07 June 2005

A - Z of L-carnitine

L-carnitine is all the rage at the moment and countless slimming products that contain this compound claim that L-carnitine will melt your fat away or help burn excess fat.

L-carnitine is all the rage at the moment and countless slimming products that contain this compound claim that L-carnitine will melt your fat away or help burn excess fat.

What is L-carnitine?
Carnitine is synthesised in humans from two of the so-called ‘essential amino acids’, lysine and methionine. It is also believed that vitamin B6 is necessary for the synthesis of carnitine.

How does it work?
Research has shown that carnitine plays an important role in transporting fatty acids into the mitochondria. The mitochondria are those parts of body cells, which act like power houses and make energy available to the body.

So if carnitine helps produce energy in the human body, why can’t it help with weight loss? Carnitine does transport fatty acids into the mitochondria, but it cannot fetch fat stored in the hips and thighs and tummy and burn it up.

The amount of carnitine made by the human body is generally not sufficient to meet bodily requirements, so we need to obtain some carnitine from our diet. Meat and dairy products like milk, cheese and yoghurt, are rich sources of carnitine.

A carnitine deficiency can cause a condition called acute encephalopathy, which causes vomiting, mental confusion and sleepiness. Patients with a carnitine deficiency tend to suffer from muscle weakness, as is the case in babies with ‘floppy-baby syndrome’.

A lack of carnitine can also affect brain function and it is essential that baby formulae contain some L-carnitine to ensure proper brain development.

The claims
It is suppose to promote weight loss, and L-carnitine has been hailed as a so-called ‘ergogenic compound’. In other words, L-carnitine is supposed to increase athletic performance. The logic goes like this - if carnitine improves fat oxidation (efficient energy release obtained from burning fat) then it should also improve athletic performance.

What it cannot do
It definitely does not promote weight loss.

Because of this possible link between L-carnitine and athletic performance, a number of carefully-controlled scientific studies were conducted to determine if supplementation with L-carnitine boosts muscle levels of carnitine, and therefore provides athletes with more energy. All these studies found no increase in muscle carnitine levels when athletes took L-carnitine supplements.

Harmful effects

Who may benefit
L-carnitine supplements are used for individuals with a defined carnitine deficiency, babies with ‘floppy-baby syndrome’ and individuals who develop a deficiency, because of taking certain of the anti-epileptic drugs which contain a chemical called ‘valproic acid’. In such cases, the use of L-carnitine is indicated and plays an important role in improving muscle tone, brain function and preventing encephalopathy.

People at risk of carnitine deficiency are mainly children with floppy muscles or hypotonia, who fail to thrive, have repeated infections, encephalopathy, hypoglycaemia and heart muscle infections. If these children are treated with L-carnitine, their symptoms generally improve.

It stands to reason that anyone who eats a strict vegetarian or vegan diet, which excludes all milk, dairy products, meat, fish and eggs, also runs the risk of developing a carnitine deficiency. It may, therefore, be a good idea for strict vegetarians and vegans to take an L-carnitine supplement.

Sufficient scientific evidence
No. There is thus no scientific evidence that L-carnitine can improve athletic performance.


Can L-carnitine help you lose weight?. The answer to this question is a resounding no. Neither can it improve athletic performance.

The promises made by manufacturers of slimming products and sports performance boosters that contain L-carnitine are therefore just so much wishful thinking. You will achieve more weight loss if you eat a low-fat, high-fibre diet and improve your athletic performance dramatically if you eat a high-carbo diet, than if you swallow all those expensive L-carnitine supplements.

(Dr I.V. van Heerden, DietDoc)


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