Major interaction on record — check this product against your medications before combining. Based on 7 of 10 ingredients. Check your meds →
Dietary supplement

Essential Amino Acids Ingredients & Drug Interactions

by GNC Pro Performance

Essential Amino Acids label
See full label image
Tablet Or Pill Category: Amino Acid/protein
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 23, 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 GNC Pro Performance with 10 active ingredients. Its ingredients are commonly taken for muscle building and recovery, increasing daily protein intake, weight management.Based on those ingredients, 455 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are L-Tryptophan, hydrolyzed Whey Peptide Complex, L-Phenylalanine. 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 GNC Pro Performance

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

Pharmacist-reviewed data Checks every ingredient Answer in seconds
Prefer a human? Send your question to our licensed pharmacists — free, answered by email within 24 hours.

HelloPharmacist Scorecard of Essential Amino Acids by GNC Pro Performance

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

Low disclosure
Ingredient Transparency · database check
Low

Most active ingredients don't disclose an individual amount — you can't tell how much of each you're getting.

Why this rating?
  • The label discloses an exact amount for 1 of its 10 active ingredients.
  • “Micro-Peptide Essential Amino Complex” is a proprietary blend — the label gives one combined amount (1,600 mg) without saying how much of each component you get.

GNC Pro Performance Essential Amino Acids contains 10 active ingredients: hydrolyzed whey peptide complex, a micro-peptide essential amino complex (a blend of component amino acids listed individually), and eight standalone amino acids — L-histidine, L-lysine, L-methionine, L-phenylalanine, L-threonine, L-tryptophan, L-isoleucine, L-leucine, and L-valine. Essential amino acids are the nine amino acids your body cannot make on its own and must get from food or supplements; this product delivers most of them in concentrated form.

The product also contains inactive ingredients — cellulose, stearic acid, titanium dioxide, magnesium stearate, vegetable acetoglycerides, natural vanilla mint flavor, caramel color, and stevia leaf extract — which serve as fillers, binders, colorants, and flavorings in the tablet.

Does it work?

Moderate evidence
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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: Supports muscle recovery and growth.
  • We looked for evidence on: Athletic performance, Exercise-induced muscle damage, Muscle strength, Sarcopenia, Wound healing, Protein synthesis — and 2 related terms.
  • The strongest evidence on file: Whey Protein is rated "Possibly Effective" for Athletic performance (Natural Medicines).
  • Also on file: Methionine is rated "Insufficient Reliable Evidence To Rate" for Wound healing.
  • Also on file: Lysine is rated "Insufficient Reliable Evidence To Rate" for Athletic performance, Muscle strength.

Effectiveness data for most individual amino acids in this product shows limited evidence. Whey peptide is possibly effective for athletic performance but possibly ineffective for osteoporosis or COPD.

L-phenylalanine is possibly effective for vitiligo but possibly ineffective for ADHD. L-lysine is possibly effective for cold sores (herpes labialis).

L-methionine may be possibly effective for preventing neural tube birth defects. For the other amino acids — L-histidine, L-threonine, and L-tryptophan — evidence in our data is insufficient or the data shows they are possibly ineffective for their proposed uses.

Since this product combines multiple amino acids in one formula, it's unclear how the mixture performs together for any single condition. Talk with your doctor about whether this formulation fits your goals.

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

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 6 of the 7 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 7 of 7.
  • General safety write-ups exist for 7 of 7.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Whey peptide is generally well tolerated by healthy adults when used as directed, but concentrated supplement products haven't been well studied — check with your doctor before starting. Most common side effects from whey are dose-related and include acne, bloating, cramps, diarrhea, fatigue, headache, nausea, and reflux.

A small number of case reports link whey protein to acne worsening in teenagers and young adults, which resolved after stopping. Among the amino acids, L-lysine commonly causes abdominal pain, diarrhea, and indigestion at high doses.

L-phenylalanine may cause anxiety, constipation, headache, heartburn, insomnia, and nausea. L-tryptophan causes drowsiness and can produce diarrhea, headache, nausea, and stomach pain; it has a history of contamination from a single manufacturer in Japan in 1989 (traced to one supplier, now addressed), though modern products are monitored.

L-methionine and L-threonine at typical food amounts are well tolerated, but high-dose supplement safety is less certain. L-histidine safety at supplement doses isn't well established.

We do not hold pregnancy and breastfeeding data for whey peptide or L-lysine — talk with your doctor before use in pregnancy or while nursing.

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

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?
  • 5 of the 7 matched ingredients can interact with medications — Lysine, L-tryptophan, Phenylalanine, Whey Protein, Threonine.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: Parkinson's medications.
  • For scale: 455 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 any of these: levodopa (Major severity — whey peptide and phenylalanine both reduce its effect and may worsen Parkinson symptoms), NMDA antagonists (Major — threonine may reduce their effect), CNS depressants like sleep aids or opioids (Major — tryptophan may intensify drowsiness), serotonergic antidepressants or migraine drugs (Moderate — tryptophan adds to their serotonin effects), quinolone or tetracycline antibiotics (Moderate — whey peptide reduces absorption), bisphosphonates (Moderate — whey peptide reduces absorption), baclofen (Moderate — phenylalanine competes for absorption), or MAOIs (Moderate — phenylalanine raises blood pressure risk). If you don't take any medications, no interactions are documented for the amino acids we could check.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFormula with limited ingredient disclosure with some supporting evidence for its stated purpose. Major medication interactions have been identified, and safety information is well characterized.

This product is an amino acid blend that may support athletic performance or general protein intake if you're not getting enough from food. If you take any medications — especially levodopa for Parkinson's, antibiotics, bisphosphonates, antidepressants, sleep aids, or older blood pressure medications — you need to check this product against your specific drugs first because interactions are documented.

Pregnancy and breastfeeding safety varies by ingredient; discuss it with your doctor or pharmacist before starting.

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

Assessment coverage: 7 of 10 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jul 25, 2017.

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 GNC Pro Performance
Barcode (UPC) 048107169626
Net contents 60 Tablet(s)
Market status On market
Date entered into DSLD Jul 25, 2017
DSLD ID 74718
Product type Amino Acid/protein
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten Free
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 GNC Pro Performance, 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:
2 Tablet(s)
Maximum serving Sizes:
2 Tablet(s)
Servings per container
30
UPC/BARCODE
048107169626
IngredientAmount% DV
hydrolyzed Whey Peptide Complex100 mg--
Micro-Peptide Essential Amino Complex1600 mg--
L-Histidine0 NP--
L-Lysine0 NP--
L-Methionine0 NP--
L-Phenylalanine0 NP--
L-Threonine0 NP--
L-Tryptophan0 NP--
L-Isoleucine0 NP--
L-Leucine0 NP--
L-Valine0 NP--

Other ingredients: Cellulose, Stearic Acid, Titanium Dioxide, Magnesium Stearate, Vegetable Acetoglycerides, natural Vanilla Mint flavor, Caramel color, Stevia leaf extract

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.
Precautions

Keep out of reach of children.

Contains: Milk.

Warning: Consult your physician prior to using this product if you are pregnant, nursing, taking medication, or have a medical condition.

Discontinue use two weeks prior to surgery.

Storage

Store in a cool, dry place.

FDA Disclaimer Statement

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

Formula

1700mg Micro-Peptide Complex

Contains: Milk.

General Statements

Essential amino acids

Supports muscle recovery & growth

Conforms to USP <2091> for weight. Meets USP <2040> disintegration.

When used in conjunction with a resistance exercise program.

FDA Statement of Identity

Dietary Supplement

General

CODE 988411 FRG

Suggested/Recommended/Usage/Directions

Directions: As a dietary supplement, take 1-2 servings daily.

Formulation

No artificial colors, no artificial flavors, sodium free, no wheat, gluten free, no soy, yeast free.

Seals/Symbols

GF Gluten free

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

See for yourself

Essential Amino Acids by GNC Pro Performance 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 GNC Pro Performance

These are the 10 active ingredients this product is made of. Select any to open its full monograph.

Serving size2 Tablet(s) Dosage formTablet Or Pill Servings per container30 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.

Hydrolyzed Whey Peptide Complex

Interacts with
53 drugs
100 mg per serving

Whey protein is a high-quality, complete protein made from cow's milk that can help people meet protein needs and support muscle growth when combined...

Hydrolyzed Whey Peptide Complex monograph & interactions

Micro-Peptide Essential Amino Complex

1600 mg per serving

Other (inactive) ingredients: Cellulose, Stearic Acid, Titanium Dioxide, Magnesium Stearate, Vegetable Acetoglycerides, Natural Vanilla Mint flavor, Caramel color, Stevia leaf extract. These complete the product’s ingredient list but are not active constituents.

Interaction report

Essential Amino Acids by GNC Pro Performance 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
455Drugs
256 Major 199 Moderate

Ingredients driving the most interactions

L-Tryptophan 394
hydrolyzed Whey Peptide Complex 53
L-Phenylalanine 16
L-Threonine 3
L-Lysine 1

Individual Drug Interactions

The ingredients in Essential Amino Acids interact with 455 drugs. Click any drug to see the details.

5 of the 10 ingredients in Essential Amino Acids interact with drugs. Each result below shows which ingredient is responsible. L-Tryptophan hydrolyzed Whey Peptide Complex 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

hydrolyzed Whey Peptide Complex4 drug types · 53 drugs

Levodopa

Theoretically, whey protein might decrease levodopa absorption.
Small clinical studies show that concomitant ingestion of protein or high doses of leucine or isoleucine (100 mg/kg) and levodopa can exacerbate tremor, rigidity, and the "on-off" syndrome in patients with Parkinson disease.

Likelihood Probable Evidence D
Bisphosphonates

Theoretically, whey protein might reduce the absorption of bisphosphonates.
Whey protein contains minerals such as calcium that bind bisphosphonates in the gut. Advise patients to take bisphosphonates at least 30 minutes before whey protein, but preferably at a different time of day.

Likelihood Probable Evidence D
Quinolone Antibiotics

Theoretically, whey protein might decrease quinolone absorption.
Whey protein contains minerals, such as calcium, that can bind to quinolones in the gut. To avoid this interaction, advise patients to take oral quinolones at least 2 hours before or 4-6 hours after whey protein.

Likelihood Probable Evidence D
Tetracycline Antibiotics

Theoretically, whey protein might decrease tetracycline absorption.
Whey protein contains minerals, such as calcium, that bind to tetracyclines in the gut. To avoid this interaction, advise patients to take oral tetracyclines at least 2 hours before or 4-6 hours after whey protein.

Likelihood Probable Evidence D
hydrolyzed Whey Peptide Complex 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.

GNC Pro Performance

See all GNC Pro Performance products
Name
General Nutrition Corporation
City
Pittsburgh
State
PA
ZipCode
15222
Phone Number
1-888-462-2548
Web Address
gnc.com
Pharmacist Counseling Corner

Essential Amino Acids by GNC Pro Performance: Common Questions

Does Essential Amino Acids by GNC Pro Performance interact with any medications?
Yes. Based on its ingredients, Essential Amino Acids has a known interaction with 455 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 10 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?
Pregnancy safety varies by ingredient. We hold no data for whey peptide or L-lysine, and phenylalanine is flagged as unsafe in pregnancy. L-methionine and L-tryptophan are rated possibly unsafe. Others like L-histidine and L-methionine are rated likely safe, but supplement doses in pregnancy haven't been well studied. Talk with your doctor before taking this product during pregnancy.
Is this safe while breastfeeding?
Safety data while breastfeeding is limited or missing for most ingredients here. L-phenylalanine should be avoided, and L-tryptophan safety isn't established while nursing. We hold no data for whey peptide or L-lysine, and supplement doses of others haven't been well studied. Check with your doctor or pharmacist before taking it.
Will this help me build muscle or improve athletic performance?
Whey peptide is rated possibly effective for athletic performance in our data. The other amino acids don't have established effectiveness for muscle building in our held evidence. Results depend on your total protein intake, training, and overall diet — talk with a coach or registered dietitian about how this fits your plan.
What's the most common side effect?
From whey peptide, the most common side effects are bloating, cramps, and diarrhea, which are dose-related. From the amino acids, L-lysine frequently causes abdominal pain and diarrhea, and L-phenylalanine may cause constipation or headache. Start with a low dose and see how your stomach tolerates it.
Can I take this with my antidepressant?
It depends which antidepressant. If it works through serotonin (like SSRIs), L-tryptophan in this product theoretically adds to those effects and could raise the risk of serotonin-related side effects. If you're on an older antidepressant called an MAOI, phenylalanine in here raises blood pressure risk. Check your specific medication with your doctor before starting.
Why are there three amino acids (isoleucine, leucine, valine) we couldn't check for interactions?
We hold no interaction monographs for those three branched-chain amino acids, so we cannot tell you whether they interact with medications. If you're on any prescription drugs, ask your doctor or pharmacist to check those specific amino acids against your medications before you start.

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

Whey Protein

Interacts with 53 drugs

Whey protein is a high-quality, complete protein made from cow's milk that can help people meet protein needs and support muscle growth when combined with exercise. It is generally safe for...

Read the full Whey Protein 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

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 → 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

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 →
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 92 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.

Whey Protein 25 references
  1. Martindale W. Martindale the Extra Pharmacopoeia. Pharmaceutical Press, 1999.
  2. Maton PN, Burton ME. Antacids revisited: a review of their clinical pharmacology and recommended therapeutic use. Drugs 1999;57:855-70.
  3. Bell SJ. Whey protein concentrates with and without immunoglobulins: a review. J Med Food 2000;3:1-13. PubMed
  4. 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
  5. 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
  6. Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. PubMed
  7. 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
  8. Semla TP, Beizer JL, Higbee MD. Geriatric Dosage Handbook. 4th ed. Hudson, OH: Lexicomp, 1998.
  9. Pletz MW, Petzold P, Allen A, et al. Effect of calcium carbonate on bioavailability of orally administered gemifloxacin. Antimicrob Agents Chemother 2003;47:2158-60.. PubMed
  10. Peters ML, Leonard M, Licata AA. Role of alendronate and risedronate in preventing and treating osteoporosis. Cleve Clin J Med 2001;68:945-51. PubMed
  11. Micke, P., Beeh, K. M., and Buhl, R. Effects of long-term supplementation with whey proteins on plasma glutathione levels of HIV-infected patients. Eur.J Nutr 2002;41(1):12-18. PubMed
  12. Chitapanarux, T., Tienboon, P., Pojchamarnwiputh, S., and Leelarungrayub, D. Open-labeled pilot study of cysteine-rich whey protein isolate supplementation for nonalcoholic steatohepatitis patients. J Gastroenterol.Hepatol. 2009;24(6):1045-1050. PubMed
  13. Sataloff, R. T., Bittermann, T., Marks, L., Lurie, D., and Hawkshaw, M. The effects of glutathione enhancement on sensorineural hearing loss. Ear Nose Throat J 2010;89(9):422-433.
  14. Zhu, K., Meng, X., Kerr, D. A., Devine, A., Solah, V., Binns, C. W., and Prince, R. L. The effects of a two-year randomized, controlled trial of whey protein supplementation on bone structure, IGF-1, and urinary calcium excretion in older postmenopausal
  15. Bjorkman, M. P., Pilvi, T. K., Kekkonen, R. A., Korpela, R., and Tilvis, R. S. Similar effects of leucine rich and regular dairy products on muscle mass and functions of older polymyalgia rheumatica patients: a randomized crossover trial. J Nutr Health A
  16. Brun, A. C., Stordal, K., Johannesdottir, G. B., Bentsen, B. S., and Medhus, A. W. The effect of protein composition in liquid meals on gastric emptying rate in children with cerebral palsy. Clin.Nutr 2012;31(1):108-112. PubMed
  17. Gouni-Berthold, I., Schulte, D. M., Krone, W., Lapointe, J. F., Lemieux, P., Predel, H. G., and Berthold, H. K. The whey fermentation product malleable protein matrix decreases TAG concentrations in patients with the metabolic syndrome: a randomised plac
  18. Errichiello, L., Pezzella, M., Santulli, L., Striano, S., Zara, F., Minetti, C., Mainardi, P., and Striano, P. A proof-of-concept trial of the whey protein alfa-lactalbumin in chronic cortical myoclonus. Mov Disord. 2011;26(14):2573-2575. PubMed
  19. Carcillo, J. A., Dean, J. M., Holubkov, R., Berger, J., Meert, K. L., Anand, K. J., Zimmerman, J., Newth, C. J., Harrison, R., Burr, J., Willson, D. F., and Nicholson, C. The randomized comparative pediatric critical illness stress-induced immune suppres
  20. Chungchunlam, S. M., Moughan, P. J., Henare, S. J., and Ganesh, S. Effect of time of consumption of preloads on measures of satiety in healthy normal weight women. Appetite 2012;59(2):281-288. PubMed
  21. Rencuzogullari I, Börekçi A, Karakoyun S, et al. Coronary thrombosis in three coronary arteries due to whey protein. Am J Emerg Med. 2017;35(4):664.e3-664.e4. PubMed
  22. Silverberg NB. Whey protein precipitating moderate to severe acne flares in 5 teenaged athletes. Case Reports Cutis. 2012;90(2):70-2.
  23. Simonart T. Acne and whey protein supplementation among bodybuilders. Dermatology. 2012;225(3):256-8. PubMed
  24. Pontes TC, Costa Fernandes Filho GM, Pereira Trindade AS, Sobral Filho JF. Incidence of acne vulgaris in young adult users of protein-calorie supplements in the city of Jo&atilde;o Pessoa-PB. An Bras Dermatol. 2013;88(6):907-12.
  25. Adebamowo CA, Spiegelman D, Berkey CS, et al. Milk consumption and acne in teenaged boys. J Am Acad Dermatol. 2008 May;58(5):787-93. PubMed

See these in context on the Whey Protein 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 →

Lysine 7 references
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  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
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  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
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  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.

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Methionine 12 references
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  2. Btaiche IF, Khalidi N. Parenteral nutrition-associated liver complications in children. Pharmacotherapy 2002;22:188-211.. PubMed
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  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
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  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

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Phenylalanine 23 references
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  2. Sturtevant FM. Use of aspartame in pregnancy. Int J Fertil 1985;30:85-7.
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  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
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  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 →

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

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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
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  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 →

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