Thursday, October 9, 2008

Acid-Base Balance

Numerous health authorities have proposed that the acid-base balance of a diet contributes to its effects on health, including Dr. Loren Cordain. Here's how it works. Depending largely on its mineral content, food yields net acid or base as it's metabolized. This is not the same as the acidity of a food as you eat it; for example, lemons are base-yielding. The pH of the body's tissues and blood is tightly regulated, so it must find ways to resist pH changes. One way it deals with excess acid and base is by excreting it. Acidifying food causes the urine and saliva to become more acidic, while alkalinizing food has the opposite effect.

Another mechanism some believe the body uses to neutralize acidity is by drawing calcium from the bones. The modern diet tends to be acid-yielding. Vegetables and fruit are base-yielding while meat, refined carbohydrate, dairy and most other foods are acid-yielding. Some authorities believe this leads to osteoporosis, cancer and a number of other health problems. This is one of the reasons we're told to eat immoderate quantities of vegetables.

I've always been skeptical of the acid-base balance theory of health. This mostly stems from the fact that many hunter-gatherer societies were essentially carnivorous, yet they didn't suffer from osteoporosis, tooth decay or any other signs of calcium deficiency. Also, if acid-yielding diets strip calcium from the bones, how did calcium get into the bones to begin with? The body clearly has mechanisms for creating and preserving bone density in the face of an acid-yielding diet, it's just a question of whether those mechanisms are working properly.

I came across a gem of an article today on acid-base balance by none other than Dr. Weston Price. As usual, he hits it out of the ballpark. There are two tables in the article that sum it up beautifully. In the first, he compares the occurrence of cavities in healthy non-industrial groups to genetically identical groups living on modern foods (wheat flour, sugar). As you know by now if you've been reading this blog, the modern groups have 5-100 times more cavities than their non-industrial counterparts, along with crooked teeth, feeble frames and a number of other problems.

In the second table, he lists the acid-base balance of the same non-industrial and modern groups. There is no real pattern. Some of the non-industrial groups ate a diet that was heavily acid-yielding (Inuit, he calls them Eskimo), while others were fairly balanced or even base-yielding (South sea islanders). The unhealthy modern versions, ironically, were fairly balanced between acid and base-yielding foods. This is not consistent with the idea that acid-base balance contributes to the diseases of civilization.

There was one consistent trend, however. The non-industrial diets tended to be higher in both acid and base-yielding foods than their modern counterparts. That means they were richer in minerals. Just as importantly if not more so, their diets were rich in fat-soluble "activators" of mineral absorption and metabolism that ensure the proper use of those minerals. These are the fat-soluble vitamins A, D and K2. Here's what Weston Price says:
It is not my belief that [tooth decay, dental/skeletal deformity, general poor health] is related to potential acidity or potential alkalinity of the food but to the mineral and activator content of the nutrition during the developmental periods, namely, prenatal, postnatal and childhood growth. It is important that the very foods that are potentially acid have as an important part of the source of that acidity the phosphoric acid content, and an effort to eliminate acidity often means seriously reducing the available phosphorus, an indispensable soft and hard tissue component.
In other words, the acid-base balance isn't what matters, it's getting enough minerals and the vitamins you need to make good use of them.

Why were the diets of healthy non-industrial people so rich in minerals? It's simple: they ate whole foods. "Empty calorie" foods such as sugar, vegetable oil and refined grains constitute more than half of the calories in the modern diet. Eliminating those "foods" and replacing them with whole foods instantly doubles your mineral intake. Properly preparing grains and legumes by soaking, sprouting or fermenting further increases their mineral availability. Add some grass-fed dairy, organ meats, shellfish and eggs for the vitamins and you're in business!

27 comments:

Half Navajo said...

I always was skeptical about the alkinizing theory too. I read that article awhile back at the price pottenger foundation site, and its in the back of the new edition of Nutrition and Physical Degeneration, it layed that to rest for me. I wish he was still here.

t r o y

Methuselah said...

As ever, informative and well-referenced - thanks Stephan.

Anna said...

Thanks, that clears up why reading about the acid-base theories always made my head hurt so much!

Peter N said...

Hi-
This is a general Price question I've wondered about for a while: how did he die? I've been looking around a bit and I can't find info on this. This, of course, wouldn't be the most compelling piece of evidence proving or disproving the ability of the whole-foods diet he supported to prevent heart disease, stroke, etc., but it wouldn't be entirely irrelevant either. *If* we assume that he followed his own dietary advice (perhaps we shouldn't?), he was probably in a minority of westerners who ate that way, and he should have been offered a good deal of protection from the diseases of civilization if such protection were inherent to that way of eating.

Debs said...

I've always been really skeptical about the acid-base balance idea. It seems like an association, and a weak one at best. Thanks for the Price connection!

To Peter: According to his NY Times obituary, Weston Price died at 77 of a "heart ailment." If you google the topic, there is some argument back and forth about whether he died of a heart attack. There are also statements that he died at 68 from people who apparently can't do math.

I'm not sure whether he followed his own advice, but remember that he did much of his research in the 1930s and 1920s, when he was already middle aged and late middle aged. He was nearly 70 when Nutrition and Physical Degeneration was published. Even if he'd started following his advice, that would be a pretty late start to a healthy diet.

Debs
Food Is Love/Seattle Local Food

Richard Nikoley said...

I'd been asked a question about this acid balance thing, had no answer, and was going to look into it.

Thanks for saving me the time. This sounds dead on to me.

You know, the more I evaluate my own experiences, results and evolving appetite, the more I am becoming convinced that it's about pre-agricultural Real Food and those not too far off (like dairy), and way less about high-fat, low-fat, low carb, acid balance, or any other "trick."

This began when I noticed that lots of the low-carb, Atkins people seem way too obsessive-compulsive about food.

As I have tried to model an EvFit / Paleo path over the last year, with Real Food, some fasting, good sleep, and some brief but very intense physical activity, the less and less I care about food in the sense of always obsessing over it.

In the end, eat a varied diet from high fat to low fat, and everything in between, flexibly and intermittently but avoid grains, refined sugars, and processed / packaged / junk / fast food like the plague.

Get lots of sleep, go hungry now and then, and work yourself hard but briefly when you're hungry.

I'm betting you do great.

ItsTheWooo said...

My posts seem to be getting deleted? This is the second time I posted something and then it vanished?

Anna said...

Do I remember right that Price has some dental problems early in adulthood? Or was it just his patients? Note to self: must get N&PD out and reread it (actually, I never finished it, but I should).

Anna said...

itsthewooo, your first comment showed up on my gmail reader, cited at 10:44am, but it doesn't show on the blog. Strange.

Another thing, can't figure out what itsthewooo stands for; I'm curious.

Stephan said...

Debs,

Thanks for the information. I'm open to the idea that Price didn't have the full picture. He didn't seem to mind wheat, and I don't believe he made the connection that the non-industrial cultures he studied all treated their grains in certain ways. Sally Fallon and others have expanded on his conclusions by making the latter point.

Richard,

That's a good attitude. I try to cultivate something similar. I like to keep things as simple as possible. Other people think I obsess about food, but I don't see it that way. I just follow a few simple rules.

Itsthewoo,

I'm sorry your comments keep disappearing; I promise I'm not deleting them! Someone else mentioned the same thing happened to them the other day. It must be a bug.

Anna,

Yes, he did have dental problems due to an illness IIRC. When he returned to his family farm the cavities healed rapidly.

ItsTheWooo said...

Grr bugs... reason had told me this is the cause but my paranoia had me questioning if reason was correct.

ItsTheWooo is a stupid catchphrase of an accidental comedic duo "bubb rubb and lil sis". This was a popular video online circa 2001. Bubb Rubb says: "its that woo WOOO". I thought this was hysterical at the time and made it my online handle for the first low carb message board I joined, and now it's stuck. REGRET IT I DO, people tend to think it's a narcissistic proclamation or something.

Stephan said...

I think it's useful to point out that life expectancy was 68 in 1950, so Price outlived the mean by 9 years.

Richard Nikoley said...

What a coincidence. Guess what Cordain's email newsletter was about, today? I can't find these on the web, otherwise I'd give a link. Here's the text:

Dear Dr. Cordain,

Q - I recently read an article pertaining to Acid/Alkaline balance of foods. It said you should not believe that it matters whether foods are acidic or alkaline, because no foods change the acidity of anything in your body except your urine. Your stomach is so acidic that no food can change its acidity, and foods (citrus fruits, vinegar, and vitamins such as ascorbic acid or folic acid) do not change the acidity of your stomach or your bloodstream. So does it really matter?

Thank you,

Mike Hoover
Novi, MI

A - Thank you for your question Mike. It is a common misunderstanding that because the food you eat does not change the pH of your blood or stomach acid, it is inconsequential to your health.

Bone mineral content is based upon net calcium balance. This is the amount of calcium you take in minus the amount of calcium you excrete. This helps explain why the U.S. has one of the highest rates of osteoporosis in the world despite having one of the highest calcium intakes worldwide.

All digested food ultimately reports to the kidneys as either acid or base. If the diet yields a net acid load, the acid must be buffered by the alkaline stores of base in the body. The highest acid-producing foods are hard cheeses, cereal grains, salted foods, meats, fish and eggs. The only alkaline, base-producing foods are fruits and vegetables. Because the average American diet is overloaded with grains, cheeses, salted processed foods, and fatty meats at the expense of fruits and vegetables, virtually everyone in the U.S. has chronic low-grade metabolic acidosis.

Many nutritionists think the degree of this metabolic acidosis is mild and inconsequential since it does not affect blood pH. However, this perturbation of systemic acid-base balance is, in part, responsible for the age-related loss of bone and skeletal muscle mass. To buffer the excess acid, alkaline calcium salts are released from bone. Glutamine is released from the muscles and utilized for the generation and excretion of ammonium, gradually leading to sarcopenia.

Many studies with kidney patients have shown that a chronic metabolic acidosis leads to bone loss1 and muscle loss2. For most folks, the dietary-induced damage to the skeleton, skeletal muscle, and kidneys is cumulative over a lifetime and appears later in life.

Studies by Dr. Anthony Sebastian's team have shown that when healthy people were given potassium bicarbonate (a base) in order to reverse metabolic acidosis, it improved biomarkers of bone health3 and reduced muscle loss4. Likewise in 2006, an intervention study found that fruits and vegetables (as opposed to grains) improved bone health5.

Among Eskimos, age related bone loss starts earlier in life and is more pronounced than it is among Westerners due to the combination of an almost exclusively animal diet and very low calcium intake in the Eskimo diet.

It's also important to mention that some studies have shown that hypertension could also result from a disturbance in the acid-base balance. Further evidence of this link comes from the fact that chloride seems to be a major determinant of the diet's net acid load6, and from the fact that old studies show that chloride raised blood pressure to a significantly higher level than did sodium7.

Normal adult humans eating the typical Western diet, whose metabolism yields more acids (sulphuric acid from meat, fish, eggs, dairy and cereal grains) than base (bicarbonate from fruits and vegetables), have chronic, low-grade metabolic acidosis. This is aggravated by the normal age-related decline in overall renal function.

To correct this low-grade metabolic acidosis, focus on eating a high amount of fruits and vegetables, and lower consumption of grains, hard cheese, and chloride. This will bring the body back into acid/base balance, which naturally brings it back into calcium balance, and has numerous other health benefits. Remember, the goal is to avoid a net acid load on your kidneys.

References are available at www.ThePaleoDiet.com/v4n13.shtml.

Stephan said...

Sorry it was actually 65.5 for men (68 was the average for both sexes). So he outlived the mean by 11.5 years.

Robert Andrew Brown said...

MANY THANKS

Great Post Stephan as usual.

The Weston Price link is a gem.

Omega 3 and 6 are big factors in bone modelling.

Omega 6 intake was only in its early years in today's consumption terms in the 1930s

Higher Omega 3/DHA and or lower Omega 6 protects against bone loss in men and women, and reduces osteoporosis.

Arguably excess Omega 6 intake is a big factor in osteoporosis and all related conditions

This is what a review on bone modelling said

"Even though several localized compounds act
on bone cells, the prostaglandins (PG) seem to be the principle
mediators of bone cell function since their biosynthesis
and release from bone cells and associated tissues can be
induced by several cytokines as well as systemic factors.
PGE2, which is synthesized from arachidonic acid, is a potent
stimulator of bone resorption and, to date, is the primary
PG affecting bone metabolism....Similar to the PGs, leukotrienes (LTs), the metabolites
of the 5-lipoxygenase (5-LO) pathway, also participate in
the local control of bone metabolism (93–95). In most cases,
these compounds are believed to be local regulators of bone
metabolism by stimulating bone resorption and inhibiting
bone formation. . . In these experiments, animals
given long-chain n-3 fatty acids tended to show an
increased rate of bone formation, suggesting a stimulatory
effect on osteoblastic activity. The favorable effect of n-3
fatty acids on bone modeling in growing animals is supported
by the observation of reduced bone mineral loss in
ovariectomized rats supplemented with eicosapentaenoic
acid (EPA 20:5n-3) (103). The bone-sparing effect of
20:5n-3 may be associated with diminished bone resorption
or increased bone formation...These results demonstrated that the dietary
ratio of n-6/n-3 fatty acids modulates bone PGE2 production
and the activity of serum bone-specific alkaline phosphatase
in growing rats"

http://www.ebmonline.org/cgi/reprint/226/6/485

Omega six seems to play a big part in bone breakdown, particularly following fracture, which is what one might expect given its wider role in inflammation tissue formation and breakdown etc.

Fish and particularly shellfish are very good sources of minerals.

Mineral depletion in vegetables due to soil depletion in the last 50 years varies between about 20% - 70% depending on mineral. ( which goes up the food chain through depletion in grass etc)

So may be we should all supplement minerals if not on a high mixed seafood diet.

Robert Andrew Brown

Author Omega Six The Devils Fat

www.omegasixthedevilsfat.com

(A revised version is in preparation which gives more emphasis to minerals)

Robert Andrew Brown said...
This post has been removed by the author.
Robert Andrew Brown said...

Omega-3 Polyunsaturated Fatty Acids and
Skeletal Health1
Sorry all I forgot to credit the source of the quote properly. Trying to do too much at once again.

Thanks

Robert


BRUCE A. WATKINS,*,†,2 YONG LI,* HUGH E. LIPPMAN,* AND MARK F. SEIFERT†
*Department of Food Science, Lipid Chemistry and Molecular Biology Laboratory, Purdue
University, West Lafayette, Indiana 47907; †Department of Anatomy and Cell Biology, School of
Medicine, Indiana University Purdue University Indianapolis, Indiana 46202

Stephan said...

Richard,

As usual, Dr. Cordain is well-reasoned. I just don't think what he says squares with the most empirical data available. According to his own data, hunter-gatherers weren't too big on veggies. I'd like to see where he got his data on bone loss in the Inuit. I'd be willing to bet the data are from modernized rather than pre-modern Inuit.

Robert,

Thanks for the information. Although Price didn't know about the importance n-3 and n-6 fats at the time, all the cultures he studied had a favorable ratio, and most had a low PUFA intake. He did recognize that modern vegetable oils are not healthy.

Peter said...

ItsTheWoo,

Blogger has done this to me too on occasions. A bug, but I know what you mean!

Good old Cordain, as always, he almost hits the mark.

Peter

Mari said...

I was wondering if at some point you could tackle this recent Science Daily write up regarding IGF-1, protein comsumption, and longevity.

http://www.sciencedaily.com/releases/2008/09/080924151018.htm

I usually follow JK's recommendations of 0.8-1 grams per kg of body weight but sometimes it's more.

Fat and protein seem to really help diminish appetite and sometimes I like the bulk that a little extra protein seems to offer.

I know CRONIES, McGlothin and Averill addressed the issue of IGF-1 in their recent book "The CR Way." As a consequence they don't eat much animal protein (about 45-55 g per day) and get extra calories with grain consumption (barley). Sometimes CRONIES appear to be somewhat muscle wasted to me.

http://www.calorierestriction.org/the_cr_way

Thanks for your great blog. I look forward to each new post.

Stephan said...

Hi Mari,

Yes I heard about those IGF-1 findings. I wouldn't go restricting your protein just yet. The science is interesting but complicated.

Yes, CR extends lifespan in pretty much every organism under lab conditions. But if you catch wild mice and put them under CR, it doesn't extend life. So what are we more like, the lab mice or the wild mice? I don't know the answer.

I am skeptical of the CRON approach. First of all, I can guarantee most of these people have no idea what "ON" is. Popping a multivitamin along with your whole wheat toast and low-fat salad is not going to cut it.

Furthermore, lifespan extension by CR may just be a hormetic effect. For example, you can get the same effect in mice using alternate-day fasting even if calories aren't restricted. The wild mice may have already reached their hormetic potential due to hard living in the wild so CR doesn't do anything. Humans might be able to do the same thing by intermittent fasting, cold swimming, exercise or other hormetic processes.

The science is too uncertain to make yourself miserable over it at this point.

Mari said...

Thanks Stephan, I feel better already!

donny said...

Studies that show potassium bicarbonate improves bone and muscle mass don't show that acidosis causes bone and muscle loss; they just perhaps show that potassium bicarbonate improves bone and muscle mass. And of course you need calcium to build bone. But that taking calcium or potassium bicarbonate may treat acidosis may be beside the point.
I think it's way more important to know the requirements for individual nutrients, like potassium, phosphorus, etc., than for classes of nutrients, like acid or alkaline. It's not like calcium and potassium are interchangeable. It's like being low in iron and your doctor tells you to try to get more metal in your diet.
I've never seen anything about the acid/alkaline theory that made any attempt to explain lions tigers or polar bears.

Bruce K said...

The Acid-Base theory is typical nonsense from Cordain. He used to hype vegetarian diets, too. Also, I would not be so sure that lemons yield a base. Maybe the acid strips minerals out of your skeleton and makes it seem like you're more alkaline, but the reality is that meat boosts your bone density more. Cordain is spouting a theory and treating it like a fact. He's ignoring the scientific method. Where is the proof that a diet of meat will break down your bones, or that eating loads of fruits and vegetables prevents bone loss in old age? People say that dairy causes osteoporosis, because the countries that eat the most dairy have the most hip and forearm fractures. But that doesn't mean anything. The countries eating more milk also eat more sugar and processed sodas.

Epidemiology can't prove cause & effect, no matter how much the anti-milk zealots and vegans want to believe that it does. Also, you would have to control for milk processing, additives, and other factors to prove that milk was really the cause.

MIGUEL said...

Regarding Acid-Base balance, I sugest the following papers by a professor of Nephrology that spent his entire career studying this topic (Dr. Anthony Sebastian of The University of California, San Francisco):

Frassetto L, Morris RC Jr, Sebastian A. Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. J Clin Endocrinol Metab. 1997 Jan;82(1):254-9.

Frassetto L, Morris RC Jr, Sebastian A.. Long-term persistence of the urine calcium-lowering effect of potassium bicarbonate in postmenopausal women. J Clin Endocrinol Metab. 2005 Feb;90(2):831-4. Epub 2004 Nov 30.

Frassetto L, Morris RC Jr, Sellmeyer DE, Todd K, Sebastian A. Diet, evolution and aging--the pathophysiologic effects of the post-agricultural inversion of the potassium-to-sodium and base-to-chloride ratios in the human diet. Eur J Nutr. 2001 Oct;40(5):200-13.

Frassetto L, Morris RC, Jr., Sebastian A. Effect of age on blood acid-base composition in adult humans: role of age-related renal functional decline. Am J Physiol 1996; 271:1114–1122.

Frassetto L.A., Morris Jr R.C., Sebastian A. A practical approach to the balance between acid production and renal acid excretion in humans. J Nephrol. 2006 Mar-Apr;19 Suppl 9:S33-40.

Sebastian A, Frassetto LA, Sellmeyer DE, Merriam RL, Morris RC Jr. Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors. Am J Clin Nutr. 2002 Dec;76(6):1308-16.


Frassetto LA, Todd KM, Morris RC Jr, Sebastian A. Estimation of net endogenous noncarbonic acid production in humans from diet potassium and protein contents. Am J Clin Nutr 1998; 68: 576-83.

Morris RC Jr, Schmidlin O, Frassetto LA, Sebastian A. Relationship and interaction between sodium and potassium. J Am Coll Nutr. 2006 Jun;25(3 Suppl):262S-270S

Frassetto LA, Nash E, Morris RC, Sebastian A. Comparative effects of potassium chloride and bicarbonate on thiazide-induced reduction in urinary calcium excretion. Kidney Int 2000; 58: 748-52.

Sebastian A, Harris ST, Ottaway JH, Todd KM, Morris RC, Jr. Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate. N Engl J Med 1994; 330: 1776-81.

Frassetto L, Morris RC Jr, Sebastian A. Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. J Clin Endocrinol Metab. 1997 Jan;82(1):254-9

Frassetto L, Morris RC Jr, Sebastian A. Long-Term Persistence of the Urine Calcium-Lowering Effect of Potassium Bicarbonate in Postmenopausal Women. J Clin Endocrinol Metab 90: 831–834, 2005


I also sugest some papers by Remer and Manz, from Germany:

Rylander R, Remer T, Berkemeyer S, Vormann J. Acid-base status affects renal magnesium losses in healthy, elderly persons. J Nutr. 2006 Sep;136(9):2374-7.

Remer T, Manz F. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am J Clin Nutr 1994; 59: 1356-61.

Remer T, Manz F. Potential renal acid load of foods and its influence on urine pH. J Am Diet Assoc 1995;95:791-797.

Berkemeyer S, Vormann J, Günther AL, Rylander R, Frassetto LA, Remer T. Renal net acid excretion capacity is comparable in prepubescence, adolescence,
and young adulthood but falls with aging. J Am Geriatr Soc. 2008 Aug;56(8):1442-8.

Remer T, Dimitriou T, Maser-Gluth C. Renal net acid excretion and plasma leptin are associated with potentially bioactive free glucocorticoids in healthy lean women. J Nutr. 2008 Feb;138(2):426S-430S.

See also the following papers:

Murakami, K; Sasaki, S; Takahashi, Y; Uenishi, K. Association between dietary acid-base load and cardiometabolic risk factors in young Japanese women. Br J Nutr. 2008;100:642–51


Lanham-New, SA. The balance of bone health: tipping the scales in favor of potassium-rich, bicarbonate-rich foods. J Nutr. 2008;138:172S–177S. [PubMed]


Tucker, KL; Hannan, MT; Kiel, DP. The acid-base hypothesis: diet and bone in the Framingham Osteoporosis Study. Eur J Nutr. 2001;40:231–7.


Wynn, E; Lanham-New, SA; Krieg, MA; Whittamore, DR; Burkhardt, P. Low estimates of dietary acid load are positively associated with bone ultrasound in women older than 75 years of age with a lifetime fracture. J Nutr. 2008;138:1349–54. [PubMed]


Dawson-Hughes, B; Harris, SS; Ceglia, L. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 2008;87:662–5.


Murakami, K; Sasaki, S; Takahashi, Y; Uenishi, K. Association between dietary acid-base load and cardiometabolic risk factors in young Japanese women. Br J Nutr. 2008;100:642–51.


Maurer, M; Riesen, W; Muser, J; Hutler, HN; Krapf, R. Neutralization of Western diet inhibits bone resorption independently of K intake and reduces cortisol secretion in humans. Am J Physiol Renal Physiol. 2003;284:F32–40.


Ashizawa, N; Fujimura, R; Tokuyama, K; Suzuki, M. A bout of resistance exercise increases urinary calcium independently of osteoclastic activation in men. J Appl Physiol. 1997;83:1159–63.

Cardinale, M; Leiper, J; Farajian, P; Heer, M. Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study. J Sports Sci. 2007;25:111–9. doi: ]

Robergs, R; Hutchinson, K; Hendee, S; Madden, S; Siegler, J. Influence of pre-exercise acidosis and alkalosis on the kinetics of acid-base recovery following intense exercise. Int J Sport Nutr Exerc Metab. 2005;15:59–74.


Gannon, RH; Millward, DJ; Brown, JE; Macdonald, HM; Lovell, DP; Frassetto, LA; Remer, T; Lanham-New, SA. Estimates of daily net endogenous acid production in the elderly UK population: analysis of the National Diet and Nutrition Survey (NDNS) of British adults aged 65 years and over. Br J Nutr. 2008;100:615–23.

darnoconrad said...

"CR extends lifespan in pretty much every organism under lab conditions. But if you catch wild mice and put them under CR, it doesn't extend life."

Maybe it's that the lab mice are being force fed bad food from the beginning, so when you take it away by fasting you reduce the amount of poison they are intaking. An example would be, if a high carber fasts; it may be to his benefit because he is intaking less bad food and thus less poison.

Stephan said...

Conrad,

That's a definite possibility. Laboratory rodent food is awful stuff.