Quick answer

Ask your pharmacist or doctor before combining. Official sources document two supplements for MAOIs: L-tryptophan and protein products. The phenelzine label tells people taking it not to take L-tryptophan, and to avoid aged, fermented, pickled or smoked high-protein foods, yeast extract and fava bean pods.^1,2,3

Key facts

The phenelzine label tells people taking it not to take L-tryptophan and lists it among the over-the-counter products to avoid.¹
The same label says to avoid aged, fermented, pickled or smoked high-protein foods, yeast extract and fava bean pods.²
MedlinePlus names phenylalanine (DLPA), rauwolfia, tyrosine and tryptophan as nonprescription or herbal products that may interact with phenelzine.³
MedlinePlus also says to avoid foods and drinks that contain caffeine during phenelzine treatment.³

What are MAOIs, and why are supplements a special concern?

MAOIs are monoamine oxidase inhibitors, a class of antidepressants. MedlinePlus, using phenelzine as its example, says phenelzine is used for depression in people other medicines have not helped, and that it works by increasing the amounts of certain natural substances needed for mental balance. The same page warns of a serious reaction with foods high in tyramine, which turns up in aged, smoked, fermented or spoiled foods.³

The two entries below come from the phenelzine label, which names supplement-type products in its warnings about what to avoid. The sources checked do not address other MAOIs, which have their own labels. That is not a finding either way, so ask your pharmacist about the one you take.^1,2

Why does the phenelzine label say not to take L-tryptophan?

Avoid the combination unless your doctor advises it

The label of phenelzine, an MAOI antidepressant, tells people taking it not to take L-tryptophan: it lists it with compounds that can trigger a dangerous rise in blood pressure with MAOIs, and among the over-the-counter products to avoid. It also says MAOIs combined with tryptophan have been reported to cause disorientation, confusion, agitation, shivering, unsteadiness and other nervous system effects.¹

On the medicine's label

This is the one entry here that carries the avoid label, the strongest of the site's four severity labels. MedlinePlus's phenelzine page agrees with the label by listing tryptophan among the products that may interact. The entry names L-tryptophan, and MedlinePlus also names tyrosine and phenylalanine, so ask your pharmacist about any amino acid product you use.^1,3

Can protein powder interfere with an MAOI?

Ask your pharmacist or doctor first

The label of phenelzine, an MAO inhibitor, tells people to avoid high-protein foods that have been aged, fermented, pickled or smoked, along with yeast extract and fava bean pods, because of the tyramine or dopamine they can contain. Ask before using a protein powder made with fermented yeast or fava bean protein.²

On the medicine's label

The label does not name protein powder. It names aged, fermented, pickled or smoked high-protein foods, plus yeast extract and fava bean pods, because of the tyramine or dopamine they can contain. The ask is about ingredients, not protein itself, so read the ingredient list for yeast extract, fermented ingredients and fava bean protein.²

Which other supplements does MedlinePlus name for phenelzine, an MAOI?

MedlinePlus's phenelzine page lists four nonprescription or herbal products that may interact: phenylalanine (DLPA), which it says is contained in aspartame-sweetened products among others, rauwolfia, tyrosine and tryptophan. These four are not among the entries above, so treat them as questions to take to your pharmacist.³

The same page says to avoid foods and drinks that contain caffeine during treatment with phenelzine. Whether caffeine in a supplement counts, such as in a pre-workout or energy product, is a question for your pharmacist.³

What do the 'avoid' and 'ask first' labels mean on this page?

The two MAOI entries, with the label shown and how each is known^1,2
Supplement	What the label says	Label shown	How it is known
L-tryptophan	Do not take it with an MAOI; it is listed with compounds that can raise blood pressure dangerously	Avoid the combination unless your doctor advises it	On the medicine's label
Protein products made with yeast extract or fava bean	Avoid aged, fermented, pickled or smoked high-protein foods, yeast extract and fava bean pods	Ask your pharmacist or doctor first	On the medicine's label

Both entries rest on the phenelzine label, and neither is merely expected. The difference is that the label names L-tryptophan itself, while for protein it names ingredients that some protein products contain.

What to ask your pharmacist if you take an MAOI

Which MAOI am I taking, and does its label list the same products as phenelzine's?
Do any of my supplements contain tryptophan, tyrosine or phenylalanine?³
Does my protein powder or any shake contain yeast extract, fermented ingredients or fava bean protein?
Do I need to count caffeine from supplements as well as drinks?³
Which foods and drinks must I avoid completely, and which can I have in small amounts?³

Questions people ask

What supplements should you avoid with MAOIs?

The sources checked document two: L-tryptophan, which the phenelzine label tells people not to take, and protein products made with yeast extract or fava bean, which it says to ask about. MedlinePlus also names tyrosine, phenylalanine and rauwolfia for phenelzine.^1,2,3

What vitamins should you not take with MAOIs?

No vitamin is documented for MAOIs in the sources checked: the two entries are an amino acid and a protein product. That is not a finding either way, so ask your pharmacist about any vitamin or other supplement you take.¹

Which supplements interact with MAOIs?

The phenelzine label and MedlinePlus name tryptophan, and the label names yeast extract and fava bean pods. Other MAOIs have their own labels, so ask your pharmacist about yours.^1,3

Is L-tryptophan dangerous with an MAOI?

The phenelzine label says MAOIs combined with tryptophan have been reported to cause disorientation, confusion, agitation, shivering and unsteadiness. It lists tryptophan with compounds that can trigger a dangerous rise in blood pressure and tells people not to take it.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.