Methionine, Carnitine, Creatine Flashcards
Methionine
Methionine is a sulphur containing essential amino acid.
Methionine: Food Sources
High in animal foods Beef, eggs, chicken etc. Brazil nuts, sunflower seeds, beans, whole grains (e.g. quinoa).
Methionine: Functions
Methionine is a major methyl donor in the body (for methylation reactions such as the homocysteine cycle, and in phase 2 liver detoxification). Raised homocysteine damages the vascular endothelium and increases the risk of atherosclerosis and miscarriage.
- Use B6, folate and B12 to support methylation, whilst restricting dietary methionine (animal sources) to lower homocysteine.
Methionine: Caution
Excess methionine also increases acidity in the body.
Carnitine
• Carnitine is an amino acid derivative that can be obtained from the diet or synthesised in the body from methionine and lysine. This production requires iron, vitamin C, B3, B6.
• Deficiency of carnitine (rare) results primarily from errors of metabolism, and not from insufficient dietary intake, as the body is usually able to synthesise adequate quantities
• Mutations of the ‘SLC22A5’ gene can make it a conditionally essential amino acid.
• Direct food sources: nuts, seeds, avocado, asparagus, spinach, red meats, dairy.
• Carnitine acts as a peripheral thyroid hormone antagonist, so it can be used therapeutically in cases of hyperthyroidism.
Carnitine: Functions
Assists ATP synthesis from fatty acids
Carnitine: ATP synthesis
Functions:
• Carnitine facilitates the transport of long chain fatty acids across the mitochondrial membrane so they can be oxidised (‘burnt’) to create ATP. For example, in myocardial cells.
• Its also removes potentially toxic metabolites out of mitochondria, and acts as an antioxidant.
Therapeutic Uses:
• Weight loss
• Heart failure
• Infertility improves sperm count, motility; also reduces oxidative damage (highly concentrated in the testes).
• Fatigue and concentration
• Athletic performance
• ADHD ( also shown to increase dopamine and acetylcholine production).
Carnitine Supplementation: Dosage
Supplemental Dosage: 1 2g twice a day (consider capsule / tablet rather than powder due to its unfavourable smell).
Carnitine Supplementation: Drug Interaction
Supplementing carnitine alongside anticoagulants (e.g. warfarin) increases the blood thinning effects.
Thyroid hormones due to carnitine’s effects as a peripheral thyroid hormone antagonist, and thus high dose carnitine is contraindicated with hypothyroidism.
Carnitine Supplementation: Caution
L-carnitine use has been associated with nausea, vomiting, abdominal cramps, heartburn, gastritis, diarrhoea, body odour and seizures, but only at high doses . One of its metabolites
can cause the urine, breath and sweat to have a fishy odour.
Creatine
• Creatine is a small peptide made of the amino acids arginine, glycine and methionine. It is formed in the liver, kidneys and pancreas.
• About 95% of body creatine is found in muscles (with some also in the brain), and functions as a fast source of ATP in the form of ‘creatine phosphate’.
• Creatine supplementation was first introduced to the public in the 1990s after Olympic athletes were reported to be using it to improve performance.
• Direct food sources (it can be obtained from the diet, but is otherwise created by the body): meat, fish and eggs.
Creatine Functions
A storage form of ATP (energy)
Creatine: ATP storage
Functions:
• It enables explosive power in the muscles for up to 8 to 12 seconds.
• Enhances muscular activity, including skeletal as well as cardiac muscle.
Therapeutic Uses:
• Enhancing muscular performance (especially high intensity training)
• Heart failure and coronary artery disease (it is the first molecule to be depleted in cardiac ischaemia)
Creatine Supplementation and Saturation
Skeletal muscle has a saturation point, beyond which additional supplemental creatine will not increase intracellular levels. This occurs within the first few days of loading.
E.g. if a weight trainer was to supplement 20g for 5 days, they would then need to reduce the dose.
0.3g/kg body weight for 5 days, then down to dose of 0.03g/kg.
Creatine: Drug Interactions
Combining caffeine, ephedra and creatine may lead to ischaemic stroke. High doses of creatine might affect renal function and combining creatine with nephrotoxic drugs (e.g. NSAIDs, some antibiotics) might have other harmful effects on kidney function.
