Jennifer Aniston uses it and the England rugby squad swears by its metabolism-boosting qualities. Coconut oil is being touted as the health food of 2008 - but is this just more 'superfood' hype?

When Jennifer Aniston was spotted with a shopping trolley full of coconut oil, the manufacturers of this little-used fat must have jumped for joy. Coconut oil has had a bad press because of its high saturated-fat content, but devotees claim it is misunderstood. It is heart-healthy and fantastic for weight loss, they say, because it speeds up the metabolism. It is also cholesterol-free and - according to some of the wilder proponents - can cure anything from Candida to cancer. The coconut is being touted as the health food of 2008, but a closer look at the science behind the claims highlights the hyperbole that is rife in the "superfoods" industry. Can the answer to all modern ills really be found up a palm tree?

Coconut oil - which is derived from the flesh of the fruit, and not to be confused with coconut milk - is certainly catching on among British athletes. It was included in the diet of the England rugby squad in 2007, who were an average of 2kg of muscle heavier than the 2003 team, and the new squad is already using it. According to rugby union nutritionist Matt Lovell, virgin coconut oil can raise the metabolic rate and therefore help the body to burn fat more effectively. "It is the most misunderstood of all fats," he says. "It is what we call a 'functional food' because it provides many health benefits beyond its nutritional or calorie content."

At first glance, the so-called "fat that makes you thin" argument looks distinctly suspect. Like butter, coconut oil is extremely high in saturated fat.

However, it differs from fats such as butter because it contains a lot of medium-chain triglycerides (MCT). "[These are] absorbed directly by the liver so they burn very much like carbohydrate," says Lovell. "This means they provide instant energy and are suitable for endurance-based events." Other fats, such as butter, contain long-chain fatty acids, which are deposited in fat cells and burn off more slowly.

Even though coconut oil is calorie-dense (about nine calories a gram), coconut enthusiasts maintain that because of the MCTs, the body burns off these calories far more quickly than it would calories from other fat sources. One 2003 study published in Obesity Research seemed to confirm this when it found that coconut oil could help overweight men to burn more calories and lose weight.

"There is a small amount of evidence that MCTs are metabolized and processed differently from LCTs," agrees Bridget Aisbitt, a nutrition scientist at the British Nutrition Foundation. "But ultimately it is the balance of calories in versus calories out that determines weight loss or gain, and one of the simplest ways to reduce calories in is to reduce the amount of fat in the diet. Gram for gram, fat has more than double the calories of carbohydrate or protein."

As it is a saturated fat, you would assume that coconut oil is bad for the heart. However, Lovell points out that "virgin coconut oil, unlike other saturated fats, actually contains no cholesterol, so it does not increase blood serum cholesterol level." Furthermore, he says, "It actually possesses healing properties far beyond that of any other culinary oil and is extensively used in traditional medicine among Asian and Pacific populations."

Others are less enthusiastic. "Of course coconut oil doesn't contain cholesterol," says Professor Peter Emery, head of the department of nutrition and dietetics at King's College London. "The same applies to all plant-derived oils. As always, there is a grain of truth behind the exaggeration. Yes, it does contain a lot of medium-chain triglycerides, which are absorbed straight into the liver [from the small intestine]. And there is some evidence that MCTs do increase the metabolic rate slightly. But the amount you could realistically consume in place of other oils would have a minimal effect on energy balance or weight loss."

Dr Christine Tomlinson, director of the National Candida Society, believes in the antibacterial properties of coconut oil, and advises Candida sufferers (those with a yeast overgrowth) to include it in their diet. Elsewhere, there are claims that it can help with hyperthyroidism, diabetes, pancreatic and thyroid function, vitamin absorption, the immune system and digestive problems.

Ultimately, of course, we should all be ditching saturated fats (such as butter) in our diet in favor of plant-based ones. "The evidence on coconut oil is minimal, certainly when you compare it to the substantial amount of scientific evidence to show that polyunsaturated (vegetable-based oils and spreads) and monounsaturated (such as olive oil or rapeseed oil) help to lower cholesterol levels," says Steer. "Used sparingly, as you would normal cooking oil, coconut oil will certainly do you no harm."

Indeed, there may be some good reasons to give it a go. Virgin coconut oil is organic, tastes surprisingly good in a stir-fry, and can be used as a body lotion or hair conditioner - or even to grease your bike chain.