leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: a white crystalline essential amino acid C6H13NO2 that is obtained by the hydrolysis of dietary protein (as of eggs, soy, or fish) and plays an important role in various physiological functions (as the regulation of insulin secretion and stimulation of protein synthesis in skeletal muscle)

Examples of leucine in a Sentence

Recent Examples on the Web Challenging workouts and proper fueling will be your best muscle builders. BCAAs BCAAs contain three essential amino acids: leucine, isoleucine, and valine. Donavyn Coffey, TIME, 1 Apr. 2024 This product, from Optimum Nutrition, delivers that plus a hearty 24 grams of protein per serving, including 3 grams of leucine. Jenny McCoy, Glamour, 2 Feb. 2024 Branched-chain amino acids (BCAAs) are three critical amino acids known as leucine, isoleucine, and valine. Amber Smith, Discover Magazine, 16 Nov. 2022 Some dietary supplements, such as resveratrol, especially when used in combination with an amino acid called leucine, also help with weight loss, mobility and insulin sensitivity in people and horses. Jane Manfredi, The Conversation, 25 July 2023 These include leucine, valine, isoleucine and a handful of other amino acids your body cannot naturally produce. Dallas News, 15 Feb. 2022 High-quality protein is any protein that contains all of the nine essential amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) that our bodies don’t make on their own. USA TODAY, 2 July 2023 Some are even fortified with more leucine than most casein or whey powders on the market. Paul Kita, Men's Health, 5 Apr. 2023 These essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenyalinine, threonine, tryptophan and valine. Alyssa Jung, Good Housekeeping, 5 Oct. 2021

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'leucine.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


French, from leuc- leuk-

First Known Use

1826, in the meaning defined above

Time Traveler
The first known use of leucine was in 1826

Dictionary Entries Near leucine

Cite this Entry

“Leucine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/leucine. Accessed 18 May. 2024.

Kids Definition


leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: an amino acid that is very important in the nutrition of human beings

Medical Definition


leu·​cine ˈlü-ˌsēn How to pronounce leucine (audio)
: a white crystalline essential amino acid C6H13NO2 obtained by the hydrolysis of most dietary proteins
abbreviation Leu

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