Some claim that those MCTs can turn up the temperature of your metabolic furnace, thereby promoting weight loss. But while animal studies suggest some weight-loss effects from substituting MCTs for LCTs, preliminary human studies have not, says John La Puma, an internist and author of ChefMD's Big Book of Culinary Medicine: A Food Lover's Road Map to Losing Weight, Preventing Disease, and Getting Really Healthy. "If it has any potential at all to produce extra heat, it is pretty small or not there at all, depending on who you ask," he says. And there is certainly no long-term evidence to suggest any lasting weight effects from coconut oil consumption.
Those MCTs may also act differently on your heart. Evidence shows that virgin coconut oil either doesn't raise cholesterol or primarily raises HDL, the good cholesterol, thus improving the all-important ratio of good cholesterol to the bad kind. When you look at that ratio, coconut oil "doesn't look too bad," although it's not as good as a combination of plant oils like olive and canola oil, says Walter Willett, chair of the department of nutrition at the Harvard School of Public Health. But whatever the short-term effects, it's unclear whether eating coconut oil over a long time raises the risk of heart attack or stroke any less than other saturated fats, says La Puma. Research on Pacific Island and Asian populations whose diets are naturally very high in coconut oil has shown unexpectedly low rates of heart disease, but those people also eat a mostly plant-based diet and are far more active than the average American, making direct comparisons pretty tough.
There is simply not enough evidence to substantiate any sweeping claims for coconut oil, says Evelyn Tribole, a dietitian and author of The Ultimate Omega-3 Diet. Coconut oil certainly merits more research, and what we have learned so far points toward the notion that "we can't just look at classes of fat—we have to look at the individual [type of] fat," she says. But based on the current research, "I wouldn't go out of my way to add it to my diet."
La Puma says that while coconut oil is no cure-all, it and oil-rich coconut milk—in small amounts—are a great way to add flavor to foods you make at home. "Its role is in sensible cooking, as a special treat—the way you might think about butter or sour cream," he says. It still has calories, so it should be a substitute for other oils or fats, not an addition. And don't mistake virgin coconut oil for the partially hydrogenated variant found in packaged goods; the latter has been chemically altered to contain trans fats, which absolutely no one is claiming are good for your health.
[See: Best Heart-Healthy Diets]
Updated on 3/6/2012: This story was originally published on August 10, 2009.