Coconut oil is not usually recommended in healthy diets because of its high saturated fat content yet the media is awash with reports about the wonderful health benefits of coconut oil. Is this new science or marketing hype?
Among vegetable oils, coconut oil is one of the richest in saturated fat – about 86-87% of all its fatty acids are saturated. Given the latest advice to replace saturated fat with unsaturated fat it would appear that coconut oil is the last vegetable oil a credible nutritionist would recommend. Wouldn’t all that saturated fat just raise blood cholesterol and increase heart disease risk?
The case for coconut oil
Coconut oil advocates argue that not all saturated fat is the same and that the health effects of coconut oil are better than might be expected. It is true that saturated fat is not a single entity – it’s a collection of different saturated fatty acids, each with its own effect on blood lipids. Medium-chain length saturated fatty acids (6-10 carbons) appear to have little effect, whereas the longer-chain saturated fatty acids (12-16 carbons) all raise total blood cholesterol. Stearic acid, which has 18 carbons, is cholesterol neutral but continues to be treated with suspicion (see below).
By far, the major saturated fatty acid in coconut oil is lauric acid (12 carbons), which the coconut oil lobby conveniently re-badges as medium-chain length and therefore a ‘good’ saturated fatty acid.
This is hard to justify – lauric acid strongly raises total blood cholesterol, which places it with the other longer-chain saturated fats. But this is where it gets interesting. Most of the rise in blood cholesterol with lauric acid comes from an increase in HDL-cholesterol, thought to be the protective fraction, and the effect lauric acid on the total/HDL-cholesterol ratio is more like that of unsaturated fatty acids. So does the coconut oil lobby have a case?
The case against coconut oil
The observational evidence tells a different story about coconut oil and lauric acid. Hu and colleagues investigated the effects of individual saturated fatty acids on the risk for coronary heart disease in a large cohort of women. They found that short- and medium-chain saturated fatty acids were not associated with heart disease risk, consistent with their neutral effect on blood lipids. In contrast, each of the longer-chain saturated fatty acids, including lauric acid, was associated with increased risk.
Another Harvard study also found that intake of all the longer-chain saturated fatty acids was associated with increased risk for heart disease.
Interestingly, in both studies intake of stearic acid was also associated with increased coronary risk. As stearic acid is cholesterol neutral we have to assume that it may have adverse effects on heart health via other mechanisms, perhaps an effect on blood clotting or blood vessel function (CSIRO study).
Countries that use coconut oil as the predominant fat don’t stand out as pillars of heart health. On the surface the Sri Lankan diet may look pretty good, just 25% of energy from fat, yet heart disease rates are much higher than would be expected. Not much support for coconut oil from this quarter.
How can we explain these conflicting lines of evidence? The key may be lauric acid’s effect on HDL-cholesterol – the assumed strength may actually be a weakness. We have all learned that HDL-cholesterol is protective against heart disease yet recent research is showing that the reality is much more nuanced.
HDL is complicated. When researchers put a new class of HDL-raising drugs to the test in recent trials the results were perplexing. HDL-cholesterol levels in the blood rose markedly yet the risk for heart disease did not fall and was even increased in one study. There was plenty of HDL but apparently it wasn’t ‘functional’. As discussed in a recent review on HDL functionality, the question about HDL is not simply how much is present but also how effective the HDL is.
Lauric acid and the other longer-chain saturated fatty acids all raise HDL levels but is it giving rise to ‘good’ HDL that lowers heart disease risk or non-functional HDL that does nothing? A study conducted in Sydney was the first to show that the quality of HDL could be changed by the food we eat. It showed that feeding saturated fat impaired the anti-inflammatory effects of HDL i.e. it lowered HDL functionality.
The marketing push
With a variety of good unsaturated vegetable oils available I would certainly not recommend coconut oil for inclusion in a healthy diet.
But it’s all a bit academic because the coconut oil marketing machine is already in overdrive. The claims are totally over-the-top with coconut oil being positioned as some sort of wonder drug that lowers the risk for just about everything. Here’s a taste:
The health benefits of coconut oil include hair care, skin care, stress relief, maintaining cholesterol levels, weight loss, increased immunity, proper digestion and metabolism, relief from kidney problems, heart diseases, high blood pressure, diabetes, HIV and cancer, dental care, and bone strength.
Don’t you love it? Eat coconut oil to treat HIV! If it wasn’t so cruel it would be funny.
The carriers of the coconut oil message are primarily alternative practitioners, presumably because scientifically trained dietitians and nutritionists would run the risk of being barred from their professional associations if they carried on like this.
The problem for us is that the general public is now hearing dietary advice that’s not supported by good science and, if implemented, would probably damage public health.
So what are you going to do about it?