Ed,

I've some comments on the potassium (K+) and acid/base discussion.

One of the first lessons every medical student has to learn is about the
sensitivity of the blood K+ -level. The correct function of many
physiologic systems severely depends on it, especially the rhythm of the
heart contraction. If he doesn't, he will have to learn it the hard way:
you can kill a laboratory animal (or a patient) very efficiently and fast
by carelessly playing around with K+ - containing infusions. Another
clinical experience is that the only reliable method to bring a high K+
-level down is a slow infusion of insulin (if necessary plus glucose).
This even works if the patient is diabetic! If he is not, a pure glucose
infusion will do, because this slowly raises the patients own insulin
production. Now imagine what happens, if somebody with a normal or even
low K+ blood level gets a long lasting glucose infusion from his gut, let
us assume from white bread with butter and honey, that is not accompanied
by an adequate amount of K+. Keep in mind that 98% of the K+ is inside of
our cells and that the K+ content of the extracellular space may only
change by about half a gram (contained in 150 g of lean meat) without
severe consequences. Right! This sounds like an emergency situation for
some of our electrolyte watchdogs! And now imagine this happens three or
more times a day, 40 years long! Most likely, the controller will give it
up some day and care for the correct K+ level instead of glucose disposal.
There's at least one prospective study that shows a low K+ intake as one
risc factor for diabetes [1].
Let me mention some well accepted facts, that can be found in every
pharmacology or physiology/biochemistry textbook.

i) The insulin sensitivity/resistance of the insulin target cells,
especially muscle cells, strongly depends on their K+ -content. K+ -uptake
is not only needed for glucose storage as glycogen but also for the
activation of many glycolytic enzymes. E.g., the insulin resistance seen
after the therapy with certain diuretics (thiazides) is caused by their K+
-wasting properties. K+ -deficiency is always an intracellular one (98% of
the stock). (For a clinical example, see [2].)

ii) The insulin secretion of the pancreatic beta-cell strongly depends on
its K+ -content. The K+ -level is the common final path of many metabolic
and regulatory mechanisms leading to the secretion of insulin. During the
last ten years, the receptors (look for SUR1, Kir6.x in medline) of the
sulfonylurea class of oral antidiabetics have been identified as an
inhibitor of ATP-dependent K+ -releasing membrane pores. The so called
"persistent hyperinsulinemic hypoglycemia of infancy" has been proven to
be caused by a mutation in the genes coding for these pores leading to
high K+ and thus uncontrollable high insulin levels [3]. This state can be
bettered by agents, that lower the K+ in the beta-cell.

Needless to say, that many metabolic disorders (like hypertension [4]) are
characterized by K+ -deviations and that for many diseases, insulin
resistance is a common feature or a risc indicator/factor.

Man is specialised on food that contains mainly intracellular substances.
So one should await that the insulin actions on all these components, like
amino acids, glucogenetic equivalents, K+, phosphate [5], magnesium, are
tied together very closely.
As protein is converted to glucose in a 7:4 relation and 21g protein is
accompanied by about 360 mg K+ in meat, we should ingest about 360 mg for
every 12g glucose. Or more than 10g for 360 g carbs (western diet: 2-4g).

But even if we eat paleo-style, we possibly are not free to feast solely
on blueberrys or bone marrow! Insulin has not only anabolic properties. It
promotes the catabolism of energy by stimulation of glycolysis and thus
supports heat production and physical activity. For our medical
grandfathers in the pre-insulin era a low-energy diet was one of the few
therapeutical options to treat diabetes, i.e. the lack of insulin action
as we call it today. In a diet, where "food intake" and not "glycemic
load" triggers insulin, energy intake could be another parameter that is
tied to K+. A 40% / 60% protein-fat relation from meat would mean 6g K+ in
3000 kcal.

An important additional factor for the cellular K+ -content is the blood
pH. If blood becomes more acidic, this leads to a H+ -shift from blood to
cells and a reverse K+ -shift. The K+ shifted to the extracellular space
is excreted by the kidneys and thus lost. In a low carb diet, this danger
always is present (Ketosis! See recently [6]). This is not a question of
acid-base-balance! Additional 100g protein contains additional 16g
nitrogen = 1,14 mol that could be excreted as positively charged ammonia
instead of neutral urea by the kidneys, sparing 1,14 * 39g = 45g K+, if
necessary! A person eating 280 g of protein instead of 80g theoretically
may excrete 2280 mVal more basic equivs as NH4+. This is often not
considered by those acid-base-balance people. Protein is the most basic
nutrient one can find!

There is another side aspect of this. Protein is a very good buffer. If
you eat something very basic (like potash or soda) or a good buffer (like
protein) your stomach will have to secrete many H+ (and Cl-) -ions to make
its content acid. These ions are drawn from the blood, making blood more
basic which is followed by a H+ shift from cells to blood. The following
K+ -shift into the cells lowers blood K+ -levels, preparing the blood for
the uptake of ingested K+, renders the beta-cells more sensitive for
scretion stimuli, and makes muscle cells more insulin sensitive. All this
happens before anything enters the gut!

Our veggie-friends always insist on how good they feel if they eat only
fruits and vegetables. Why shouldn't we believe them? But let's do a
rational analysis. We all know that vegetables are not those vitamin bombs
(besides of C) they are thought to be. And even the invention of the
vitamin pill has not brought mankind to olympic hights of healthiness,
beauty and power. And trace elements are surely important but very
inconsistently found in different plants and very dependent on their
availability in the soil. So everything boils down to high sugar and
kationic mineral content (like Mg++ and K+, potash). The combination
sugar / K+ seems to make people feel well.
What can a paleo-dieter do to stay K+ -replete?

i) Avoid metabolic acidosis.
ii) About 2g K+ in 1000 kcal plus additional 3g for every 100 g carbs.
iii) The K+ must be present in the meals.

[1] Colditz, Am J Clin Nutr 1992 May;55(5):1018-23
[2] Tourniaire J, IS 0338-1684, Diabete Metab 1988 Dec;14(6):717-20
[3] Reis, Diabetes Metab 2002 Feb;28(1):14-9
[4] Resnick, Hypertension 2001 Sep;38(3 Pt 2):709-12
[5] Lind, Am Heart J 2001 Oct;142(4):720-4
[6] Westman, Am J Med 2002 Jul;113(1):30-6)


                    roro

   NNNN   NNNN      roland rohde, md, +49 (511) 906 35- Tel -03 FAX -69
 NN     N     NN    mailto:[log in to unmask]
NN      N  NN  NN   Leibniz Research Labs for Biotechnology
NN      N      NN   and Artificial Organs (LEBAO)
 NN     N     NN
  NN         NN     Hannover Medical School (MHH)
    NN              http://www.mh-hannover.de
      NN   LEBAO    Department of Cardiovascular Surgery