What are medium chain triglycerides (MCTs)?

Fats along with the carbohydrate and protein constitute the major macronutrients required by our body. Fats are hydrocarbon molecules made up of carbon and hydrogen atoms. Apart from serving as source and storage form of energy, fats play an important role in cell signaling and structural functions mainly maintaining cell membranes structures (1). Depending upon the degree of saturation, fats are classified as saturated (absence of double or triple bonds between the carbon atoms in the chain) and unsaturated fats (double or triple bonds are present between the carbon atoms). Lipids and fats are synonymously used but fats are a kind of lipids which are mainly composed of three fatty acids chain attached to a glycerol moiety normally called triglycerides. More often than not fatty acids in triglycerides molecule chain range from 4 carbon atom to 24 carbon atom long and could be saturated or unsaturated fatty acids and are commonly classified into 3 groups (i) as short chain triglycerides (SCTs; up to 4 C), (ii) medium chain triglycerides (MCTs; from 6 to 12 C) and long chain triglycerides (LCTs; more than 12 C). MCTs are generally saturated fats and are not readily oxidized as other oil containing long chain fatty acids do.  In the popular perception, saturated fatty acids are considered to be unhealthy however, heterogeneous nature of fatty acids lend differential health benefits.

Significance of MCTs-rich diets

MCTs and diets rich in MCTs /SCTs (short chain triglycerides) have gained consumers’ attention in recent years due to their role in prevention and cure of many health related issues including its utility in weight loss, neuro-protective role, cancer prevention, cognitive health improvement and in the prevention of cardiovascular diseases. Naturally MCTs can be obtained from coconut oil, palm kernel oil and dairy products, desi ghee or they can be commercially extracted in the laboratories by processing coconut and palm kernel oils. Coconut oil possess more than 60% MCTs while palm oil contains 50% MCTs. Desi ghee contains 25% or higher short-chain and medium-chain triglycerides (SCTs and MCTs) (Table 1) and has been used in traditional therapeutics for its unique medicinal properties such as in the improvement of memory functions, treatment of ulcers, burn wounds, and even to slow down the progression of cancer and certain other diseases.  As oils/diets rich in MCTs are ketogenic in nature, they provide the main physiological alternative to glucose for brain function and hence age-related cognitive decline could be delayed by including MCT rich foods like coconut oil, desi ghee in our diets on a regular basis. The ketogenic diet and MCTs/SCTs also help in cancer prevention as it raises the levels of ketone bodies impairing the proliferation of various malignant cells because these tumor cells could not utilize the ketone bodies to fulfill their metabolic requirement (2). MCTs are also used as medicinal supplement for treating various health ailments. A tablespoon (15 mL) of MCT oil contains 14 grams of fat and 115 calories. Furthermore, MCTs have a high smoking point, hence, oils high in MCTs, such as coconut  oil and desi ghee (250 °C /482 °F),  are suitable for deep frying unlike other oils  characterized with low smoking point ((200 °C /392 °F) that turn rancid upon heating. The anti-microbial and anti-inflammatory properties of ghee due to high content of conjugated linoleic acid (MCTs) makes it a suitable first-aid choice for cuts, bruises and burn wounds.  Ghee is rich in butyric acid (SCT) which regulates gastro-intestinal tract motility and gut microbiome composition and also improves digestion and absorption of various nutrients. Additionally, it helps in absorption of fat soluble vitamins like vitamin A, D and E. Apart from these beneficial triglycerides, ghee also contains Omega 3, 6 and 9 fatty acids and vitamins A, D, E and K2 (Table 1).

Table 1: Fat and vitamins composition of oil/ghee that is rich in medium chain triglycerides (MCTs)

(Source: USDA, self nutrition data and Firestone, 2013; Sankararaman and Sferra, 2018; Derewiaka, 2011)

Digestion and absorption nuances of MCTs

MCTs are easily digested and metabolized compared to LCTs due to shorter carbon chain. Structural differences between MCFA (medium chain fatty acids) and LCFA (long chain fatty acids) affect their solubility and molecular size which causes differences in their metabolism and transportation in tissues and organs. MCTs are degraded into fatty acids and glycerol by pancreatic lipase and are transported to liver for further oxidation through portal circulation whereas LCTs are transported to lymphatic system in the form of chylomicrons (Fig.1). Moreover, MCTs do not require bile salts for their digestion. They pass very rapidly through mitochondrial double membrane layer as they don’t require carnitine molecule for their transportation and hence serves as an immediate source of energy in the form of ketone bodies. Calorific value provided by MCTs is 8.3 calories per gram while LCTs provide 9 calories/gram (3).  As they are readily metabolized due to shorter carbon chain, they are stored as fats in adipose tissue to lesser extent and serves as energy fuel for immediate use by organs and muscles. MCTs are thus an excellent choice for athletes with increased energy needs, post-surgery care, and to provide energy for senile population when energy production is at its low and in malnutrition condition.

Health benefits of MCTs

a) Weight management, gastro-intestinal disorder and antimicrobial effect

Studies have demonstrated that MCT-rich foods are less obesogenic (4) as it is rapidly metabolized and absorbed and hence are less likely to be stored in adipose tissues. Also, MCTs help in burning of excess calories (5), so, it could be the most favoured choice for inclusion in the weight loss diet-regimen.

Lauric acid and monolaurin has antibacterial properties due to their chemical nature as the anionic part of the molecule alters the digestive tract environment and renders it incompatible for the microbes existing there. MCTs have been found to be effective in controlling the infection caused by Salmonella, Clostridium spp. and  E. coli and Candiada albicans.

Butyric acid, present in desi ghee has anti-inflammatory properties and it helps in treating patients suffering from ulcerative colitis.

b) Prevention of atherosclerosis

MCTs have also been reported to be effective in preventing and controlling the heart diseases. Some studies in rats showed that MCTs reduces plasma cholesterol level by reducing the absorption of bile acids in the small intestine which plays an important role in cholesterol metabolism. Also, MCTs have been found to increase good cholesterol, high density lipo-protein (HDL), and hence unlike other fats, MCTs are not atherosclerotic (plaque-forming).

  c) Neuroprotective role

Diets rich in MCTs serve as an alternate source of glucose as they raise plasma ketone level which is an instantaneous source of energy for brain nerve cells. Therefore, MCTs are used in the treatment of Alzheimer’s disease and epilepsy (6) and improvement in memory and seizure control post-treatment with MCTs are documented.

MCTs and Medicine

Owing to their unique properties such as rapid digestion and absorption, MCTs have been found very useful in treating a number of health disorders such as impaired lipid metabolism, liver disease, obstructive jaundice and for food absorption disorders like diarrhea, fat digestion, and celiac disease. Absorption of amino acids and calcium and magnesium was found to be improved with the consumption of diets rich in MCTs. Thus, the diets of malnourished people can be supplemented with MCTs to fulfill their calorie requirement.

The simple metabolism of MCTs and rapid energy production makes it a healthier choice for athletes and elderly with low metabolic rate as a source of energy. It is no wonder their constructive role in controlling and preventing many health ailments has drawn the attention of researchers and consumers towards them.

References

1.Subramaniam S, Fahy E, Gupta S, Sud M, Byrnes RW, Cotter D, Dinasarapu AR, Maurya MR.  (2011). "Bioinformatics and systems biology of the lipidome". Chemical     Reviews. 111 (10): 6452–90. doi:10.1021/cr200295k. PMC 3383319.PMID 21939287.

2. Klement R J and  Kämmerer U (2011) “Is  there a role for carbohydrate restriction in the   treatment and prevention of cancer? Nutr Metab (Lond).  8: 75.

3. Carol Rees Parrish, M.S., R.D., Series Editor Nutrition Issues In Gastroenterology, Series #160.   February 2017.

4. Mumme K, Stonehouse  W (2014). “Effects of medium-chain triglycerides on weight loss and body composition: a meta-analysis of randomized controlled trials”. J Acad Nutr Diet 2015;115:249–63. doi:10.1016/j.jand.2014.10.022.

5 St-Onge, MP; Jones, PJ (2002). "Physiological effects of medium-chain triglycerides: potential agents in the prevention of obesity". The Journal of Nutrition. 132 (3): 329–332.

6. Chang P, Terbach N, Plant N, Chen PE, Walker MC, Williams RS (2013). "Seizure control by ketogenic diet-associated medium chain fattyacids" Neuropharmacology. 69: 105–114.     doi:10.1016/j.neuropharm.2012.11.004.