MCTs passively diffuse from the GI tract to the portal system (longer fatty acids are absorbed into the lymphatic system) without requirement for modification like long-chain fatty acids or very-long-chain fatty acids. In addition, MCTs do not require bile salts for digestion. Patients that have malnutrition or malabsorption syndromes are treated with MCTs because they do not require energy for absorption, utilization, or storage.
The fatty acids found in MCTs are called medium-chain fatty acids. The names of the medium-chain fatty acids (and the corresponding number of carbons) found in MCTs are caprylic acid (C8) and capric acid (C10). Like all triglycerides (fats and oils), MCTs are composed of a glycerol backbone and three fatty acids, hence the name triglyceride; in the case of MCTs, 2 or 3 of the fatty acid chains attached to glycerol are medium chain in length.
The milk fats of humans and guinea pigs are largely made up of long-chain fatty acids. The milk fats of cows, sheep, and goats are rich in short-chain fatty acids. The milk fats of horses contain large amounts of medium-chain fatty acids.
Some studies have shown that MCTs can help in the process of excess calorie burning, and thus weight loss. MCTs are also seen as promoting fat oxidation and reduced food intake. There has also been interest in MCTs from endurance athletes and the bodybuilding community. While there seem to be health benefits from MCTs, a link to improved exercise performance is weak.
Medium-chain triglycerides are generally considered a good biologically inert source of energy that the human body finds reasonably easy to metabolize. They have potentially beneficial attributes in protein metabolism but may be contraindicated in some situations due to their tendency to induce ketogenesis and metabolic acidosis.
Due to their ability to be absorbed rapidly by the body, medium-chain triglycerides have found use in the treatment of a variety of malabsorption ailments. MCT supplementation with a low-fat diet has been described as the cornerstone of treatment for primary intestinal lymphangiectasia (Waldmann's disease). MCTs are an ingredient in parenteral nutritional emulsions. Studies have also shown promising results for neurodegenerative disorders (e.g. Alzheimer's and Parkinson's disease) and epilepsy through the use of ketogenic dieting.
MCTs are bland compared to other fats, and do not generate off-notes (dissonant tastes) as quickly as LCTs. They are also more polar than LCTs. Because of these attributes, they are widely used as solvents for flavours and oral medicines and vitamins.
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