L-carnitine supplementation

L-carnitine can be administered in different forms: L-carnitine fumarate or propionate, propionyl-L-carnitine, and acetyl L-carnitine, with each having different properties and actions in chronic processes.

In supplements, it is preferable to use L-carnitine fumarate or tartrate salts and acetyl L-carnitine for their stability, significantly improving plasma levels of L-carnitine.

Intake and deficiencies

Low carnitine levels are common in elderly people, mainly when they suffer from chronic diseases.

Carnitine has antioxidant, anti-inflammatory, and detoxifying action (Bloomer 2009; Sinatra 2009; Rajasekara 2007; Cruciani 2004; Davis 2009; Uzuner 2002).

Intake. Approximately 75% of carnitine intake is through the consumption of meat (particularly red meats), fish, and dairy products; vegetables, on the other hand, contain almost no carnitine (Rajasekara 2007; Rajasekarb 2007; Cruciani 2004; Marriage, 2003). In an omnivorous diet, people generally consume 20–200 mg/day, while vegetarians consume much less.

Endogenous synthesis. Endogenous carnitine is synthesized in the liver and kidneys from the amino acids lysine and methionine (Soukoulis 2009; Rajasekara 2007; Rajasekarb 2007; Marriage 2003), while the skeletal muscles, where approximately 90% of carnitine is concentrated, and the heart, which contains the highest concentration of carnitine per gram of tissue, are unable to synthesize it (Marriage 2003).

Endogenous biosynthesis of L-carnitine requires lysine, methionine, iron, vitamin C, vitamin B6, and niacin in the form of nicotinamide adenine dinucleotide (NAD). Vitamin C is necessary for carnitine synthesis, and a deficiency of this vitamin results in deficient carnitine synthesis. Methionine is the essential amino acid that is found in the smallest amount in all foods, especially in vegetables, and its deficiency may be common in chronic pathologies.

The amount of carnitine synthesized depends on nutrient intake and on the existence of chronic processes such as kidney failure, chronic liver disease, diabetes, heart disease (Hoppel 2003), and cancer (Cruciani 2009; Cruciani 2004).

Deficiencies. Tissue levels of L-carnitine fall with age in humans and animals (Noland 2009; Costell 1989). EAnalysis of muscle tissue samples from healthy humans shows a dramatic reduction in carnitine in elderly people (Costell 1989).

This reduction can be more pronounced if the diet includes little meat or fish. Carnitine has antioxidant, anti-inflammatory, and detoxifying action (Bloomer 2009; Sinatra 2009; Rajasekara2007; Cruciani 2004; Davis 2009; Uzuner 2002).

• Low carnitine levels are common in elderly people, mainly when they suffer from chronic diseases.
• Low carnitine levels are common in heart disease and diabetes.
• In heart disease, L-carnitine helps to improve the following: cardiac function, exercise capacity, quality of life, and evolution.
• In intermittent claudication, L-carnitine helps to improve symptoms.
• In obesity, fibromyalgia, chronic fatigue, and COPD, L-carnitine can help improve their control.
• The usual doses of L-carnitine for long-term treatments are 1.5–2.0 g/day.
• In supplements, tartrate or fumarate salts of L-carnitine should be used due to their stability.
• L-carnitine has an excellent safety profile, with no side effects, in the recommended forms and doses.

REFERENCE VALUES

No reference values or upper levels have been defined for L-carnitine.

FOODS WITH L-CARNITINE

Meat (especially red meats), fish, and dairy products contain L-carnitine; vegetables, on the other hand, contain almost no L-carnitine.

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