Coconut milk used to be something that came in a can and was good to have on hand for making pina coladas or Thai curries. These days, coconut milk can also be found in cartons in the milk aisle and in pints in the ice cream section — and as yogurt, coffee creamer and even kefir.
Some consumers are turning to coconut-milk products because they're eager for a new dairy alternative, but others are switching to them in the belief that they promote weight loss.
Consumers should be aware that the evidence in support of such claims is very slim — and that coconut milk in any form is high in saturated fat, says Ruth Frechman, a spokeswoman for the American Dietetic Assn.
In the 1980s, coconut products, especially the coconut oil once widely used in processed foods, acquired a bad reputation for being high in heart-harming saturated fat. And with reason. Traditional coconut milk — the kind that comes in a can — has a somewhat astounding 550 calories per cup and provides more than 250% of the daily recommended limit for saturated-fat intake, according to the U.S. Department of Agriculture.
Many of the newer coconut-milk beverages have a far better nutritional profile, however. The So Delicious unsweetened coconut milk beverage, for example, contains 50 calories per cup and provides 25% of the daily recommended limit for saturated fat. But not all saturated fat is the same. The labels of So Delicious declare that the drink is rich in ones called MCFAs.
MCFAs, or medium-chain fatty acids, are a type of saturated fat found in coconut milk consisting of eight to 10 carbon atoms strung together in a row. Long-chain fatty acids, or LCFAs, contain 12 or more carbon atoms in a row and are more prevalent in meat and dairy products. A few decades ago, animal studies demonstrated that LCFAs were more likely to end up as fat deposits in the body compared with MCFAs, which were quickly metabolized by the liver.
Subsequent studies showed that animals fed a greater proportion of MCFAs gained less weight than animals eating more LCFAs.
In the 1990s, researchers began looking at the effects of MCFA consumption in humans.
Two studies, one conducted in Italy and one in Switzerland, showed that men who ate meals that contained about 30 grams of MCFAs (in place of LCFAs) had a roughly 5% higher metabolic rate compared with those who ate LCFAs. But the two studies were small, involving just eight and 12 men, respectively, and measured changes in the men's metabolism after only a single meal.
More recently, researchers at McGill University in Canada examined the effects of consuming MCFAs for longer periods of time. In one study, published in the American Journal of Clinical Nutrition in 1999, 12 women ate meals enriched with either MCFAs from butter and coconut oil or LCFAs from beef fat. After 14 days, the women who ate the MCFA oil were burning 0.14 more kilojoule (a unit of energy) per minute than the women who had eaten LCFA oil.
But it's not clear that this higher metabolic rate translates into weight loss. In 2003, the McGill researchers published findings from a similar study in the International Journal of Obesity; the women who ate the MCFA-fortified meal (this time for two 27-day periods) burned slightly more calories than women who ate LCFAs, but they didn't shed any more pounds. (There was actually a very small difference in weight loss between the two groups, but it was too small to be considered statistically significant; researchers surmised that the similar weight loss between the two groups may have been due in part to the women in the study incorrectly reporting what they ate.)
Other research has reported weight loss, however. In a study of 40 men and women who ate meals containing either LCFA oil or a proprietary blend of MCFA oil while in a weight loss program for 16 weeks, those who ate the MCFA oil lost an average of just over 3 kilograms (or 6.6 pounds), whereas those who ate the LCFA oil lost 1.5 kilograms (3.3 pounds). The study was published in the American Journal of Clinical Nutrition in 2008.
But even if such research suggests that MCFAs, like those found in coconut milk, might help speed up metabolism and help promote weight loss, there's still no proof that they're any healthier for the heart than other forms of saturated fat.
A 2004 study of 17 men published in the American Journal of Clinical Nutrition found that total cholesterol levels were 11% higher in those who ate a diet containing MCFAs compared with those who ate a diet containing sunflower oil, which is rich in unsaturated fats. The level of LDL, so-called bad cholesterol, was 12% higher in the men who ate MCFAs.
The bottom line: MCFAs' unproven potential to speed up metabolism doesn't make coconut milk products health foods — at least not until researchers confirm their effects on weight and put to bed concerns about their effects on LDL cholesterol levels.
"Every study on the subject links saturated fats, regardless of how short or long chain they are, with heart disease," says Dr. Karol Watson, a professor of cardiology at UCLA Medical Center. When it comes to fats, she says, "saturated is saturated."