Major interaction on record — check this product against your medications before combining. Based on 6 of 9 ingredients. Check your meds →
Dietary supplement

Essential Amino Acids Ingredients & Drug Interactions

by Double Wood Supplements

Essential Amino Acids label
See full label image
Capsule Category: Amino Acid/protein
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Essential Amino Acids against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Essential Amino Acids is a dietary supplement by Double Wood Supplements with 9 active ingredients. Its ingredients are commonly taken for acetaminophen (tylenol) overdose support, liver health, urinary tract acidification.Based on those ingredients, 407 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are L-Tryptophan, L-Phenylalanine, L-Threonine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Essential Amino Acids by Double Wood Supplements

Ask about any prescription or over-the-counter medication and we check it for interactions with Essential Amino Acids by Double Wood Supplements — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Essential Amino Acids by Double Wood Supplements

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 23, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 9 of its 9 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Essential Amino Acids contains 9 active amino acids: L-leucine, L-isoleucine, L-methionine, L-phenylalanine, L-valine, L-histidine, L-threonine, L-tryptophan, and L-lysine. Amino acids are the building blocks your body uses to make and repair proteins, support muscle function, and produce neurotransmitters and other important molecules.

The product also contains inactive ingredients—gelatin capsule, cellulose, and magnesium stearate—which help form and stabilize the capsule.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: supports workout and muscle recovery.
  • We looked for evidence on: Athletic performance, Muscle strength, Wound healing, protein synthesis, tissue repair, recovery.
  • The closest evidence on file: Methionine is rated "Insufficient Reliable Evidence To Rate" for Wound healing (Natural Medicines).
  • Also on file: Lysine is rated "Insufficient Reliable Evidence To Rate" for Athletic performance, Muscle strength.
  • Also on file: L-tryptophan is rated "Insufficient Reliable Evidence To Rate" for Athletic performance.

The evidence for these amino acids varies widely by condition. L-lysine is possibly effective for herpes labialis (cold sores).

L-methionine is possibly effective for neural tube birth defects. L-phenylalanine is possibly effective for vitiligo but possibly ineffective for ADHD.

L-histidine is possibly effective for cholera. For most other conditions listed—including depression, anxiety, athletic performance, multiple sclerosis, spasticity, and kidney failure—the evidence in our data is insufficient to rate.

We don't have established effectiveness ratings for all conditions this product might be marketed for, so talking with your doctor about what you're hoping to achieve is important.

The evidence, ingredient by ingredient Methionine Phenylalanine Histidine Threonine L-tryptophan Lysine

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 5 of the 6 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 6 of 6.
  • General safety write-ups exist for 6 of 6.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

L-phenylalanine, L-tryptophan, L-methionine, L-histidine, L-threonine, and L-lysine are generally well tolerated at typical food and supplement doses. Common side effects are mild: L-phenylalanine may cause anxiety, constipation, headache, or heartburn; L-tryptophan can cause drowsiness, headache, nausea, or diarrhea; L-threonine may cause headache or minor gastrointestinal upset; L-lysine may cause abdominal pain or diarrhea.

L-tryptophan has a historical safety note: in 1989, a contaminated batch from a single Japanese manufacturer caused over 1,500 cases of a serious neurological condition (eosinophilia-myalgia syndrome). Modern L-tryptophan products have strict quality controls, but the history is worth knowing.

For pregnancy and breastfeeding: L-methionine is likely safe; L-histidine is likely safe; L-phenylalanine is rated unsafe during pregnancy and should be avoided; L-tryptophan is possibly unsafe in pregnancy and should be avoided while breastfeeding; L-lysine and L-threonine lack sufficient pregnancy/breastfeeding safety data. If you're pregnant, planning pregnancy, or breastfeeding, discuss this product with your doctor or pharmacist before starting.

Side effects, ingredient by ingredient Methionine Phenylalanine Histidine Threonine L-tryptophan Lysine

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 4 of the 6 matched ingredients can interact with medications — Lysine, L-tryptophan, Phenylalanine, Threonine.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: Parkinson's medications.
  • For scale: 407 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, double-check with your doctor or pharmacist if you take levodopa (for Parkinson disease), any CNS depressant (sedatives, sleep aids, alcohol), serotonergic antidepressants or other serotonin-boosting drugs, baclofen (muscle relaxant), an MAOI antidepressant, an NMDA antagonist (memantine, ketamine), or a 5-HT4 agonist (prucalopride). These are the medication types with documented or theoretical interactions.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Major medication interactions have been identified, and safety information is well characterized.

This product may be worth considering if you're looking for amino acid supplementation and don't take levodopa, CNS depressants, serotonergic drugs, baclofen, MAOIs, NMDA antagonists, or 5-HT4 agonists. If you do take any of those or have phenylketonuria (PKU), or if you're pregnant or breastfeeding, talk with your doctor or pharmacist first — some ingredients carry real risks or lack safety data in those contexts.

Even if you don't take those specific drugs, run your full medication list through this page's search tool or check with your pharmacist before starting, since nearly 400 individual medications are affected by the ingredients here.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 6 of 9 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jan 22, 2021.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Essential Amino Acids, straight from the product label.

Brand Double Wood Supplements
Barcode (UPC) 859793007617
Net contents 225 Capsule(s)
Market status On market
Date entered into DSLD Jan 22, 2021
DSLD ID 241772
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Essential Amino Acids by Double Wood Supplements, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
3 Capsule(s)
Maximum serving Sizes:
3 Capsule(s)
Servings per container
75
UPC/BARCODE
859793007617
IngredientAmount% DV
L-Leucine205 mg--
L-Isoleucine115 mg--
L-Methionine35 mg--
L-Phenylalanine72 mg--
L-Valine141 mg--
L-Histidine37 mg--
L-Threonine141 mg--
L-Tryptophan37 mg--
L-Lysine185 mg--

Other ingredients: Gelatin Capsule, Cellulose, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
General Statements

Product information: Amino Acids are most commonly known as the building blocks of proteins and are compounds which play may essential roles in the body ranging from the building of proteins to the synthesis of hormones and neurotransmitters. Essential Amino Acids are the 9 Amino acids that the body cannot synthesize itself and must be obtained through dietary sources. Double Wood's Essential Amino Acid supplement contains all 9 of the essential amino acids.

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, take 3 capsules per day on an empty stomach. Do not exceed 12 capsules in one day.

Formula

Contains all 9 essential amino acids

Formulation

Supports workout and muscle recovery Supports nutrient absorption

FDA Statement of Identity

Dietary Supplement

Precautions

Warning: Consult your physician before use.

Do not use Essential Amino Acids if you are pregnant, nursing, or are under 18 years of age.

Discontinue use and consult your doctor immediately if any adverse reactions occur.

Do not use Essential Amino Acids and operate heavy machinery until you know how it affects you.

Do not use Essential Amino Acids if you are pregnant, nursing, or are under 18 years of age. Keep out of reach of children.

Do not exceed 12 capsules per day.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Essential Amino Acids by Double Wood Supplements label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Essential Amino Acids label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Essential Amino Acids by Double Wood Supplements

These are the 9 active ingredients this product is made of. Select any to open its full monograph.

Serving size3 Capsule(s) Dosage formCapsule Servings per container75 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

L-Leucine

205 mg per serving

L-Isoleucine

115 mg per serving

L-Methionine

No known
interactions
35 mg per serving

Methionine is an essential amino acid that your body needs for protein building and many basic chemical reactions. Most people get enough from a norma...

L-Methionine monograph & interactions

L-Phenylalanine

Interacts with
16 drugs
72 mg per serving

Phenylalanine is an essential amino acid the body uses to make brain chemicals like dopamine and norepinephrine. Some people take it for mood, vitilig...

L-Phenylalanine monograph & interactions

L-Valine

141 mg per serving

L-Histidine

No known
interactions
37 mg per serving

Histidine is an essential amino acid your body needs to build proteins and to make compounds like histamine and carnosine. Most people get enough from...

L-Histidine monograph & interactions

L-Threonine

Interacts with
3 drugs
141 mg per serving

Threonine is an essential amino acid your body needs but cannot make, so you must get it from food or supplements. Most people get plenty from a norma...

L-Threonine monograph & interactions

L-Tryptophan

Interacts with
394 drugs
37 mg per serving

L-tryptophan is an essential amino acid the body uses to make serotonin and melatonin, and people take it to support sleep and mood. The evidence for...

L-Tryptophan monograph & interactions

L-Lysine

Interacts with
1 drug
185 mg per serving

Lysine is an essential amino acid your body cannot make on its own, so it must come from food or supplements. People most often take extra lysine to t...

L-Lysine monograph & interactions

Other (inactive) ingredients: Gelatin Capsule, Cellulose, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Essential Amino Acids by Double Wood Supplements Drug Interactions

Want to check YOUR meds against Essential Amino Acids?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
407Drugs
256 Major 151 Moderate

Ingredients driving the most interactions

L-Tryptophan 394
L-Phenylalanine 16
L-Threonine 3
L-Lysine 1

Individual Drug Interactions

The ingredients in Essential Amino Acids interact with 407 drugs. Click any drug to see the details.

4 of the 9 ingredients in Essential Amino Acids interact with drugs. Each result below shows which ingredient is responsible. L-Tryptophan L-Phenylalanine L-Threonine L-Lysine

Each ingredient & the kinds of drugs it affects

For each ingredient in Essential Amino Acids with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

L-Tryptophan2 drug types · 394 drugs

Cns Depressants

Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.
Clinical research shows that L-tryptophan can cause fatigue and drowsiness.

Likelihood Probable Evidence B
Serotonergic Drugs

Theoretically, combining L-tryptophan with serotonergic drugs might cause additive serotonergic effects.
L-tryptophan is a precursor to serotonin. Theoretically, combining serotonergic drugs with L-tryptophan might increase the risk of serotonergic side effects, including serotonin syndrome and cerebral vasoconstrictive disorders.

Likelihood Possible Evidence D
L-Tryptophan full monograph & interactions

L-Phenylalanine3 drug types · 16 drugs

Levodopa

Phenylalanine, especially in high doses, can reduce the effectiveness of levodopa.
Phenylalanine competes with levodopa for carrier-mediated transport into the brain. The resulting reduction in levels of levodopa in the brain can exacerbate tremor, rigidity, and the "on-off" phenomenon in patients with Parkinson disease.

Likelihood Probable Evidence B
Baclofen

Concomitant intake of phenylalanine may reduce the intestinal absorption of baclofen.
Phenylalanine and baclofen share the same intestinal carrier for absorption; phenylalanine competitively inhibits the absorption of baclofen, reducing its plasma levels.

Likelihood Possible Evidence D
Monoamine Oxidase Inhibitors (Maois)

Theoretically, concomitant use of L-phenylalanine and non-selective MAOIs might increase the risk of hypertensive crisis.
L-phenylalanine is metabolized to tyrosine. Some evidence suggests that L-phenylalanine, given with the non-selective MAOI pargyline, might prevent the elimination of tyramine, increasing the risk of hypertensive crisis. However, this was not reported in a small number of patients when using L-phenylalanine with the partially selective MAO-B inhibitor, selegiline.

Likelihood Possible Evidence D
L-Phenylalanine full monograph & interactions

L-Threonine1 drug type · 3 drugs

Nmda Antagonists

Theoretically, threonine might decrease the effects of NMDA antagonists.
Threonine increases central nervous system (CNS) glycine levels. Glycine seems to bind a site on NMDA receptors and enhance the activity of the receptors.

Likelihood Likely Evidence B
L-Threonine full monograph & interactions

L-Lysine1 drug type · 1 drug

5-Ht4 Agonists

Theoretically, lysine may reduce the effects of 5-HT4 agonists.
Animal research suggests that L-lysine is a partial serotonin receptor 4 (5-HT4) antagonist and inhibits diarrhea induced by the 5-HT4 agonist, 5-hydroxytryptophane.

Likelihood Unlikely Evidence D
L-Lysine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Essential Amino Acids, from the product label.

Double Wood Supplements

See all Double Wood Supplements products
Name
Double Wood LLC
Street Address
3510 Scotts Ln Ste 219
City
Philadelphia
State
PA
ZipCode
19129-1573
Web Address
www.doublewoodsupplements.com
Pharmacist Counseling Corner

Essential Amino Acids by Double Wood Supplements: Common Questions

Does Essential Amino Acids by Double Wood Supplements interact with any medications?
Yes. Based on its ingredients, Essential Amino Acids has a known interaction with 407 medications, including 256 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Essential Amino Acids contains 9 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take this if I'm pregnant or breastfeeding?
Some ingredients here aren't safe in pregnancy — L-phenylalanine is rated unsafe and should be avoided. L-tryptophan is possibly unsafe in pregnancy and should be avoided while breastfeeding. L-methionine, L-histidine are likely safe, but L-lysine and L-threonine lack enough safety data. Talk with your doctor or pharmacist before using this product during pregnancy or while breastfeeding — they can advise you based on your individual situation.
Is this safe if I have PKU (phenylketonuria)?
No. L-phenylalanine should not be used by people with PKU because their bodies cannot properly metabolize this amino acid. Tell your doctor or pharmacist if you have PKU before starting any amino acid supplement.
What are the most common side effects I might notice?
The most common side effects from these amino acids are mild and include headache, nausea, diarrhea, constipation, heartburn, and drowsiness. Most people tolerate them well at typical doses, but if side effects bother you, talk with your pharmacist about whether to reduce the dose or stop.
Will this help me build muscle or improve athletic performance?
The evidence in our data doesn't support that L-tryptophan is effective for athletic performance. We don't have established effectiveness ratings for muscle growth or sports performance for most of the other amino acids in this product either. If you're interested in amino acids for fitness, chat with your doctor about whether supplementation makes sense for your goals.
Does this contain any fillers?
Yes — the inactive ingredients are gelatin capsule, cellulose, and magnesium stearate. These are excipients (binders and fillers) that help form and stabilize the capsule. If you need to avoid any of these, check the label or ask your pharmacist.
What was that about L-tryptophan and a safety scare?
In 1989, contaminated L-tryptophan from a single Japanese manufacturer caused over 1,500 cases of a serious neurological condition called eosinophilia-myalgia syndrome. The FDA recalled and restricted L-tryptophan products after that. Modern L-tryptophan has strict quality controls, so that specific contamination shouldn't happen again — but it's part of the ingredient's history you should know.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Essential Amino Acids is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Essential Amino Acids label
Go deeper

The Full Monographs Behind Essential Amino Acids’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Methionine

Methionine is an essential amino acid that your body needs for protein building and many basic chemical reactions. Most people get enough from a normal diet, and supplements are generally no...

Read the full Methionine monograph → Herb & supplement monograph

Phenylalanine

Interacts with 16 drugs

Phenylalanine is an essential amino acid the body uses to make brain chemicals like dopamine and norepinephrine. Some people take it for mood, vitiligo, or pain, but the evidence is mostly l...

Read the full Phenylalanine monograph → Herb & supplement monograph

Histidine

Histidine is an essential amino acid your body needs to build proteins and to make compounds like histamine and carnosine. Most people get enough from a normal diet, and good-quality researc...

Read the full Histidine monograph → Herb & supplement monograph

Threonine

Interacts with 3 drugs

Threonine is an essential amino acid your body needs but cannot make, so you must get it from food or supplements. Most people get plenty from a normal diet, and high-quality evidence for ta...

Read the full Threonine monograph → Herb & supplement monograph

L-tryptophan

Interacts with 394 drugs

L-tryptophan is an essential amino acid the body uses to make serotonin and melatonin, and people take it to support sleep and mood. The evidence for supplement use is limited and mixed, and...

Read the full L-tryptophan monograph → Herb & supplement monograph

Lysine

Interacts with 1 drug

Lysine is an essential amino acid your body cannot make on its own, so it must come from food or supplements. People most often take extra lysine to try to prevent or shorten cold sores, but...

Read the full Lysine monograph →
Sources

Sources & How We Checked

Essential Amino Acids's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 67 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Methionine 12 references
  1. La Vecchia C, Negri E, Franceschi S, Decarli A. Case-control study on influence of methionine, nitrite, and salt on gastric carcinogenesis in northern Italy. Nutr Cancer 1997;27:65-8. PubMed
  2. Btaiche IF, Khalidi N. Parenteral nutrition-associated liver complications in children. Pharmacotherapy 2002;22:188-211.. PubMed
  3. Cottington EM, LaMantia C, Stabler SP, et al. Adverse event associated with methionine loading test: a case report. Arterioscler Thromb Vasc Biol 2002;22:1046-50.. PubMed
  4. Anon. Should methionine be added to paracetamol formulations? Drug Ther Perspect 1997;10:11-3. DOI
  5. Smulders, Y. M., Rakic, M., Slaats, E. H., Treskes, M., Sijbrands, E. J., Odekerken, D. A., Stehouwer, C. D., and Silberbusch, J. Fasting and post-methionine homocysteine levels in NIDDM. Determinants and correlations with retinopathy, albuminuria, and c
  6. McAuley, D. F., Hanratty, C. G., McGurk, C., Nugent, A. G., and Johnston, G. D. Effect of methionine supplementation on endothelial function, plasma homocysteine, and lipid peroxidation. J.Toxicol.Clin.Toxicol. 1999;37(4):435-440. PubMed
  7. Hanratty, C. G., McGrath, L. T., McAuley, D. F., Young, I. S., and Johnston, G. D. The effects of oral methionine and homocysteine on endothelial function. Heart 2001;85(3):326-330. PubMed
  8. Ward, M., McNulty, H., McPartlin, J., Strain, J. J., Weir, D. G., and Scott, J. M. Effect of supplemental methionine on plasma homocysteine concentrations in healthy men: a preliminary study. Int.J.Vitam.Nutr.Res. 2001;71(1):82-86. PubMed
  9. Yaghmai, R., Kashani, A. H., Geraghty, M. T., Okoh, J., Pomper, M., Tangerman, A., Wagner, C., Stabler, S. P., Allen, R. H., Mudd, S. H., and Braverman, N. Progressive cerebral edema associated with high methionine levels and betaine therapy in a patient
  10. Talukdar R, Murthy HV, Reddy DN. Role of methionine containing antioxidant combination in the management of pain in chronic pancreatitis: a systematic review and meta-analysis. Pancreatology 2015;15(2):136-44. PubMed
  11. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press, 2005. Available at: https://doi.org/10.17226 DOI
  12. Khairan P, Sobue T, Eshak ES, et al. Association of B Vitamins and Methionine Intake with the Risk of Gastric Cancer: The Japan Public Health Center-based Prospective Study. Cancer Prev Res (Phila) 2022;15(2):101-110. PubMed

See these in context on the Methionine monograph →

Phenylalanine 23 references
  1. Rouse B, Azen C, Koch R, et al. Maternal phenylketonuria collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. Am J Med Genet 1997;69:89-95. DOI
  2. Sturtevant FM. Use of aspartame in pregnancy. Int J Fertil 1985;30:85-7.
  3. Silkaitis RP, Mosnaim AD. Pathways linking L-phenylalanine and 2-phenylethylamine with p-tyramine in rabbit brain. Brain Res 1976;114:105-15.
  4. Lehmann WD, Theobald N, Fischer R, Heinrich HC. Stereospecificity of phenylalanine plasma kinetics and hydroxylation in man following oral application of a stable isotope-labelled pseudo-racemic mixture of L- and D-phenylalanine. Clin Chim Acta 1983;128 PubMed
  5. Mosnik DM, Spring B, Rogers K, Baruah S. Tardive dyskinesia exacerbated after ingestion of phenylalanine by schizophrenic patients. Neuropsychopharmacology 1997;16:136-46. PubMed
  6. Siddiqui AH, Stolk LM, Bhaggoe R, et al. L-phenylalanine and UVA irradiation in the treatment of vitiligo. Dermatology 1994;88:215-8. PubMed
  7. Birkmayer W, Riederer P, Linauer W, Knoll J. L-deprenyl plus L-phenylalanine in the treatment of depression. J Neural Transm 1984;59:81-7. PubMed
  8. Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease. Relation to levodopa absorption and transport. N Engl J Med 1984;310:483-8. PubMed
  9. Baruzzi A, Contin M, Riva R, et al. Influence of meal ingestion time on pharmacokinetics of orally administered levodopa in parkinsonian patients. Clin Neuropharmacol 1987;10:527-37. PubMed
  10. Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. PubMed
  11. Eriksson T, Granerus AK, Linde A, et al. "On-off" phenomenon in Parkinson's disease: relationship between dopa and other large neutral amino acids in plasma. Neurology 1988;38:1245-8. PubMed
  12. Baker GB, Bornstein RA, Rouget AC, et al. Phenylethylaminergic mechanisms in attention-deficit disorder. Biol Psychiatry 1991;29:15-22.. PubMed
  13. Wood DR, Reimherr FW, Wender PH. Treatment of attention deficit disorder with DL-phenylalanine. Psychiatry Res 1985;16:21-6.. PubMed
  14. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press, 2002. Available at: http://www.n
  15. Cederbaum S. Phenylketonuria: an update. Curr Opin Pediatr 2002;14:702-6. PubMed
  16. Cejudo-Ferragud, E., Nacher, A., Polache, A., Cercos-Fortea, T., Merino, M., and Casabo, V. G. Evidence of competitive inhibition for the intestinal absorption of baclofen by phenylalanine. Int J of Pharm (Amsterdam) 1996;132:63-69. DOI
  17. Fischer, E., Heller, B., Nachon, M., and Spatz, H. Therapy of depression by phenylalanine. Preliminary note. Arzneimittelforschung. 1975;25(1):132.
  18. Beckmann, H., Strauss, M. A., and Ludolph, E. Dl-phenylalanine in depressed patients: an open study. J.Neural Transm. 1977;41(2-3):123-134. PubMed
  19. Sabelli, H. C., Fawcett, J., Gusovsky, F., Javaid, J. I., Wynn, P., Edwards, J., Jeffriess, H., and Kravitz, H. Clinical studies on the phenylethylamine hypothesis of affective disorder: urine and blood phenylacetic acid and phenylalanine dietary supplem
  20. Cotzias, G. C., Van Woert, M. H., and Schiffer, L. M. Aromatic amino acids and modification of parkinsonism. N Engl.J Med 2-16-1967;276(7):374-379. PubMed
  21. Kravitz, H. M., Sabelli, H. C., and Fawcett, J. Dietary supplements of phenylalanine and other amino acid precursors of brain neuroamines in the treatment of depressive disorders. J Am Osteopath.Assoc 1984;84(1 Suppl):119-123. DOI
  22. Mann, J., Peselow, E. D., Snyderman, S., and Gershon, S. D-phenylalanine in endogenous depression. Am.J.Psychiatry 1980;137(12):1611-1612. PubMed
  23. Katoulis AC, Alevizou A, Bozi E, et al. A randomized, double-blind, vehicle-controlled study of a preparation containing undecylenoyl phenylalanine 2% in the treatment of solar lentigines. Clin Exp Dermatol 2010;35(5):473-6. PubMed

See these in context on the Phenylalanine monograph →

Histidine 3 references
  1. Histidine — MedlinePlus (U.S. National Library of Medicine) Source
  2. Amino Acids — MedlinePlus (U.S. National Library of Medicine) Source
  3. Dietary Supplements: What You Need to Know — NIH Office of Dietary Supplements Source

See these in context on the Histidine monograph →

Threonine 4 references
  1. Tandan R, Bromberg MB, Forshew D, et al. A controlled trial of amino acid therapy in amyotrophic lateral sclerosis: I. Clinical, functional, and maximum isometric torque data. Neurology 1996;47:1220-6. PubMed
  2. Lee A, Patterson V. A double blind study of L-threonine in patients with spinal spasticity. Acta Neurol Scand 1993;88:334-8. PubMed
  3. Blin O, Pouget J, Aubrespy G, et al. A double-blind placebo controlled trial of L-threonine in amyotrophic lateral sclerosis. J Neurol 1992;239:79-81.
  4. Roufs JB. L-threonine as a symptomatic treatment for amyotrophic lateral sclerosis (ALS). Med Hypotheses 1991;34:20-3. PubMed

See these in context on the Threonine monograph →

L-tryptophan 18 references
  1. Messiha FS. Fluoxetine: adverse effects and drug-drug interactions. J Toxicol Clin Toxicol 1993;31:603-30. PubMed
  2. Devoe LD, Castillo RA, Searle NS. Maternal dietary substrates and human fetal biophysical activity. The effects of tryptophan and glucose on fetal breathing movements. Am J Obstet Gynecol 1986;155:135-9. DOI
  3. Lieberman HR, Corkin S, Spring BJ. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 1985;42:366-70. PubMed
  4. U. S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements. Information Paper on L-Tryptophan and 5-hydroxy-L-tryptophan, February 2001.
  5. Sullivan EA, Kamb ML, Jones JL, et al. The natural history of eosinophilia-myalgia syndrome in a tryptophan-exposed cohort in South Carolina. Arch Intern Med 1996;156:973-9. DOI
  6. Philen RM, Hill RH, Flanders WD, et al. Tryptophan contaminants associated with eosinophilia-myalgia syndrome. Am J Epidemiol 1993;138:154-9. PubMed
  7. Bohme A, Wolter M, Hoelzer D. L-tryptophan-related eosinophilia-myalgia syndrome possibly associated with a chronic B-lymphocytic leukemia. Ann Hematol 1998;77:235-8. PubMed
  8. Singhal AB, Caviness VS, Begleiter AF, et al. Cerebral vasoconstriction and stroke after use of serotonergic drugs. Neurology 2002;58:130-3. PubMed
  9. Priori R, Conti F, Luan FL, et al. Chronic fatigue: a peculiar evolution of eosinophilia myalgia syndrome following treatment with L-tryptophan in four Italian adolescents. Eur J Pediatr 1994;153:344-6..
  10. Klein R, Berg PA. A comparative study on antibodies to nucleoli and 5-hydroxytryptamine in patients with fibromyalgia syndrome and tryptophan-induced eosinophilia-myalgia syndrome. Clin Investig 1994;72:541-9.. PubMed
  11. Simat TJ, Kleeberg KK, Muller B, Sierts A. Synthesis, formation, and occurrence of contaminants in biotechnologically manufactured L-tryptophan. Adv Exp Med Biol 1999;467:469-80.. PubMed
  12. Shaw K, Turner J, Del Mar C. Tryptophan and 5-hydroxytryptophan for depression. Cochrane Database Syst Rev 2002;(1):CD003198. PubMed
  13. Kilbourne EM, Philen RM, Kamb ML, Falk H. Tryptophan produced by Showa Denko and epidemic eosinophilia-myalgia syndrome. J Rheumatol Suppl 1996;46:81-8.
  14. Horwitz RI, Daniels SR. Bias or biology: evaluating the epidemiologic studies of L-tryptophan and the eosinophilia-myalgia syndrome. J Rheumatol Suppl 1996;46:60-72.
  15. Shapiro S. Epidemiologic studies of the association of L-tryptophan with the eosinophilia-myalgia syndrome: a critique. J Rheumatol Suppl 1996;46:44-58.
  16. Mayeno AN, Gleich GJ. The eosinophilia-myalgia syndrome: lessons from Germany. Mayo Clin Proc 1994;69:702-4. PubMed
  17. Carr L, Ruther E, Berg PA, Lehnert H. Eosinophilia-myalgia syndrome in Germany: an epidemiologic review. Mayo Clin Proc 1994;69:620-5. PubMed
  18. Ullrich SS, Fitzgerald PCE, Giesbertz P, Steinert RE, Horowitz M, Feinle-Bisset C. Effects of intragastric administration of tryptophan on the blood glucose response to a nutrient drink and energy intake, in lean and obese men. Nutrients 2018;10(4). pii: PubMed

See these in context on the L-tryptophan monograph →

Lysine 7 references
  1. Thein DJ, Hurt WC. Lysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis. Oral Surg Oral Med Oral Pathol 1984;58:659-66. PubMed
  2. McCune MA, Perry HO, Muller SA, O'Fallon WM. Treatment of recurrent herpes simplex infections with L-lysine monohydrochloride. Cutis 1984;34:366-73.
  3. DiGiovanna JJ, Blank H. Failure of lysine in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Arch Dermatol 1984;120:48-51. DOI
  4. Milman N, Scheibel J, Jessen O. Lysine prophylaxis in recurrent herpes simplex labialis: a double-blind, controlled crossover study. Acta Derm Venereol 1980;60:85-7.
  5. Griffith RS, Walsh DE, Myrmel KH, et al. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Dermatologica 1987;175:183-90. DOI
  6. Lo JC, Chertow GM, Rennke H, Seifter JL. Fanconi's syndrome and tubulointerstitial nephritis in association with L-lysine ingestion. Am J Kidney Dis 1996;28:614-7. PubMed
  7. Smriga M, Torii K. L-Lysine acts like a partial serotonin receptor 4 antagonist and inhibits serotonin-mediated intestinal pathologies and anxiety in rats. Proc Natl Acad Sci U S A. 2003 Dec 23;100(26):15370-5.

See these in context on the Lysine monograph →

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DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

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