Doctor's Best Pure L-Glutamine Powder Review
Doctor's Best Pure L-Glutamine Powder is presented as a science-based nutrition product that supports muscle mass and strength. The page lists the product as Non-GMO, Gluten Free, Soy Free and Vegan. A linked fact sheet (DRB-00491 Pure L-Glutamine Fact Sheet) is provided on the page. The brand describes its L-Glutamine formula as offering benefits in muscle and hydration support, aiding in strength-building endeavors, alongside the essential support from amino acid nutrition for people pursuing dedicated gym efforts. The stated benefits are: supports muscle mass and strength, assists in muscle hydration, and facilitates post-workout recovery. The Supplement Facts panel lists a serving size of 1 scoop (about 5 grams) with approximately 60 servings per container, providing 5 g of L-Glutamine per serving; the Daily Value is not established. Other ingredients are listed as none. Suggested use is to add one level scoop to 8 ounces of juice or protein shake and mix well. For best results, the page advises drinking it one hour before exercise, and repeating after exercise or before bedtime, or as recommended by a nutritionally informed physician. Warnings state to avoid use if pregnant, lactating, or having liver problems. People sensitive to monosodium glutamate (MSG) may be sensitive to glutamine because the body converts glutamine to glutamate. The page recommends supplementing with B vitamins when taking L-glutamine long term. Storage instructions say to keep the product in a cool, dry place. The page notes that packaging and ingredients may change and that items may occasionally ship with alternate packaging, while freshness is guaranteed. Statements have not been evaluated by the FDA, and the product is not intended to diagnose, treat, cure, or prevent any disease.
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Study, Trial or Testing Result Summary
Members Only16 human studies · 8 improved
At three scoops a day this powder gives 15 grams of glutamine, the amount that worked in studies. In 106 adults with diarrhea-type irritable bowel syndrome that began after an infection, 15 grams a day for 8 weeks greatly reduced symptoms in about 80 percent of people versus about 6 percent on placebo, with fewer bowel movements and firmer stools [1]. In 50 adults with irritable bowel syndrome following a low fermentable carbohydrate diet, 15 grams a day for 6 weeks improved symptoms in 88 percent versus 60 percent on placebo [2]. A pooled analysis of 23 trials in people having pelvic radiation found glutamine did not prevent bowel side effects of that treatment, a different situation from everyday sensitive bowels [3]. Other studies that reported less bloating and better gut symptoms used glutamine mixed with probiotics, fish oil or herbs, so glutamine's own share of the benefit is unclear [4][5]. A single high dose caused more stomach discomfort, nausea and belching in healthy men, though it was generally well tolerated [6]. Animal and cell studies are never counted.
See all 16 studies →Hide the studies
- In a pooled analysis of 23 trials with 1919 patients having pelvic radiotherapy, glutamine did not reduce acute bowel side effects, though probiotics, synbiotics and polyphenols did.The role of dietary supplements, including biotics, glutamine, polyunsaturated fatty acids and polyphenols, in reducing …
- In 225 children with abdominal Henoch-Schönlein purpura, alanyl-glutamine nutritional support reduced a med use and weight loss but did not change hospital stay or recurrence of digestive symptoms.[Clinical effect of alanyl-glutamine-enriched nutritional support in the treatment of children with abdominal Henoch-Sch…
- In 190 stroke patients with lung infection, tube feeding with probiotics, glutamine and fish oil over up to 21 days reduced abdominal pain, bloating and diarrhoea and improved feeding tolerance versus standard feeding.Enteral ecoimmunonutrition reduced enteral permeability and serum ghrelin activity in severe cerebral stroke patients wi…
- In 106 adults with diarrhoea-type irritable bowel syndrome after an infection, 15 grams of glutamine a day for 8 weeks cut symptom scores by 50 points or more in 79.6% versus 5.8% on placebo, with fewer bowel movements and firmer stools.Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome.
- In 104 people with diarrhea-predominant irritable bowel syndrome, a Chinese herbal capsule outperformed a glutamine compound capsule over 3 weeks, but glutamine was only the comparator and was not tested against placebo.[Effects of Changjishu soft elastic capsule in treatment of diarrhea-predominant irritable bowel patients with liver-qi …
- In 60 children and adults with cryptosporidium infection, all of whom received a glutamine-based rehydration drink for 2 weeks, adding paromomycin to mirazid improved symptoms more than either drug alone, but the glutamine drink was not tested separately.Mirazid alone or combined with Paromomycin in treating cryptosporidiosis parvum in immunocompetent hospitalized patients…
- In 50 adults with irritable bowel syndrome on a low FODMAP diet, 15 grams of glutamine a day for 6 weeks improved symptoms by more than 45% in 88% versus 60% with placebo.Glutamine Supplementation Enhances the Effects of a Low FODMAP Diet in Irritable Bowel Syndrome Management.
- In 46 patients with acute radiation bowel inflammation, a nutrition mix with probiotics, fish oil and glutamine for 14 days gave better tolerance, with less abdominal pain, bloating and diarrhoea than controls.The impact of microbial immune enteral nutrition on the patients with acute radiation enteritis in bowel function and im…
- In 40 adults, a hydration drink with alanine and glutamine taken for 4 weeks was well tolerated at one to three packets a day, with only mild bloating and cramping changes noted.Randomized Trial to Assess the Safety and Tolerability of Daily Intake of an Allulose Amino Acid-Based Hydration Beverag…
- In 19 healthy young adults, a litre of drink with alanyl-glutamine and electrolytes led to less reported stomach bloating than plain water in a single-session crossover test.The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein.
- In 14 healthy men, a single high dose of L-glutamine caused more stomach and digestive discomfort, nausea and belching over 24 hours than lower doses, though most symptoms were mild and the drink was generally well tolerated.Gastrointestinal Tolerance of Low, Medium and High Dose Acute Oral l-Glutamine Supplementation in Healthy Adults: A Pilo…
- In 43 adults with digestive disorders, a herbal and nutrient gut formula containing glutamine, taken up to 10 g per day for 4 weeks after a control phase, improved upper and lower gut symptoms by 60% to 80% over 16 weeks in an uncontrolled before-and-after study.Herbal formula improves upper and lower gastrointestinal symptoms and gut health in Australian adults with digestive dis…
- In 20 cancer patients after bowel surgery, a feed containing glutamine dipeptides at 500 ml per day for 3 days was well tolerated with no product-related adverse events, and plasma glutamine rose; bowel symptoms were not shown to improve.Early enteral gut feeding with conditionally indispensable pharmaconutrients is metabolically safe and is well tolerated…
- In 14 patients after upper gut surgery, 30 g per day of glutamine dipeptides with antioxidants for 5 days was well tolerated, with only minor nausea, hiccups, or gas in 3 of 14; the study did not measure improvement in bowel symptoms.Safety and intestinal tolerance of high-dose enteral antioxidants and glutamine peptides after upper gastrointestinal su…
- In 78 patients with severe acute pancreatitis, adding glutamine to standard treatment led to faster relief of bloating and abdominal pain and faster return of bowel function, along with lower inflammatory markers.Ulinastatin combined with glutamine improves liver function and inflammatory response in patients with severe acute panc…
- In colon tissue samples taken from 12 people with diarrhea-predominant irritable bowel syndrome and incubated in the lab, higher glutamine concentrations increased the gut-lining protein claudin-1 compared with low glutamine.Glutamine Restores Tight Junction Protein Claudin-1 Expression in Colonic Mucosa of Patients With Diarrhea-Predominant I…
Review Totals and Summary
Members Only8,463 reviews · 94% positive
Doctor's Best Pure L-Glutamine Powder is well liked across the stores that sell it, which together carry about 5,969 ratings. Buyers mostly praise its lack of taste, easy mixing and its use for gut health and workout recovery, and complaints are few. Only the powder is covered here; reviews of other forms were left out. **What buyers say it did for them:** Gut and digestion come up most. One buyer says it is "really seems to be helping my IBS," and another uses it daily for "gut and stomach support." Store summaries add reports of reduced diarrhea, easier digestion and help with leaky gut. Athletes and gym users describe better muscle recovery; one calls it "essential for recovery and gut health" on high-training days. Other buyers mention deep sleep, and one used it in a drink mix to curb sugar cravings during weight loss: "it only took a week before I stopped thinking about having desserts." Some store-page reviewers also mention an energy boost. **What buyers complain about:** Complaints are few. One buyer returned it after two days because of low back pain, though they still said they were "confident this product will work for most people." Another "did not notice a meaningful impact," while allowing that experience may differ. The iHerb summary says a smaller number found the taste unpleasant or noticed no real benefit. That summary calls this the main criticism in the written feedback. **Taste, smell and form:** Most reviewers find it tasteless. One says "No taste goes great with a shake or pre workout," and another says "I could not taste it in my smoothies." It is described as mixing well into water, juice, shakes or green drinks, and several reviewers call the powder very fine. One buyer with a sensitivity to off-notes found the taste "relatively clean." A few buyers found the taste unpleasant. Packaging and the dosage instructions are called convenient and clear, and delivery and packaging were praised as excellent. **Value for money:** Buyers see it as good value. One says, "It's a big jar for the price," and the iHerb summary says the container lasts a long time and that affordability is a plus. Several buyers also like that it has no extra additives and see it as a clean product. **Who it seems to suit, and who it did not:** It seems to suit people taking it for digestive comfort, gym-goers who want help with recovery, and anyone who wants an unflavored powder to stir into drinks or shakes. Reviewers value that it works best when used consistently. It suited less well the buyer who got low back pain, and the buyers who felt no noticeable effect. A few store-page reviews were originally posted on another site, so they could not be checked against buyers at the store where they appear. Overall, the written feedback is positive, with the doubts about individual results and the odd taste complaint.
Biohacker Summary
Members Only6 of 10 recommend it
Most of the panel recommends or uses glutamine, and the main reason is gut support: eight of the ten spoke about healing the gut lining, easing leaky gut or calming gut inflammation. Other reasons include supporting immune function during travel, illness or poor sleep, cutting sugar cravings, a calming effect during stress, and recovery after training. Doses are mostly about 5 grams a day, taken with meals by one panelist, and two of them raise it to 15 to 20 grams when sick, traveling or short on sleep; one panelist suggests periodic use rather than daily use, and powder is the form mentioned most. Cautions came up too: two warn against taking it near bedtime because it is stimulating and can disrupt sleep, one says it can break ketosis and should not be taken while fasting, and one notes that tumor cells also use it as fuel. Pairings were few, with one panelist blending it into a recovery smoothie with whey protein, glucosamine and flaxseed oil, and nobody said they stopped taking it.
See all 9 biohackers →Hide the biohackers
Thomas DeLauer · Glutamine · neutral
- Mentions a previous breakdown on how 5 grams of glutamine can double autophagy in the brain and reduce neuroinflammation.
- States that glutamine is the primary fuel source for intestinal cells, and its availability is crucial for the integrity of the gut barrier.
- Recommends supplementing with glutamine for a calming effect, especially when experiencing high stress, injury, illness, or increased training volume, as it acts as a precursor to GABA and helps the body produce more of it.
- Loads up on extra glutamine during muscle building phases.
- Recommends glutamine as one of the things that support the gut lining.
- Is familiar with glutamine being important for maintaining gut barrier function, though he has not done specific research on it in his lab.
- Recommends Glutamine as a great tool for gut cells when stressed or overworked, but advises not to take it every day.
- Mentions that glutamine is a main source of fuel for the gut and is also important for muscles, and a lack of it can lead to leaky gut during intense exercise.
- Recommends taking 5 to 10 grams of glutamine daily, stating that it directly feeds the cells lining the gut, thereby improving gut permeability and protecting the gut mucosal layer.
- Recommends supplementing with 5g of glutamine when dealing with gut issues, as there is strong evidence it repairs the genes that turn on the repair of tight junctions in the gut.
Dr. Eric Berg · Glutamine · recommends
- Recommends taking glutamine or consuming foods high in glutamine to block the effects of grains.
- States that glutamine is an important amino acid for colon cells and is essential for intestinal permeability, greatly supporting the gut and benefiting inflammatory conditions.
- Notes that glutamine is an amino acid that promotes gut healing.
- Mentions that carnivore can help increase glutamine, which is a healing amino acid for the gut.
- Recommends L-glutamine to boost growth hormone naturally.
- States that glutamine is good for gut health and can also increase growth hormone.
- Notes that glutamine, found in red meat, is vital for combating oxidative damage and building up antioxidant reserves.
- Personally needed more glutamine to build up their antioxidant reserve and got it from red meat.
- Notes that cabbage contains glutamine, which is good for leaky gut and fuels cells in the colon, also found in red meat, bone broth, and eggs.
- Recommends L-glutamine as good for healing a leaky gut.
Dr. Mark Hyman · Glutamine · neutral
- Mentions glutamine as something that might be helpful for gut repair.
- Recommends L-glutamine to help with gut barrier repair and healing leaky gut.
- Recommends glutamine to help repair the gut lining.
- Recommends glutamine for targeted support in healing the gut and recalibrating the immune system.
- Recommends glutamine, an amino acid, for its ability to help soothe the gut lining.
- Recommends L-glutamine, found in bone broth, for gut healing and collagen support.
- Recommends glutamine as a gut-healing nutrient.
- Dr. Hyman mentions the amino acid glutamine as one of the many things that help repair the gut lining.
- Mentions giving certain compounds like glutamine that are known to help repair the gut.
- Uses L-Glutamine for increased intestinal permeability, which they commonly observe in patients, including professional athletes.
Dr. Rhonda Patrick · Glutamine · uses
- Supplements with glutamine.
- Always packs Glutamine when traveling, taking a baseline of 5 g/day and increasing to 15-20 g/day when sleep-deprived or exposed to illness, as it is an important fuel source for immune function.
- Warns that Glutamine has stimulating properties that increase arousal, interfering with sleep onset, and should be avoided too close to bedtime.
- Warns against taking glutamine at night for sleep because it is activating and can cause insomnia, citing examples of athletes who experienced this.
- Uses 5 grams of L-Glutamine to support gut-immune axis integrity and may reduce infection risk during travel.
- Says L-Glutamine has been added to their supplement stack recently, convinced by Dr. Rhonda Patrick on its benefits.
- Rhonda's current supplement routine includes Glutamine.
- Rhonda's regimen includes ~5.6g/day of L-glutamine with her morning coffee, upping it to 20g if she feels illness coming on.
- Lists glutamine as a supplement for enhancing exercise performance and recovery.
- Mentions that glutamine can transfer over to brain health, specifically post-concussion protocols, and that it came out as a pretty clear one in their published review on preventative and post-brain injury supplementation.
Siim Land · Glutamine · neutral
- Mentions that glutamine is one of the main precursors needed for glutathione.
- States that glutamine is a good gut supplement that helps heal the gut lining, recommending it periodically for gut healing purposes.
- Recommends supplementing glutamine to address intestinal inflammation and permeability, as it maintains tight junctions and intestinal permeability, with a meta-analysis showing 30 grams a day for less than two weeks reduced intestinal permeability.
- Recommends Glutamine as a good supplement for gut healing purposes, particularly for healing the gut lining, but advises against regular daily use.
- Mentions glutamine as one of many different leaky gut protocols that can be used to help promote the healing of the gut.
- Takes L-glutamine for gut health, along with creatine.
- Notes there is some evidence that glutamine can improve gut barrier function, but he believes lifestyle factors like a high-fiber diet and exercise are the best way, and testing systemic biomarkers is essential to see if glutamine supplementation is actually working for an individual.
- Does not take glutamine himself, believing he gets enough from his high-protein diet, and notes some controversial evidence about it potentially feeding cancer cells.
- Siim Land's amino acid supplement also contains glutamine, which he notes is useful for other purposes.
- Notes that if glutamine is in a meal, there will be a net reduction in calories absorbed, with some research suggesting as much as 37%.
Dave Asprey · Glutamine · recommends
- Asks what happens if you put glutamine in the skin, suggesting that manipulating amino acids in the skin and elsewhere is a fertile ground for more research.
- Recommends L-glutamine to support the gut barrier.
- Gave his yoga teacher glutamine to help with brain fog and autoimmune issues, which helped his energy return.
- Notes that companies are now creating pre- and post-op surgical supplementation with glutamine, similar to what he had figured out years ago.
- Warns that glutamine will take one out of ketosis and should not be taken during the fasting phase, but is acceptable after a workout.
- Recounts a story from their film where a mother used glutamine powder to get rid of her son's mouth sores during chemotherapy, which impressed the doctors.
- States that in their experience, giving glutamine to depressed patients helps heal their gut lining and can improve their mood in about 10 minutes.
- Recommends taking l-glutamine, an amino acid, to support the gut lining and improve gut barrier function.
- Discusses glutamine supplementation.
- States that if he were very ill, he would be on a serious L-glutamine regimen, as it can reduce IL-6 and make one feel better quickly, though it can throw you out of ketosis.
Andrew Huberman · Glutamine · recommends
- Supplementing with L-glutamine may reduce sugar cravings, and anecdotally, it works.
- Discusses glutamine supplementation in relation to leaky gut and sugar cravings.
- Takes L-glutamine daily at 5g, increasing to 15-20g in 5g increments when her son is sick, she is exposed, during season, or when traveling, because she believes it helps her not get sick.
- He highlights specific nutrients, including glutamine, and discusses their recommended doses and dietary sources for offsetting sugar cravings.
- Recounts an anecdote about taking a teaspoon of L-glutamine in half-and-half twice a day, which he believes helped him wean off sugar, though he acknowledges it could be a placebo effect.
- Mentions that some people find ingesting a teaspoon of L-glutamine a few times a day helps with sugar cravings, noting that this method has anecdotal data but has not been peer-reviewed.
- Discusses L-glutamine supplementation for leaky gut, noting it is controversial with no randomized controlled trials, but some people swear by it, possibly due to increasing L cells.
- Discusses the emerging idea that glutamine, taken as a teaspoon or so in water a couple of times a day, can help reduce sugar cravings by activating gut neurons that signal to the dopamine pathway.
- Recommends looking at plasma glutamine semiannually as an important marker.
- Suggests Glutamine as a tool to reduce sugar cravings.
Ben Greenfield · Glutamine · neutral
- Mentions glutamine as a supplement that provides glucose to the brain, supporting neurotransmitter functions, as suggested by a guest.
- Recommends taking about five grams of L-glutamine with each meal for around four to eight weeks to help heal a leaky gut.
- Recommends taking about 5 grams of glutamine powder with each meal as a simple way to reduce IBS issues.
- Mentions that gut issues can be mitigated with L-Glutamine.
- Mentions that a report for a client with high gut inflammation suggested using glutamine.
- Recommends 5 grams of L-glutamine for those with leaky gut, gut issues, or irritable bowel, noting it works similarly to colostrum.
- Mentions discussing when to take glutamine and when taking glutamine may cause further damage to the body.
- Ben asks Nayan about glutamine, and Nayan says that glutamine is not a good idea in large amounts, especially for those with early onset dementia or neurological disorders, and advises people to stay away from it as much as possible. He says that 15 grams a day would be too much if you don't have a leaky gut problem.
- Ben recommends taking 5 grams of glutamine powder with breakfast, lunch, and dinner for several weeks as part of a leaky gut protocol.
- Recommends supporting the natural mucosal lining with glutamine if one frequently cleanses or does juice fasts.
Peter Attia · Glutamine · recommends
- Notes that glutamine has been shown to increase the survival rate in ICU patients.
- Recommends glutamine as a nutrient the body needs to heal the gut.
- Warns that glutamine is essential for the immune system and gut health, so blocking it with drugs for cancer treatment must be done strategically to avoid compromising these systems. He also notes that tumor cells use glutamine as fuel, so it's a double-edged sword.
- Would make a smoothie with whey protein isolate, glutamine, glucosamine, and flaxseed oil for recovery after his run.
RAL Summary
Members OnlyTier 4 for Digestion and Bloating
The no-effect verdict rests on a pooled analysis of radiation-induced bowel side effects, which is not this goal, while the two placebo-controlled trials in irritable bowel syndrome at 15 grams a day show clear improvement. So it is graded Tier 4, as the studies disagree.
- Emerging: not enough evidence to rank higher yet.
Where the evidence disagrees: 7 of the 16 human studies found no effect.
More Details
Members OnlyBody systems · Combine with · Possible side effects
Body systems: Digestive system
Combine with: For gut lining support, pair L-Glutamine with zinc carnosine, a multi-strain probiotic (Lactobacillus and Bifidobacterium), and soluble fiber such as partially hydrolyzed guar gum or psyllium to nourish the microbiome. Collagen peptides and aloe vera extract may further support mucosal comfort. For post-workout recovery, combine with BCAAs or complete EAAs, creatine monohydrate, and magnesium. If the real aim is cellular and DNA repair, choose targeted compounds instead, such as NMN or NR with TMG, resveratrol or pterostilbene, quercetin and fisetin, alpha-lipoic acid, and glycine with NAC to support glutathione. Consult a healthcare provider before starting new supplements, especially with kidney or liver conditions.
Possible side effects: A single high dose caused more stomach discomfort, nausea and belching in a small study, though symptoms were mostly mild. Reviews report few complaints, with one buyer reporting low back pain.
Supplement Facts
L-Glutamine 5 g
| L-Glutamine | 5 g | † |
Directions: Suggested Adult Use: Add 1 scoop to 8 ounces of juice or protein shake and mix well. For best results, drink 1 hour before exercise. Repeat after exercise or before bedtime, or as recommended by a nutritionally informed physician. It is recommended to supplement with B vitamins if taking L-glutamine long term.
Barcode (UPC) 753950004917 · Label source: NIH label database · Report a label change
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Graded November 11, 2026 by the Reverse Age Lab evidence engine, from human studies, real reviews and our biohacker panel. How we grade. Is this medical advice? No. Rala organizes the published evidence; go over any change with your doctor, especially if you take meds.
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