New evidence is cracking open some of the positive health claims made about coconut oil. Combining the findings from 16 published studies, investigators found that use of coconut oil was associated with increases in low-density lipoprotein (LDL) and total cholesterol levels, potentially placing people at higher risk for cardiovascular disease (CVD).
Compared to nontropical olive, soybean, or canola oil, high consumption of coconut oil substantially increased LDL cholesterol. Consuming 3 to 4 tablespoons of coconut oil daily was associated with an estimated 10-mg/dL increase ― about a 9% jump ― in LDL levels.
"The main message is that scientific studies in humans do not support a beneficial effect of coconut oil consumption on body fatness, inflammation, blood sugar, or heart health," senior author Rob M. van Dam, PhD, told Medscape Medical News.
"There is thus no good reason to consume coconut oil to improve health," he said.
The systematic review and meta-analysis was published online January 13 in Circulation.
The type of fat common in coconut oil could be the culprit, said van Dam, professor of epidemiology and vice dean of academic affairs at the National University of Singapore. "Coconut oil consists of about 90% saturated fat, which is higher than the proportion of saturated fat in butter or lard."
The Devil Is in the Details?
Proponents of the health benefits of coconut oil point out that medium-chain fatty acids typically are absorbed by the portal vein "rather than used to produce cholesterol in the body," van Dam said.
However, a medium-chain fatty acid in coconut oil, lauric acid, may metabolize differently from others in the class. "It is absorbed and transported like long-chain fatty acids rather than other medium-chain fatty acids," he added. In other words, coconut oil may not be as healthy as some people believe.
Furthermore, about a quarter of coconut fat consists of the long-chain saturated fatty acids myristic acid and palmitic acid. "Thus, based on a more detailed understanding of the fatty acid composition of coconut oil and the biology of these fatty acids, our findings are not surprising," van Dam said.
The current findings contrast with a previous network meta-analysis that reported no significant increases in LDL cholesterol associated with coconut oil vs nontropical oils. "However, the authors of the network meta-analysis included only 6 trials on coconut oil," the researchers note.
The results of other studies on coconut oil consumption and serum cholesterol levels are mixed, the researchers state. Some suggest that, beyond lipid levels, coconut oil can alleviate inflammation, improve glucose homeostasis, and reduce body fatness.
Seeking a more definitive answer, van Dam and colleagues, with lead author Nithya Neelakantan, PhD, conducted a search that identified 873 potentially relevant articles. Their analysis included 16 articles with a total of 17 trials that involved 730 participants.
Anticipating methodologic variations across studies, including study design, population, type of control oil used, and amount of coconut oil intake, "we a priori decided to use a random-effects model for this meta-analysis," they noted.
For each outcome, pooled mean differences and 95% confidence intervals (CIs) were calculated using DerSimonian and Laird random-effects models. Heterogeneity in study results was tested using the Cochran Q statistic and was quantified by the I2 statistic. "I2 values of 25%, 50%, and 75% indicated low, moderate and high degrees of heterogeneity, respectively," they write.
Compared with nontropical oils, coconut oil significantly increased total cholesterol by 14.69 mg/dL (95% CI, 4.84 – 24.53; I2 = 91%).
Likewise, coconut oil increased LDL cholesterol by 10.47 mg/dL (95% CI, 3.01 – 17.94; I2 = 84%), and it increased high-density lipoprotein (HDL) cholesterol by 4.00 mg/dL (95% CI, 2.26 – 5.73; I2 = 72%).
The estimated percent change in LDL cholesterol was 8.6%, and the percent change in HDL cholesterol was 7.8%.
Coconut oil did not significantly change concentrations of triglycerides compared to nontropical oils.
Four of the included studies compared coconut oil with palm oil, which contains about 50% saturated fat.
In these studies, coconut oil significantly increased total cholesterol by 25.57 mg/dL (95% CI, 7.30 – 43.84; I2 = 79%), LDL cholesterol by 20.50 mg/dL (95% CI, 5.96 – 35.04; I2 = 67%), and HDL cholesterol by 2.83 mg/dL (95% CI, 0.21 – 5.44; I2 = 29%).
Again, triglyceride levels did not differ significantly.
Van Dam and colleagues report that coconut oil had no significant effect on body weight, waist circumference, percentage body fat, C-reactive protein levels, or fasting plasma glucose levels compared with nontropical vegetable oils. The number of studies that included palm oil was insufficient to evaluate these factors in a meaningful way.
The results of the systematic review and meta-analysis demonstrate that there is "no good reason to consume coconut oil to improve health. In contrast, high coconut consumption increases blood LDL-cholesterol concentrations and may thus increase risk of heart disease," van Dam said.
"Clinicians should recommend against regular consumption of animal fats or tropical cooking oils, including coconut oil, and instead recommend nontropical vegetable oils, such as olive, canola, soybean, or sunflower oil, for the prevention of heart disease," he said.
"However, limited sporadic use of coconut oil for taste in cooking is unlikely to have a substantial detrimental effect," he added.
The ideal next step in the research would be to study how coconut oil consumption affects CVD outcomes, van Dam said.
One of the "Most Deleterious" Cooking Oils
"Overall, this meta-analysis is rigorously conducted and reported, putting the results in the context of CVD prevention," Frank M. Sacks, MD, departments of nutrition and molecular metabolism, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, notes in an accompanying editorial.
A 2016 survey showed that 72% of Americans viewed coconut oil as a "healthy food," he added. "This represents a remarkable success in marketing by the coconut oil and related industries calling coconut oil a natural, healthful product, despite its known action to increase LDL cholesterol, an established cause of atherosclerosis and cardiovascular events."
Coconut oil may be viewed as one of the "most deleterious" cooking oils that increases risk for CVD, Sacks said.
Replacing coconut oil with nontropical unsaturated vegetable oils, especially those rich in polyunsaturated fat, will have a health benefit, Sacks noted. The results of the current study could guide nutritional recommendations.
He added that in culinary practice, coconut oil should not be used as a regular cooking oil, "although it can be used sparingly for flavor or texture."
Van Dam and Sacks have disclosed no relevant financial relationships.
Medscape Medical News © 2020
Cite this: Coconut Oil Consumption Linked to Increased LDL - Medscape - Jan 20, 2020.