Donna Mae,
I take the Kirkland™ brand calcium citrate tablets that also contain vitamin D, magnesium and zinc all in one tablet. I get them at Costco... If you can't get to Costco, you can get the same basic formula by taking Citracal Plus Bone Density Builder™ tablets. Most food stores carry them.
Dennis, you're quite correct and your chemistry is spot on. The calcium citrate mineral supplements combined with the citric acid in lemonade (and lime juice) act as a buffer on the stomach's gastric juices (hydrochloric acid) that have a normal pH range of 1 to 2.5. That's a very acidic solution...
The calcium citrate and lemonade (citric acid) combination acts as a buffer on the stomach contents and elevates it up to a pH of 4.0 and maintains this pH level for up to 5 hours. That's still acidic but no where near the normal level of stomach content acidity. See the link at: bja.oxfordjournals.org/cgi/reprint/77/5/642.pdf for more details.
Under normal conditions, the small intestine requires the stomach contents (chyme) to be pH neutral (7.4) so chemo receptors in the upper part of the small intestine signal the pancreas to dump a bicarbonate solution into the small intestine to neutralize the acidity and elevate the chyme up to pH 7.4. If you want more information on this process, see the following link at:
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The trick here is the stomach effluents (chyme) that have been buffered up to a pH of 4.0 still look acidic to the chemo receptors in the small intestine. When the pancreas dumps in the same amount of bicarbonate to elevate the chyme's pH of 1 to 2.5, there's an overshoot... and the contents of the small intestine are pushed above a pH of 7.4 making the chyme in the small intestine more alkaline.
Here's the payoff... As the arteries and capillaries in the small intestine pull nutrients from its contents... and the contents have an elevated pH above 7.4 by virtue of the pancreatic reaction to the mineral supplements and citric acid buffer, the pH of the bloodstream elevates to more alkaline levels above a pH of 7.4 and this sets off another chain reaction.
The body regulates arterial pH through a number of homeostatic processes... When it senses the elevated pH >7.4, it interprets this as not enough carbon dioxide. As a first and most rapid reaction, the elevated pH triggers a reduction in the respiration rate and vasoconstriction to slow the loss of CO2 from the lungs. This happens in a matter of a few minutes and with a little luck, the vasoconstriction resulting from the mineral supplement and lemonade buffer, prevents the cluster headache triggering mechanism from triggering an attack.
The second reaction to the elevated arterial pH takes much longer (several hours) as the kidneys start retaining the H
+ ion and slowing its passing into the urine to increase the acidity of the bloodstream back towards the neutral pH of 7.4. If you want to read more on homeostasis and blood pH see the following link at:
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The bottom line is better living through chemistry... and a couple margaritas a day can keep the beast away...

Take care,
V/R, Batch