A common complaint we sometimes here is that people experience heartburn after taking L-cysteine (CysReplete). There are a couple probable reasons for this and both have solutions.

The Cause of the Pain

When people complain about stomach upset or heartburn after taking CysReplete or L-cysteine, ask some questions. You’ll likely find that the discomfort usually presents in the lower substernal region. If this is the case, the likely culprit is the CysReplete adhering to the distal esophagus then dissolving. This causes irritation of the esophagus along with the reported pain.

Interestingly, we’ve found a couple solutions that seem to work well with most people. First, proper posture while taking the pills is important; if a person is slumped forward while taking pills, it is much more likely they will experience this substernal burning. Therefore, the solution is to have them stand up straight while taking the pills. In addition, we’ve found that if they leave the capsules in their mouth with water for 20-30 seconds before swallowing, the pills go down much easier. Follow those pills with ~12 ounces of water (and/or some food) and this will almost insure that the pills will dissolve in the mouth and not the distal esophagus (bye-bye pain!).

We’ve also found that some people do not tolerate taking L-cysteine in the morning. I don’t know why this occurs, but it occurs often enough (~20% of people) to tell me that it’s real. We’ve found that simply moving the L-cysteine to another time of day (i.e., lunch, dinner and bedtime) usually fixes the problem.

L-Cysteine Intolerance

If these suggestions don’t help and a person has experienced several days of heartburn following ingestion of the capsules, discontinue the CysReplete/L-cysteine for five days then restart following the recommendations above.

If this doesn’t work, change to L-methionine and add 400 mcg selenium (total daily amount). However, be sure and routinely check homocysteine levels in these people. If homocysteine levels are elevated, check B12, folate and B6 metabolism (using and organic acids test) and treat accordingly.