Threonine is one of the nine essential amino acids, meaning your body cannot produce it and you must obtain it through diet or supplementation. It is found in high-protein foods like meat, eggs, and dairy, and plays a central role in building proteins throughout the body. Unlike some amino acids that get most of their attention for muscle building, threonine is especially valued for what it does in the gut, liver, and immune system.

Threonine is the main building block of mucin proteins, which form the protective mucus layer lining your digestive tract — essentially the gut's first line of defense. It is also a key component of collagen and elastin, the structural proteins in skin, tendons, and connective tissue. In the liver, threonine helps regulate fat metabolism and prevents unhealthy fat accumulation, while in the immune system it contributes to the production of antibodies and immune cells.

Threonine supplements are most commonly available as free-form L-Threonine powder, which mixes easily into water or smoothies, or in capsule and tablet form. It is also present in complete protein supplements and some amino acid blends. The free-form powder is typically the most bioavailable option for therapeutic dosing.

• Leaky gut and intestinal permeability
• Liver health and fatty liver
• Muscle recovery and protein synthesis
• Skin, hair, and nail strength
• Immune system support
• Nervous system and neurological support
• Wound healing
• Low protein / malnutrition recovery

• Intestinal barrier breakdown (by maintaining mucin layer thickness)
• Hepatic fat accumulation in the context of low-protein diets

• Beef and poultry — Animal meats are among the richest dietary sources of threonine, providing over 1,000 mg per 100g serving of lean meat.
• Eggs — A single large egg provides around 250–300 mg of threonine, and the protein profile is highly bioavailable.
• Dairy (cottage cheese, Greek yogurt) — High-protein dairy products are solid threonine sources, with cottage cheese offering roughly 400–500 mg per half-cup serving.
• Fish and seafood — Fish like tuna, salmon, and cod provide substantial threonine alongside other essential amino acids and omega-3 fatty acids.
• Lentils and legumes — For plant-based eaters, lentils, black beans, and chickpeas offer meaningful threonine, though at lower amounts than animal proteins — combining with grains helps complete the profile.

• Nausea at high doses (typically above 3,000 mg/day)
• Loose stools or mild digestive upset
• Headache in sensitive individuals at very high doses
• Elevated liver enzymes theoretically possible with chronic very high intake — though not well-documented in clinical studies at normal supplemental doses

• Recommended daily: 500–2,000 mg/day for general support; up to 3,000 mg/day may be used for specific gut or liver therapeutic purposes under professional guidance
• Best time of day: Can be taken any time; some people prefer morning or around meals for digestive support
• With or without food: Can be taken either way — with food may reduce any chance of nausea, especially at higher doses; on an empty stomach may offer slightly faster absorption
• Time to effect: 2–6 weeks for gut lining and connective tissue benefits; some people notice improved digestion or energy within the first 2 weeks
• How long to take it: Can be taken continuously as part of a maintenance protocol. If using therapeutically (e.g. for gut repair), a focused 8–12 week course is reasonable, followed by reassessment. No established need for cycling.