Glutamine

Marek Glutamine is a pure, high-dose L-glutamine powder designed to support digestive health, gut lining integrity, and recovery during periods of high physical demand‡. Each serving provides 5 grams of pure L-glutamine.

In supplement language, L-glutamine usually refers to the biologically relevant form of glutamine used in dietary supplements. Marek Glutamine provides pure L-glutamine powder without added flavors, colors, fillers, or sweeteners.

Five grams is the dose most consistently used in research for daily gut-barrier and recovery support — enough to deliver meaningful substrate to the cells that depend on it, while sitting well below the range where excess glutamine becomes a concern.‡

Glutamine is a conditionally essential amino acid: your body normally makes enough on its own, but under physical stress, prolonged exercise, illness, fasting, or low protein intake, demand can outstrip supply. The cells that feel that gap most quickly are enterocytes — the rapidly dividing epithelial cells lining the small intestine — for which glutamine is the preferred fuel source, required for proper cell proliferation, differentiation, integrity, maintenance, and repair of the intestinal epithelial barrier. Adequate availability also supports tight-junction protein expression, which helps maintain a healthy gut barrier.‡ Wang et al., Amino Acids, 2014: https://pubmed.ncbi.nlm.nih.gov/24965526/

Glutamine is the preferred fuel source for enterocytes — the rapidly dividing epithelial cells that line the small intestine and form the gut barrier. Most cells in the body run primarily on glucose; enterocytes are different. They pull a large share of their energy directly from glutamine, and because they turn over every three to five days, the integrity of the gut lining depends on a steady supply of glutamine for proliferation, differentiation, and tight-junction maintenance.‡

Under normal conditions, the body synthesizes enough glutamine on its own. Glutamine is a conditionally essential amino acid — usually self-sufficient, sometimes not. Under physical stress, prolonged or intense exercise, illness, fasting, or recovery from injury, demand can outpace supply, and the gut is one of the first tissues to feel that gap. Adequate availability also supports tight-junction protein expression, which helps maintain a healthy gut barrier.‡

Marek Glutamine provides 5 grams of pure L-glutamine per serving — the dose most consistently used in research on gut-barrier and digestive support, and well below the range where excess glutamine becomes a concern.‡

Reference: Wang et al., Amino Acids, 2014 — https://pubmed.ncbi.nlm.nih.gov/24965526/

Yes. Glutamine is also a fuel source for other rapidly dividing cells, including immune cells.‡ During training blocks, illness, surgery recovery, or sustained stress, glutamine levels can dip, and a daily 5 g serving helps keep this substrate available.‡

Supporting the gut lining matters here too, because much of the body's immune tissue sits in and around the gut wall.‡

Mix one scoop (5 g) into cool or room-temperature water, first thing in the morning on an empty stomach. Wait 20–30 minutes before eating or drinking anything else.‡

There are two reasons for the empty-stomach protocol:

First, delivery. Most glutamine transporters share specificity for other neutral or cationic amino acids, so when glutamine is taken alongside a protein-containing meal or drink, it has to compete with leucine, alanine, and the rest of the amino acid pool for absorption at the intestinal wall. On an empty stomach, that competition is minimal and gastric emptying is faster.‡

Second, timing. The overnight fast leaves enterocytes in a low-nutrient state, which is when they most readily pull glutamine from the lumen as fuel.‡

A few practical notes:

• Use cool or room-temperature water. Glutamine can degrade in heat, so skip hot coffee or tea — and skip bone broth, which contains its own competing amino acids.
• Avoid co-mixing with protein shakes, milk, or BCAAs for the same absorption-competition reason.
• If a fully empty stomach bothers you, a piece of fruit or a few sips of juice alongside is fine. Consistency matters more than perfect timing.
• The taste is mild and faintly sweet — it dissolves cleanly into water without grit and isn't unpleasant on its own.

Reference: Kim & Kim, Int J Mol Sci, 2017 — https://pmc.ncbi.nlm.nih.gov/articles/PMC4127817/

It depends on what you're fasting for.‡

By strict caloric definition, yes. Five grams of glutamine contains roughly 20 calories, so a fully calorie-free fast — black-coffee-and-water purist territory — would count it as a break.

For intermittent fasting or time-restricted eating focused on metabolic goals, effectively no. The caloric and glucoregulatory impact of 5 g is small enough to be irrelevant for most of those goals.

For an autophagy-focused fast, yes — and this is the one to take seriously. Glutamine activates mTORC1, the master kinase that suppresses autophagy. A 2017 Nature Communications study found that supplementation with glutamine alone is sufficient to restore mTORC1 activity during prolonged amino acid starvation. If your specific reason for fasting is to drive autophagy, glutamine cuts against the goal mechanistically. Take it 30 minutes before your first meal instead.‡

For a gut-rest fast, glutamine isn't really "breaking" what you're fasting for — it's the preferred fuel for enterocytes, so it supports the cells you're trying to rest rather than disrupting them.‡

The Marek protocol — 5 g in water first thing in the morning, before breakfast — is designed around the 12–16 hour intermittent-fasting window commonly used by people pursuing metabolic and digestive benefits. In that context, 5 g of glutamine in water is generally compatible. For longer, autophagy-targeted fasts, shift the dose toward your first meal of the day.‡

Reference: Jewell et al., Nature Communications, 2017 — https://www.nature.com/articles/s41467-017-00369-y

Yes — Marek Glutamine is designed to fit into a foundational daily routine and pairs cleanly with the rest of the modular formulary. A few thoughts on stacking:

• Take glutamine first thing in the morning on its own, before other supplements or food. The empty-stomach window matters for absorption.
• Move capsule-based formulas (Daily D3/K2, Calm, P5P+, Berberine⁵, Methylate, Thyroid Support, Liver Support) to a meal later in the day (i.e., with breakfast).
• Mag² + Boron and Marek Glycine — both common evening-routine products — don't conflict with morning glutamine.
• If you take a protein shake or BCAAs around training, try to separate those from your glutamine dose to avoid amino acid transporter competition.

Consult your healthcare provider before starting Marek Glutamine if you:

• Have kidney or liver problems.
• Take prescription medications.
• Are pregnant, nursing, or trying to conceive.
• Are under medical care for a serious or digestive condition.

Marek Glutamine is a dietary supplement and is not intended to diagnose, treat, cure, or prevent any disease. If you are under medical supervision, work with your provider to decide whether glutamine fits your protocol.