Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: neilep on 05/08/2004 20:45:03
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Hi People,
If the acid in our stomach is so strong (it is isn't it?), then how come it doesn't destroy all the nutrients and proteins etc etc...and if it is so strong , then how come we get tummy aches from eating 'dodgy' foods and food poisoning ?....why doesn't the extra strong stomach acid kill the bad stuff too ?........don't know if I've asked my question clearly but hope you understand.
Many Thanks
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The acid in your stomach is about 1M in hydrogen ion concentration. This really isn't that bad in terms of acidity, compared to many concentrated acids. It will denature some proteins, but that aids the digestion process in that it allows the proteins to be broken down into amino acids for use in your own body's protein synthesis. Molecules like sugars and vitamins are either unreactive to all but the strongest acids or are acids in their own right. Folic acid is one of the B vitamins...I believe vitamin C is citric acid or one of its metabolic byproducts.
As for the microbes, it only takes one to form a colony. If it's hiding inside a clump of food or if you drink enough liquids to dilute the stomach acids, some of the billions you just ingested could survive to proliferate in the intestinal tract. Also, some bacteria are inherently resistant to low pH. They're called acidophiles. E. Coli is one example. You normally have E. coli in your intestine, but one particular strain is what causes illness, and it's pretty resistant to stomach acids since it evolved to survive in digestive tracts.
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Just to add, citric acid is NOT vitamin C - that's a common misconception. Vitamin C, a water-soluble antioxidant, is actually known as ascorbic acid and is often found with, but is not the same as, citric acid, one of the dominant acids in citrus fruits.
In relation to stomach acids, the pH of the stomach is usually around 2. It provides a chemical barrier against food-bourne infection but, as highlighted by Jason (above), this line of defence is not perfect and bugs can slip through the net. Moreover, some bacteria and viruses are specifically adapted to tolerate highly acidic conditions and use to their advantage the relative protection that it offers. For example, rather like some plants that depend on fire to germinate their seeds, some viruses (like rotaviruses which cause food poisoning) rely on the harsh environment of the stomach to partially digest the outer coat of the virus to make it infectious. And Helicobacter pylori, which causes ulcers and gastric cancer, secretes a metaphorical suit of armour in the form of a thick protective alkaline mucus that keeps out the stomach acid.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thanks Jason and Chris.... Your answers have cleared it all up for me, and I shall afford my tummy extra respect from now on.
I once had an upper endoscopy (no anaesthetic, cos the thought of being forced to sleep or semi conscious scared the heebeegeebees out of me)...and it was found that I had patchy ulceration across the lining of my tummy...I even looked down the endescope myself !..and since then, I've wondered about the incredible strength of the acid in my tummy, and it was after a rather queezy evening that led to me asking the question...thanks again.
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