From the Guidelines
L-carnitine consumption has been shown to improve exercise performance and reduce fatigue in patients with intermittent claudication, with a typical dosage of 2g orally twice per day. The evidence from a randomized, placebo-controlled trial suggests that L-carnitine can improve absolute walking distance in patients with peripheral arterial disease 1. Additionally, L-carnitine may benefit people with certain medical conditions like heart disease, diabetes, or kidney disease requiring dialysis by improving energy metabolism and reducing symptoms.
Some key points to consider:
- L-carnitine is a cofactor for skeletal muscle metabolism and can help transport fatty acids into mitochondria for energy production.
- Typical dosages range from 500-2000mg daily, with higher doses (2-4g) sometimes used for specific conditions.
- L-carnitine may help reduce fatigue and support recovery after intense exercise.
- The body naturally produces L-carnitine from amino acids lysine and methionine, but supplementation may be beneficial for vegetarians, older adults, or those with certain health conditions.
- L-carnitine is generally well-tolerated, though high doses may cause digestive issues like nausea or diarrhea.
- For best absorption, it should be taken with meals, particularly carbohydrate-containing foods.
It's worth noting that while the evidence is promising, more research is needed to fully understand the effects of L-carnitine supplementation on exercise performance and fatigue reduction. However, based on the available evidence, L-carnitine supplementation appears to be a safe and potentially effective way to improve exercise performance and reduce fatigue in patients with intermittent claudication 1.
From the FDA Drug Label
Gastrointestinal reactions may result from a too rapid consumption of carnitine. The safety and efficacy of oral levocarnitine has not been evaluated in patients with renal insufficiency Chronic administration of high doses of oral levocarnitine in patients with severely compromised renal function or in ESRD patients on dialysis may result in accumulation of the potentially toxic metabolites, trimethylamine (TMA) and trimethylamine-N-oxide (TMAO), since these metabolites are normally excreted in the urine Gastrointestinal Reactions: Various mild gastrointestinal complaints have been reported during the long-term administration of oral L- or D,L-carnitine; these include transient nausea and vomiting, abdominal cramps, and diarrhea.
L-carnitine consumption may cause gastrointestinal reactions, such as:
- Nausea and vomiting
- Abdominal cramps
- Diarrhea It may also lead to the accumulation of potentially toxic metabolites in patients with severely compromised renal function. 2 2
From the Research
L-Carnitine Consumption Effects
- L-carnitine is a nutrient that contributes to energy production and fatty acid metabolism 3
- It can improve myocardial functionality and metabolism in ischemic heart disease patients, as well as athletic performance in individuals with angina pectoris 3
- L-carnitine supplementation can enhance contractile performance and structural integrity of the cardiac muscle by maintaining efficient energy production and reducing oxidative stress 4
- It may have a pivotal role in cardiovascular health due to its energy metabolism, anti-oxidative stress, and endothelial role 4
- L-carnitine supplementation can improve body strength, sports endurance, and exercise capacity, as well as delay the onset of fatigue 5
- It can increase muscle mass, improve physical effort tolerance, and cognitive function in centenarians 6
- L-carnitine supplementation can reduce hypertension, hyperlipidemia, diabetic ketoacidosis, hyperglycemia, insulin-dependent diabetes mellitus, insulin resistance, and obesity, which can enhance cardiovascular pathology 7
Potential Risks and Considerations
- L-carnitine supplementation can generate trimethylamine-N-oxide (TMAO), a compound linked to faster atherosclerosis progression 4, 6
- The safety and effectiveness of L-carnitine administration remain an issue for scientific investigation 4
- The intestinal metabolism of L-carnitine can produce TMAO, which may be pro-atherogenic 6
- Additional studies are needed to focus on long-term supplementation and its longitudinal effect on the cardiovascular system 6
Dosage and Administration
- The correct dosage of L-carnitine supplementation to obtain improvements in physical performance is still unknown, but 2 g/dL for 4 weeks at rest and 1 g/dL for 3 weeks after exercise may be effective 5
- The supplementation should have a correct dosage to have a maximum effect, and other robust trials are needed to find the best dosage to obtain positive results in metabolic parameters and physical performance 5