In a recent column, you said oils that are high in saturated fat aren't heart-healthy. But I've read about the benefits of tropical oils, especially coconut oil. What's up?
The standard guidance to limit intake of saturated fats, including those from tropical oils, to 10 percent of total calories hasn't changed. That message is nearly universally recognized as sound advice.
But research on diet and health is ongoing. What you're witnessing is the scientific method in action. That is, scientists conduct studies and publish data and analyses; other scientists review those findings and either build on them or dispute them.
Eventually, consensus builds and standard guidance develops -- which is then questioned, tested, adapted, supported or refuted, and on and on.
For example, for decades, evidence has accumulated to show that saturated fat increases blood cholesterol, thus raising the risk of heart disease. But in 2010, an analysis of 21 studies was published in the American Journal of Clinical Nutrition; it concluded that the link between saturated fats and heart disease is questionable. But in the same issue, the journal published an editorial questioning the findings, and a later issue included a letter from other researchers questioning the authors' methods.
One of the confounders in this debate is that not all saturated fats are created equal. Different kinds have different types of fatty acids: lauric, palmitic and stearic, for example, and they have different effects. For instance, about half of the saturated fat in virgin coconut oil (the type that's not hydrogenated) is lauric acid, which raises HDL cholesterol -- the "good" cholesterol -- even while raising LDL cholesterol -- the "bad" type. Also, since they are plant-based foods, coconut and other tropical oils also contain antioxidants, which have their own positive health effects.
But be skeptical about some of the claims being made -- that coconut oil combats everything from HIV and Alzheimer's disease to acne and weight gain. While you might hear compelling anecdotal evidence and even read some preliminary studies, so far there's insufficient data to warrant changes in consumer guidance on intake of coconut oil or other saturated fats.
At the same time, evidence is mounting that if people reduce saturated fat but instead eat more refined carbohydrates, they're actually worse off in terms of heart health. But it appears that replacing saturated fats with unsaturated fats remains beneficial.
The scientific process can lead to confusion, or even mistrust of the scientific community. But over time, it has proven its worth.
Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or firstname.lastname@example.org.
Editor: Chow Line is taking a two-week break. Watch for the next column on Jan. 11, 2013.
This column was reviewed by Julie Kennel, nutrition program specialist for OSU Extension and director of the Dietetic Internship Program in the Department of Human Nutrition in the College of Education and Human Ecology.