It's hard to ignore the ever-growing popularity of coconut oil, which is heavily promoted through websites, magazine articles and endorsements by celebrities, to name but a few. 

You’ve probably heard all of the health claims about coconut oil  – preventing and treating cardiovascular disease, improving digestion and even symptom relief for irritable bowel syndrome and inflammatory bowel disease, assisting weight loss, lowering insulin resistance, preventing dental cavities, improving thyroid function, treating Alzheimer’s disease, AIDS and herpes infections – such impressive claims for one specific food inevitably prompt scepticism from healthcare professionals, but is there any truth to the cardiovascular and weight management claims which directly affect practise as healthcare professionals?

Cardiovascular health

The cardio-protective health claim stemmed originally from observations of populations in Polynesia and Sri Lanka where the incidence of cardiovascular disease is low, despite a diet high in tropical oils like coconut oil.^1,2,3,4 However, many of these small, case-control studies were limited by their lack of consideration of the role that genetics, physical activity behaviours and other dietary factors may play in the incidence of cardiovascular disease.

Lauric acid, the main saturated fat present in coconut oil, can increase our total cholesterol, our ‘good’ cholesterol; high density lipoprotein (HDL), and to a lesser extent, our ‘bad’ cholesterol; low density lipoprotein (LDL).^5,6 While this results in overall higher cholesterol and LDL, it also has a positive influence on the HDL:LDL ratio, a widely acknowledged marker of cardiovascular disease risk.⁷

However it is important to consider coconut oil in the context of the whole diet. The effect of coconut oil on cholesterol levels is likely to depend on the type of lipid it replaces in the diet. For example, replacing foods rich in polyunsaturated fatty acids (PUFAs) like sunflower oil with coconut oil would probably raise LDL cholesterol, while replacing saturated fats like butter or trans fats like cakes or biscuits would probably have a neutral or lowering effect on LDL, respectively. This was demonstrated in the Polynesian studies where replacement of coconut oil with PUFA-rich oils resulted in a more favourable lipid profile.^1,2

Despite emerging research⁸ on the effect of coconut oil on short-term cardiovascular disease markers, there is currently a lack of evidence to support the use of coconut oil for long-term heart health, particularly within the context of our typical western diet.⁹

Weight management

Around 58% of the fatty acids in coconut oil are medium chain triglycerides (MCTs) – lauric acid 44%, caprilic acid 8%, and capric acid 6%. MCTs, specifically caprilic and capric acid, require more energy to be metabolised than long chain triglycerides (LCTs)¹⁰, and are used by the body instantly rather than being stored as adipose tissue. 

However, it is scientifically wrong to liken lauric acid, which accounts for three-quarters of the MCT in coconut oil, to a true MCT as it is not metabolised in the same way.¹⁰ Therefore, the vast majority of fats in coconut oil do not imbibe these so-called ‘fat burning’ properties.¹¹

Two human studies have demonstrated a small but significant reduction in waist circumference, although not weight loss itself. One of these studies was small, had no control group and only found significant results in males but not females;¹² the other was a slightly larger randomised double-blinded clinical trial.¹³ Ultimately, coconut oil, like all edible lipids, is high in calories, providing nine calories per gram (around 120kcal per tablespoon) and should be used sparingly in a weight reducing diet.

Health claims

Beware of coconut oil health claims based on animal studies. Hypotheses from animal studies need to be tested in humans before we can draw meaningful conclusions, and to date only a few human studies have been published. 

Coconut oil is high in saturated fat. Lauric acid, the main fatty acid in coconut oil, does not behave like a true MCT so the results of MCT research cannot be applied to coconut oil. Coconut oil raises total cholesterol, LDL cholesterol and HDL cholesterol. Coconut oil trumps trans fats. The effect of coconut oil on cholesterol levels is likely to depend on the type of lipid it replaces in the diet. 

Research to date suggests that displacing partially hydrogenated (trans) fats (eg. biscuits, cakes, pies, pastries, savoury snacks and confectionary or butter) with coconut oil may have a positive effect on cholesterol levels. However, remember that partially hydrogenated coconut oil will contain trans fats too, and should be avoided. 

Unsaturated plant oils are the winners. We still don’t know what role coconut oil plays in long-term risk of cardiovascular disease. Until we know that, any claim that coconut oil is more heart-healthy than other fats or oils is purely speculative. The vast weight of evidence still supports choosing MUFAs (olive oil, rapeseed oil, etc) and PUFAs (sunflower oil, safflower oil, corn oil, etc) as our first choice. 

All lipids are high in calories. Don’t lose sight of the bigger picture – overall diet, eating pattern and including a variety of foods is more important than focusing on individual foods. 

For dietitians interested in reading more on this topic, Dr Laurence Eyres published Coconut oil and the heart in 2014, a comprehensive review of the evidence for coconut oil in relation to heart health.¹⁴ Additionally, the Irish Nutrition and Dietetic Institute and the British Dietetic Association have developed fact sheets addressing fats and cooking oils.^15,16

Conclusion

Unless a recipe calls for the specific tropical flavour or functional properties of coconut oil, there is no benefit in consuming large amounts of it. Unsaturated vegetable oils like rapeseed and olive oils are far less expensive, are rich in omega-3s, MUFAs and antioxidants, and do not raise LDL cholesterol. 

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References

1. Kaunitz H, Dayrit CS. Coconut oil consumption and coronary heart disease. Philipp J Intern Med 1992; 30: 165-171 
2. Prior IA, Davidson F, Salmond CE, Czochanska Z. Cholesterol, coconuts and diet on Polynesian atolls: a natural experiment: The Pukapuka and Tokelau Island studies, Am J Clin Nutr 1981; 34: 1,552-1,561 
3. Lipoeto NI, Agus Z, Oenzil F, Wahgvist M, Wattanapenpaiboon N. Dietary intake and the risk of coronary heart disease among the coconut consuming Minangkabau in West Sumatra, Indonesia. Asia Pac J Clin Nutr 2004; 13(4): 377-384 4. Kumar PD. The role of coconut and coconut oil in coronary heart disease in Kerala, south India. Trop Doct 1997; 27(4): 215-217 
4. Nevin KG and Rajamohan T. Beneficial effects of virgin coconut oil on lipid parameters and in vitro LDL oxidation. Clin Biochem 2004; 37(9): 830-835  
5. Nevin KG and Rajamohan T. Influence of virgin coconut oil on blood coagulation factors, lipid levels and LDL oxidation in cholesterol fed Sprague-Dawley rats. Clin Nutr 2008; 3(1): e1-e8 
6. Millán J, Pintó X, Muñoz A, Zúñiga M, Rubiés-Prat J, Felipe Pallardo L et al. Lipoprotein ratios: Physiological significance and clinical usefulness in cardiovascular protection. Vasc Health Risk Manag 2009; 5: 757-765 
7. Feranil AB, Duazo PL, Kuzawa CW, Adair LS. Coconut oil is associated with a beneficial lipid profile in pre-menopausal women in the Philippines. Asia Pac J Clin Nutr 2011; 20(2): 190-195 
8. Natural Medicines Comprehensive Database: Coconut oil: Effectiveness. www.naturaldatabase.therapeuticresearch.com [Accessed October 9, 2015] 
9. DeLany JP, Windhauser MM, Champagne CM, Bray GA. Differential ocidation of individual dietary fatty acids in humans. Am J Clin Nutr 2000; 72(4): 905-911 
10. Vannice G and Rasmussen H. Position of the academy of nutrition and dietetics: dietary fatty acids for healthy adults. J Acad Nutr Diet 2014; 114(1): 136-153 
11. Liau KM, Lee YY, Chen CK, Rasool AH. An open-label pilot study to assess the efficacy and safety of virgin coconut oil in reducting visceral adiposity. ISRN Pharamacol 2011; 949686 
12. Assunção ML, Ferreira HS, dos Santos AF, Cabral CR Jr, Florêncio TM. Effects of dietary coconut oil on the biochemical and anthropometric profiles of women presenting abdominal obesity. Lipids 2009; 44(7): 593-601 
13. Eyres L on behalf of the New Zealand Heart Foundation. Coconut oil for the heart. Available at: www.heartfoundation.org.nz/news-blogs-stories/press-releases/coconut-oil-and-the-heart [Accessed October 22, 2015] 
14. McCarthy A on behalf of the Cardiology Interest Group, Irish Nutrition and Dietetic Institute. Fact sheets: heart health: the great cooking oil debate. 2014. Available at: https://www.indi.ie/diseases,-allergies-and-medical-conditions/heart-health/746-the-great-cooking-oil-debate.html [Accessed October 20, 2015]
15. Donovan L on behalf of the British Dietetic Association. Food fact sheet: Fats. 2015. Available at: https://www.bda.uk.com/foodfacts/FatFacts.pdf [Accessed October 22, 2015]