I think parasites can definitely cause low stomach acid. I recently took Yomesan to get rid of Tapeworm larvae in the gut, and immediately after taking magnesium sulphate noticed my bloating improved and I had a huge craving for orange juice or tomato juice. At first I thought maybe my body was craving vitamin C (I am deficient in that as well) but now that I tested for low stomach acid I believe that may have been the reason.
I now wonder if I could possibly have some parasites left in there since I still have low acid. This problem has caused me years of acid reflux and now esophagitis. :-(
Oh and if you think you might have parasites, just treat them and don't bother with the tests which won't be accurate anyway. If you have a lot of parasites like me you would need meds, not herbal remedies.