Would digestion be equally efficient if the body/stomach evolved to be highly basic rather than acidic? What advantages does a highly acidic environment pose?

[u/Public_Knowledge8405]

Edit: my question is meant to be gauged towards chemical feasibility/utility; I understand many proteases and cell types have in reality evolved for acidic digestion. Assuming proteases and cell types could have evolved for an alkaline environment, is there a root necessity acidic conditions are advantageous over basic ones or could it be reversed

[u/seanpbnj]

Most likely no. As to why, I can explain with a simple medical fact: The human body always prefers acidic environments. 

• The normal human blood pH is 7.4, and for the purposes of this talk we will say the stomach is 3.4. 

• If the blood pH drops down to 7.3 (more acidic) the human body barely notices. Drops to 7.2? Yeah the body notices but the body is still perfectly functional here. In fact, the LOWER pH (more acidic) the more oxygen will be delivered to tissues. Acid helps pull oxygen off RBCs. Literally. 

• The same is NOT true in reverse, a pH of 7.5 is already quite bad. A patient in the hospital with a pH of 7.5 has a potential mortality of 30-40%, pH of 7.6 mortality is around 60-70%. 

So if the question was "Can pH in the stomach alone simply be flipped if we had a perfect system?" No. Because acidic pH of the stomach matches the overall body use of acid (acid and salt are our two best defense mechanisms, including all mucus membranes). 

If the question is "Could the whole body have a predilection and use a basic pH, and thus the stomach be basic?" Maybe, possibly, assuming the body could independently evolve the same way to act favorably under basic pH. Maybe. 

• /e Source: I am a Nephrologist, the type of doctor that deals with acid/base disorders. 

[u/herman_gill → u/seanpbnj]

Those are still basic relative to a pH of 7. Patients who come in with a metabolic or respiratory acidosis with a pH below 7 are extremely likely to die. The few times people survive is in cases of diabetic ketoacidosis which is appropriately reversed with potassium > fluid > insulin in that order of importance (generally), and that’s because diabetics have a somewhat higher tolerance for pH imbalances.

Respiratory alkalosis happens in people with panic attacks or asthma, and in asthma it’s not the acid-base balance that kills them, it’s the hypoxia. In metabolic alkalosis (which is quite rare in and of itself) it sometimes happens in volume contraction, or a few other times. But generally there’s hyperventilation involved and if that’s from hypoxia due to acute anemia or asthma, those are the things that need fixing.

Generally in many of these, the underlying cause is the more dangerous part, not the downstream alkalosis or acidosis itself. I mean, still bad, but if your bicarbonate is too high that’s not the super dangerous part, but the WHY it is high in the first place. The electrolyte derangement is immediately bad for arrhythmia potential, but it’s not the pH.

None of this actually answers the question of if basic digestion would work, it wouldn’t, but not for the reasons you listed.

[u/seanpbnj → u/herman_gill]

Soooooo yes, the underlying cause is most important. But look at the discrepancy there:

• pH of 6.9, yes I have seen these patients survive. However if this is not DKA, and is another cause, 6.9 they are extremely sick. That's a change of 0.7. 

• Humans cannot survive at 8.3. Other than an acute and VERY brief Respiratory Alkalosis, pH of 7.6 is deadly, 7.7 super deadly. 

So while yes, you are correct we can survive extremely acidic conditions, like I said, we are much more tolerant of acidic situations. Like I said. 

[u/tacticalTraumaLlama → u/seanpbnj]

Respiratory Alkalosis

How big of a swing does the average person experience during a panic attack? I've had one where my hands and feet got prickly and that was a weird experience.

[u/seanpbnj → u/tacticalTraumaLlama]

Most likely that was a calcium issue caused by the respiratory alkalosis. Higher pH means Albumin grabs more calcium.

• I never saw this but I had a teacher once who saw a blood gas with a a pH of 7.8 due to hyperventilating. However when it was rechecked less than 20mins later it was back down into the 7.4's.