail fungus STOPPED. As in, a clear line across the two nails corresponding with the cessation of wheat. While the fungus has been fighting a rear guard action since then, it’s just about all gone. No Lamitrol (???) needed, no wheat need apply. “Hidden in plain sight.”(Having said all that, I’m going to treat myself to a hot dog bun and corn on the cob on Memorial Day. As the father of toxicology famously said, “The poison is in the dose.”)
Mark, after reading through the plethora of text there, I don’t think we’re in dispute. I think the part that is disputed is the places where they say “excessive meat consumption” as opposed to pointing to the high grain load of most modern diets. As I pointed out, the body does deal with acidity, though I don’t know that it’s necessarily in any of the ways commonly touted, such as by depleting the bones, at least if the diet includes sufficient nutrient intake.For instance, meat increases calcium absorption to help buffer it. But other particular dietary components that we’re told to replace our meat intake with don’t. So while acknowledging that there is some validity to the acid-base hypothesis, I am disputing most of the commonly claimed reasons.Again, maybe I’m wrong, but I don’t think you and are in disagreement here.CheersScott
I agree…even when they get the problem right (such as “high acid,” perhaps), they tend to get the treatment wrong (such as “avoid meat”).Eat that corn on the cob! I love it, grilled and smothered in butter. I consider that to be about the same as rice…not really all that much to worry about.CheersScott
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