Question: If my tryptophan is low, and I'm on a low-carb diet, would you recommend 5-HTP supplements or tryptophan supplements or both?   There are multiple reasons why tryptophan could be low. It could be that you are not eating enough protein, or it could be that you have a high utilization of the tryptophan. I would look in the test and see if the 5-hydroxyindoleacetate is elevated — because if it is, then that would suggest high serotonin production, and that might explain the low tryptophan.   If that is the case, you may want to look into other explanations. In this particular case, we have talked about high estrogen levels and how they might be one of those things. In which case the root cause is the high estrogen levels and you need to address it at that level.   Repleting the tryptophan maybe isn't necessarily the goal unless you have symptoms that are related to low tryptophan levels. If you're overproducing serotonin, if anything, you might have symptoms that are more related to high serotonin levels.    You might not have any symptoms that are related to low melatonin levels, which is downstream from serotonin, in which case the main negative effect of depleting the tryptophan would probably be related to niacin because tryptophan is used to synthesize niacin — in which case the goal would probably be best served by supplementing niacin instead of tryptophan.    Something to note: if you're trying to put on lean mass and it's not working, it could theoretically conceivably be possible that serotonin overproduction would be depleting the tryptophan to the point where you didn't have enough tryptophan to put on the lean mass you want. If the tryptophan is being diverted into serotonin, that's why it's low, again, judgeable by whether 5-hydroxyindoleacetic is elevated, then it makes no sense to put 5-HTP into the system because your problem isn't that you have low serotonin. If anything, it's that you have a high serotonin.    The only other explanation I would say is if you have a low protein intake, you might need to increase your protein intake. But if that were the case, you would probably see other amino acids more across the board that were depleted and not just tryptophan.    This Q&A can also be found as part of a much longer episode, here: https://chrismasterjohnphd.com/podcast/2019/03/08/ask-anything-nutrition-feb-23-2019   If you would like to be part of the next live Ask Me Anything About Nutrition, sign up for the CMJ Masterpass, which includes access to these live Zoom sessions, premium features on all my content, and hundreds of dollars of exclusive discounts. You can sign up with a 10% lifetime discount here: https://chrismasterjohnphd.com/q&a