In food and the body

In the body

Skeletal muscle holds the most. Human muscle contains about 17 to 25 mmol per kilogram of dry muscle (Mannion et al. 1992, cited in HMDB). Fast-twitch (type II) fibres hold more than slow-twitch fibres. Men have more than women, and the soleus muscle loses carnosine with age (Everaert 2011).

Horse muscle holds some of the highest concentrations measured. Type II fibres hold about five times more than type I (Sewell 1992).

The heart holds carnosine, but published values do not agree, ranging from about 10 mmol/L in one review to under 0.1 mmol/kg in a tissue survey. This site treats the heart value as uncertain.

In the brain, humans hold mostly homocarnosine. Carnosine itself is low or absent except in the olfactory bulb (Progress in Neurobiology 1999). Smaller amounts occur in the kidney, liver, gut and fat (Nutrients 2023 review).

How the body makes it

Carnosine synthase (gene CARNS1) joins beta-alanine and L-histidine using ATP (Reactome). The enzyme binds histidine about 100 times more tightly than beta-alanine, so beta-alanine supply, not histidine, limits how much carnosine muscle makes (Open Heart review 2014). This is why sports studies give beta-alanine rather than carnosine: 3 to 6 g of beta-alanine a day for four or more weeks raised muscle carnosine by about 30 to 50 per cent in the trials reviewed by Stellingwerff 2020. Washout after loading is slow, about 2 per cent a week (Baguet 2009).

How the body breaks it down

Two enzymes break carnosine. Serum carnosinase (CN1, gene CNDP1) circulates in the blood of humans and other higher primates. Tissue carnosinase (CN2, gene CNDP2) works inside cells. Carnosine’s half-life in human serum is under five minutes (Nutrients 2023 review). Rats, mice, dogs and most other mammals lack serum CN1, which is one reason animal results do not carry over cleanly to people. See Carnosinase and absorption.

In food

There are no plant sources. Meat and fish contain carnosine and its methylated relative anserine. In a UK survey, beef and pork held mostly carnosine, while chicken, turkey and tuna held mostly anserine (Jones, Smith and Harris 2011, Proceedings of the Nutrition Society). Values in that survey are per kilogram of dry matter, which is roughly four times the fresh weight: beef rump about 1,590 mg carnosine per 100 g dry matter, pork rump about 1,250, chicken breast about 1,220 carnosine and 3,460 anserine. An Italian survey found horse meat and pork highest in carnosine (Peiretti 2011, Food Chemistry). A literature value for fresh chicken breast is about 290 mg per 100 g.

Vegetarians have lower muscle carnosine. In 149 adults, 12 vegetarian men had about 26 per cent less carnosine in the gastrocnemius than omnivores (Everaert 2011).