L-Lysine | whatsinit

About

What it is and where it shows up.

L-lysine is an essential amino acid that the human body cannot synthesize and must obtain from dietary sources such as meat, fish, dairy, eggs, and legumes. It is added to foods, infant formula, and nutritional supplements to improve protein quality and correct deficiencies that are common in cereal-based diets.

Safety summary

The regulatory and scientific consensus.

L-lysine is well-tolerated at normal dietary and supplemental intakes; human clinical studies have established a NOAEL of approximately 6 g/day and a LOAEL of 7.5 g/day for supplemental use in healthy adults. No formal Acceptable Daily Intake (ADI) has been set by international bodies because it is a naturally occurring dietary nutrient. High supplemental doses may cause mild gastrointestinal symptoms, and individuals with impaired renal or hepatic function should exercise caution due to increased nitrogen metabolism demands.

Regulatory landscape

What food-safety regulators have decided.

Jurisdiction	Status	Note
EFSA (European Food Safety Authority) (European Union)	Approved	No E number assigned; L-lysine is listed as a permitted amino acid source in food supplements under Directive 2002/46/EC; multiple EFSA FEEDAP Panel opinions have concluded the amino acid itself is safe for consumers and is authorised as a nutritional additive in animal feed under Regulation (EC) No 1831/2003.source
FSSAI (Food Safety and Standards Authority of India) (India)	Approved	Permitted amino acid under FSSAI Health Supplements, Nutraceuticals, Food for Special Dietary Use and Food for Special Medical Purpose Regulations (amended 2021); also permitted in infant formula and cereal-based complementary foods solely to improve nutritional value of the protein mixture.source
FDA (Food and Drug Administration) (United States)	Approved	Permitted as a direct food additive (nutrient) under 21 CFR 172.320 for use in foods for special dietary purposes, including infant formula and meal-replacement products; also recognised as safe as a dietary supplement ingredient.source

Who should approach with care

Whose guidance would steer them away.

Kidney Disease — High-dose L-lysine supplementation increases dietary nitrogen load and may exacerbate renal strain in individuals with compromised kidney function who have a reduced ability to excrete nitrogenous waste.

Liver Disease — Impaired hepatic amino acid metabolism in liver disease may affect the safe processing of high supplemental doses of lysine, warranting medical guidance before use.

Research citations

The sources behind this verdict.

1FDA. Code of Federal Regulations Title 21, Part 172.320 – Amino Acids. accessdata.fda.gov
2PubMed. Tolerable Upper Intake Level for Individual Amino Acids in Humans: A Narrative Review of Recent Clinical Studies, 2023. pmc.ncbi.nlm.nih.gov
3EFSA. Safety and efficacy of a feed additive consisting of concentrated liquid l-lysine, l-lysine monohydrochloride and concentrated liquid l-lysine monohydrochloride produced by Escherichia coli NITE BP-02917 for all animal species, 2022. efsa.europa.eu
4FSSAI. Food Safety and Standards (Health Supplements, Nutraceuticals, Food for Special Dietary Use, Food for Special Medical Purpose, Functional Food and Novel Food) Regulations – Compendium (amended September 2021), 2021. fssai.gov.in
5EFSA. Safety and efficacy of concentrated liquid l-lysine (base) and l-lysine monohydrochloride produced by fermentation with Corynebacterium casei KCCM 80190 as feed additives for all animal species, 2020. efsa.europa.eu

Independently researched5 citations