What is Glutamine?
Glutamine is the most abundant free amino acid in the human body, playing a vital role in various metabolic pathways. It is synthesised, stored in skeletal muscle, and released significantly during stress [1]. Glutamine is considered a conditionally essential amino acid, meaning that it becomes necessary under severe clinical conditions when its consumption exceeds its synthesis [2].
What is Carnitine?
Carnitine, or gamma-trimethyl-beta-hydroxybutyrobetaine, is a small molecule found in all cells, from prokaryotic to eukaryotic. It is the sole carbon and nitrogen source in some bacteria and serves as an osmoprotectant in others. In mammals, carnitine is primarily known for transporting long-chain fatty acids into the mitochondria for beta-oxidation, a process crucial for energy production [3].
Uses of Glutamine
In the body: Glutamine is crucial in various bodily functions. It is often used to promote digestive health, boost the immune system, and aid muscle recovery after intense workouts. Glutamine is involved in amino acid and nucleotide synthesis, the tricarboxylic acid cycle, and ureagenesis [4]. It is also a significant fuel for rapidly dividing cells, such as those lining the gut, and is vital in nitrogen transport between organs [5].
In the Medical Field: Glutamine is also used in medical settings to help patients recover from surgeries or injuries. It can help maintain the gastrointestinal tract's health, which is particularly beneficial for individuals with conditions like inflammatory bowel disease.
In addition, glutamine is used to alleviate the side effects of medical treatments such as chemotherapy and radiation, which can cause damage to the cells in the intestines.
Uses of Carnitine
In the body: Carnitine, specifically L-carnitine, is a vital nutrient in energy production and fatty acid metabolism. It is often used as a supplement to improve athletic performance and endurance by enhancing the body's ability to use fat for energy.
In the Medical Field: Carnitine treats various medical conditions. It is effective in managing cardiovascular disorders, including angina, acute myocardial infarction, congestive heart failure, and peripheral vascular disease [6, 7].
Carnitine also shows promise in treating skeletal muscle oxidative stress and atrophy conditions, as it can accelerate muscle formation and induce morphological changes that signify the start of the hypertrophy process [8].
Furthermore, carnitine has been used to enhance the absorption of drugs that are poorly absorbed from the gastrointestinal tract, making it a potential absorption-enhancing agent for a variety of drugs [9].
Side effects of Glutamine
Common side effects: Glutamine is often used in dietary supplements and enteral feeding. However, it can cause side effects, especially when consumed in high quantities. Common side effects include constipation, nausea, and headaches [10, 11]. In some cases, abdominal pain and coughing may also occur [11].
Severe side effects: In more severe cases, glutamine can cause liver damage. This was observed in a case where a female athlete experienced severe abdominal pain and scleral icterus after consuming glutamine powder for three weeks [12].
Long-term glutamine supplementation can also lead to altered amino acid transport and metabolism, ammonia transport, and immune system function. It may also affect tumour growth and cause health problems upon withdrawal [13].
In the context of kidney health, both short-term and long-term glutamine supplementation in healthy athletes were associated with no significant adverse effects. However, it can cause glomerulosclerosis and serum creatinine level elevation in the setting of diabetic nephropathy [14].
Side effects of Carnitine
L-carnitine is another amino acid supplement often used by athletes and bodybuilders. While the risks and benefits of L-carnitine on kidney health have not been thoroughly evaluated, it is generally considered safe in doses up to 6000 mg/day in healthy adults [14].
Choosing what's suitable for you
Glutamine is the more suitable supplement if you aim to enhance recovery from intense exercise, improve muscle glycogen storage, or aid in weight loss.
On the other hand, carnitine might be the better choice if you're looking to boost energy production, particularly if you have a diet low in lysine.
It's important to note that the safety of these supplements can vary based on individual health conditions and the dosage consumed. Always consult with a healthcare provider before starting any new supplement regimen.