Putting paid to the coconut oil myth once and for all

In a recent review and meta-analysis of randomized controlled trials (Circulation 2020;141:803-814), an international team of researchers identified 16 randomized controlled trials that compared the effects of the intake of coconut oil with other common vegetable-based oils, such as soybean oil, olive oil, or safflower oil.

From their analysis, the authors excluded studies that were *not* randomized controlled trials; those that included infants, animals, mice, or cell studies [that is, in vitro studies]; were literature reviews, cross-sectional, or prospective studies; were shorter than 2 weeks in length; compared coconut oil with "inappropriate" interventions, such as comparing coconut oil with fresh coconut, coconut milk, oils from mixed sources, oils that were nothing but lauric acids (one of the well-regarded sources of fats in coconut oils), or fish oils; or compared coconut oil to oils to artificial oils. Further, the included studies had to last at least 2 weeks and focus on the oils' effects on cholesterol scores; weight; body fat; waist circumference; glucose scores; or other clinical scores.

The authors of this study identified just 17 published randomized controlled trials that met the criteria. These included 730 participants.

Seven of the studies were performed in the United States, 2 in Europe, 6 in Asia, and 2 in Brazil, and most participants had normal cholesterol scores at the start of their studies. 10 of the trials provided either foods or entire meals for the participants' consumption while 5 provided cooking oils for the participants to use at home and 2 provided coconut oil in a capsule for daily consumption.

The authors obtained the data from each included study and pooled the results after standardizing the data gathered. They found that compared to non-tropical vegetable oils (that is, oils that were not coconut oil or palm oil), those who consumed the coconut oil saw an 8.6% increase in their LDL cholesterol (the bad cholesterol), a 7.8% increase in their HDL cholesterol (the good cholesterol), with no significant change in triglycerides but a statistically significant increase in total cholesterol.

Compared with palm oil (note that this is not 'palm kernel oil'), coconut oil increased total, LDL, and HDL cholesterol, but again, not triglycerides.

When the authors focused on whether coconut oil consumption affected body weight, waist circumference, body fat percentage, or glucose scores, the authors note only that the number of studies were too small for "a meaningful meta-analysis."

What this means for you

In brief, "Our results on the adverse effects of coconut oil as compared with alternative cooking oils on LDL-choolesterol concentrations... align with dietary recommendations to replace saturated fat with polyunsaturated fat." Further, "there was no convincing evidence to support the consumption of coconut oil over nontropical vegetable oils for [cardiovascular] risk reduction."

The proponents of coconut oil have argued that the fats in coconut oil are made of medium-chain fatty acids (MCFAs), which are more rapidly absorbed than long-chain fatty acids (the more usual saturated fatty acids) and are therefore less harmful than most saturated fats.

The problem is that about half of the total fatty acids in coconut oil are lauric acids, which although chemically are considered MCFAs, are treated by the body more like long-chain fatty acids. In addition, another 25% of the fat in the fat in coconut oil is more standard long-chain fatty acids.

While more randomized controlled trials into coconut oil's effects on body weight, waist circumference, body fat, etc., might be worthwhile, it's clear that unless quite convincing evidence is presented, coconut oil should be treated as the mostly saturated fat it is: one to mostly avoid in favor of oils higher in poly- and mono-unsaturated fats.

First posted: May 6, 2020