Coconut Oil
Chester J. Zelasko, Ph.D. | August 28, 2007

Coconut oil is touted on several Internet websites to lower serum cholesterol, reduce heart disease, and stimulate weight loss. However, most of the websites that recommend the use of this oil high in saturated fat also happen to sell it.

In response to several questions about the potential benefits of coconut oil, I decided to check the research to separate fact from hype. This Newsletter will examine the claims about coconut oil and whether the research substantiates those claims.

Coconut Oil Basics
As one might expect, coconut oil comes from the fruit of the coconut palm tree, although by some definitions it’s considered a seed. The flesh of the coconut is the source of the oil.

Coconut oil contains close to 90% saturated fat, much higher than other nuts such as almonds and peanuts (1). One difference is that the primary saturated fat in coconut oil is a medium-chain triglyceride (MCT) called lauric acid. This is important because many of the health claims are related to this high lauric-acid content.

Because the melting point of coconut oil is about 75 degrees, the form found in foods is usually hydrogenated to keep it solid at room temperature. The hydrogenation process also creates trans-fatty acids that have been shown to increase the risk of heart disease; the use of hydrogenated coconut oil in food preparation is being curtailed for that reason. The form sold over the Internet and in health foods stores is not hydrogenated; while the processing varies by company, most oils are minimally processed to insure the oil is as close to what’s found in the coconut flesh as possible.

Coconut Oil and Cholesterol
One of the primary claims made for coconut oil is that it will help lower serum cholesterol. A PubMed search using the keywords “coconut oil” and “cholesterol” revealed over 400 studies. Most studies were performed on rabbits because the rabbit has been the primary model for examining the effects of diet on cholesterol. Examining the relevant studies, most uses of coconut oil produced an increase in cholesterol and triglycerides whether the oil was hydrogenated or not.

Limiting the search to studies on humans did not shed much light on the issue. In the only well-designed study, researchers examined the effects of butter, coconut oil, and safflower oil used as the primary dietary fats (2). Patients with elevated cholesterols completed six weeks using each type of fat in a cross-over design. There were no reductions in total cholesterol while on the diets rich in butter or coconut oil, but there were on the safflower oil-rich diet. However, the safflower oil diet contained less overall fat, which could explain the cholesterol reduction.

What’s remarkable is the lack of any well-controlled studies in humans examining whether coconut oil will lower serum cholesterol. In the few studies done, coconut oil increased serum cholesterol with or without added dietary cholesterol. There’s no real basis to make any claim relating the use of coconut oil to reducing serum cholesterol.

Coconut Oil and Heart Disease
While heart disease and cholesterol may seem like the same problem because of the relationship of saturated fat and serum cholesterol, they’re not the same. Two studies are cited most often as proof that coconut oil doesn’t contribute to heart disease. Here’s a summary of those studies.

A population study was conducted in two islands in the Polynesian atolls (3). These islands were chosen because at the time of the study, the local diet had not been influenced by the Westernized diet, and coconut was a significant source of calories in both islands at 34% and 63% respectively. The coconut-oil advocates state that the benefit of a high-coconut diet--and thus a diet high in coconut oil--is the low rate of heart disease. While that seems to be true, there are distinct differences between the two islands. The total serum cholesterol is close to 35 mg/dl higher in the island that gets 63% of their calories from coconut. In addition, the people are also much heavier and some age groups would be considered obese. While the rate of heart disease might be lower, there are other factors that were not considered such as increased physical activity or lower stress. While the fat intake was high, it doesn’t prove that people living in Westernized society could lower their risk of heart disease by using coconut oil.

Another approach to justify the use of coconut oil is the high-MCT content. In a study that examined the types of fat found in arterial plaque, researchers found a higher proportion of polyunsaturated fat (PUFA) than saturated fat (4). This led them to conclude that the trend toward increasing PUFA in the diet should be considered. This study is used by advocates of coconut oil to justify the use of coconut oil due to the high lauric-acid content.

However, in a study published by the same researchers just three years later using more sophisticated techniques for analyzing the plaque, saturated fat represented 50% of the fatty acid found in the arterial plaque (5)--but that study isn’t cited by the coconut-oil advocates. Further, in either study, there’s no evidence that any subjects used coconut oil before their deaths. Again, there’s no evidence of a benefit from using coconut oil.

Coconut Oil and Weight Loss
There are no direct studies that examine the role of coconut oil and weight loss. However, due to the high levels of MCT in coconut oil, people have associated comparative research on MCT versus oils containing long-chain triglyceride (LCT) fatty acids to be indicative of what might happen with coconut oil. In a review study by researchers from McGill University, diets higher in MCT appear to increase the energy expenditure for up to 24 hours after ingesting the MCT-containing oils (6). However, most studies were done on animals and the few that include human subjects were really too brief to make any conclusions--some were as short as 24 hours.

But there’s a better reason to dismiss any potential benefit from the use of a high-MCT diet as it relates to metabolism. In one of the studies cited, subjects had to add 260 calories from high-MCT oils to increase their metabolic rate. How many extra calories did they burn? Only 115 calories. The net effect was that the subjects ended every day with a surplus of 145 calories. You don’t have to be a math expert to see that this looks like a sure way to gain weight, not lose it.

One could say that if coconut oil were substituted for other saturated fats in the diet, any increase in metabolism would help stimulate weight loss; that’s what the researchers concluded. However, there’s no evidence of that fact; the research did not examine substitutions to the diet, just additions. The subjects’ metabolic rate may have been increased because they took in extra calories.

Again, there’s no evidence to suggest that using coconut oil will stimulate weight loss. As further evidence, the researchers of the McGill study recommended that overweight people should eat a low-fat diet.

Bottom Line
There’s no evidence that the regular use of coconut oil in the diet has any health benefits. What’s apparent after a look at all the available research cited by the proponents of coconut oil is that they use a selective examination of the data to embellish the health claims on coconut oil. It may be that future research will show some health benefits of coconut oil, but it hasn’t happened yet.

What strikes me is that after almost 50 years, a well-funded study could have and should have been performed by those who promote the use of coconut oil. That it hasn’t speaks volumes.

References:
  1. www.nutritiondata.com

  2. Cox, C, et al. Effects of coconut oil, butter, and safflower oil on lipids and lipoproteins in people with moderately elevated cholesterol levels. J. Lipid Res. 1995;36:1787-1795.

  3. Prior, IA, et al. Cholesterol, coconuts, and diet on Polynesian atolls: a natural experiment: the Pukapuka and Tokelau Island studies. Am. J. Clin. Nutr. 1981;34:1552-1561.

  4. Felton, CV, et al. Dietary polyunsaturated fatty acids and composition of human aortic plaques. Lancet. 1994;344(8931):1195-6.

  5. Felton, CV, et al. Relation of Plaque Lipid Composition and Morphology to the Stability of Human Aortic Plaques. Arteriosclerosis, Thrombosis, and Vascular Biology. 1997;17:1337-1345.

  6. St-Onge, MP and PH Jones. Physiological Effects of Medium- Chain Triglycerides: Potential Agents in the Prevention of Obesity. J. Nutr. 2002; 132: 329–332.
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