Coconut Oil: What the Research Shows
“Miraculous.” “Amazing.” “Life Saving.”
For some reason, people love coconut oil. Really love it.
Most of the affection isn’t directed toward conventional coconut oil, which is added to some candies, coffee creamers, movie theater popcorn, and other foods.
Instead, people have gone gaga over “virgin” oil, which is made by puréeing coconut meat and gently heating it. (To make conventional oil, coconut is cooked and treated with chemicals like hexane to extract the oil.) Here’s what the evidence shows.
Claim: Coconut oil can help you lose weight by speeding up metabolism.
The Facts: Dr. Oz thinks it can. He calls coconut oil “the miracle fat that fights fat.” Yet the only study that tested whether it helps people shed pounds came up empty.
In 2009, a master’s degree student in Brazil gave 40 obese women either coconut oil or soybean oil and asked them to cook with two tablespoons of the oil every day. After three months, the women given coconut oil didn’t weigh any less—and had no smaller waists—than those given soybean oil.
However, the published paper tagged the trivial drop in average waist size (from 39 inches to 38.5 inches) in the coconut oil users as “statistically significant.” It wasn’t.
Yet that’s all osteopath Joseph Mercola needed to shout about “The Amazing Oil That Trims Women’s Waistlines” on mercola.com (where he will happily sell you coconut oil).
Researchers have had more success using oil made entirely of medium-chain triglycerides, or MCTs. (Coconut oil is about 60 percent MCTs.) People metabolize MCTs differently from the long-chain triglycerides found in most other oils.
“MCTs are transported directly from the intestinal tract to the liver, where some of them are burned off as fuel and raise the metabolic rate slightly,” explains Marie-Pierre St-Onge, an assistant professor at Columbia University’s Obesity Research Center. How slightly?
“The increase amounts to about an extra 60 calories a day for someone who consumes one to two tablespoons of MCTs a day,” says St-Onge. “It’s likely much less with coconut oil, which is only about half MCTs, but nobody knows. The research hasn’t been done yet.”
In several small studies, dieters who ate one to two tablespoons of MCT oil a day for three to four months lost about one more pound a month than dieters who ate other oils.
That’s partly due to the small rise in metabolic rate and partly due to MCT oil’s modest impact on appetite.
“We estimate that the dieters ate about 40 fewer calories a day on the MCT diets,” says St-Onge. Overall, MCT oil leads to “a small amount of weight loss that can gradually add up,” she notes. “But it’s not a magic bullet.”
And it’s not cheap. MCT oil costs about five times more than other oils.
Claim: Coconut oil is good for the heart.
The Facts: Researchers haven’t looked at whether people who replace other fats with coconut oil suffer fewer heart attacks or strokes. But they have tested what coconut oil does to LDL (“bad”) and HDL (“good”) cholesterol.
In a study from Malaysia (a major coconut-oil exporter), researchers fed young people diets that got 20 percent of their calories from either coconut oil or olive oil. After five weeks, LDL was 8 percent higher on the coconut oil diet. HDL was 7 percent higher. But HDL may not matter.
“Raising LDL cholesterol clearly increases the risk of heart disease, but we’re no longer sure that raising HDL cholesterol lowers risk,” says Dutch fats expert Martijn Katan, of the Vrije Universiteit Amsterdam.
“Drugs that raise HDL, for example, haven’t prevented heart attacks as we expected. So coconut oil, which raises both LDL and HDL, may not be as healthy for the heart as an oil like canola or soy, which lowers LDL and has little effect on HDL.”
Claim: Coconut oil can protect the brain from dementia.
The Facts: It’s not likely…despite Joseph Mercola’s claims (“Four tablespoons of this ‘brain food’ may prevent Alzheimer’s”).
No good studies have tested whether coconut oil can prevent or treat Alzheimer’s or other dementias. So why might coconut or MCT oil help?
In Alzheimer’s, the brain loses its ability to use glucose, but it may still be able to use compounds called ketones. “And the liver can convert MCTs into ketones,” explains pharmacologist Alok Sharma, of MCPHS University in New Hampshire. But that doesn’t mean that MCTs or MCT oil can help, adds Sharma.
For one thing, consuming coconut or MCT oil doesn’t raise ketone levels in the brain high enough, says Richard Veech, a senior investigator with the National Institutes of Health.
The only large trial that gave Alzheimer’s patients MCTs or a placebo reported a benefit in those without ApoE4, a version of a gene that increases Alzheimer’s risk. But the study, which was funded by the MCTs’ man¬ufacturer, was riddled with irregularities.
Claim: Coconut oil fights bacteria, as well as viruses like HIV.
The Facts: Howstuffworks.com doesn’t mince words: coconut oil is “an ideal way to prevent infections.” Don’t bet on it.
Coconut oil has never gone up against viruses or bacteria in a well-designed study in people. In mice, it flunked.
Sources: Lipids 44: 593, 2009; J. Nutr. 131: 2853, 2001; J. Atheroscler. Thromb. 10: 290, 2003; Metabolism 56: 985, 2007; Am. J. Clin. Nutr. 87: 621, 2008; Am. J. Clin. Nutr. 94: 1451, 2011; Nutr. Metab. 6: 31, 2009.
Article from Nutrition Action: http://www.nutritionaction.com