You are probably getting around 30 to 50 milligrams of ascorbic acid in one lemon [on average]. see: http://www.nal.usda.gov/fnic/foodcomp/cgi-bin/list_nut_edit.pl
As "grist for your mill," I myself have taken a "bowel tolerance" dose (in HEALTH, not illness) - http://www.orthomed.com/titrate.htm
of ascorbic acid every day since 1994, amounting to, on average, 30,000 to 60,000 milligrams (approximately 1 to 2 ounces) in 5 to 10 divided doses (and will continue to do so for the rest of my life). This is MY bowel tolerance dosage. Your bowel tolerance dosage may be more, or less, than mine, and will undoubtedly vary depending on your current overall health and diet. Each person must find their own bowel tolerance dose each day (although ingesting ANY ascorbate is MUCH better than none). Virtually any mammal you can name (standardized to 154 pounds/70 kilos) produces a minimum of from 2,000 to 13,000 milligrams of ascorbic acid EVERY day of its life, and under "stress" one was recorded to have produced 100,000 milligrams in 24 hours. Need we wonder why their health always seems to be so much better than ours?
If you have any questions and/or concerns, and would like to get my viewpoint on any or all of them, please feel free to write.